Public debate and technical policies about ecology : views on forest decay, ten years later ; Ecologie, débat public et politiques techniques: le dépérissement des forêts dix ans après

17 ref. ; International audience ; The aim of this article is to provide an overall analysis on the « acid rains/dying forests file » as it has developed over the last decade. A short review gives the background of the international discussions on the effects of atmospheric pollution, the highly polemic scientific debate on the dying forests, and the initiation of a French interministerial research programme called DEFORPA. Illustrations are given of the transborder effects and the recent evolution of the main polluant emissions — maintenance of the NOx level, considerable drop in SO 2. The state of scientific knowledge on the forest decay phenomenon and on other possible physically far-reaching effects of atmospheric pollution is summarised. The impact of this pollution is both more varied than certain experts initially predicted (certain forms of dying out, increased soil and river acidity, eutrophication of the flora) and clearly less catastrophic than what other, more pessimistic experts predicted early in the 1980s. A logical overview that includes factors that predispose forests to waste away, and that initiate or aggravate the process has been drawn up for two of the main causes affecting coniferous mountain trees ; for fir trees, climatic anomalies and silvicultural background, essentially natural, seem to be the major cause for the fir trees, while for the spruce, continued acid rains, indeed, seem to be the main, although not the only explanation for tree yellowing. As scientific discussion progressed, rules on emission were quickly enacted (protocol on SO2 in 1985, on NO x in 1988, on hydrocarbons in 1990). Technical measures (fuel quality, parafiscal tax on emissions, etc.) issued in France to ensure respect of national commitments are briefly presented. Last, an analysis is made of the importance of the very topical concept of « critical load » that seeks to replace the idea of systematic reduction of emissions by a minimum cost emissions reduction system to protect the vulnerable ecosystems. The ...