Air pollution impacts on forests in a changing climate

Abstract

Growing awareness of air pollution effects on forests has, from the early 1980s on, led to intensive forest damage research and monitoring. This has fostered air pollution control, especially in Europe and North America, and to a smaller extent also in other parts of the world. At several forest sites in these regions, there are first indications of a recovery of forest soil and tree conditions that may be attributed to improved air quality. This caused a decrease in the attention paid by politicians and the public to air pollution effects on forests. But air pollution continues to affect the structure and functioning of forest ecosystems not only in Europe and North America but even more so in parts of Russia, Asia, Latin America, and Africa. At the political level, however, attention to climate change is focussed on questions of CO2 emission and carbon sequestration. But ecological interactions between air pollution including CO2 and O3 concentrations, extreme temperatures, drought, fire, insects, pathogens, and fire, as well as the impact of ecosystem management practices, are still poorly understood. Future research should focus on the interacting impacts on forest trees and ecosystems. The integrative effects of air pollution and climatic change, in particular elevated O3, altered nutrient, temperature, water availability, and elevated CO2, will be key issues for impact research. An important improvement in our understanding might be obtained by the combination of long-term multidisciplinary experiments with ecosystem-level monitoring, and the integration of the results with ecosystem modelling within a multiple-constraint framework