Outside Cancún climate conference, Caribbean Sea testifies to global warming

This summer’s extreme heat may seem like a distant memory as winter approaches the United States.

But the summer that broke heat records across the Northern Hemisphere is still being felt below the surface of the Caribbean Sea: 2010 will likely be one of the most deadly years on record for coral reefs.

If diplomats attending the two-week global climate change talks that opened Monday in Cancún, Mexico, want more evidence of the negative and potentially devastating affects of warming temperatures, they need look no further than the blue sea outside their hotels. Researchers say that throughout the Caribbean coral reefs are “bleaching,” a condition that occurs when they are under extreme stress due to warmer-than-normal sea temperatures.

The last major bleaching, in 2005, resulted in the death of 40 percent of corals in parts of eastern Caribbean. When full results are in, this year is likely to be worse, scientists said.

“When we average out the net bleaching events and severity across the Caribbean basin, 2010 (and more than likely 2011) will go down in the record books as having the most severe bleaching and coral mortality in over 20 years,” says Rick MacPherson, conservation programs director of the Coral Reef Alliance (CORAL).

Coral feels heat

Under normal conditions, algae live symbiotically within the coral, giving it color and providing it with a source of food. But under stress, the coral expels the algae, leaving it whitened, or “bleached.” The longer the coral remains bleached, the more likely it is to die, according to marine biologists.

Following a hot summer – the fourth hottest on record for the US, according to the National Oceanic and Atmospheric Administration (NOAA) – nearly the entire Caribbean was at risk for bleaching. While some bleaching occurs every year, this year stands out.

“Temperatures are high in the Caribbean, and we expect this to continue. This season has the potential to be one of the worst bleaching seasons for some reefs,” Mark Eakin, coordinator of NOAA’s Coral Reef Watch, said in a statement in late September.

The phenomenon is not confined to the Caribbean. Coral reefs in Southeast Asia and in the Indian Ocean are experiencing their worst bleaching since 1998. Scientists expect similar results for the Great Barrier Reef off the coast of Australia.

Reefs worth $375 billion a year

The environmental and economic impacts are potentially enormous.

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