Large-scale ecosystem experiments: ecological research and European environmental policy

During the last three decades the experimental manipulations of whole ecosystems have been a useful and widely-used tool for investigation of the effects of air pollution, air pollution reduction strategies and management practices on the health and productivity of forests and the acidification of catchments and fresh waters. NITREX and EXMAN projects involve whole-ecosystem manipulations of forest ecosystems in Europe. The aims of these ecosystem experiments have been to investigate the impact of a continued or increased load of air pollutants on the ecosystems, and the possibilities of reversing the acidifying effects by soil amelioration, addition of buffer-acting substances or by removal of the air pollutants. Along with the field experiments, models have been used to predict future effects and dynamics in the ecosystems under different air pollution scenarios. The major findings from those projects have been used in political decisions on reduction of sulphur emission in Europe via the sulphur protocol signed in 1994. Today work is going on to formulate a NO x protocol. NITREX and EXMAN results contribute to the scientific information base for these protocols. Large-scale ecosystem manipulation projects have increased our understanding of ecosystem function and response to external change and created scientific evidence for political environmental decisions and legislation. In the future, controlled-ecosystem experiments clearly play an important role in new research on ecological effects of changes in the global atmosphere and climate.