BIOTIC CONTROL OVER THE FUNCTIONING OF ECOSYSTEMS

Changes in the abundance of species-especially those that influence wa ter and nutrient dynamics, trophic interactions, or disturbance regime -affect the structure and functioning of ecosystems. Diversity is also functionally important, both because it increases the probability of including species that have strong ecosystem effects and because it ca n increase the efficiency of resource use. Differences in environmenta l sensitivity among functionally similar species give stability to eco system processes, whereas differences in sensitivity among functionall y different species make ecosystems more vulnerable to change. Current global environmental changes that affect species composition and dive rsity are therefore profoundly altering the functioning of the biosphe re.