Interaction of Climate Change and Acid Deposition - Climate Change Impacts on Freshwater Ecosystems - page 152

7
Interaction of Climate Change
and Acid Deposition
Richard F. Wright, Julian Aherne, Kevin Bishop, Peter J. Dillon,
Martin Erlandsson, Chris D. Evans, Martin Forsius, David W.
Hardekopf, Rachel C. Helliwell, Jakub Hruška, Mike Hutchins,
Øyvind Kaste, Jiˇí Kopáˇek, Pavel Krám, Hjalmar Laudon,
Filip Moldan, Michela Rogora, Anne Merete S. Sjøeng
and Heleen A. de Wit
Introduction
Both climate change and acidification ultimately involve chemical changes in the
atmosphere and, not surprisingly, the two are strongly linked. Particular focus
here is on how climate change might delay recovery of acidified, and hence
damaged, aquatic ecosystems. Data come from acid-impacted areas of Europe
and eastern North America and involve large-scale experiments with altered local
climate, conducted in small catchments and lakes. Long-term datasets (30+
years) have also been analysed to link variations in acid deposition and climate
on water chemistry and biology. Together, the experimental and empirical data
have been used to develop, modify and calibrate statistical and process-orientated
models. These models have then provided tools to predict ecosystem changes,
given the future scenarios of acid deposition and climate.
Chronic emissions of sulphur (S) and nitrogen (N) compounds to the atmo-
sphere, long-range transport and the resultant deposition of S and N pollutants
have caused acidification of freshwaters over large regions of Europe and eastern
North America (Overrein et al . 1980; Schindler 1988; Clair et al . 1995; Driscoll
et al . 2001; Jeffries et al . 2003). In Europe, S emissions were greatest in the late
1970s/early 1980s and have since declined strongly, while N emissions have had
a much more modest decline (Fig. 7.1).
Ecological damage included loss of salmon and trout populations from
thousands of water bodies and changes in the species composition of invertebrate,
aquatic macrophyte and algal communities. In Scandinavia, for example, a survey