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May 12-15, 1975 marked the First International Symposium on Acid Precipitation and the Forest Ecosystem. The aims of the meeting were:
The Seventh International Conference on Acid Deposition, Acid Rain 2005, will be faithful to these same aims, building on understanding gained since 1970. Enormous environmental progress has been made since 1970 with a cleaner atmosphere, from sharply reduced emissions (and deposition) of S and many metals. Considerable understanding has been gained about the history and modern extent of atmospheric pollution from monitoring and various natural archives, and about the long-term effects of S on terrestrial and aquatic systems from integrated research. Chemical and biological recovery in surface water from reduced S input has not been linear, or easily predictable, except in heavily polluted systems. Recovery of many surface waters and especially forest soil has not generally been as expected because of confounding influences related to climate change. These include widespread increases in dissolved organic carbon (DOC), hydrologic and temperature effects on water chemistry, cycles of drought, variable soil CO2, and long-term changes in the input of marine aerosols. Also intensive forestry has been recognized as an important contributor to soil and water acidification. Unsolved major aspects of acidification focus on the biogeochemistry of N, which is dominated by climate variation and atmospheric deposition, but also impacted by past land use and other poorly understood factors. Emerging issues linking air pollution, global climate, and ecosystem health include nutrient availability in terrestrial (the base cations Ca and Mg, and N) and aquatic systems (P, N), altered metal mobility and toxicity (e.g., increased DOC and Hg, or Hg-marine aerosol linkages), persistent organic pollutants (POPs), and ozone. Budgets of several important elements such as N and Hg are still poorly defined because of possible importance of uncharacterized gaseous fluxes. Long-term regional and site-specific monitoring, commonly with international cooperation and coordination, are now providing us with the ability to identify short-term to decadal time scale processes. Study of chemically manipulated ecosystems has clarified many processes. Monitoring and manipulation permit an assessment of the effectiveness of legislated reductions in atmospheric emissions and allow us the ability to better project ecosystem health with empirical and experimental data, and improve and constrain process-oriented models. Acid Rain 2005 marks a transition from “Acid Rain” being viewed somewhat in isolation, to its being viewed as linked with climate change, land use, biodiversity, and human health.
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Conference Statement