Coral reefs and environmental change: Adaptation to what?

Abstract

SYNOPSIS. The present concern about future climate change and sea-level rise due to the enhanced greenhouse effect is put in the context of past changes. Best estimates of future changes are detailed, with an explanation of methods and uncertainties. Considerable progress is being made in regard to estimates of future sealevel rise and its regional variation, and towards predicting likely changes in the behaviour of the El Nino-Southern Oscillation (ENSO) and tropical cyclones. Changes in rainfall amounts and intensity, and in extremes of surface temperature are other critical climatic variables for coral reefs. Impacts on coral reefs will result from a combination of stresses arising from several aspects of global change, including stresses due to sea-level rise, extreme temperatures, human damage (from mining, dredging, fishing and tourism), and changes in salinity and pollutant concentrations (nutrients, pesticides, herbicides and particulates), and in ocean currents, ENSO, and storm damage. These may be exacerbated by any reduction in calcification rates of corals due to changes in ocean chemistry. In view of ongoing uncertainties regarding future rates of change, especially at the local scale, impact and adaptation assessments cannot provide unequivocal answers, but rather must be couched in terms of probabilities and risk. Reef communities which are presently under stress are likely to be particularly vulnerable. Both autonomous and managed (or planned) adaptations should be considered.