TERRESTRIAL ECOSYSTEM FEEDBACKS TO GLOBAL CLIMATE-CHANGE

Anthropogenic greenhouse gases are expected to induce changes in globa l climate that can alter ecosystems in ways that, in turn, may further affect climate. Such climate-ecosystem interactions can generate eith er positive or negative feedbacks to the climate system, thereby eithe r enhancing or diminishing the magnitude of global climate change. Imp ortant terrestrial feedback mechanisms include CO2 fertilization (nega tive feedbacks), carbon storage in vegetation and soils (positive and negative feedbacks), vegetation albedo (positive feedbacks), and peatl and methane emissions (positive and negative feedbacks). While the pro cesses involved are complex, not readily quantifiable, and demonstrate both positive and negative feedback potential, we conclude that the c ombined effect of the feedback mechanisms reviewed here will likely am plify climate change relative to current projections that have not yet adequately incorporated these mechanisms.