Caribbean Corals May Die Out due to Global Warming

Global warming may help kill off Caribbean coral reefs, the World Conservation Union said after assessing the full extent of damage to the organisms caused by the temperatures of 2005, the warmest year on record.

Sea temperatures as much as 3 degrees Celsius (5.4 degrees Fahrenheit) above normal extended across vast areas of the Caribbean in 2005, killing off swathes of reef, including more than half of the corals in the US Virgin Islands, the union said on Thursday in a report on its website.

With temperatures forecast to rise further this century, and years like 2005 expected to become more common, reefs may be killed off altogether without human actions to reduce pollution, over-fishing and emissions of the greenhouse gases blamed for global warming, the union said.

Corals are an important marine ecosystem, providing shelter and food for animals including crabs and sponges. They also add about $4.6 billion to the Caribbean economy through tourism, fishing and coastal protection, according to the union, known by its old acronym, the IUCN.

Warmer temperatures help cause bleaching, when corals expel an algae that provide energy for their growth. While the organisms are usually symbiotic, excessive temperatures cause the algae to produce toxic compounds that it transfers to its coral host. The coral then ejects the algae, leaving the host more susceptible to death by starvation and disease.

From late June to October 2005, so-called hot-spots, with sea temperatures as much as 3 degrees Celsius above normal, extended across parts of the Caribbean, the union said.

About 51.5 percent of corals in the U.S. Virgin Islands died, as did up to 20 percent in Barbados, 11 to 30 percent in the French West Indies, and 38 percent at some sites in the Dominican Republic. In Trinidad and Tobago, 73 percent of two species died off.