Barrier reef bleaching worsens

Coral bleaching caused by global warming could devastate swaths of Australia's Great Barrier Reef within 50 years, according to a report.

The study, commissioned by the Queensland government, found that bleaching could be an annual occurrence by 2050.

Coral bleaching happens when high water temperatures kill off the algae which live alongside coral polyps and give reefs their vibrant colours. At first the only serious damage is to the reef's appearance, but serious bleaching can destroy coral altogether.

Scientists classify the event as catastrophic if high temperatures occur for more than 100 days in a year. Such reefs do not regain their appearance for 10 years, and can take 50 years to recover their ecological diversity.

Annual bleaching catastrophes would be expected if sea temperatures were to go up 4.5C (8.1F) by 2050.

Queensland's premier, Peter Beattie, said: "Increasing global greenhouse production could lead to more extensive coral deaths ... and put at risk industries such as tourism."

Average year-round temperatures on the reef have risen by 0.5C since 1870.