Coral Reefs And Climate Change

Coral reefs are very sensitive to slight changes in water temperature and light intensity levels making them the best barometers of global warming. And life is heating up on coral reefs!

Currently reef-building corals are living close to their upper thermal limit and become stressed by higher than normal light intensities that cause coral bleaching. Elevated ocean temperatures of as little as 2.7 degrees F. (1.5 degrees C) over the average summer temperature destroy the symbiotic algae resident in corals. This causes the coral animal to become transparent, revealing the white limestone coral skeleton beneath, hence the term "coral bleaching." This causes corals to die in great numbers if conditions do not return to normal. The worst coral bleaching event on record occurred in 1998, which saw the complete loss of live coral from some reefs around the world. This is best explained as a result of global climate warming, according to many experts.

According to our records, the worst bleaching event in the Keys occurred in 1997. Images from Craig Quirolo's Photomonitoring Survey can be found on the website in the section entitled Coral Stress and Disease. Recently published scientific information on the subject is available on our web-site in the Science Section (

The recent paper released by Greenpeace entitled Climate Change, Coral Bleaching and the Future of the World's Coral Reefs by Ove Hoegh-Guldberg, Associate Professor, School of Biological Sciences, University of Sydney concluded that:

1. Coral bleaching is due to warmer than normal temperatures causing zooxanthellae to become supersensitive to light;

2. Increased sea temperature is the primary reason for why coral bleaching has occurred with increasing intensity and frequency over the past two decades.

3. Mass coral bleaching began to occur in 1980 due to the steady rise in sea temperatures that have pushed reef-building corals closer to their thermal maxima. El Nino events (warmer than normal years) push corals above their maxima and cause bleaching to occur.

4. Corals do not appear to be showing any signs that they are able to acclimate or adapt fast enough to keep pace with these changes in sea temperature.

5. Coral bleaching events are projected to steadily increase in frequency and intensity until they occur every year by 2030-2070 if greenhouse gases emissions continue to rise unabated.

6. Some regions, (e.g. Caribbean Sea and Southeast Asia) are expected to experience the effects of climate change on their reefs sooner than other areas (e.g. Central Pacific).

This is very alarming for those of us who live around and care for coral reefs. The direct links between coral reefs and climate change have been the subject of another document from the World Wildlife Fund Climate Change Campaign. America's Global Warming Solutions (Bernow et al 1999) reports that if the United States were to reduce its annual carbon dioxide emissions by about 654 metric tons of carbon by 2010, the result would be a net economic savings, almost 900,000 net additional jobs and significant decreases in pollutant emissions that damage the environment and are harmful to human health, especially of children and elderly. See

Even tourism affects the climate, especially air travel, the fastest growing source of greenhouse gas emissions according to Tourism: facing the challenge of climate change, compiled by World Wildlife Fund from a report by David Viner and Maureen Agnew of the Climatic Research Unit, University of East Anglia, Norwich, U.K. Numbers are forecast to leap from 594 million international travelers in 1996 to 702 million by next year, 1018 million by 2010 and 1600 million in 2020.
We should be making our best efforts to stop polluting our atmosphere. This is a huge project, both on a large-scale through governments and international companies and on a small-scale through our own personal efforts. Beginning on a personal level, we can all do our part by reducing our use of fossil fuels (that means getting out the bicycle or walking instead of driving or car-pooling or using public transportation, if available; by recycling; and by cutting down on our use of plastics.

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