Coral reefs release carbon dioxide to the atmosphere due to the chemistry of calcium carbonate precipitation. Biological And Economic Values Coral reefs are among the most biologically diverse ecosystems on the planet. Although tropical rainforests contain more species than coral reefs, reefs contain more phyla than rainforests. Phyla are large groupings of organisms that are thought to be related. New studies indicate that biodiversity on coral reefs may be even higher.
Reefs are also extremely valuable as breakwaters and draws for tourism.
Threats Coral reefs are among the most endangered ecosystems on earth. Coral reefs in 93 of the 109 countries containing them have been damaged or destroyed by human activities. Destructive fishing techniques such as fine mesh nets, cyanide poisoning, and dynamiting are common in coral reefs, and have actually come to dominate fishing in parts of Indonesia and the Philippines. Physical damage to coral reefs by scuba divers and tourists would probably be a minor threat if the number of visitors to reefs were limited to moderate levels and if water quality was always high enough to support rapid recovery of corals. However, tourism often results in large numbers of visitors, which leads to extensive physical damage, sewage pollution, and other adverse water quality impacts which slow or eliminate recovery.