THE EFFECTS OF GLOBAL CHANGE ON TROPICAL ECOSYSTEMS

Alteration of land use will continue to be the dominant driver of envi ronmental change in the tropics for the next several decades. It can t ake the form of fundamental vegetation cover transformation, or of int ensification of existing land use without substantial change in cover type. Atmospheric composition changes and resultant climate changes co uld become ecologically significant within the next century. Changes i n atmospheric composition in the tropics are essentially the same as t hose in higher latitudes, despite differences in the source and sink s trengths for trace gases. Such changes can affect the functioning of t ropical ecosystems through several processes, principally those relate d to carbon and nutrient assimilation and their interactions. Atmosphe ric composition may also have an indirect affect on tropical ecosystem s via its effects on the climate. Predicted temperature increases in t he tropics are less extreme than at high latitudes, but could still be biologically significant, especially at the tropical margins. The str ucture and productivity of ecosystems of the subhumid and dry tropics are very sensitive to changes in water balance, which could be caused by a combination of changes in precipitation and temperature. It is pr esently not possible to predict rainfall changes at ecologically meani ngful scales with any confidence. (C) 1997 Elsevier Science B.V.