A global perspective on forest decline

Abstract —,;Carbon dioxide, the major plant food, is on the rise, but forests on both sides of the Atlantic are known to be declining, and industrial pollution is widely suspected to be the principal cause. However, significant contemporary forest declines also are occurring in several Pacific forests, in areas completely unaffected by industrial pollution. This paper focuses on researched forest declines in the Pacific area (New Zealand, Japan, and the Hawaiian and Galápagos islands), where canopy dieback was found to be a natural aspect of forest dynamics. It then summarizes characteristics of forest decline in central Europe (Czechoslovakia and Germany), where decline relates mostly to anthropogenic causes. Commonalities among the natural causes in the Pacific and anthropogenic causes in the European forests are emphasized through recognition of a third factor complex, the demographic component, which so far has been largely neglected in the European forest decline research. The natural cause complexes identified as demographic, disturbance, and biotic components are placed into a causal hierarchy theory based on cohort senescence. It is suggested that this may serve as a framework for comparative ecosystem research of forest declines at the global level, which includes a consideration of ongoing biotic impoverishment and climate change.