The Great Barrier Reef's chances of survival from even moderate climate change are poor and ''catastrophic damage'' may not be avoided, a new report has warned. The Reef Outlook Report concludes that the rate of climate change backed by the Australian Government would result in ''severe mass coral bleaching'' and threaten the habitats of key species on the reef. In a series of dire predictions for the World Heritage-listed natural wonder, the Great Barrier Reef Marine Park Authority's report finds that carbon dioxide in the atmosphere will have to be kept under 400 parts per million (ppm) if important animal species and coral are to have a low to medium vulnerability to climate change. The current level of carbon dioxide in the atmosphere is 387 ppm. The report finds that if carbon dioxide reaches 450 ppm in the atmosphere, which is currently predicted for 2035, it would result in ''severe mass bleaching'' and destroy the reef's ability to grow new coral. Eminent marine researcher and former chief scientist of the Australian Institute of Marine Science Charlie Veron, who helped prepare the report, said the Rudd Government-backed 450 ppm target would result in the complete death of the reef by 2050. ''Mr Rudd would not be supporting the 450 target if he knew the facts,'' Mr Veron said. ''This isn't a theory � all the science is incredibly concrete now and it is backed by everybody in the coral research field.'' Environment Minister Peter Garrett said the report found that the Barrier Reef continued to be one of the world's healthiest coral systems, but that the emerging threat from climate change required effective action on global warming. ''The world's only got one Great Barrier Reef, Australia has only got one Great Barrier Reef. It is our most important natural environmental asset,'' Mr Garrett said.