We would expect that he official causeof deterioration of coral reefs would be announced as human in origin. But that is not the case. There is much difficulty in relating deterioration in coral reefs to sizable human populations, with their water polluting ways.
In one example, the coral reefs in highly populated areas would be expected to be subject to overfishing and pollution, but with changes in global climate and exposure to ultraviolet radiation, it has been difficult to determine what exactly it is that causes alarming coral damage in less populated Belize that rivals damage in highly populated Jamaica!
In Belize, a phenomenon called "coral bleaching" has been occuring. Belize is small and has a much smaller population than other Carribean countries. Several surmisals include, ultraviolet radiation, an increase in unusually violent storms, and trends toward higher ocean temperatures.
What is "coral bleaching". The algae that live within the coral reefs give the coral their color and food. When the algae die off, the coral die. The coral and the algae are highly sensitive to temperature change, and even one degree of increase can sicken or kill coral. The opposite is algae large scale cover, which happens when there is either too much warming or there are not enough fish around to keep the algae in check. The coral cannot get the sunlight that they need and they die.
With violent storms or runoff, or diversion of land to sea runoff, there can be increased sediment that chokes off the coral and the algae's ability to get sunlight and to conduct photosynthesis.
Apparently, the worst damage indicator of coral bleaching is caused by natural issues, ultraviolet exposure and the warming oceans. There is actually a trend toward agreement that global warming is the most powerful culprit. And there is some agreement that the trend over the next years is that increased ocean warming will continue.
There is also disease which attacks the weakened corals. In limited cases of bleaching, the corals are not quite dead and eventually recover over time. In the Philippines, over 70 percent of the reefs have died off.
Thus, nature contributes the majority of reasons for coral reef die offs or bleaching. But human pollution and contributions must be addressed, too.
In some gross situations, fishermen use dynamite or even cyanide and crowbars to get the coral out of the way and to get the fish. If there is agreement that human contributions to global warming have caused the oceans to warm and the protections against UV radiation to wear away, then general human pollution is affecting the reefs through climate change. The worst contributions of humans is in the gross destruction of the reefs and the ecosystems in order to get at the fish. As human populations increase, or as demand for fish increases, more desperate, illegal and destructive measures are taken to get them. The fish eat the algae, and the algae over grow and kill the photosynthesis that is needed for the coral to survive.
The good news is that, when humans find out that humans are the destructive force, we find ways to build new coral reefs, to educate the population about overfishing and destructive fishing, and we start campaigns to boycott buying fish that are obtained through destructive methods. There are great movements afoot to reduce our pollution that is affecting the atmosphere, mostly in the introduction of hydrocarbons.