Coral reefs normally thrive in seawater temperatures between 77 and 84 degrees Fahrenheit [25-29° C], depending on their location. But the narrow temperature range for healthy coral is very close to the lethal temperature. An increase of one or two degrees above the usual summer maximum can be deadly. While various causes can be identified for localized coral bleaching and its subsequent demise, many scientists suspect that a common worldwide cause may be global warming. Scientific American magazine reported on this conclusion: “The 1987 reports of coral bleaching coincided with escalating concern about global warming. It was not surprising, therefore, that some scientists and other observers reached the conclusion that coral reefs served as the canary in the coal mine—the first indication of an increase in global ocean temperatures. Although it appears that elevated local seawater temperatures caused bleaching, linking this effect to global warming cannot be conclusive at this time.”

U.S.News & World Report said: “Recent studies of the Caribbean have supported the hypothesis that abnormally warm oceans provoked the recent outbreaks.” Thomas J. Goreau, who heads the Global Coral Reef Alliance, pessimistically compared the plight of the reefs with the shrinking of the Amazon rain forest. “There will still be some rain forests left in fifty years,” he said, “but at the rate the coral reefs are going now, they won’t be around anywhere near that long.”

The severe bleaching indicates that the general warming during the 1980s may have had a drastic effect on the coral reefs and may foretell the future of the reefs if the greenhouse effect leads to even warmer temperatures. Sadly, global warming and environmental deterioration will almost certainly persist and become more acute, increasing the frequency of worldwide bleaching cycles.”