The World Heritage-listed Great Barrier Reef has had two episodes of mass coral bleaching in the past 10 years, and faces numerous other threats, the report says.
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SYDNEY: Australia's Great Barrier Reef (GBR) is in serious jeopardy as global warming and chemical runoff threaten to kill marine species and cause serious outbreaks of disease, a new report warns.
Another study found that reefs around the world are worth hundreds of billions of dollars to the world economy - and that this income is threatened by climate change.
The World Heritage-listed Australian reef was already showing the impacts of climate change, with two episodes of mass coral bleaching in the past 10 years, the GBR Marine Park Authority's inaugural reef outlook report said.
Disease and pests
"While populations of almost all marine species are intact and there are no records of extinctions, some ecologically important species, such as dugongs, marine turtles, seabirds, black teatfish and some sharks, have declined significantly," the authors wrote.
Coral disease, outbreaks of toxic blue-green algae and infestation by pest species such as the crown-of-thorns starfish appeared to be becoming more frequent and more serious, it added.
The 345,000-square-kilometre reef had deteriorated significantly since European settlement in 1788 and was at a "crossroads", the report warned. "Almost all the biodiversity of the Great Barrier Reef will be affected by climate change, with coral reef habitats the most vulnerable," the report said.
"Coral bleaching resulting from increasing sea temperature and lower rates of calcification in skeleton-building organisms such as corals because of ocean acidification, are the effects of most concern and are already evident."
Fertiliser runoff
Ocean acidification, caused by increasing levels of dissolved carbon dioxide, is a newly recognised and serious threat to the reef.
The runoff of nitrogen-based pesticides from local farming areas was a particular concern, the report said, adding that their impact remained "largely unknown".
Australian Environment Minister Peter Garrett said the report showed strong decisive action needed to be taken, and he pledged to halve agricultural runoff by 2013 and to reduce sediment loads by 20% by 2020.
"Improving the quality of water flowing into the reef is one of the most important things we can do to help the reef withstand the impacts of climate change," Garrett said.
