Coral reefs provide habitat for more than a quarter of the world's marine life. A half-billion people also depend on these reefs for their survival. The reefs attract fish and tourists, both valuable commodities. But the future looks bleak for coral reefs. In fact, it's estimated that more than half of all coral reefs will be killed within the next few decades unless drastic measures are soon undertaken.
Fishermen pose one of the most obvious threat to coral reefs. That's because some fishermen resort to drastic measures when a reef becomes overfished. In order to maintain their hauls, these fishermen will use explosives to kill the smaller fish that are difficult to catch with more traditional methods. The coral reefs, of course, are blown apart in the process.
Other fishermen use poisons like cyanide to stun fish, which makes them easier to capture. The poison also harms the coral polyps, which are the pinhead-sized invertebrates that build the coral reefs. According to statistics from the Coral Reef Alliance, some 400,000 pounds of cyanide are sprayed and dumped onto the reefs surrounding just the Philippines each year.
Pollution is another obvious culprit. Untreated sewage, petroleum products, and trash all harm coral reefs. Likewise, the run-off from land-based construction and agriculture can have an adverse impact. If dirt, silt, or sand cloud the water near a reef, the coral there is essentially smothered due to a lack of adequate sunlight.
The greatest threat by far, though, is the one posed by global warming. When ocean temperatures reach a certain point, coral polyps die. The process is known as coral bleaching. As the water in which coral lives heats up, the coral starts to expel the microscopic plants inside it that color it. And without these plants, the coral can't survive.
Widespread bleaching occurred two years ago when ocean temperatures rose by several degrees as a result of El Niño weather patterns. The damage to coral reefs was extensive. Some islands in the Indian Ocean subsequently lost as much as 90 percent of their coral. Even worse, with the global-warming trend expected to continue, such losses may soon become the norm worldwide.