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The Digital Aquarium The Coral Reef — An Endangered Ecosystem Coral reefs are dynamic ecosystems , but they are also one of the most endangered on our planet . If the present rate of destruction continues , 70 percent of the world ' s coral reefs will be destroyed within our lifetime . Corals and coral reefs are very sensitive . Even the smallest change in the natural reef environment can have a disastrous effect . Coral reefs develop in shallow , warm , sunlit water , usually near land . They provide a rich habitat to many different kinds of marine life , such as fish , plants , algae * and other living creatures . This is why coral reefs have been called the " rainforests of the sea . " Although coral reefs cover less than one percent of the Earth's surface , over 25 percent of all the fish in the oceans live in and around coral reefs . Without the reef , they would die . Coral reefs have many important functions in the global ecosystem . First , the marine life removes and recycles carbon dioxide from the ocean . This process helps keep the balance of gases on our planet and reduces the threat of global warming . Second , coral reefs slow down the water before it reaches the shore . This helps protect coasts from strong currents and waves . Finally , many natural resources can be found in coral reefs . One tenth of the world's coral reefs has already been destroyed , and another third may be gone within the next 20 years unless we take action soon . Scientists believe that warmer ocean water may have disastrous effects on coral and coral reefs . Polluted water blocks the sunlight that the coral needs to survive . Blast fishing ( using explosives to kill the fish ) also damages the coral and the coral reefs . When divers and tourists touch or collect coral , they destroy coral reefs too . Coral reefs provide food for 30-40 million people each year . In addition , scientists believe that organisms living in the coral reefs may provide natural resources for medications . Most of the threats to coral reefs are the result of human actions . Marine biologists say that we must keep the coral and coral reefs healthy . They are an essential link in both local and global ecosystems . * algae — very simple . small plants living in or near water .

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