CORAL reefs in various parts of the world are getting bleached and scientists are debating whether this is an early warning of global warming, or simply a local warming of sea waters.

Tom Goreau of the Global Reef Alliance says bleaching results from "expulsion by the coral of their symbiotic algae. Bleaching is always an indicator of severe, life-threatening stress. The question is what is causing this stress." A pilot programme to monitor 50 representative coral reef sites is being undertaken by the World Conservation Union and three UN bodies. About 110 countries have coral reefs.

According to Goreau, all the sites where mass bleaching had been reported since 1983 were located in "hot spots" where ocean waters were 1OC above long-term average temperatures. Danny Elder of the World Conservation Union points out that scientists disagree on whether bleaching is the result of global warming. "Our ignorance of marine phenomena is enormous," says Elder.