Great Barrier Reef under serious threat: report

The World Heritage-listed reef was already showing the impacts of climate change, with two episodes of mass coral bleaching in the past 10 years, the Marine Park Authority's inaugural reef outlook report said.

"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 authority wrote.

Coral disease, outbreaks of toxic blue-green algae and infestation by pestilent species such as the crown-of-thorns starfish appeared to be becoming more frequent and more serious, it added.

The 345,000-square-kilometre (133,000-square-mile) attraction 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."

The runoff of nitrogen-based pesticides from local farming areas was a particular concern, the report said, adding that their impact remained "largely unknown".

Environment Minister Peter Garrett said the report showed strong decisive action needed to be taken, and pledged to halve agricultural runoff by 2013 and to reduce sediment loads by 20 percent 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.

Australia's centre-left government has already pledged 52 million dollars (42 million US) to improve water quality on the reef.

It has also agreed to cut greenhouse gas emissions to 25 percent of 2000 levels by 2020 if world leaders sign up to an ambitious reduction goal in Copenhagen in December.

Without an agreement, Australia's target will remain unchanged at five percent.

(c) 2009 AFP