Careless boating, diving, fishing, and other recreational uses of coral reef areas can cause damage to coral reefs. Dropping anchors onto reefs can crush or break coral. When people grab, kick, w alk on, or collect coral, they also contribute to coral reef destruction. Marine-Based Pollution Petroleum products and other chemicals dumped near coastal waters by passing ships eventually find their way to reefs. Oil and gas leaked or spilled near a coral reef poison coral polyps and other marine life.
Overexploitation affects the vast majority of the world s reefs.
At a minimum, overfishing results in shifts in fish size, quantity, and species differentiation within reef communities. Removal of key herbivore and predator species may ultimately affec t large scale ecosystem changes. Overfished reefs and desperate fisherman produce a deadly combination when reefs are dynamited to harvest small fish. Cyanide, one of the most toxic poisons known, is being used to catch live fish in the South Pacific and Southeast Asia. The process itself wreaks havoc on coral heads.