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The Legacy of EPA’s Acid Rain Research

Published August 18, 2020

In EPA’s 50 years of research, one of the most significant environmental challenges the nation faced was the problem of acid rain. Although evidence of acid rain’s harmful effects emerged centuries ago, it wasn’t until the early 1980s that it was recognized as a major threat. In taking part in the national effort to combat acid rain, EPA scientists helped usher in a new chapter of environmental science.

Acid rain forms mainly through reactions with the chemicals sulfur dioxide and nitrogen oxide found in fossil fuel emissions. It can take the form of acidic rain, snow, or dust and can travel hundreds of miles in the air before falling to the Earth’s surface. While normal rainwater is slightly acidic at a pH of 5.6, by 1980 the average rainfall in the United States was at a pH level of 4.6, about ten times more acidic and trending more acidic.

The effects of increasing acidity were widespread. Acid rain negatively affects aquatic and terrestrial life, damages structures by corroding metal, paint and stone, and threatens public health. In the early to mid ‘80s, scientists observed that many lakes and streams were becoming too acidic to support fish, amphibians, and other aquatic life. On land, acid rain was stripping nutrients from soil and foliage that plants needed to grow. Acid rain also contributed to increased weathering of buildings, statues, and gravestones.

In 1980, Congress directed EPA, along with five other federal agencies, four national laboratories, and partners from the private sector to form the National Acid Precipitation Assessment Program (NAPAP). With increased funding to investigate acid rain, NAPAP scientists achieved a greater understanding of acid rain in just a few years.

EPA scientists played a major role in several of the program's research areas, providing support for policies like the Acid Rain Program, which helped achieve major reductions in sulfur dioxide and nitrogen oxide emissions. These research efforts contributed advancements that reverberate through the scientific community to the present day.

EPA ecologist Paul Ringold, Ph.D., joined NAPAP in 1984 and continued to focus on acid rain for a decade. "EPA had a couple of visionaries who were involved in acid rain research," he said, "and in order to address the policy questions of acid rain, they did things that revolutionized the practice of environmental science."

Monitoring the nation's waters

One of the biggest impacts of acid rain was its effects on surface water, especially in lakes in Northeastern U.S. and Canada, which exhibited higher sensitivity to acidifying chemicals. To answer questions about acid rain’s impact on these lakes, scientists needed to develop new approaches to studying ecology.

Dr. Ringold explained that in the past, many ecologists tended to study individual sites in-depth—so, while scientists understood the impact of acid rain on specific lakes, they needed to look at the population of lakes to understand the extent of the problem and to respond to key science questions.

"The key questions on the ecological side were, how many acid lakes are there, and how many of them have become acidic as a result of acid rain?" Dr. Ringold said. "And, if we change acid rain, how will we change the number of acidic lakes?"

In 1983, EPA began the National Surface Water Survey to investigate the effects of acid rain on America's lakes and streams. Instead of attempting the impossible feat of sampling every lake and stream, researchers used statistical sampling methods to narrow down which were most likely to be susceptible to acid rain.

This approach to ecological research revolutionized the way EPA and similar federal programs developed datasets to monitor the environment, according to Dr. Ringold. The methods developed to answer questions about acid rain translated to other environmental questions, laying the groundwork for later monitoring programs like EPA's Environmental Monitoring and Assessment Program (EMAP) and the National Aquatic Resource Surveys (NARS). Both EMAP and NARS have advanced environmental monitoring practices and provided critical data on the health of the nation’s ecosystems.

Innovations in atmospheric modeling

Robin Dennis, Ph.D., spent 30 years in EPA's former National Exposure Research Laboratory before retiring in 2015. Soon after he joined EPA in the mid-'80s, Dr. Dennis became involved in evaluating NAPAP's newly developed air quality model. The Regional Acid Deposition Model (RADM) enabled scientists to simulate how emissions interacted with the atmosphere to form acid rain, and where it would be transported and deposited. Dr. Dennis explained RADM was instrumental in answering questions about acid rain because it modeled atmospheric chemistry more accurately than other models used at the time.

"The nice thing about what EPA had done is we pulled together the tools needed to see the whole causal chain of acid rain deposition," Dr. Dennis said. "Hardly anybody has the luxury of that kind of a complete causal chain being modeled and studied."

The methods behind RADM carried over into the present-day Community Multi-scale Air Quality (CMAQ) modeling system, now a key model for air quality management. Donna Schwede is a physical scientist in ORD's Atmospheric and Environmental Systems Modeling Division. She said her team's work developing CMAQ is important for "predicting acid rain or wet deposition values, as well as looking at the ability of different proposed control strategies to reduce acid rain and its harmful effects on ecosystems." 

Today, EPA continues to work to understand the impacts of acid rain through measurement and modeling. Scientists from EPA are active participants and leaders in the National Atmospheric Deposition Program, which monitors the chemistry of precipitation in the U.S. as part of the National Trends Network.

"We also continue to improve our modeling capabilities for atmospheric deposition," Schwede said. "While SO2 emissions have been greatly reduced, other pollutants can also be acidifying, and controlling those emissions remains a challenge."

While some pieces of the acid rain puzzle remain, EPA scientists have played a critical role in the effort to mitigate the effects of acid rain, then and now. To date, initiatives like the Acid Rain Program have had great success in reducing the emissions causing acid rain. The national average of  SO 2  annual ambient concentrations decreased 93 percent  between 1980 and 2018. Wet sulfate deposition – a common indicator of acid rain –  decreased 86 percent  reduction from 2000-2002 to 2016-2018. Data from EPA’s Long-Term Monitoring program show marked improvements in the acidification of lakes and streams, while better air quality has led to a decrease in adult mortality and will prevent an estimated 230,000 premature deaths this year alone. In their work to address acid rain, EPA scientists not only advanced the field of environmental science, but also helped achieve substantial benefits for the environment and human health.

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The USGS has been at the forefront of studying the impacts of acid rain for decades. How does acid rain form? What does it do to the landscape? Can it burn you like battery acid? Keep reading to find out more...

Acid rain is the term commonly used by scientists to describe rain that is abnormally acidic. What does that mean? Well, plain distilled water, like that used in laboratories, is neutral (not acidic or basic). Since rain naturally has things dissolved in it, it will always be slightly acidic. However, when rain reacts with certain air pollutants, such as sulfur or nitrogen oxides, the water vapor converts into very diluted forms of sulfuric or nitric acids. The acidity of this rain is on par with that of grapefruit juice, which may not seem like much, but is much more caustic than plain water.

The main sources of pollutants that trigger acid rain are vehicles and industrial and power-generating plants. The areas of greatest acidity are in the northeastern United States. This pattern of high acidity is caused by the large number of cities, the dense population, and the concentration of power and industrial plants in the Northeast. In addition, the prevailing wind direction brings storms and pollution to the Northeast from the Midwest.

IMPACT OF ACID RAIN ON FORESTS

Acid rain can dissolve certain more soluble elements from the soil, like aluminum. The dissolved aluminum begins to accumulate and can reach toxic levels as it enters local streams and wetlands. Acid rain also removes important nutrients from the soil, such as calcium, potassium, and magnesium. The lack of nutrients can negatively affect the health of plants and animals. Lastly, the combination of reduced calcium and excessive aluminum can make forests more susceptible to pests, disease, and injury from freezing and drought, as a proper balance of these nutrients is vital to forest health.

WHAT USGS AND OTHERS DOING ABOUT ACID RAIN?

Scientists from many disciplines study acid rain and its impact. The National Acid Precipitation Assessment Program (NAPAP), a Federal program involving representatives from more than a dozen Federal agencies, has sponsored studies on how acid rain forms and how it affects lakes, crops, forests, and materials. Because buildings and monuments cannot adapt to changes in the environment, as plants and animals can, historic structures may be particularly affected by acid precipitation. Scientists are studying effective control technologies to limit the emissions from power plants and automobiles that cause acid rain. The impact and usefulness of regulations that would require limits on air pollution are also being studied. Finally, scientists are examining the processes of deterioration to find effective ways to protect and repair our historic buildings and monuments. Agencies like the National Park Service, which are charged with protecting and preserving our national heritage, are particularly concerned not only about the impact of acid rain but also about making the best choices for maintaining and preserving our historic buildings and monuments.

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The USGS investigates the chemistry, source, fate, and transport of airborne pollutants and their affect on the landscape.

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The USGS produces many types of multimedia products. Use the links below to browse our offerings of photographs, podcasts and sound files, and videos related to acid rain.

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The USGS reports on the occurence, magnitude, and impacts of acid rain across the country. Here are a few useful publications that showcase USGS acid rain science.

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Acid Rain Effects on Forest Soils begin to Reverse

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How does acid precipitation affect marble and limestone buildings?

When sulfurous, sulfuric, and nitric acids in polluted air and rain react with the calcite in marble and limestone, the calcite dissolves. In exposed areas of buildings and statues, we see roughened surfaces, removal of material, and loss of carved details. Stone surface material may be lost all over or only in spots that are more reactive. You might expect that sheltered areas of stone buildings...

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Acid rain and air pollution: 50 years of progress in environmental science and policy

Peringe grennfelt.

1 IVL Swedish Environmental Research Institute, PO Box 53021, 40014 Gothenburg, Sweden

Anna Engleryd

2 Swedish Environmental Protection Agency, Virkesvägen 2F, 10648 Stockholm, Sweden

Martin Forsius

3 Finnish Environment Institute, Latokartanonkaari 11, 00790 Helsinki, Finland

Øystein Hov

4 The Norwegian Meteorological Institute, P.O. Box 43, Blindern, 0313 Oslo, Norway

Henning Rodhe

5 Department of Meteorology, Stockholm University, 10691 Stockholm, Sweden

Ellis Cowling

6 Department of Forestry and Environmental Resources, NC State University, 5211 Glenhope Court, Cary, NC 27511 USA

Because of its serious large-scale effects on ecosystems and its transboundary nature, acid rain received for a few decades at the end of the last century wide scientific and public interest, leading to coordinated policy actions in Europe and North America. Through these actions, in particular those under the UNECE Convention on Long-range Transboundary Air Pollution, air emissions were substantially reduced, and ecosystem impacts decreased. Widespread scientific research, long-term monitoring, and integrated assessment modelling formed the basis for the policy agreements. In this paper, which is based on an international symposium organised to commemorate 50 years of successful integration of air pollution research and policy, we briefly describe the scientific findings that provided the foundation for the policy development. We also discuss important characteristics of the science–policy interactions, such as the critical loads concept and the large-scale ecosystem field studies. Finally, acid rain and air pollution are set in the context of future societal developments and needs, e.g. the UN’s Sustainable Development Goals. We also highlight the need to maintain and develop supporting scientific infrastructures.

Introduction

Acid rain was one of the most important environmental issues during the last decades of the twentieth century. It became a game changer both scientifically and policy-wise. For some time, particularly during the 1980s, acid rain was by many considered to be one of the largest environmental threats of the time. Observations of fish extinction in Scandinavian surface waters and forest dieback on the European Continent were top stories in the news media. Even in North America acid rain received large public and policy attention.

During the cold war, with almost no contacts between East and West, acid rain broke the ice and formed an opening for scientific and political collaboration, resulting in a treaty under the United Nations’ Economic Commission for Europe (UNECE), the Convention on Long-range Transboundary Air Pollution (often mentioned as CLRTAP but in this paper we call it the Air Convention) signed in 1979. Eight protocols have been signed under the Air Convention committing parties to take far-reaching actions, not only with respect to acid rain but also with respect to several other air pollution problems (Table  1 ). Emissions of all key air pollutants have been reduced significantly and for the most important acidifying compound, sulphur dioxide, emissions in Europe have decreased by 80% or more since the peaks around 1980–1990 (Fig.  1 ).

Table 1

The Convention on Long-Range Transboundary Air Pollution and Its Protocols

European emissions of sulphur dioxide (SO 2 —black), nitrogen oxides (NO x , calculated as NO 2 —green) and ammonia (NH 3 —blue) 1880–2020 (updated from Fig.  2 in Schöpp et al. 2003 )

In this paper, we present and discuss how the acid rain problem became a key environmental issue among industrial countries from the late 1960s and the following decades (Fig.  2 ). We view the problem from a science-to-policy interaction perspective, based on a Symposium in Stockholm in the autumn 2017 organised to manifest 50 years of international air pollution science and policy development. The Symposium involved both a testimony from a number of those involved in science and policy during the first decades of the history but also a discussion of what we have learned and how the experience can be used in the future. Further information about the symposium and its outcome can be found at http://acidrain50years.ivl.se .

The timeline of science and policy interactions in Europe and North America 1967–2018. (updated from Driscoll et al. 2012). Abbreviations not occurring in text. NAAQS: National Ambient Air Quality Standards under the US Clean Air Act; CCAA: Canadian Clean Air Act; RADM: Regional Atmospheric Deposition Model; MAGIC Model of Acidification of Groundwater in Catchments. It should be mentioned that Canada and US are both parties to the Air Convention and they have also signed and ratified most of its protocols

Our historical review will be limited to some of the issues brought up at the Symposium. For more information on the early history see Cowling ( 1982 ). A comprehensive description of the acid rain history has recently been published by Rothschild ( 2018 ). The history of the first 30 years of the science–policy interactions under the Air Convention is also described in Sliggers and Kakebeeke ( 2004 ).

Short historical review

The discovery and the early acid rain history.

In a deliberatively provocative article in the Swedish newspaper Dagens Nyheter in October 1967, entitled “An Insidious Chemical Warfare Among the Nations of Europe”, the Swedish scientist Svante Odén (Fig.  3 ) described a new and threatening environmental problem—Acid Rain. He pointed to the significant decrease in pH of rainwater and surface waters that had occurred over the previous decade and linked it to the large and increasing emissions of sulphur dioxide in Europe.

Svante Odén around 1970 (photo Ellis B. Cowling)

The discovery received immediate attention by the Swedish government and, a few weeks after Odén’s article, the minister of industry presented the issue at the Organisation for Economic Cooperation and Development (OECD), but it did not receive any political attention at that time. The issue was also brought up in OECD’s Air Pollution Management Committee by the Swedish delegate Göran Persson. Also, here the message was met by scepticism and the common opinion among the members in the committee was that sulphur dioxide was a local problem, which easily could be solved by tall stacks. It was not until Persson felt he was going to “loose the case” he “played his last card” and pointed to the observations of intercontinental transport of radioactivity from the Chinese nuclear bomb experiments. The opinion then changed and the meeting agreed that acid rain might be an issue to look into. From now on, OECD and the western world realised that air pollution might be a problem of international political dimensions.

Odén’s discoveries were to a large extent based on the regional precipitation networks that were running in Sweden and Europe. In 1947, the Swedish scientist Hans Egnér set up a Swedish network to investigate the importance of atmospheric deposition for the fertilisation of crops. In 1954, the network was expanded forming the European Air Chemistry Network (EACN) through initiatives by Egnér, Carl Gustav Rossby, and Erik Eriksson (Egnér and Eriksson 1955 ; see also Engardt et al. 2017 ). Data from these networks together with a Scandinavian surface water network set up by Odén in 1961 formed the basis for Odén’s observations on the ongoing acidification (Odén 1968 ).

Acid rain and many of its ecological effects were, however, recognised long before 1967–1968. In fact, many features of the acid rain phenomenon were first discovered by an English chemist, Robert Angus Smith, in the middle of the nineteenth century! In 1852, Smith published a detailed report on the chemistry of rain in and around the city of Manchester, England. Twenty years later, in a very detailed book titled “Air and Rain: The Beginnings of a Chemical Climatology”, Smith first used the term “acid rain” and enunciated many of the principal ideas that are part of our present understanding of this phenomenon (Smith 1872 ). Unfortunately, however, Smith’s pioneering book was substantially ignored by nearly every subsequent investigator.

In Norway salmon catches decreased substantially in the early 1900s and in 1927, Professor Knut Dahl hypothesised that acidification of surface waters could be a factor of importance for the extinction of fish. Later Alf Dannevig assumed that “The acidity of a lake is dependent on the acidity of the rainwater and the contributions from the soil” (Dannevig 1959 ).

Based on detailed field observations and experimental studies both in England and in Canada, beginning in 1955 and continuing through 1963, Eville Gorham and his colleagues built a significant foundation for contemporary understanding of the causes of acid precipitation and its impacts on aquatic ecosystems, agricultural crops, soils, and even human health (Gorham 1981 ; Cowling 1982 ). Thus, Gorham and his colleagues as well as Dahl and Dannevig had discovered major aspects of the causes of contemporary changes in the chemistry of atmospheric emissions and deposition and their effects on aquatic ecosystems.

But these pioneering contributions, like those of Smith a century earlier, were not generally recognised—neither by scientists nor by society in general. Gorham’s researches, like those of Smith a century before, were met by what Gorham himself acknowledged as a “thundering silence”, not only by the scientific community, but also by the public at large.

It was not until 1967 and 1968 when Svante Oden published both his deliberatively provocative article in Dagens Nyheter and his carefully documented Ecological Committee Report (Odén 1968 ) that the acid rain problem was brought to both public and scientific considerations. The report included a huge body of scientific and policy-relevant evidence that long-distance transport and deposition of acidifying pollutants were causing significant environmental and ecological impacts, even in countries far away from pollutant-emitting source areas in other countries.

The Swedish case study and the OECD project

Two years after Odén’s article, the Swedish government decided to prepare a “case study” as a contribution to the UN Conference on the Human–Environment in Stockholm 1972 (Royal Ministry of Foreign Affairs and Royal Ministry of Agriculture 1972 ). Bert Bolin at the Stockholm University was appointed chair of the study, which included Svante Odén, Henning Rodhe, and Lennart Granat as authors. The report included a broad environmental assessment of the sulphur emission problem including sources, atmospheric and surface water chemistry, and effects on ecosystems and materials. Finally, it also included scenarios and estimated costs for environmental damage and control; in fact it was probably the first full systems analysis of an environmental problem.

In the report, a first estimate was made of the relative contributions of domestic and foreign emissions to the sulphur deposition in Sweden (Rodhe 1972 ). Estimates were also made of the effects of sulphur emissions on excess mortality and showed that 50% of the Swedish lakes and rivers would reach a critical pH level within 50 years (assuming continuation of present emission trends). Even if some aspects of the report received criticism, the overall case study was well received by the UN conference and in its final report (see http://www.un-documents.net/aconf48-14r1.pdf ) regional air pollution was explicitly mentioned (§85) with a citation of the Swedish study.

The Swedish initiative in the OECD resulted in a collaborative project to investigate the nature and magnitude of the transboundary transport of emitted sulphur dioxide over Western Europe, in which 11 countries participated. To initiate the project, a Nordic organisation on scientific research, Nordforsk, was asked to plan and develop methodologies for the investigation. Scientists and institutions from Norway, Sweden, Denmark, and Finland established an expert group in April 1970, which became central for the development and implementation of the OECD project. The Norwegian Institute for Air Research (NILU) offered through its director Brynulf Ottar to coordinate the project. The project included emission inventories, measurements of atmospheric concentrations, and deposition, together with model development and application for the assessment of the transport. A key part of the model calculations was to prepare the so-called “blame matrices”, through which the transport of pollutants between countries could be quantified.

The main conclusion from the OECD project, published in 1977, was that “Sulphur compounds do travel long distances in the atmosphere and the air quality in any European country is measurably affected by emissions from other European countries” (OECD 1977 ). Even if there still were hesitations about the magnitude of the transport, the common opinion was that transboundary transport of air pollution is an issue that needs collaboration across national borders. These conclusions paved the road for a pan-European scientific collaboration on air pollution, the European Monitoring and Evaluation Programme (EMEP) starting in 1977. The findings from the project also formed the basis for the Air Convention (Table  1 ). EMEP was already from the beginning included in the Convention as a key element, strongly contributing to the scientific credibility of the policy work.

Threats to forests boosted the interest

In 1980, the German scientist Bernhard Ulrich warned that European forests were seriously threatened from atmospheric deposition of sulphur. From his long-term experiments in the Solling area, he concluded that the high deposition of atmospheric pollutants had seriously changed the soil chemistry (Ulrich et al. 1980 ). Ulrich pointed to the links between sulphur deposition and the release of inorganic aluminium. His findings became a policy issue not only in Germany but in Europe as a whole, and even in North America. The alarms—often exaggerated—went like a wildfire through media and changed many attitudes throughout Europe. Newspapers were filled with photos of dying forests, in particular from “The Black Triangle”, the border areas between Poland, East Germany, and Czechoslovakia, characterised by large combustion of brown coal with high sulphur content. Forest inventories showed crown thinning and other effects on forests, but it became difficult to finally determine that acid deposition was the (only) cause for the observed effects.

The increasing interest in regional air pollution also paved the way for the first international agreement on emission control under the Air Convention. As a start, countries with a large interest in taking actions formed a “club” under the Convention, aiming for a 30% reduction in emissions. This ambition then became the basis for the first emission reduction protocol, the Sulphur Protocol signed in 1985. While Germany and some other West European countries acted almost immediately on the alarms, the progress in emission control in Eastern Europe was very slow during the 1980s, even though several of these countries signed the protocol. In fact, substantial decrease in emissions did not take place in the East until after the break-down of the communist regimes and the industrial collapse around 1990.

Critical loads and advanced policies

One of the most well-known characteristics for the control of the acid rain problem is the concept of Critical Loads (Nilsson 1986 ; Nilsson and Grennfelt 1988 ). The Executive Body, the highest decision-making body of the Air Convention, decided in 1988 that new negotiations on the control of sulphur and nitrogen emissions should be based on critical loads, and all parties to the Convention were requested to prepare their own critical load maps. The Netherlands offered to take a lead and prepared mapping manuals and initiated an international network, which became crucial for the scientific and policy acceptance of the concept (Hettelingh et al. 1991 ; De Vries et al. 2015 ; Fig.  4 ). (The critical loads concept is further discussed later in the paper)

The outcome of emission control of SO2, NOx, and NH3 between 1990 and 2010 presented as maps on exceedance of critical loads of acidity. Such maps have played an important role for illustrating outcomes of future policies as well as of actions taken (from Maas and Grennfelt 2016 )

When critical loads became a basis for further protocols, Integrated Assessment Models (IAMs) offered a method to calculate how to achieve a prescribed ecosystem effect reduction in the most cost-effective way. A couple of different approaches were developed, but the model at the International Institute for Applied Systems Analysis (IIASA) became the official model on which the Second Sulphur Protocol signed in 1994 was agreed (Hordijk 1995 ).

When revising or developing a new protocol for nitrogen oxides the concept could, however, not be used in the same way as for sulphur and acid deposition, since the NO x emissions contributed to several effects and, in addition, a strategy would need to take additional compounds into account. Instead, a more advanced approach was suggested by which both several effects and several compounds could be considered simultaneously (Grennfelt et al. 1994 , Fig.  5 ). IIASA and other bodies under the Air Convention were asked to develop an integrated assessment model that fitted into a broader approach and a more comprehensive model was developed, which made it possible to simultaneously take into account the effects of acidic deposition, nitrogen deposition, and ozone—the so-called multi-pollutant, multi-effect approach. The calculations became the basis for the Gothenburg Protocol (GP) that was signed in 1999 (Amann et al. 1999 ). The GP and the parallel EU National Emissions Ceilings (NEC) Directive from 2001 outlined control measures for 2010 and beyond.

Links between sources and effects used as an illustration in the preparation of the Gothenburg Protocol. From Grennfelt et al. 1994

After 2000—Health effects and integration with other policies became main drivers

The basis for the GP was almost entirely ecosystem effects. Around 2000, however, public health effects from air pollution became increasingly important. Large epidemiological studies indicated that air pollution was a significant source of premature deaths and that particles were a main cause of the health effects (WHO 2018 ). When the European Commission started its work to revise the NEC directive, health effects became central and the Air Convention followed. Further studies have supported the role of air pollution for health effects and when the GP was finally revised in 2012, health effects dominated as a policy driver for the establishment of national emission ceilings, and for the first time particulate matter was included in an international protocol (Reis et al. 2012 ).

When considering further actions after signing the GP in 1999, it was realised that for some pollutants under the Air Convention, emission control needed to be considered over larger geographic scales than Europe and North America alone. Ozone was of particular importance, since long-term objectives in the form of critical levels and public health standards could not be reached without taking into account sources outside the areas considered so far. Future policies therefore needed to include the ozone precursors methane and to some extent carbon monoxide. A task force on Hemispheric Transport of Air Pollution (HTAP) was set up under the Convention in 2004, with a primary objective to quantify the intercontinental transport of pollutants. The outcome of its work clearly showed the importance of considering air pollution in a wider geographic perspective than had been done so far (Dentener et al. 2010 ).

Climate change has for more than a decade become an issue of increasing interest for air pollution science and policy. In many cases, the emission sources are the same and there are obvious co-benefits (and some trade-offs) in handling them together. One aspect that has received large interest is the option to decrease short-term temperature increase through control measures directed towards atmospheric pollutants that also contribute to the warming of the atmosphere, in particular black carbon and methane (for methane both by itself but also as a tropospheric ozone precursor) (Ramanathan et al. 2001 ). Compounds contributing to both air pollution effects and to the radiation balance in the atmosphere have been named Short Lived Climate Pollutants (SLCPs). SLCPs thus also include compounds that are cooling the atmosphere, i.e. small secondary aerosols, e.g. sulphate particles. Recent research has focused on a better understanding of these compounds’ contribution to both air pollution and climate as well as on opportunities for selective control of these compounds (e.g. Sand et al. 2016 ).

Reactive nitrogen species are another group of compounds that has received increased attention after the turn of the century. Around 2006 several initiatives were taken in Europe, including a special task force on Reactive Nitrogen under the Air Convention, a large-scale EU project on nitrogen, and the preparation of a European Nitrogen Assessment (Sutton et al. 2011 ). Here nitrogen was considered both as a traditional atmospheric pollutant and within a societal and industrial context. A cascade perspective, where one fixed nitrogen molecule could contribute to a series of effects before it returns to molecular nitrogen again, was introduced (Galloway et al. 2003 ). The studies have pointed to the importance of the agricultural sector for the intensification of reactive nitrogen cycling, determined by food production mechanisms and dietary choices.

North America

In North America, the acid rain problem developed to a large extent in parallel with the situation in Europe. Lake acidification became already from the beginning a main driver, and monitoring programmes were set up both in the United States and Canada (Driscoll et al. 2010 ). The US National Atmospheric Deposition programme (NADP) started in 1976 and is still running. Both countries have taken part in the Air Convention activities and have signed most of the protocols and achieved decreases in SO 2 emissions of the order of 80% between 1980 and 2015. The US has however taken a different approach with respect to policy in comparison to Europe. Instead of developing a strategy based on integrated assessment modelling, it was decided to establish an emissions trading programme for the large electric generation sources under the Clean Air Act (See also UNECE 2016 ).

Characteristics of the science–policy interactions

In this section we will, from a science–policy perspective, briefly discuss some characteristics of the history of acid rain and transboundary air pollution that have become central for the international collaboration, not only on air pollution but also for international environmental collaboration in general. We will bring up monitoring, modelling, and data collection (including field experiments and long-term studies carried out in order to understand and quantify effects to ecosystems), development of bridging concepts that have served the implementation of strategies, and finally the dynamics in the science–policy interactions.

Monitoring, modelling, and data collection

Monitoring of atmospheric concentrations, deposition, and ecosystem effects has been a key for understanding the causes, impact, and trends in acid rain, both in Europe and North America and later in other geographic areas (Table  2 ). The original EMEP network has since the start over 40 years ago formed a broad atmospheric monitoring system. The originally established simple monitoring stations have over time been complemented with more advanced monitoring, and some stations are today advanced atmospheric chemistry platforms with continuous collection of a multitude of atmospheric parameters (Fig.  6 ). The EMEP database is nowadays widely used for a variety of scientific purposes including computation of long-term trends, exposure estimates, and as a basis for modelling. EMEP has also become a model for monitoring networks related to other geographical regions, conventions, and purposes. One example is the acid deposition monitoring network in East Asia (EANET). It is obvious that having a qualified centre for data collection and storage, standardisation, and intercalibration of methods has served the international policy system extremely well. Its open nature is part of the success. The financial support to EMEP, regulated through a separate protocol, has been fundamental for the development and progress of the monitoring activities.

Table 2

Long-term monitoring activities in relation to acid rain and other pollutants

Atmospheric monitoring stations have been of importance for understanding the long-range transport and chemical conversions of atmospheric pollutants. Pallas air pollution background station in Northern Finland (Photo Martin Forsius)

Monitoring of air pollution effects in a systematic way under the Air Convention started a few years later than EMEP and was organised through so-called International Cooperative Programmes (ICPs). Separate programmes were set up for forests, waters, vegetation (primarily ozone), materials, and integrated monitoring. A separate ICP was set up for developing critical load methodologies and coordinating European-scale mapping activities (ICP Modelling and Mapping). The ICPs are of great importance for general understanding of the magnitude and geographical distribution of the effects and for showing how decreases in emissions have led to beneficial conditions in ecosystems and decreased material corrosion (Maas and Grennfelt 2016 ). Ecosystem monitoring is also important for the development and verification of ecosystem models. Since their start, the responsibility for the ICPs has been taken by different parties of the Air Convention (Table  2 ). The distributed responsibility has been of large importance for the establishment of networks of monitoring sites among the Convention parties, but the system has not had a stable financial support in the same way as for EMEP. This has resulted in the lack of a common source for easily accessible data or adequate resources for standardisation and intercalibration.

Monitoring and other data collection (i.e. emissions and critical loads) under the Air Convention are responsibilities of every country, and data are then used for the assessments on the Convention level as well as for the development of EU air pollution policies. The bottom-up process in data collection is important for the development of national expertise and, not the least, for the establishment of national policies. In this way, direct communication links between the science and the policy levels within countries have evolved.

Numerical modelling of atmospheric pollution is also a long-term commitment under EMEP. The atmospheric chemistry models are necessary for the understanding of the nature of transboundary transport but also to make budget estimates of the exchange of pollutants over Europe and North America, and later on a hemispheric scale. The Meteorological Synthesizing Centre West at the Norwegian Meteorological Institute together with the Eastern Centre in Moscow took the lead in this work. In addition to calculating transboundary fluxes, the centres are important for coordinating modelling efforts done by other groups, forming a basis for scrutinising models and support further modelling.

Field experiments and long-term studies—a way to understand processes and trends, and to visualise the problems

Some of the most important and reliable findings regarding acid rain and its effects on ecosystems emanate from long-term field experiments. These experiments, which are known from the sites where they are run, include Hubbard Brook (US), Solling (Germany), Risdalsheia (Norway) and Lake Gårdsjön (Sweden) (Fig.  7 ). The studies there have shown how acid deposition and the impact of other air pollutants have changed the ecosystems, but also how ecosystems respond to decreased emissions (e.g. Wright et al. 1988 ; Likens et al. 1996 ). A central feature in all these field experiments was the establishment of ion budgets, from which the chemical effects on acid deposition can be analysed and understood (Reuss et al. 1987 ).

Field experiments have played an important role for the overall understanding of the interactions between atmospheric deposition and ecosystem effects. The photo illustrates the covered catchment experiment to study the recovery of ecosystems at reduced emissions in Risdalsheia Norway (Photo NIVA)

In the intense research period during the 1970s and 1980s, a number of large-scale research programmes and experiments of temporary nature were set up, some of them in connection with the above-mentioned sites. The first research programme of some magnitude was the Norwegian programme “Acid precipitation—effects on forest and fish” (SNSF), which run between 1972 and 1980 (Overrein et al. 1981 ). At that time the scientific understanding was limited, and the programme received a lot of attention. The results were important for the general acceptance that long-distance transport of sulphur caused acidification of surface waters, with a serious die-off of fresh water fish populations (salmon and trout) as a main consequence. On the other hand, the studies on Norwegian forests did not give any significant evidence for acid rain effects. The SNSF project was a joint effort across disciplinary and organisational boundaries, with scientists mainly from the research institute sectors outside of traditional academia. This project served as a model for later research programmes and provided educational opportunities for a new generation of scientists working together on all aspects of the acid rain issue—emissions and their control, atmospheric transport and deposition, impact on ecosystems, health and materials, and finally development of pollutant-control policies.

The long-term field experiments served another important task. The sites became exhibition platforms, at which policymakers, experts, scientific journalists, and leaders of non-governmental organisations (NGOs) and others can be informed about the problem directly on site. During the most intense period in the 1980s and early 1990s, politicians and industry leaders, often directly involved in decisions on the highest levels, visited many of these experimental sites. For example, US congress members travelled across Europe to see and understand the issue in preparation for the 1990 amendment of the Clean Air Act.

Bridging concepts and approaches

Concepts developed, such as critical loads and similar approaches, formed links between science and policy, and were essential for the understanding and scientific legitimacy of the policy measures. These concepts also formed a basis for priority setting in agreements under the Convention and the EU, but also to some extent for national policies. Even “acid rain” can be considered as a bridging concept. While the acidity from sulphur and nitrogen compounds is threatening ecosystems through a chemical change, the expression also gives the impression of a threat to the life-giving rain, a fundamental necessity for life on Earth.

The quantification of transboundary fluxes was very important politically. The establishment of national budgets and so-called blame matrices formed the first bridging concept. The development of mathematical models to calculate source–receptor relations was a scientific challenge but when the annual tables were prepared showing the interdependence between countries with respect to atmospheric emissions and deposition, they served as an important basis for the need for common action. Anton Eliassen, the leader of the modelling centre at the EMEP Meteorological Synthesising Centre West (MSC-W) during many years (the Eastern center is in Moscow—MSC-E), was key to this development as well as for the communication of the results to policymakers.

As earlier mentioned, critical loads played an outstanding role for the development of the more advanced strategies leading to the Second Sulphur Protocol and the GP. Critical loads formed a successful link between science and policy that became crucial for the negotiations and agreements. The concept, first discussed in 1982, was taken from the original idea to application quite quickly during the 1980s. The Swedish expert Jan Nilsson was a key leader for the success of the concept, and the Nordic Council of Ministers played a unique role for forming the links between science and policy. Through a series of workshops involving both key scientists and key policymakers, the concept gained the legitimacy on which policies were developed. According to Jan Nilsson, it all started with requests from both industry and negotiators to have a sounder base for emission control, something that could express the long-term objectives for emission control policies. The concept was first met by scepticism, not least from scientists, but after a couple of workshops, the interest turned around and the concept became widely accepted (Nilsson 1986 ; Nilsson and Grennfelt 1988 ). When critical loads were included in the plans for the next rounds of the sulphur and nitrogen protocols in 1988, it changed the way the Air Convention operated.

The application of the critical loads concept has encouraged intense research over several decades where the main objective has been to find simple chemical parameters that can mimic the (often biological) real effects or effect risks. For lake acidification, where the effects of dissolved aluminium on fish often were chosen as the main biological effect, the acidity of the water, mostly expressed as acid neutralising capacity (ANC), is used (e.g. Henriksen et al. 1989 ; Forsius et al. 2003 ; Posch et al. 2012 ). For forests, where the toxicity of aluminium to tree roots is considered as critical, the Al 3+ to Ca 2+ ratio in soil water has become the main effect parameter (Sverdrup et al. 1990 ; de Vries et al. 1994 ).

Integrated assessment modelling (IAM) also has been a bridging concept. The idea of applying systems analysis goes back to the work at IIASA in the beginning of 1980s. A conceptual model was formulated by Joseph Alcamo, Pekka Kauppi, and Maximilian Posch for the interactions between emissions, their control (including costs), and the effects on ecosystems (Alcamo et al. 1984 ). Their work of bringing together the scientific knowledge to a comprehensive systems analysis tool formed a new way of framing environmental policies. Under the leadership of Leen Hordijk, the new idea was introduced to and accepted by the policy side, which had asked for more targeted methods for policies than simple percentage decreases in amounts of emissions. IAMs as a policy-supporting concept was then taken further by Markus Amann, who led the development of the more advanced RAINS (later GAINS) models that were used as a basis for the GP and later agreements (Amann et al. 2011 ). From the strategies strictly directed at ecosystem effects, the approach is now widened to include health effects, local air pollution impact, climate policies, and reactive nitrogen.

All the bridging concepts are to varying degrees dependent on underlying models, assumptions, and simplifications. For these to be accepted among policymakers, it is important to keep transparency and confidence in the underlying data and to scientifically evaluate and scrutinise them. This is particularly important for the IAMs, which are the final step in a chain of inputs (Fig.  8 ). The models have often been criticised, not least from industry and other stakeholders that are questioning the priorities that result from the IAM calculations. IIASA, as a provider of the model calculations, has, however, been transparent, and countries and stakeholders have always had the option to re-check data and take this into account when developing their own negotiation positions.

The scientific support to regional air pollution policies consists today of a series of steps. The policy side may often only see the integrated assessment step and not realise that the legitimacy of the use of scientific support builds on an advanced system of underlying research and development

Forming science–policy credibility

In all interactions between science and policy, it becomes crucially important to maintain scientific credibility. The close involvement of scientists has been a signature of the Air Convention. Scientists have always had a role at the policy meetings, communicating results from basic scientific research over outcomes of monitoring and inventories to presenting options for control strategies. Scientists have in this way taken the responsibility to move scientific knowledge into the policy system and presenting results in a way that has been understandable and useful for the policy work. The role of the scientists has been as honest brokers , not that of issue advocates to follow the terminology of Pielke ( 2007 ). The leadership from the policy side and its sensitivity to changes in the underlying science and observations of new problems have also been important, and have resulted in repeated changes in the framings of the Air Convention to adapt to new situations: going from an initial framing around sulphur and acidification, through extension to eutrophication, human health, materials, crops, biological diversity, and finally to links to climate, urban air quality, and societal changes. A balanced interplay between the two communities has in this way been developed and maintained over time.

Another factor is the building of networks. The strong networks of scientists and policymakers pushed the politicians. The whole field of international diplomacy during these four decades of the Convention is built on incremental developments forming protocols of increasing capability to solve specific environmental issues by cutting emissions in a cost-effective way.

Future challenges

New approaches necessary.

International air pollution control is by many considered as a success story. However, the success is in many ways limited to Europe and North America and a few additional industrialised countries (including Japan and Australia), where emissions of sulphur dioxide, nitrogen oxides, VOCs, and some other compounds have been decreased significantly (Maas and Grennfelt 2016 ). But even in the areas, where air pollution has been a top priority for several decades, air pollution remains a problem. Ecosystem effects, which were the main reason for the establishment of the Convention, are to some extent reduced, but the acidification effects of historical emissions will remain for decades (Wright et al. 2005 ; Johnson et al. 2018 ) and the emissions of ammonia have so far only been reduced by 20–30% in Europe and even less in North America. Looking at health effects, it is difficult to talk about success, when hundreds of thousands of inhabitants on both continents are predicted to meet an earlier death due to air pollution.

But the problem is even larger and more urgent when looking outside the traditional industrialised world. The focus is today on the large urban regions in the countries that are facing rapid population growth and industrialisation. Although large efforts now are being made to decrease sulphur emissions in China—the world’s leading sulphur emitter—major challenges remain. In India and several other countries, sulphur emissions are still increasing. Estimates indicate that more than four million people die prematurely due to outdoor air pollution globally ( https://www.who.int/airpollution/ambient/health-impacts/en/ ). It is assumed that fine particles (PM2.5) are a main cause for the health effects. The new and great challenge is therefore to control air pollution in relation to health risks, in particular by decreasing exposure to the small particles.

There is, however, a risk that control measures will only to a limited extent focus on the right sources and the right measures. In Paris, several air pollution episodes with high concentrations of particles have occurred during recent years. At first, these episodes were considered to be caused essentially by local emissions. More thorough analysis has, however, shown that they were to a large extent caused by regional emissions and buildup of high concentrations over several days when urban emissions of oxides of nitrogen from traffic mix with ammonium emissions from surrounding agricultural areas to form particulate nitrate. Similar situations are also often encountered in urban regions in developing countries, e.g. by agricultural waste burning, and need to be considered. Air pollution problems are, as previously mentioned, also linked to intercontinental and hemispheric scales.

It is also obvious that the research communities within air pollution and climate change need to work more closely together. Health aspects are of importance both from air pollution and climate change perspectives, and heat waves carry poor air quality as winds are often very low and the atmospheric boundary layer stagnant. During heat waves, the soil and vegetation dry up and increase the likelihood of fires, which also can cause severe air pollution, as seen in wildfires around the world (e.g. California in 2018).

Despite the large progress in atmospheric and air pollution science, basic questions still need further investigations to develop the best policies. Such areas include a better understanding of health effects from air pollution, nitrogen effects to ecosystems, and air pollution interactions with climate through carbon storage in ecosystems and impacts on radiation balances. Modelling is a scientific area where much progress has been made and where increased computer power, as in climate change research, has allowed integration of atmospheric chemistry into the climate models formulated as Earth system models, coupling the atmosphere, ocean, the land surface, cryosphere, biogeochemical cycles, and human activities together. This has allowed studying air pollution and climate change simultaneously. The modelling approach can be further developed when observations are designed to map Earth system component boundaries to understand and quantify the flows and interactions between different compartments, including terrestrial and aquatic ecosystems. Air pollution should be an integrated part of such models. In this context, global-scale concepts such as “planetary boundaries” and “trajectories of the Earth system vs. planetary thresholds” have been developed (Rockström et al. 2009 ; Steffen et al. 2018 ).

Solutions are available; driving forces and investments are lacking

In 2016, the Air Convention launched a scientific report “Towards Cleaner Air”, in which the actual air pollution situation within the UNECE region was updated (Maas and Grennfelt 2016 ). The report also presented future challenges and ways forward to solve the air pollution problems. It also showed that solutions are available for most of the identified problems at affordable costs below the health and ecosystem benefits of the control actions.

Even if solutions are available, many parts of the world are facing large problems in implementing them. There are several reasons, but often there is a lack of knowledge and resources. This is particularly true in many developing countries. Another reason is the lack of political interest. Air pollution is still not of top priority among politicians, even if there is overwhelming evidence that air pollution is one of the most common causes of shortened life expectancies. Another reason may be that other interests (e.g., industry and agriculture) are forming strong lobbying forces delaying actions.

Air pollution is a problem that cannot be seen in isolation. Future policies need to take into account climate change and climate change policies. Whereas some air pollutants—in particular black carbon particles—contribute to warming, others, including sulphate particles, tend to cool the climate. A reduction in sulphur dioxide emissions, although highly desirable from health and ecosystems perspectives, will therefore contribute to warming. On the other hand, a reduction of black carbon will be a win–win solution. It is also important to see air pollution control in the perspective of sector policies, such as energy, agriculture, transportation, and urban planning in order to meet the challenges to decrease air pollution problems.

Internationally coordinated actions and infrastructures are keys for success

The perspective of international cooperation on air pollution is changing. Policy development is no longer limited to long-range transport in line with that developed under the Air Convention. The ranking of air pollution as a top ten cause of premature deaths in the world has given high priority to the issue within fora such as the WHO and UN Environment. Both organisations have adopted resolutions calling for actions (WHO 2015 ; UN Environment 2017 ). Additional initiatives are taken by other organisations, such as the World Meteorological Organisation (WMO), the Climate and Clean Air Coalition (CCAC), and the Arctic Monitoring and Assessment Programme (AMAP). WMO is particularly important as a global technical agency for weather and climate observations, research and services, and it is rapidly developing its regional and global capacities in Earth system observations, modelling, and predictions to the benefit of mitigating a range of environmental threats and for global use. The research is done in large programmes like Global Atmosphere Watch (GAW) and the World Weather Research Programme (WWRP). Even if the starting point and modes of action can be different, all initiatives are aiming for the same goal, cleaner air. It is also worth mentioning the initiative taken by the International Law Commission, under which a proposal for a Law for the Protection of the Atmosphere has been prepared ( http://legal.un.org/ilc/summaries/8_8.shtml ) but in the current international atmosphere there is a lack of political support to implement it. Our hope is that the situation will change soon—the initiative is too important to fail.

The UN has put forward a very strong agenda in order to reach the Sustainable Development Goals (SDGs), and air pollution is an integral part of several of the SGDs, like goal No 2: No Hunger, No 3: Good health and well-being, No 6: Clean Water, No 7: Affordable and clean energy, No 9: Industry, innovation and infrastructure, No 11: Sustainable cities and communities, No 13: Climate action, No 14: Life below water, No 15: Life on Land, No 16: Peace and Justice, and No 17: Partnerships for the Goals. The approach taken to develop multiple pollutant—multiple impacts protocols under the Air Convention can serve as important learning ground to meet the ambitions of many of the SDGs. Air pollution plays an integral role in the evolution of the food production and ecosystem services, the health of the population, the shape of the energy and transportation systems, and the availability of clean water. Climate change is a very significant common and cross-cutting factor.

The Air Convention has taken some steps in promoting air pollution on a wider scale. Due to its long history and well-developed structure, it has taken a role of making sure that international organisations having air pollution on its agenda are aware of each other and to invite to further collaboration and development. Initiatives are taken both within the formal Convention structure and through dedicated workshops (UNECE 2018 ; Engleryd and Grennfelt 2018 ). The approach developed under the Air Convention, which has proven successful in linking scientific evidence, monitoring, and integrated assessment modelling directed towards cost-effective solutions, may also serve as a working model for environmental problems in other fields.

These new international initiatives have a strong emphasis on policy development. The experience from the 50 years of international air pollution development is the value of well-defined scientific objectives and activities supporting policy. The increased interest from WHO and UN Environment is welcome and there are expectations of an active role from these organisations in combatting the situation in many parts of the world. However, for these organisations, air pollution is just one of several priority areas, and priorities may change. Further, none of these organisations are likely able to set up advanced infrastructures with respect to emission inventories, monitoring, and research. Here WMO needs to live up to its mission and capitalise on global research and development efforts and improve the global operational capability to observe, analyse, and forecast the development of the Earth system and its components, air pollution being an important part. This is in line with the WMO strategic plan and with fast growing capabilities in some countries and in global centres like The European Centre for Medium Range Weather Forecast (ECMWF). WMO, through GAW, is also developing a research-driven operational system (IG3IS) for top-down determination of greenhouse gas emissions, to complement the usual bottom-up-based inventories where emission factors and fuel consumption or production statistics form the basis for the emission estimates ( https://library.wmo.int/doc_num.php?explnum_id=4981 ). The Air Convention and the science support for the policy work there has been a model for the WMO ambitions on a global basis. However, current investments in these new capabilities are not enough to get the societal return they would offer.

Therefore, we see a need for developing long-lasting infrastructures that can continuously develop science-based control policy options, potentially as part of a wider network of global observatories for comprehensive monitoring of interactions between the planet’s surface and atmosphere (Kulmala 2018 ). Such a network should be able to support policies from local to the global levels. The challenge is how to organise and raise resources for scientific support on a wider scale. Financial institutions such as the World Bank and/or regional banks may step in and make sure that control measures and investments are made on a sound basis with respect to global air pollution.

There is also a need to mobilise new generations of scientists, scientists that are willing to cross boundaries and focus on thematic problems and to build legitimacy among policymakers (e.g. Bouma 2016 ). Today we have more developed and stronger political institutions to handle environmental problems, which may make it harder for scientists and individuals to influence and make a difference. It is also important to mobilise new generations of dedicated policymakers. Unfortunately, we also see that politicians often are questioning science and seeing science as just a special interest. Public awareness may be a key for forming stronger interests and put pressure on decision-makers. During the acid rain history, NGOs played an important role in driving the awareness at a wider scale than local or national actions and could be important for a more global movement towards cleaner air. We also see the need for a deeper responsibility not only from politicians but also from industry. The so-called “diesel gate” exposed the cynic view from parts of the industry to peoples’ health, which hopefully will not occur in the future. Instead we hope that it was an eye-opener and that industry instead can play a role as a forerunner and a positive power for a cleaner atmosphere.

Final remarks

The Acid Rain history taught us that when science, policy, industry, and the public worked together, the basis was formed for the successful control of, what was considered, one of the largest environmental problems towards the end of the last century. We learnt from experience that science-based policy advice worked well when the best available knowledge was provided, and used to understand the specific problems, generate, and evaluate the policy options and monitor the outcomes of policy implementation.

However, the world does not look the same today, and we cannot just apply the ways the international science community worked together then on today’s problems. But there are lessons to be learnt. Most important is the building of mutual trust between science advisers and policymakers, and that both communities are honest about their values and goals. In this way, a fruitful discussion around critical topics within society can be formed. The advice works best when it is guided by the ideal of co - creation of knowledge and policy options between scientists and policymakers (SAPEA 2019 ).

Acknowledgement

Open access funding provided by The Swedish Environmental Protection Agency. The Symposium could not have been arranged and this paper written without financial support from the Nordic Council of Ministers, the Swedish Environmental Protection Agency, the Mistra Foundation, and other organisations and institutes in the Nordic countries. We are also grateful to all participants of the Symposium and their contributions with background material for this paper. We also thank the two anonymous reviewers of the manuscript. Their comments greatly improved the quality of this paper.

Biographies

is a former Scientific Director at the Swedish Environmental Research Institute IVL. His main scientific activities include transboundary air pollution and environmental science–policy interactions.

is a Senior Policy Advisor at the Swedish Environmental Protection Agency. For the last 15 years, she has been a lead negotiator on air pollution for the Swedish Government in several international fora. Since 2014, she is the chair of the Executive Body to the UNECE convention on long-range transboundary air pollution. She has a background in energy efficiency and agronomy.

is a Research Professor at the Finnish Environment Institute SYKE. His research interests include impacts of air pollutants and climate change on biogeochemical processes.

is the Secretary General of The Norwegian Academy of Science and Letters and adviser to the Director General of the Norwegian Meteorological Institute. His research interests include atmospheric chemistry and earth system modelling.

is a Professor Emeritus at the Department of Meteorology and Bolin Centre for Climate Research at Stockholm University. His research interest includes atmospheric transport processes and climate impact of aerosol particles.

is University Distinguished Professor At-Large Emeritus at North Carolina State University in Raleigh, North Carolina. He was founding leader for the US National Atmospheric Deposition Program (NADP), which played a crucial role for the development of acid rain research and policy in North America from the 1970s and onwards.

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Contributor Information

Peringe Grennfelt, Email: [email protected] .

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Øystein Hov, Email: on.tem@hnietsyo .

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Ellis Cowling, Email: ude.uscn@gnilwoc_sille .

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• Published: 05 January 2021

The Swedish initiative and the 1972 Stockholm Conference: the decisive role of science diplomacy in the emergence of global environmental governance

• Eric Paglia 1  

Humanities and Social Sciences Communications volume  8 , Article number:  2 ( 2021 ) Cite this article

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• Development studies
• Environmental studies
• Politics and international relations
• Science, technology and society

This article applies a science diplomacy lens to examine Sweden’s 1967–1968 intervention in the United Nations—the so-called “Swedish initiative”—that led to the seminal 1972 UN Conference on the Human Environment. The three classic science diplomacy typologies—science in diplomacy, diplomacy for science and science for diplomacy—are employed to structure an analysis of how Swedish diplomats skillfully leveraged science for diplomatic objectives, first for convincing member states of the need to convene a major environmental conference under UN auspices and then to mobilize scientific research internationally—particularly in developing countries—during the Conference preparatory process. The empirical study, based on archival research and the oral histories of key participants, also brings to light how problems of the human environment were conceived of and shaped by Swedish scientists and diplomats during this embryonic moment of global environmental governance. Through analysis of some of the public pronouncements and key documents drafted during the first phase of the Swedish initiative, the article further considers the role of popular science as a style of science communication that is particularly relevant in the realm of environmental diplomacy.

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Introduction

The unanimous adoption of Resolution 2398 Problems of the human environment at the twenty-third session of the United Nations General Assembly (UNGA) on December 3rd, 1968 marked the culmination of the first phase of the “Swedish initiative” that set in motion preparations for the United Nations Conference on the Human Environment (UNCHE), eventually held in Stockholm June 5–16, 1972. The diplomatic process leading up to UNGA 2398 had begun almost exactly 1 year earlier with a brief statement before the General Assembly by the deputy head of Sweden’s UN mission, an intervention that was followed by several months of interagency consultations led by the Swedish Foreign Ministry and the crafting of a diplomatic offensive to secure international support for the proposed conference. Swedish diplomats, in particular Ambassador Sverker Åström, Sweden’s permanent representative to the UN at the time, played an indispensable role in launching and laying the administrative and intellectual foundation of the Conference (Åström, 1992 ; Engfeldt, 2009 ), in part by drawing upon and skillfully leveraging the expertize of key members of Sweden’s scientific community to demonstrate that the human environment and associated international development issues warranted treatment at the highest level of world politics. This integrated effort of diplomats and scientists helped shepherd the Swedish initiative from the idea stage to what became a major undertaking within the United Nations system, largely led by the Swedish delegation during the first 2 years (Ivanova, 2010 ).

With the efforts of Swedish diplomats, government officials and scientific experts in New York and Stockholm in focus, this article examines the interaction of science and diplomacy during this formative phase of multilateral environmental diplomacy—a new dimension of international relations that emerged in the late-1960s with the initiation of the diplomatic process that led to the first major global conference on issues of environment and development (Engfeldt, 2009 , 2019 ; Grieger, 2012 ; Schleper, 2019 ), representing a milestone in environmental history and sustainable development (Sörlin, 2011 ; Selcer, 2018 ). The convergence of multilateral diplomacy and scientific expertize at the core of the Stockholm Conference process, which was launched in the midst of a popular environmental awakening in Sweden (Jamison et al., 1990 ), played a decisive role in advancing the environment as an international issue and initiating the emergence of global environmental governance, manifested in the series of major conferences, agreements and institutions such as the United Nations Environment Program that have taken shape over the past half century (Speth and Haas, 2006 ; Najam et al., 2006 ; Ivanova, 2010 ). The over 4 years of preparations leading up to Stockholm mobilized a broad array of experts and scientific institutions in a global effort to generate a comprehensive body of knowledge on the human environment, with some 20,000 pages of documentation from experts around the world being amassed and distilled into 800 pages of official material for Conference delegates (Stone, 1973 ). This process and the eventual Conference proved to be a watershed event in the influence of science on international environmental policymaking (Javaudin, 2017 ).

Drawing upon archival material, historiographical analysis and the oral histories of several key participants directly involved with the Swedish initiative, and theoretical work from the evolving field of science diplomacy (Flink and Rüffin, 2019 ; Kaltofen and Acuto, 2018 ), this article explores the nexus of science and diplomacy in advance of UNCHE—an event that catalyzed subsequent international engagement on complex global problems such as climate change and sustainable development, which today represent important focus areas for science diplomacy research (Gluckman et al., 2017 ; Flink and Rüffin, 2019 ). The article also aims to provide further insight into some of Sweden’s motivations, ambitions and strategies for securing an environmental conference under UN auspices. As the Swedish government currently prepares for the semi-centennial “Stockholm +50” environmental summit in 2022, examining the first phase of the 1972 Stockholm Conference preparatory process, circa 1967–1970, also affords an opportunity to shed new light on how problems of “the human environment” were conceptualized at this embryonic stage of international environmental politics by some of the central actors responsible for introducing the initiative within the UN system, whose ideas became embedded in the seminal documents and pronouncements of that domain. This study of the Swedish initiative, furthermore, demonstrates how new types of actors—in this case, natural scientists—came to contribute to diplomatic processes in the emergent realm of international environmental politics that took root during the course of 1968 and rapidly developed in the years leading up to the Stockholm Conference.

Science diplomacy and environmental diplomacy as lenses for historical events

Scholars of science diplomacy see the emergence and expansion of the concept over the past 10–15 years as a reflection of current trends in science policy and foreign affairs; earlier intersections of science and diplomacy were sporadic and could be considered examples of “proto-SD”, as opposed to the more “systemic” SD of today (Flink and Rüffin, 2019 ; Rungius and Flink, 2020 ). Although the application of a science diplomacy lens to a historical case that took place some 40 years before the concept’s articulation might, therefore, seem somewhat anachronistic, this study of the convergence of science and diplomacy surrounding the Stockholm Conference demonstrates that key aspects of science diplomacy, as currently conceived, have historical precedents that date back at least to the late-1960s and the emergence of international environmental politics—a realm of diplomacy that has remained highly reliant on the participation and contributions of science and scientists.

Labeling the diplomatic activities leading up to the Stockholm Conference as environmental diplomacy could likewise be considered to some extent anachronistic. Environmental diplomacy as a concept did not attain widespread scholarly purchase until the 1990s; an early volume applying that perspective, International Environmental Diplomacy (Carroll, 1988 ) was published in 1988, consisting of contributions by political scientists, legal scholars, diplomats and government officials. Diplomatic practitioners involved with the Swedish initiative, however, did in fact employ the term “environment diplomacy” in the late-1960s to describe their efforts in advance of UNCHE; Footnote 1 and the memoir of Egyptian scientist and diplomat Mostafa Tolba entitled Global Environmental Diplomacy (Tolba, 1998 ) encompasses a timespan starting in 1973 following his appointment as deputy executive director of the United Nations Environment Program after the establishment of that organization in the wake of the Stockholm Conference.

This article does not aim to separate and distinguish the science diplomacy and environmental diplomacy dimensions of the Swedish initiative. It would be more accurate to characterize the two subcategories of diplomacy—in this case, and likely many if not most instances of international environmental politics in the years since—as deeply intertwined, as science was an intrinsic aspect of Sweden’s efforts to convince other UN delegations of the urgency of environmental problems and thereby place the human environment upon the agenda of the United Nations. Yet a contradiction of sorts, explicitly stated in the opening paragraphs of UNGA 2398, can also be seen in the underlying rationale of the Conference and the science and environmental diplomacy it encompassed. The Swedish initiative, like much environmentalism of that era, incorporated a strong critique of modern science and technology, identifying them as the root of the contemporary environmental crisis. A key part of the solution proposed by Conference organizers and stated in UNGA 2398 was to cultivate and mobilize even greater scientific knowledge to expose and understand the impacts of modern society on humans and their environment, and foster public awareness and political engagement to combat the crisis.

Science diplomacy dimensions of the Swedish initiative

Sweden’s intervention exhibits characteristics of the three types of science diplomacy laid out in the landmark Royal Society report from 2010: science in diplomacy , diplomacy for science and science for diplomacy (Royal Society, 2010 ). These three categories provide a useful analytical lens and organizational structure for distinguishing and accentuating the array of applications of scientific knowledge and expertize that supported the Swedish initiative from its outset. The aim of this article is not, however, to simply reinforce and rigidly apply the Royal Society typologies. Through elaborating the innovative and multifaceted deployment of scientific resources in support of Sweden’s diplomatic initiative, the purpose is rather to fruitfully employ and further enrich the science diplomacy concept in contributing an empirical account and analysis of a turning point in environmental, as well as diplomatic, history, for which science was an essential component (Warde et al., 2018 ). The article also offers a qualitative perspective on science diplomacy by emphasizing that the intended audience of a given intervention can strongly condition its scientific content and style of presentation. An example explored below are the series of diplomatic pronouncements during the first phase of the Swedish initiative that can be characterized as performances of popular science, articulated in a style intended to educate and convince non-specialist UN delegates on the scientific merits that motivated a conference on the human environment.

In line with the Royal Society science diplomacy typologies, three dimensions of the Swedish initiative are examined in greater detail. First, how government officials instrumentally applied science in support of the diplomatic initiative. A key aspect, elaborated below at some length, is how the scientific expertize and normative convictions of Swedish biochemist, public intellectual and environmental activist Hans Palmstierna—who was officially tasked with drafting documents outlining the declining state of the global environment and the consequent societal impacts—were adapted by Sverker Åström to provide the scientific substance that underpinned and animated several decisive diplomatic interventions in 1968. The latter included Åström’s Palmstierna-inspired statements before the UN Economic and Social Council (ECOSOC), and his pivotal December 3 rd speech at the General Assembly. The co-production of diplomatically effective environmental knowledge by Palmstierna and Åström—who played the respective roles of “diplomat scientist” and “scientist diplomat” (Moomaw, 2018 )—represents an early expression of environmental diplomacy, conditioned and supported by a popularized form of scientific expertize that contained strong doses of dramaturgy and moral conviction, as well as a historical contextualization and narrative of humankind’s long-term relationship with the natural world.

Second, the article explores Sweden’s diplomatic objective of mobilizing science internationally as part of the Conference preparation process. To provide a global overview of environmental problems, and strengthen connections between scientific institutions and government authorities (particularly in developing countries), Swedish diplomats operating through the UN Secretariat called on Conference participants to draft national environmental reports, with Sweden’s own national report and a case study on acid rain promoted—among other means by Swedish embassies—as a template for other countries’ reports. Footnote 2 Related to that diplomacy for science initiative, the third dimension of this case study in Swedish science diplomacy examines the Foreign Ministry’s employment of scientific experts as de facto envoys, dispatched to developing countries in support of scientific, as well as diplomatic, objectives.

Science in diplomacy: the New York—Stockholm science diplomacy nexus

On March 13, 1968, Göran Bäckstrand—a desk officer at the Foreign Ministry in Stockholm assigned to United Nations matters—received one of several memoranda sent via telex by Sverker Åström, requesting scientific information from government agencies with knowledge on environmental issues. Footnote 3 Åström and his staff at Sweden’s UN mission in New York were in the process of developing a diplomatic strategy for convincing member states of the imperative and rationale for convening a major conference on the human environment, yet they lacked expertize on such matters. To obtain the relevant information for the Swedish mission, Bäckstrand reached out to Hans Palmstierna, whom he knew through Sweden’s Vietnam War protest movement. Footnote 4 Palmstierna had two weeks earlier taken a position at the Swedish Environmental Protection Agency, established as the first government authority of its kind in the world in July 1967 (McNeill, 2000 ; Lundgren, 2005 ). That year also saw the publication of Plundring, svält, förgiftning (Plunder, Famine, Poisoning), Palmstierna’s popular science critique on the effects of population growth and modern society’s systematic waste of natural resources that he claimed were jeopardizing the global environment and humanity’s survival as a species (Palmstierna, 1967 ). Upon its release in October, Plunder became a national bestseller of Silent Spring stature, thrusting Palmstierna into the spotlight as Sweden’s leading environmentalist and a “meta-specialist” that could broadly speak on behalf of the environment for a general audience (Warde et al., 2018 ; Heidenblad, 2018 ).

The widespread public perception of environmental crisis precipitated by Palmstierna’s polemic constituted a formative moment in Swedish environmental history (Heidenblad, 2018 ; Paglia, 2015 , 2016 ), and Plunder’s powerful societal impact in Sweden emboldened Åström in planning for the Swedish initiative, reassuring him that an environmental intervention in the United Nations would be supported domestically (Åström, 1992 ). October 1967 also saw two other high-profile scientific interventions aimed at wide audiences warning of mounting environmental risks: an article by soil scientist Svante Odén published in the daily Dagens Nyheter elaborating for the first time the problem of acid rain (Odén, 1967 ); and the mass market paperback Människans villkor: en bok av vetenskapsmän för politiker (The Predicament of Man—a book by scientists for politicians, Fichtelius, 1967 ), edited by medical doctor and public intellectual Karl-Erik Fichtelius and featuring essays by twelve prominent Swedish researchers, including physicist Hannes Alfvén and the economist Gunnar Myrdal (Heidenblad, 2018 , 2019 ), both later recipients of the Nobel Prize in their fields. It was during this autumn of surging environmental awareness that three influential Swedes engaged with the United Nations—Inga Thorsson, Alva Myrdal and Sverker Åström—concluded that Sweden should pursue a UN conference on the human environment. To this end, a proposal was put forward at the UNGA on December 13, 1967 by Börje Billner, Deputy Head of the Swedish UN Mission, initiating—if only tentatively at that point—a process that would lead to the 1972 Stockholm Conference (Engfeldt, 2009 ).

The central paragraph of Billner’s short statement, which otherwise addresses mostly procedural matters, diagnoses the problem of the human environment as conceptualized at that point by the Swedish UN delegation:

The impact of the technological revolution that is taking place around us is felt by all peoples, irrespective of their present technological level. It has far-reaching effects on the environment of man. The human body and the human mind are subjected to serious and ever-increasing inconveniences and dangers. These are caused by air pollution, water pollution, sulfur fall-out waste, etc. – in short by all the secondary effects related to the process of industrialization and urbanization. Footnote 5

The main themes of technology, urbanization and industrialization as the predominant drivers of a degraded human environment—including transboundary problems such as air and water pollution—are further developed in Åström’s aforementioned March 13 memorandum. It also puts forward a detailed diplomatic strategy and outlines what he saw as some of the general objectives of an eventual conference. The latter included what can be characterized as diplomacy for science in so far as one of Åström’s stated ambitions was to raise awareness of environmental issues among governments, researchers and the general public, and to bring together in common cause scientists and other stakeholders engaged with safeguarding the human environment—up to and including at the global level. Moreover, in an expression of the science for diplomacy ethos that infused the Swedish initiative with political legitimacy and empirical substance, the memorandum also proposes the creation of a conference preparatory committee comprised of representatives with scientific backgrounds. Their task would be to define in greater detail the topics the Conference should address.

The March 13 memorandum demonstrates Sweden’s UN ambassador’s substantial diplomatic expertize and in-depth knowledge of the bureaucratic intricacies and political sensitivities within the UN system. It also indicates a degree of reflexivity and scientific understanding on the emerging issue of the human environment—clearly articulated by Åström as not only encompassing the negative effects of modern society on nature, but also the feedbacks of environmental degradation visited back upon humankind. Yet with opposition to the idea of an environmental conference expected from global financial interests, as well as developing countries concerned that such an event might undermine the international development agenda, Footnote 6 Åström realized his diplomatic acumen would have to be convincingly coupled with a more scientifically robust narrative of an increasingly hazardous human environment, including the transboundary effects that required a coordinated effort at the global level. Hence, as Sweden’s diplomatic strategy for supporting the initiative continued to evolve during the spring of 1968, fortifying the science in diplomacy dimension became a primary area of focus in anticipation of the upcoming lobbying effort that Åström and his colleagues would mount at the United Nations.

At a meeting at the Foreign Ministry in Stockholm on April 25, 1968 attended by senior officials from an array of government ministries and agencies, Hans Palmstierna, representing the Swedish EPA, was officially tasked with producing a memorandum that could articulate the scientific basis for convening a global environmental conference. The purpose of the conference, as further elaborated at the meeting, was to stimulate international interest in the environment, find ways to regulate transnational environmental problems having no specific country of origin, and to combine efforts in managing environmental problems with the work of international development agencies in order to help developing countries avoid the costly mistakes made by the nations of the global North in the course of their own industrialization. Footnote 7

The memorandum on the state of the global environment, delivered by Palmstierna in a shorter initial draft in May 1968, Footnote 8 and a more fully developed version in July, Footnote 9 provided Swedish diplomats with science-based evidence and reasoning to help persuade UN member states, some of which had already expressed skepticism towards the initiative, on the importance of convening a global conference to combat the emerging crisis that affected all countries. The documentation delivered by Palmstierna thus enabled Åström and his staff to acquire a degree of “interactional expertize” (Collins, 2004 ) in constructing their case for a conference. Although solidly grounded in science, the memorandum, as well as additional documentation Palmstierna submitted to Sweden’s UN mission in the autumn of 1968, is animated with his profound environmental and social justice convictions, and offers various policy prescriptions for the damage humans were inflicting on the natural world.

The main themes of the Palmstierna memorandum are clearly apparent in Åström’s presentations at the ECOSOC spring session on May 24 and the ECOSOC summer session on July 19 in Geneva. Footnote 10 Preceded by a brief but procedurally important Explanatory Memoradum and cover letter addressed to UN Secretary-General U Thant that formally launched the initiative, Footnote 11 both statements before ECOSOC closely track Palmerstierna’s primary points (sans the suggested policy responses), as does Åström’s scientifically detailed and decisive speech in front of the UN General Assembly in December 1968. What is more, many of the major themes of the memorandum carry through to the unanimously adopted UN General Assembly Resolution 2398 Problems of the human environment , which was largely drafted by the Swedish mission, Footnote 12 and officially put Conference preparations on track (Engfeldt, 2019 ). Given the successful outcome of the Swedish initiative, signaled by the July 30 adoption of ECOSOC Resolution 1346 (XLV) recommending that UNGA consider proceeding with a human environment conference and followed several months later by the adoption of UNGA Resolution 2398, Palmstierna’s memorandum represents a crucial contribution of scientific substance, strongly conditioned by his normative view on the human–environment relationship, that played a significant political role in a seminal moment of global environmental governance. The co-production of effective science diplomacy as contained in Palmstierna’s memorandum and Åström’s UN statements in 1968 thus warrants examination in greater detail.

Scientist-diplomat and diplomat-scientist: analysis of the Palmstierna-Åström exchange

By way of introducing the memorandum, Palmstierna situates mankind’s contemporary predicament within a much longer historical narrative, asserting that humans have always altered their environment to improve their conditions of life. Without such changes, he argues, neither culture nor civilization would have been possible. Palmstierna then presents the previous few decades as a break from this long duration relationship between humans and nature, a time when mankind began consuming natural resources at historically unprecedented rates. Åström expands on this theme in his UN statements, describing the present period as something qualitatively different from earlier historical epochs. What is more, both Palmstierna and Åström argue that the options available to our ancestors, e.g., migrating after exhausting soil fertility in an area, were no longer possible on a fully settled planet. As stated by Åström at the July 19 ECOSOC session:

During previous historical epochs, when conditions for human life in a certain geographical region were destroyed through human action, civilization could flourish in another region, and movements of population could take place. When the natural environment is destroyed in the world of today, no emigration can solve the problem, neither from one part of the planet to another, nor to another planet. There is no escape from the problems created by the depletion of the resources and by disturbances in the living systems on the thin surface of the earth between soil, water and atmosphere.

Foreshadowing the convergence of environment and development issues that characterized the Conference, and reflecting core values of Swedish foreign policy and Social Democratic ideology, Palmstierna—a committed Social Democrat and party insider—also introduces equity and solidarity issues into human–environment interactions. Although some changes have brought long-term benefits for most inhabitants of the Earth, many have proven to be shortsighted and led to serious environmental harm, according to Palmstierna and echoed by Åström. In some cases, small groups have enriched themselves in the short term while undermining the long run conditions of life for larger populations. What was unique about the historical juncture during which Palmstierna’s generation came of age, as described in the memorandum, was the sheer scale of change and the consumption of natural resources made possible by modern science and technology, accessible to an ever-growing global population. Palmstierna implies that industrial development over the previous few decades had even endangered the survival of humankind.

An overarching theme of the Palmstierna memorandum, and almost identically articulated in Åström’s UN statements, is the idea that environmental degradation and overconsumption of natural resources had become a structural condition of the industrial world that could and should be avoided by developing countries. According to Palmstierna:

Usually the signs of environmental destruction are most pronounced in countries where industrialization and urbanization have been most highly developed. When more countries enter the path of rapid industrialization, and get still bigger cities, the problems grow global. The gross destruction of the resources of Nature, that is still the dominant feature of the developed countries, should not necessarily be repeated by the developing countries.

In his critique of industrialization to date, Palmstierna identifies “modern science and technology” as the primary drivers of environmental destruction, which had not yet been fully visited upon countries of the global South that were still in less advanced phases of development. Learning from and avoiding the mistakes of the industrialized world, where environmentally unsound ways of life had already become structural, was therefore a primary motive for convening a conference that would include countries at all levels of development. The lessons learned by the Northern industrial nations at great environmental cost, as well as those scientific and technological advances that might help reduce at least some of the negative consequences of industrialization, should, according to Palmstierna and Åström, be shared with states at an earlier stage of development.

The need for convening an environmental conference at the global level was also anchored in the scientific worldview put forward in the memorandum. Transboundary pollutant flows and the finity of natural resources on a planetary scale tied countries together in a common plight, according to Palmstierna’s conceptualization of the environmental problems that humanity collectively faced. These were embedded within and manifested through what he described as “the basic components of the physical environment of man”: fertile soil, fresh water of high quality and of sufficient quantity, living oceans, and air of the right composition and the right temperature. Humankind’s reliance on these four components of the planetary environment, which could not be contained by national borders, provided a scientific rationale for managing transboundary problems at the highest global level and necessitated an unprecedented level of global solidarity. “A prerequisite to the solution of these problems is an intimate and trustful cooperation between all the nations of this globe”, as stated by Palmstierna in the memorandum.

In terms of specific environmental impacts and their anthropogenic drivers, Palmstierna revisits three themes that had formed the basis of Plunder, Famine, Poisoning : the over-exploitation of natural resources, explosive global population growth, and the chemical contamination of the environment and human bodies, with “environmental poisons” such as DDT in focus (transported through, e.g., fresh water and the ocean currents, embedded in the food chain in the form of fish and other animals that are consumed by humans). Although these were not novel issues in the late-1960s—having already generated considerable international attention—other environmental problems taken up in the memorandum were less well known at the time, particularly among the non-specialist diplomats and political decision-makers that were Palmstierna and Åström’s intended audience. Demonstrating the cutting-edge nature of the science that underpinned Sweden’s diplomatic intervention, environmental issues that emerged more prominently in the 1970s were foreshadowed by Palmstierna and Åström, including acid rain, eutrophication and climate change. Regarding the latter, for example, Åström stated before ECOSOC on July 19, 1968, “that man has already rendered the temperature equilibrium of the globe more unstable”. Footnote 13

The December 1968 speech became the first occasion on which climate change was brought up at the United Nations General Assembly (Linnér and Selin, 2018 ). Interestingly, and indicative of the state of scientific understanding at that time, both global cooling (due to the reflectivity of particles on solar radiation) and global warming (caused by heat-trapping carbon dioxide emissions) are mentioned as potential climate change scenarios by Palmstierna and Åström in the memorandum and ECOSOC statements, respectively. By the time of Åström’s speech before the UNGA, Lars-Göran Engfeldt, a young diplomat at the Swedish UN mission who drafted the text together with Åström, had through his own reading of media reports on climate change during autumn 1968 concluded that scientific opinion was shifting towards warming as the more likely outcome of human interference in atmospheric processes. Footnote 14 Hence, in contrast to Palmstierna’s memorandum and Åström’s statements at ECOSOC earlier that year—which presented the particle-induced cooling scenario first—the UNGA speech instead foregrounded and explained in far greater detail the potential for a rise in the Earth’s surface temperature caused by increasing concentrations of carbon dioxide, which is presented in the speech as a pollutant. Footnote 15

No other forms of air pollution are mentioned in Åström’s December 1968 speech, including acid rain, which Palmstierna had in his memorandum gone into some detail in describing in terms of the scientific basis, and its environmental and economic effects. Footnote 16 Although the issue was brought up by Åström in his May 24 statement, it was excluded from his General Assembly speech in December. While preparing the latter, Engfeldt inquired with the Foreign Ministry, which in turn consulted the Swedish EPA, on whether acid rain could, on scientific grounds, be included in the speech. He was informed that there was not enough evidence to make such a claim, and therefore left out any mention of acid rain (Engfeldt, 2009 ). Footnote 17 Several years later—again reflecting the advances in scientific understanding of environmental issues during that period—Sweden’s primary national case study for UNCHE was devoted to precisely the problem of acid rain (Bolin et al., 1971 ), an influential document that was along with Sweden’s national environmental report distributed to other countries during the Conference preparatory period.

Diplomacy for science: national environmental reports and the mobilization of expertize

In the wake of the adoption of UNGA Resolution 2398, some of Sweden’s less apparent conference goals began being shaped in New York by Ambassador Sverker Åström and Lars-Göran Engfeldt, the junior diplomat who had joined the Swedish UN delegation in the autumn of 1968. Several weeks after the resolution, Phillipe de Seynes, the UN undersecretary-general for economic and social affairs, discreetly approached Åström to seek Sweden’s assistance in supporting the UN Secretariat with scientific knowledge on the environment, which was sorely lacking at the top levels of the United Nations at that time. To this end, Engfeldt became informally attached to the UN Secretariat, serving as a conduit for Swedish expertize. Sweden’s UN delegation was in this way able, at an early stage, to influence conference preparations while significantly increasing the capacity of the Secretariat and its Office of Science and Technology, where Engfeldt was placed. Footnote 18

This close association with the Secretariat enabled Åström and Engfeldt to further pursue an underlying objective of stimulating the production and coordination of environmental science in UN member states, particularly in developing countries. Many national governments and civil societies in the global South had extremely limited awareness and understanding of domestic environmental conditions. Weak institutional coordination at the national level for producing and disseminating the knowledge necessary for managing environmental problems was another significant impediment. For the Swedish diplomats, the conference—from early on in the preparation stage—was thus a means for mobilizing government authorities and building institutional capacity at the national level in developing countries. Åström realized, moreover, that decisions taken by UN representatives in New York would have little de facto impact without deeper engagement in their respective domestic contexts. This was particularly true for developing countries, which often had small delegations and weak government institutions. Footnote 19

The production of national environmental reports was, therefore, conceived of as a method for catalyzing the scientific and societal mobilization imagined by Åström and Engfeldt. On behalf of the UN Secretariat, they drafted a circular letter distributed to member states in January 1969, requesting that as part of Conference preparations, each government should produce a national report on the state of their domestic environment. This request, together with additional instructions on drafting national reports and environmental case studies in two follow-up letters, was formulated in such a way that compelled foreign ministries to engage other government agencies to answer specific questions and begin producing a national environmental report. Through the report production process, the Swedish diplomats sought to stimulate widespread governmental commitment and coordination among scientific institutions and, more generally, societal awareness and public concern over environmental issues. Broader domestic participation in preparing for the conference would, Åström and Engfeldt believed, not only lead to a more productive and politically meaningful conference, but would also bring about a more enduring impact on societies that had limited capacity for dealing with the environmental problems they were in the early stages of confronting. Footnote 20 The mobilization succeeded in enhancing the previously low-level of engagement in environmental issues and resulted in the submission of over 80 national reports (Strong, 1972 , McCormick, 1989 ). Preparing national reports, moreover, became a precedent replicated in the run-up to the Rio Earth Summit (Antrim, 1994 ).

Such a marshaling of expertize was in the works in Sweden with the formation in 1969 of the Committee for Research and Factual Issues ( Kommittén for forskning och andra sakfrågor , hereafter CRF). This ad-hoc governmental body, situated directly under the National Committee within Sweden’s organizational structure for Conference preparations, played a central role in the coordination and integration of scientific expertize and environmental diplomacy that characterized Swedish activity during the preparatory phase of the Stockholm Conference (Mårtenson, 2000 ). The Committee was led by Arne Engström, a professor of medical physics and molecular biology at the Karolinska Institute in Stockholm who also served as secretary of the Swedish Research Council. The latter position provided him direct access to the Prime Minister and afforded the CRF a degree of independence in the internal struggle between the Foreign Ministry and the Ministry of Agriculture for overall leadership of Sweden’s conference preparations. The relative autonomy enjoyed by the Committee—comprises diverse high-level experts, including Palmstierna and climate scientist Bert Bolin, Footnote 21 representing an array of government, industry and academic institutions—helped ensure that issues of scientific substance would not be compromised by Swedish domestic politics, and help influence the development of a robust, knowledge-based foundation for the conference. Footnote 22

The primary task of the Committee was to oversee the drafting of Sweden’s own national report. In addition to the national report, published in Swedish and English versions, Footnote 23 three thematic reports were produced under the auspices of the Committee, including one promoted as Sweden’s national case study for the Conference: Air pollution across national boundaries: The impact on the environment of sulfur in air and precipitation (Bolin et al., 1971 )—one of the first major scientific publications on the emerging transnational problem of acid rain. Footnote 24 Sweden’s national report, along with the thematic reports, also served as a diplomatic instrument intended to advance the Swedish objective of stimulating environmental knowledge production and scientific coordination in developing countries. For this purpose, the Swedish national report was employed as a template for developing countries in their own production of environmental reports for the conference. This process was further abetted by the Foreign Ministry, which instructed its embassies around the world to distribute the Swedish national report and acid rain study, and assist developing countries in drafting of their own national reports (Engfeldt, 2019 ). Footnote 25

Science for diplomacy: an unorthodox diplomatic offensive

Another dimension of Sweden’s pre-conference science diplomacy was the deployment of scientists as de facto diplomats operating on assignment of the Swedish Foreign Ministry. Their mission was to provide additional support to local experts and officials in certain countries in the preparation of national reports, an initiative that some other developed countries such as Canada also participated in (Rowland, 1973 ). This “unorthodox diplomatic offensive”, as one participant, Lars Ingelstam, describes it, further demonstrates a key component of Sweden’s diplomatic strategy throughout the preparation phase: the leveraging of Swedish expertize to motivate and secure UNCHE in the face of skepticism towards the conference, and to stimulate broader societal engagement with environmental issues, especially in developing countries, while establishing a geographically broad-based foundation of scientific knowledge on the global environment in advance of Stockholm. Footnote 26

Zambia and Brazil, both of which were members of the UNCHE preparatory committee, were identified by the Foreign Ministry as countries that could benefit from greater Swedish assistance in preparing national reports. Since Sweden had existing ties to Zambia through development assistance programs, Swedish government officials had some insight into the country’s scientific capacity, which were deemed insufficient for composing a comprehensive report on the environment. Herrick Baltscheffsky, a molecular biologist at Stockholm University, was in 1970, therefore, dispatched by the foreign ministry to Lusaka, where he spent several weeks leading local experts in helping to write the Zambian national report. Lars Ingelstam was sent to Brazil in a similar yet more diplomatically sensitive scientific mission. A mathematician, planning theorist and systems analyst, Ingelstam was a co-author of the acid rain case study. He had become associated with the CRF, which had commissioned the study, through an earlier association with Arne Engström, and in turn came into contact with the foreign ministry’s Göran Bäckstrand, who served as one of the Committee’s influential secretaries. As preparations for the Conference entered an increasingly fraught phase, Ingelstam’s expertize in systems theory came to represent a useful asset in Sweden’s novel science diplomacy initiative.

By 1970, Sweden’s Foreign Ministry had become concerned over the emergence of developing country discontent over the premise and intentions of the conference. That summer, the development of MIT computer engineer Jay Forrester’s systems dynamics model—which would underpin the 1972 Club of Rome report The Limits to Growth (Meadows et al., 1972 ; Rowland, 1973 ; Ingelstam, 2012 ; Warde et al., 2018 )—reinforced the growing suspicions among developing countries that the industrialized North aimed to curtail economic growth in the global South. A perception was taking shape in some developing country capitols that the upcoming UN conference was not only a distraction from the international development agenda, but an initiative intended to prevent them from exploiting their natural resources and deny them the prosperity the North had already secured for itself at the expense of the environment (Bäckstrand, 1972 ; Engfeldt, 2009 ; Marklund, 2019 ). Although such concerns were addressed and to some extent alleviated at a June 1971 gathering of development experts in Founex, Switzerland—a landmark event that concluded that environmental protection and economic development were not intrinsically incompatible (Caldwell, 1990 ; Ivanova, 2010 ), the environment-development dichotomy and North-South divide represented an enduring issue for the Conference preparation process and well beyond (Macekura, 2015 ; Paglia and Sörlin, 2021 ).

Swedish officials regarded the mounting criticism as a substantial threat that could potentially derail preparations and undermine the conference. Brazil was considered a particular cause for concern due to its outspoken opposition to any initiative that could limit its sovereignty over natural resources and constrain economic growth. In various United Nations fora, Brazil’s military government strongly criticized the upcoming conference, calling it a “rich man’s show” while leading Latin American countries in instigating opposition, and perhaps even a boycott, within the UN through the G77 (Bäckstrand, 1972 ; Kennet, 1972 ; Engfeldt, 1973 ; Engfeldt, 2009 ; Macekura, 2015 ; Marklund, 2019 ). The case was argued even from within the conference’s Preparatory Committee by Brazilian diplomat Miguel Almeida Ozorio (Strong, 2000 ). Owing to its influence as a major developing country, endowed with a rich ecological heritage, mitigating Brazil’s skepticism became a critical task for the conference organizers, including the Swedish diplomats and Foreign Ministry officials at the forefront of the preparatory process.

Under these circumstances, Lars Ingelstam was deployed as an unofficial scientific envoy to Brasilia and Rio de Janeiro, where he spent a week meeting with scientists, parliamentarians and government officials. Although his mission was ostensibly to provide expert advice and guidance in the drafting of the Brazilian national report, his primary diplomatic imperative was to clarify the scientific rationale for the Conference, and—drawing upon his expertize in systems theory—reassure officials that industrialized countries were not intent on limiting the developing world’s prospects for economic growth and prosperity. The underlying logic of the conference, as explained by Ingelstam, was rather to foster global cooperation on environmental issues in order to meet the challenges that all countries faced in common. His series of presentations were received with great interest by Brazilian officials and scientists, even if he was often informed that real decision-making power rested with the ruling military regime, which maintained its strongly pro-development stance up through the actual Stockholm Conference and after. Footnote 27

Concluding discussion

The origins of global environmental governance can, as this article has explained, be traced back to a nexus of diplomats, scientists and government officials in Stockholm and New York through which the Swedish initiative emerged and evolved, and eventually culminated in the 1972 UN Conference on the Human Environment. This late-1960s and early-1970s historical episode demonstrates how environmental diplomacy was, from the outset, closely coupled with science diplomacy. Encompassing not only trained diplomats that were able to adeptly apply scientific expertize for establishing the environment as an issue of international politics, environmental diplomacy also involved the scientists themselves—actors whose participation in the diplomatic domain played a vital role in the success of the Swedish initiative. Fortuitously, Sweden had access at the seminal moment of multilateral environmental diplomacy to a cadre of experts able to formulate a convincing scientific case for an audience composed of diplomats at the United Nations, and to follow upon the first phase of the Swedish initiative with a series of additional science diplomacy engagements.

In particular, the successful outcome of the Swedish initiative in its first year was facilitated by the expertize of a seasoned diplomat-scientist who was able to curate and adapt the writings of a scientist-diplomat who only months before had penned a popular science bestseller that—like the documents he drafted in support of Sweden’s diplomatic offensive—combined scientific knowledge with declensionist drama and a historical narrative of how modern society had come to pollute and poison the human environment. The complementary skillsets of Sverker Åström and Hans Palmstierna in this way converged in the co-production of a popularized scientific account of the societal risks driven by widespread environmental degradation that enabled the unanimous passage of UNGA 2398 in December 1968. That resolution, like the diplomats and scientists that implemented the Swedish initiative, expressed significant skepticism towards science and technology, yet called for a major expansion of international scientific cooperation as a means for better understanding and addressing the pernicious effects of modern society on the human environment. This apparent paradox in the relationship between science and technology on the one hand and protection of the environment on the other is perhaps less pronounced in public discourse today, but contrasting perspectives, between for instance pro-technology ecomodernism and values-based interventions such as Pope Francis’ 2015 encyclical on the environment Laudato Si’ , continue to divide environmentalist thought (Paglia, 2016 ).

While the science in diplomacy aspect of the Swedish initiative is apparent in Åström’s UN statements, the diplomacy for science imperative of UNCHE is also clearly stated in UNGA 2398, which expresses “ strong hope that the developing countries will, through appropriate international cooperation, derive particular benefit from the mobilization of knowledge and experience about the problems of the human environment” (UNGA, 1968 , emphasis in original). In this sense, the pathway of industrialization taken to date could serve as a cautionary tale for developing countries, with the UN conference being the catalyst and conduit for a broad range of expertize and experience flowing from North to South to promote a more environmentally benign development paradigm. During the Conference preparatory phase in the years following the resolution, knowledge mobilization was realized in substance and process through the novel national report initiative conceived by the Swedish diplomats operating through the UN secretariat. The innovative use of Swedish embassies to circulate Sweden’s national report and acid rain case study also contributed—in a subtle but substantial way—to shaping the international perception of problems of the human environment, and how such problems could be engaged with through science. Further, in cases such as those elaborated above, the mobilization of knowledge was supported by Swedish experts deployed to developing countries on missions that served both diplomacy for science and science for diplomacy purposes.

The science diplomacy intrinsic to the Swedish initiative also underpinned what was inherently a major effort in public diplomacy, initially played out within the United Nations, intended to bring environmental issues to the attention of a worldwide audience. As articulated in UNGA 2398, drafted by Sweden’s UN delegation, a main motivation for organizing a global conference was “to provide a framework for comprehensive consideration within the United Nations of the problems of the human environment in order to focus the attention of Governments and public opinion on the importance and urgency of this question and also to identify those aspects of it that can only or best be solved through international co-operation and agreement” (UNGA, 1968 ). Given the organizers’ ambition of informing, educating and mobilizing a broad stakeholder base—stimulating concrete action at the national, regional and international level was another stated goal of UNGA 2398—much of the science contained in the substantial documentation and communication efforts in advance of UNCHE (Stone, 1973 ), including material such as the unofficial Conference report Only One Earth compiled and curated by top international experts (Ward and Dubos, 1972 ), was presented in a popularized form primarily for the consumption of non-scientist delegates and general populations around the world (Stone, 1973 ; Schleper, 2019 ).

Contemporary environmental discourse and diplomacy—especially when directed towards broader public audiences—continues to encompass a significant amount of popular science, often combining data and drama in evoking a state of global crisis, communicated by diplomatic officials, environmental advocates and scientific experts alike (Paglia, 2018 ). This is particularly relevant in cases where the stakes of environmental diplomacy are understood as greater than the zero-sum games of negotiations for national advantage. For example, when the planet and humanity as a whole are conceptualized as stakeholders in common, as Sweden’s former chief climate negotiator Ambassador Bo Kjellén suggested in his aspirational idea of a “new diplomacy for sustainable development” (Kjellén, 2007 ), efforts to mobilize international opinion and awareness in support of collective action on environmental problems in effect synthesize elements of popular science and public diplomacy. From a planetary stakeholder perspective, activist-popularizers such as Al Gore and Greta Thunberg, as well as officials like former UNFCCC Executive Secretary Christina Figueres, can be seen as playing de facto public diplomacy roles when communicating, championing and popularizing IPCC science for the purpose of increasing global interest and infusing urgency into UNFCCC negotiations—otherwise conducted by diplomats and trained specialists in complex and highly technical topics such as global temperature targets (Paglia and Isberg, 2021 ).

Applying a science diplomacy lens in providing an empirical account of the Swedish initiative that led to the 1972 Stockholm Conference, this article has thus provided a qualitative perspective on a style of scientific communication—popular science—that can inform and influence policy agendas and diplomatic proceedings, as well as popular movements. Popular science has long been particularly influential in the realm of environmental politics, which from at least the early 1960s has been conditioned by polemics like Rachel Carson’s Silent Spring (Carson, 1962 ), Paul Ehrlich’s The Population Bomb (Ehrlich, 1968 ), or Palmstierna’s Plunder in Sweden. Grounded in scientific knowledge yet presented in accessible and emotive language for the purpose of convincing a potentially indifferent or skeptical lay audience of the rising importance and urgency of environmental problems, the popularized science co-produced and employed by Swedish scientists and diplomats over the course of Sweden’s 1968 intervention at the United Nations played an indispensable role in the seminal moment of multilateral environmental diplomacy and global environmental governance.

Data availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

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Acknowledgements

The author would like to thank Ambassador Lars-Göran Engfeldt, Göran Bäckstrand and Professor Lars Ingelstam for the invaluable oral histories they contributed to the research this article is based upon, and Professor Sverker Sörlin for the comments he provided during the writing of the article. This work was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program, grant agreement No 787516: “The Rise of Global Environmental Governance: A History of the Contemporary Human-Earth Relationship—GLOBEGOV” (it reflects only the author’s views and the ERC is not responsible for any use that may be made of the information it contains)”. The project is also known as SPHERE—Study of the Planetary Human–Environment Relationship.

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Paglia, E. The Swedish initiative and the 1972 Stockholm Conference: the decisive role of science diplomacy in the emergence of global environmental governance. Humanit Soc Sci Commun 8 , 2 (2021). https://doi.org/10.1057/s41599-020-00681-x

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Acid Deposition: A Case Study of Scientific Uncertainly and International Decision Making COURTNEY RIORDAN U.S. Environmental Protection Agency Ed'~or's Note: This case study of the acid deposition issue was selected and designed to illustrate some of the generic and specifw difficulties of using scientific and technical information in environmental decision making especially when the interests of more than a single nation are at stake. This chapter was prepared bya US. scientist who wasinvolved in the negotiations with Canada on an air-quality treaty in 1981-83. D': Riordan was also responsible for management of an important part of the interagency program of research on acid deposition and its effects in the United States. International concern about acid deposition was raised significantly by Sweden's case study for the United Nations' Conference on the Human Environment in 1972 which was entitled "Air Pollution Across National Boundaries: The Impact on the Environment of Sulfur in Air and Precipi- tation" (Bolin et al., 1972~. However, awareness of the "acid rain" problem in North America began in the late 1960s when scientists in Canada and the United States first began to study the changing acidity of precipitation and its effects on the continent. In both Europe and North America, scientific data pointed strongly to two important conclusions: . Emissions of sulfur dioxide (SO2) and nitrogen oxides (NO=) were causing unnaturally high acidity in precipitation; and these increased loadings of acidic substances were leading to acidi- fication of certain lakes and streams, and perhaps adversely affecting crops, forests, and human health. By the late 1970s, acid deposition had become a major domestic political issue inside the United States and a major international political issue with Canada. Studies of the geographic distribution of sources of 342

ENVIRONMENTAL MANAGEMENT CASE STUDIES 343 emissions, acidic precipitation, and acidic lakes indicated that lakes were acidic in the northeastern United States and southeastern Canada, and that a major contributing cause of the problem was the heavy concentration of SO2 emissions in the midwestern United States. In 1978, the United States Congress passed a resolution calling for bilateral discussions with Canada to Preserve and protect mutual air re- sources." This resolution was stimulated in part by concern about construc- tion of a new coal-fired power plant in western Ontario near the Boundary Waters Canoe Area of northeastern Minnesota. In response to this res- olution, the governments of Canada and the United States issued a joint statement in July 1979, and on August 5, 1980, signed a Memorandum of Intent (MOI) to negotiate a treaty on transbounda~y air pollution. The MOI noted that: The Governments share a concern about damage resulting from transboundary air pollution . . . including the already serious problem of acid rain. Are resolved to . . . improve scientific understanding of the long-range transport of air pollutants [and] develop and implement policies to combat its impact. Are convinced that the best means to protect the environment . . . is through achievement of necessary reductions in pollutant loadings. Also in August 1979, President Jimmy Carter recommended a 10-year program of research on the causes and consequences of acid precipitation. In June 1980, the United States Congress passed the Acid Precipitation Act of 1980 (Public Law 96-294~. This law added legislative authority for a 10-year research program which was later named the National Acid Precip- itation Assessment Program (NAPAP). This program was to be carried out jointly by the major agencies of the U.S. government, chief among them being the Departments of Interior and Energy, the Forest Service, the National Oceanic and Atmospheric Administration, and the Environmental Protection Agency (Cowling, 1982~. The annual budget for NAPAP grew from $17.4 million in 1983 to $85.6 million in 1987. SCIENCE, POLITICS, AND RESEARCH Although there was a certain incongruity in these two nearly simulta- neous events—establishment of a major scientific research program while conducting international negotiations there were also some benefits. The MOI called for establishment of: technical and scientific work groups to assist in preparations for and the conduct of negotiations on a bilateral transboundazy air pollution agreement.... The Work Groups shall provide reports assembling and analyzing information and identifying measures which will provide the basis of proposals for inclusion in a transbounda~y air pollution agreement. These reports shall be provided by January 1982 and shall be based on available information.

344 The topics covered in the Work Group Reports included: ECOLOGICAL RISES · the nature and extent of effects of acidic deposition (Bangay and Riordan, 1983~; · quantification of sources of emissions and costs for their reduction (Riegel and Rivers, 1982~; ~ · the relationship between decreases in emissions and decreases in acidic deposition (Ferguson and Machta, 1982~; and · alternative strategies by which to allocate and achieve emissions de- creases among geographical areas and types of pollution sources (Hawkins and Robinson, 1982~. Canadian scientists entered into the MOI work-group process with expectation that, around the beginning of 1982, an agreement would be signed by the two countries to decrease emissions of SO2 on a prescribed schedule in order to decrease existing damage and prevent future environ- mental damage from acidic deposition. However, the United States had a different perspective on the work-group process. As a result, the MOI process broke down during 1982. The Work Groups were actually able to reach agreement in a number of important areas, e.g., the amounts of emissions; the relative efficiencies and costs of technologies to decrease emissions from existing and new sources; and the relative lack of knowledge about the effects of acidic deposition on crops, forests, and materials. The Work Groups even reached agreement on the expected degree of accuracy of regional models to predict changes in annual average wet deposition in major receptor areas that would result from emissions reductions in major source regions. It was in the aquatics-effects area, however, that the work-group pro- cess and, ultimately, the entire MOI negotiation process broke down. The scientists on both sides all agreed that total sulfur loadings from atmospheric deposition were the likely cause of long-term acidification of a number of lakes in the northeastern United States and southeastern Canada. But the U.S. and Canadian scientists disagreed on the conclusions that could be reached with respect to two basic scientific questions which were of critical importance to policy makers in both countries (Bangay and Riordan, 1983~. The first question was "What is the extent of acidification of surface waters?" As is often the case in emerging environmental problems, much of the early research on acidic deposition had concentrated on known problem areas, e.g., the Adirondacks in the United States and southern Ontario in Canada. The number of lakes observed to have an average pH below 5.0 was less than 180 in the northeastern United States and less than 100 in Canada. Further, essentially no data were available on the hydrology' soils, and geology of these lakes or how these characteristics might compare to

ENVIRONMENTAL MANAGEMENT CASE STUDIES 345 those of the thousands of other lakes in the eastern United States and Canada. Ib estimate the extent of existing acidification, Canadian scientists wanted to extrapolate from the lakes that had already been studied to the entire population of lakes. The basis for this extrapolation was their conviction of a similarity in regional scale soil type and geology. However, the U.S. scientists would not support this extrapolation for two reasons. First, they were convinced that many of the already affected lakes were impacted by local smelter emissions and not just by regionally transported deposition. Second, existing knowledge indicated that subregional soil and geology variation was an important factor in determining the response of lakes to acidic deposition. The second major disagreement was related to the "target loading" issue. Canadian scientists wanted the Work Group on Impact Assess- ment to conclude that a reduction of the annual average wet deposition of sulfate to 20 kilograms per hectare per year would protect all but the most sensitive lakes from the adverse effects of acid deposition. The basis for this conclusion was empirical association. They had found acidic lakes in areas which were experiencing wet deposition greater than 25-35 kg~a/yr and had not observed acid lakes where deposition was less than 20 kg/ha/yr. The U.S. scientists would not agree to this view because they did not see the world so simply. Futher, in Norway and Sweden, there was evidence that some lakes could be acidic with wet deposition as low as 10 kg/ha/yr. In the opinion of the U.S. scientists, the difference between 10 and 20 kg/ha/yr could have been either the result of differences in the ratios of dry to wet deposition, or differences in the acid-neutralizing capacity of watersheds, or some combination of both factors. According to the U.S. scientists, a more defensible scientific position would be to estimate how many lakes would be acidic if annual average amounts of wet deposition were limited to a range of possible loadings, e.g., 10, 15, 20, 25, 30, 35, and 40 kg~alyr. In that way, policy makers would be aware that the situation was not black or white; rather, that there was a continuum on which lakes were more likely to be acidic as the amounts of annual average wet deposition increased. With reasonable scientific confidence, both the U.S. and Canadian sci- entists agreed that atmospheric deposition of sulfur had caused acidification of some lakes, on the order of a few hundred in the United States and about 100 in Canada. But the U.S. scientists were not willing to extrapolate from the limited data that were then available in order to provide an estimate of damage for the entire population of lakes in the northeastern United States and southeastern Canada. Three critical elements were lacking, in their opinion. First, there was a lack of an adequate dose/response func- tion relating acidic deposition to lake-water chemistry based on soil trans- port and transformation processes in watersheds; second, there was a lack

346 ECOLOGICAL RISKS of good empirical data on the relationships among geographical variation in surface-water quality, watershed soils, and hydrology; and finally, there was a lack of acceptable model estimates or measurements of dry deposition for lakes in the potentially affected regions (Bangay and Riordan, 1983~. Just as the MOI discussions on acidic deposition between the United States and Canada broke down during 1982, so did the ability of the United States Government to deal with its own domestic differences in perspectives about the acid deposition issue. Congressmen from the New England states, New York, Minnesota, and Wisconsin pushed for legislation to require decreases in SO2 emissions from electrical utility boilers. Some support for these proposals was offered by western states which could provide low-sulfur coal if major eastern utilities were willing to shift from high- to low-sulfur coals. However, congressmen from several midwestern states which had large deposits of high-sulfur coal, and in many cases also had large SO2 emissions, were adamantly opposed to major new decreases in SO2 emissions as was then-President Ronald Reagan Reagan. They argued that the new controls being called for would probably cost as much as $4 billion per year for as long as 20 years. They believed such costs were not justified for two reasons. First, they wanted to "wait and see" what effect the 27% decreases in SO2 emissions during the period from 1974 to 1980 would have on the problem. Second, they wanted to "do more research before making a decision;" they did not believe that existing scientific knowledge was sufficient to estimate the number of existing lakes that were acidic as a result of acid deposition, or to predict how many additional lakes might become acidic if amounts of emissions and deposition were to remain constant or to increase. They also saw gaps in knowledge of source/receptor relationships, modeling of atmospheric processes, and watershed acidification processes. Thus, in part because of scientific uncertainties, the United States faced a political stalemate. WHEN TO ACT: SCIENCE VERSUS POLICY In the United States, issues such as acid deposition are hotly debated by the scientific community, elected officials, environmental groups, industry leaders, the media, and the public at large. These debates often become confused because of the seemingly unavoidable mixing of inherently distinct functions the scientific function of discovering how nature works and how its is influenced by human activities, and the political function of deciding what values the society holds dear, and what, if anything, society ought to do about a given social, economic, environmental, or political issue.

ENVIRONMENTAL MANAGEMENT CASE STUDIES 347 The problem of handling this confusion of functions is particularly difficult for scientists in government and in the private sector. Too often, elected officials and the public look to scientists for answers to questions that are not scientific but political. The problem of acidic deposition is a good example. As early as 1981, many scientists inside and outside of government had concluded that acidic deposition had, with acceptable scientific certainty, contributed in a major way to the long-term acidification of several hundred lakes in the northeastern United States and southeastern Canada. Because the lakes that had been studied were not known to be representative of the total number of lakes, there was no mutually acceptable scientific way to estimate the total number of lakes that might become acidic in the future. Nevertheless, scientists were being asked and some were providing answers to questions on how society should decrease emissions of SO2 and thereby decrease acidic deposition. The problem with this process is that the question of whether and how much society should pay to avoid a particular pollution effect is fundamen- tally not a scientific question. Rather, it is a political one, involving complex trade-offs between differing values of individuals and groups with respect to environmental quality and other activities that also affect the quality of life, e.g., food supply, education, public health, etc. In fact, even if scientists did know how many lakes were now acidic and how many more would become acidic in the future, it would still require a careful assessment of many non-scientific values to be able to determine what trade-o~s, if any, society ought to make between the costs of emissions decreases and the costs of acidic lakes. Such questions are inherently political and require political judgment, not scientific judgment. Of course, in 1982 as well as today, scientists cannot answer some of the important scientific questions about the environmental effects of acidic deposition, to say nothing of the political questions about what society ought to do about it. In view of the scientific uncertainties, many politicians in the United States have been unwilling to adopt new legislation for the purpose of decreasing SO2 emissions below the amounts that are already being achieved in some regions under the Clean Air Act of 1970 and its amendments of 1977. In the absence of a political solution to the acidic deposition problem, the United States conducted a major research program under the Acid Precipitation Act of 1980. President Reagan and his supporters in the United States Congress believed that a rational political decision was to invest in research that would close critical gaps in scientific knowledge. Thus, a conscious decision was made based on the following assumptions:

348 ECOLOGICAL RISKS · There are critical gaps in policy-relevant scientific knowledge. · Applied research can close many of these gaps during the 10-year research program that was begun in 1980. · Widespread environmental damage at present rates of deposition is unlikely in 5-10 years. MAJOR FEATURES OF THE NAPAP RESEARCH PROGRAM The nature and scope of the NAPAP research program changed signif- icantly as a result of the political stalemate that developed domestically and internationally during the period from 1982 to 1983. The extensive political and scientific debates that occurred at this time focused attention on certain gaps in scientific knowledge that were of major concern to policy makers. Those opposed to additional SO2 controls were obliged to identify those uncertainties in the science that they believed prevented rational decisions. Those favoring additional SO2 controls insisted on three basic conditions for their willingness to support research as opposed to action: . First, those opposed to controls had to demonstrate why a gap in knowledge or uncertainty was critical to policy; · Second, NAPAP research plans and approaches had to provide reasonable assurance that major decreases in scientific uncertainties could be achieved over a period of 5-10 years; and · Third, the research had to be affordable and actually funded. During the period from 1983 to 1984, the researchers in the NAPAP program worked closely with policy makers to develop a major expansion in the applied research program to address significant cans in knowledge with projects that met the three conditions listed above. In some ways, the timing of these discussions could not have been better. Research had already provided insights about some of the causes and effects of acidic deposition. These early results provided the foundation for a larger scale applied-research effort. Thus, the bulk of the new resources in NAPAP were directed to provide better answers to policy-relevant scientific questions in the following categories: of o--r~ -~~~~ Aquatic Effects . To what extent have surface waters been acidified by acidic depo- sition? · How many more lakes and streams are likely to be acidified if deposition rates remain constant or increase?

ENVIRONMENTAL Af4NAGEMENT CASE STUDIES 349 · What is the dose/response function that relates acidic deposition to surface water acidification? Forest Ejects · Is acidic deposition alone or in combination with other factors responsible for observed growth reductions and damage to selected forests in the eastern United States? What is the extent of damage in these forests that might be at- tributable to air pollution? What is the dose/response function that relates acidic deposition to growth declines and/or damage in these forests? Emissions What are the historical and present amounts of emissions of acidic deposition precursors? · What techniques are available for decreasing these emissions and at what cost? Emission/Deposition Relationships · What are the present patterns of dry deposition? · What changes in patterns of wet and dry deposition of sulfur and nitrogen compounds would result from a change in the pattern of emissions? The research approaches used in pursuing these several applied research questions are summarized briefly below: The National Surface Water Survey (NSWS) was initiated in 1984 to provide a statistically based estimate of the number of acidified lakes and streams in various parts of the United States. In Phase I, samples were taken in regions of the country that were known to contain a significant percentage of lakes and streams with alkalinity less than 400 microequivalents per liter. In Phase II, representative subsets of lakes with alkalinity less than 200 microequivalents per liter were sampled to determine spatial and temporal variations of acidity in each lake over the spring, summer, and fall seasons. This study was also designed to determine the presence or absence of various fish species in some subregions. Phase III is a long-term monitoring program for a set of lakes with alkalinity less than 200 microequivalents per liter in areas with different acid deposition loads. The Direct/Delayed Response Program (DDRP) was designed to sup- plement the results of the NSWS by providing detailed information on the dynamic responses of watersheds and lakewater chemistry to acid inputs. The DDRP funded the development and application of models that can

350 ECOLOGICAL RISKS use data on vegetation, soils, and hydrogeology of watersheds to predict future changes in lakewater chemistry which may occur under a variety of future acid deposition scenarios. Three different models were run using the detailed data on soil type and watershed characteristics gathered for 145 watersheds in the northeastern and the southeastern sections of the United States. The three models were the so-called ILWAS (Integrated Lake-Water Acidification Study), TRICKLE DOWN, and MAGIC (Model of Acidification of Groundwater In Catchments) models. The Watershed Response Program is a watershed manipulation program designed to test critical features of the three models listed above in the field at the plot and catchment level. Simulated acidic deposition is applied to watersheds and then the response of vegetation, soils, and surface waters is observed. The data generated by these watershed-manipulation studies should provide a definitive test of the power and utility of the watershed models for predicting lakewater responses to possible future changes in acidic deposition loadings. The Forest Response Program was designed to determine the possible effects of acid deposition and other airborne pollutant chemicals on forests. During the late 1970s, acid deposition was considered a major contributing cause of damage to forests in certain areas of Germany. During the early 1980s, two sources of data for tree injury and decline that were not explained by natural causes began to appear in the United States. Many scientists were concerned that these initial reports of changes in the condition of forest trees in the United States might become comparable in magnitude and extent to those observed in Europe. A four-part program was initiated to include: deposition. · field studies to identify and quantify changes in forest health; controlled exposure/response experiments to determine the impact of acidic deposition on tree seedling growth; · research on physiological processes to identify cause-and-effect mechanisms; and development of models to predict tree and forest response to acidic After much debate about alternative approaches to the study of emis- sions/deposition relationships, NAPAP decided to develop the Regional Acid Deposition Model (RADM). This model is a six-elevation Eulerian Model with~horizontal grids that are 80 kilometers on a side. RADM 1 contains first generation descriptions of transport, clean-air chemistry, wet scavenging, and deposition. A preliminary evaluation of RADM 1 was completed during 1986 using two limited data sets: the Oxidant and Scavenging Characterization of April Rains (OSCAR) and the Cross-Appalachian Tracer Experiment

ENVIRONMENTAL MANAGEMENT CASE STUDIES 351 (CAPTEX). OSCAR measured wet deposition amounts and chemistry within certain specific weather events. CAPTEX measured plumes of inert tracer material across the northeastern United States and Canada also during selected meteorological events. The preliminary evaluation results are being used to revise RADM. NAPAP also decided that some measure of dry deposition and trends was essential Such measures were needed to improve estimates of total deposition of acidic materials in receptor areas and as a means of evaluating RADM. Unfortunately, dry deposition was a case where the need outpaced the feasibility of science and the availability of funding in the NAPAP research program. As a result, a decision was made to employ an indirect air concentration/deposition velocity approach at monitoring sites. This decision was made in the absence of demonstration that an appropriate deposition velocity algorithm could be developed for operational sites based on actual flus measurements developed at a limited number of core research sites. The rationale for this decision was that even if the technique failed, air quality information would still be available for model evaluation. NAPAP has not funded research on new combustion technologies or new post-combustion clean-up technologies. However, a great deal of research is being carried out by other programs in the U.S. government and by the private sector. NAPAP INTERIM ASSESSMENT In September 1987, NAPAP issued an Interim Assessment of its re- search program findings. The report was expected to be used by policy makers in the Executive and Legislative branches of the U.S. government in their reassessment of acid deposition policy. Although the scientific chap- ters of this Interim Assessment (NAPAP 1987b,c,d) provided a valuable summary of both NAPAP-sponsored and non-NAPAP-sponsored research findings, substantial controversy resulted from the disparities in substance and tone between the Executive Summary (NAPAP, 1987a) and the scientific chapters (LeFohn and Krupa, 1988~. From a policy perspective, the most important and most controversial conclusions related to the probability of future adverse environmental effects if current rates of acidic deposition were maintained in the future. The Executive Summary of the Interim Assessment emphasized that: · Available observations and current theory suggest that there will not be an abrupt change in aquatic systems, crops, or forests at present levels of air pollution. · Some lakes and streams in sensitive regions appear to have been acidified by atmospheric deposition at some point in the last 50 years.

352 ECOLOGICAL RISKS Available data suggest that most watersheds in the glaciated northeast are at or near steady state with respect to sulfur deposition, and that further significant surface water acidification is unlikely to occur rapidly at current deposition levels. Although no lakes and streams with a pH of less than 5.0 have been found in the Southern Blue Ridge Province, water bodies in this region are generally not at steady state with respect to sulfur deposition, and gradual increases in surface water sulfate and decreases in acid neutralizing capacity (ANC) may occur as the sulfur absorption capacity of the soil decreases. At current levels of acidic deposition, short-term direct foliar effects on crops or healthy forests are unlikely. Acidic deposition may have a cumulative effect on trees growing on certain low-nutrient soils, but this effect is expected to be gradual and has not been reported in the United States at current levels. It is unlikely that regional sulfur dioxide concentrations are causing damage to crops or forests. Bees and crops can exhibit severe damage and even mortality from high concentrations of ozone and sulfur dioxide. Such occurrences are rare today because of emission controls on most major point sources. At the more typical ambient chronic concentrations of ozone, some crop damage is observed. For many tree species in low-elevation forests, growth reduction may be occurring at ambient ozone concentrations. With the possible exception of above-cloud-base forests where high mortality has occurred from unknown causes, most U.S. forests are not expected to show an abrupt change in health at current ambient air pollutant concentration levels and deposition rates. Perhaps as important were the Interim Assessments' enumeration of scientific uncertainties which NAPAP hopes to reduce by 1990: · the sources, quantities, and reactivities of natural emissions of sulfur dioxide, nitrogen oxides, volatile organic compounds, methane, and alkaline substances (current emissions of these substances are uncertain by about a factor of about 3~; · the origin and distribution of hydrogen peroxide, a primary oxidiz- ing agent in clouds; · the influence of urban emissions on deposition locally (<30 km) and in the mesoscale (30 km to 200 km) downwind; · the source/receptor relationship resolved to a state level on a seasonal and annual basis; · the current spatial and seasonal distribution of dry deposition of sulfur dioxide and nitric acid; · identification of forest soils which are potentially sensitive to change by ambient acidic deposition and which might affect tree health;

ENVIRONMENTAL A{4NAGEMENT CASE STUDIES 353 · the relative contribution of acidic deposition, ozone, hydrogen peroxide, nitrate, and natural stresses to the decline of above-cloud-base forests in the Appalachians; · methods to extrapolate results of dose/response experiments of pollutants on seedlings and saplings to mature trees; methods to estimate change in the regional distribution of surface water chemistry (lakes and streams) over the next half~entury at present or changed rates of acidic deposition; and · the effect of episodic acidic events on the health and reproduction of fish in streams and lakes. The NAPAP Final Assessment is due to be completed in 1990 (Mahoney et al., 1989~. SUMMERY . .t In recent years, progress has been slow in resolving many scientific and public-policy questions about the causes, consequences, and management of acid deposition in North America. Part of the reason for this slow progress has been uncertainties about the science involved. But equally important has been the absence of a public consensus between Canada and the United States as well as among the several states within the United States about what, if anything, should be done about acidic deposition. It appears that the degree of scientific certainty that is required to reach a decision about such a complex issue of science and public policy is an inverse function of the degree of public consensus about the same issue. Acid deposition is certainly an example of this generalization. REFERENCES Bolin, B., et al. 1972. Air pollution across national boundaries: Lee impact of sulfur in air and precipitation. Case study prepared by Sweden for the United Nations Conference on the Human Environment. Stockholm, Sweden: Norstedt and Sons, p. 97. Bangay, G.E., and C Riordan. 1983. United States-Canada Memorandum of Intent on ansboundary Air Pollution. Final Report prepared by the Impact Assessment Work Group I. U.S. Department of State and the Embassy of Canada, Washington, DC. Cowling, E.B. 1982. Acid precipitation in historical perspective. Environmental Science and Technology 16:110A-123^ Hawkins, D.G., and R Robinson. 1982. United States-Canada Memorandum of Intent on lLansbounda~y Air Pollution. Anal Report prepared by the Strategies Development and Implementation Work Group 3^ U.S. Department of State and the Embassy of Canada, Washington, DC. Ferguson, H., and Lo Machta. 1982. United States-Canada Memorandum of Intent on lLansboundary Air Pollution. Anal Report prepared by the Atmospheric Modeling Work Group ~ U.S. Department of State and the Embassy of Canada, Washington, DC LeFohn, A., and S. Krupa. 1988. A technical amplification of NAPAP's Interim Assessment. Air Pollution Control Association, Washington DC.

354 ECOLOGICAL RISKS Mahoney, J.R., P.M. Irving, and J.L. Malanchuk. 1989. Plan and schedule for NAPAP's 1989 and 1990 assessment reports. Journal of the Air Pollution Association 38:1489-1496. NAPAP. 1987a. Executive summary. The Causes and Effects of Acidic Deposition: Interim Assessment, Volume I National Acid Precipitation Assessment Program. Washington, DC. NAPAP. 1987b. Emissions and control. The Causes and Effects of Acidic Deposition: Interim Assessment, Volume II. National Acid Precipitation Assessment Program. Washington, DC NAPAP. 1987c. Atmospheric processes. The Causes and Effects of Acidic Deposition: Interim Assessment, Volume III. National Add Precipitation Assessment Program. Washington, DC. NAPAP. 1987d. Effects of acidic deposition. The Causes and Effects of Acidic Deposition: Interim Assessment, Volume IV. National Acid Precipitation Assessment Program. Washington, DC. Riegel, Key, and M.E. Rivem. 1982. United States-Canada Memorandum of Intent on lLansboundary Air Pollution. Final Report prepared By the Emissions, Costs, and Engineering Assessment Work Group 3B. U.S. Department of State and the Embassy of Canada, Washington, DC. U.S. Department of State and the Embassy of Canada. 1980. Memorandum of Intent between the Government of the United States of America and the Government of Canada concerning transbounda~y air pollution. Washington, DC. Hi

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Acidic Precipitation: Case Study Soiling

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• E. Matzner 15  

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By using the flux-balance approach, the rates of deposition of major elements, including H + , S, and N, and the effects on ion cycling in the canopy and mineral soil were obtained in two mature forest stands of the north German Soiling region. Both stands are heavily impacted by acid precipitation, the spruce ( Picea abies Karst.) stand receiving about twice the rate of acidity as the beech ( Fagus silvatica L.) stand. The deposition of protons results in increased cation leaching from the leaves and needles with subsequent acidification of the rhizosphere. In both sites the mineralization of aboveground litter was significantly inhibited, and the amount of organic matter in the top layer almost doubled during the period of investigation. The organic top layer appears to be the major sink for deposited N. The Ca/Al and Mg/Al ratios of the soil solution have decreased in both stands to levels posing high risk of Al toxicity to tree roots. According to input-output budgets of the mineral soil sources of ions are obvious in the case of most major nutrients. In spruce the behavior of sulfate in the mineral soil changed from accumulation to release over the study period. Proton budgets reveal that the most important part of the acid load of the mineral soil stems from the deposition of strong acids. The prevailing buffer mechanism is the release of Al ions from hydroxides, sulfates, and exchangeable sites into the soil solution. The transfer of Al ions by seepage water to deeper soil layers results in a high acid load of those layers. Soil analysis showed deep-reaching acidification and emphasize the risk of groundwater and surface water acidification. The long-term effects of acid deposition on soil chemistry are superimposed by seasonal acidification phases resulting from natural excess nitrification under favorable climatic conditions. In acid soils these acidification phases cause pH reductions and additional Al releases.

• Soil Solution
• Mineral Soil
• Acid Deposition
• Seepage Water
• Acid Precipitation

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Matzner, E. (1989). Acidic Precipitation: Case Study Soiling. In: Adriano, D.C., Havas, M. (eds) Acidic Precipitation. Advances in Environmental Science, vol 1. Springer, New York, NY. https://doi.org/10.1007/978-1-4612-3616-0_2

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