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Coral Reefs: A potential climate change disaster?

 A study by Langdon et al. (2000) predicts that due to global warming, the world’s coral reefs could be reduced by as much as 40% by the year 2065. The corals secrete calcium carbonate to build the skeletons that form reefs. The reefs themselves are home to an extremely diverse ecosystem, and serve as natural breakwaters, which help to prevent beaches from eroding.

Research shows that coral growth is proportionate to carbonate concentration. As CO₂ levels increase in the atmosphere, the calcium carbonate saturation state of the ocean is reduced. This saturation state is the primary environmental factor that influences the calcification of corals, and the study indicates that the corals are unable to acclimatise to the changing saturation state of the ocean.

Anthropogenic global warming has also caused an increase in tropical sea surface temperatures, and this is thought to stimulate coral bleaching. Which is where the coral loses its symbiotic algae, causing mortality. In 1998 coral reefs around the world suffered the most extensive and severe bleaching on record, creating a high level of coral mortality (Reaser, Pomerance and Thomas, 2000). This combined with more localised anthropogenic factors could devastate the world’s coral reefs. Even protected areas, and reefs run for sustainable use are affected by global climate change, and their existence threatened. These two factors, which adversely affect coral reefs, suggest that the effect of climate change on coral reefs may be much greater than at the levels previously predicted.

Footnote on sea level rises:

July 2005: NASA (USA) have announced recent more accurate estimates of sea level rise as follows:-

“Although sea levels have been monitored since the early 20th century, it wasn't known how many changes were related to land movement. Now satellites can provide such information.

In the last 50 years, sea level has risen at an estimated rate of .07 inches (.18 centimeters) per year, but in the last 12 years that rate appears to be .12 inches (3 centimeters) per year, said Associate Professor Steve Nerem at the Colorado Center for Astrodynamics Research.

The most likely factor for sea level rise is changes in the Earth's ice cover. NASA said three-fourths of the planet's freshwater is stored in glaciers and ice sheets -- or about 220 feet (67 meters) of sea level.”