Acidic deposition: What is fact,what is speculation,what is needed?

In this presentation research findings from the symposium and from the literature are utilized to examine some of the major hypotheses that link acidic deposition with impairment of forest health and productivity in central Europe and eastern North America. Although unequivocal evidence of acid rain damage may be lacking, there is a considerable body of knowledge that implicates air pollutants in recent interference with forest nutrition and health. The nature of the evidence and the inferences that can be drawn from it are still being vigorously debated. The problem of verifying the mechanisms by which air pollutants affect forests still remains. Reports that climatic irregularities have acted as inciting or triggering factors in forest declines are relevant to understanding regional damage. More emphasis on experimental studies that assess interactions of air pollutants and natural stresses with forests is needed.