Australia's marine life hit by climate change

Tropical fish head for cooler seas, underwater forests wiped out, says report by 80 scientists
Jonathan Pearlman Straits Times 24 Aug 12;

SYDNEY - Marine life is under a growing threat from climate change in the waters around Australia. Tropical fish have been heading south for the cooler seas around Tasmania and the ocean's tall underwater forests have been virtually wiped out.

The details come in a new report by 80 Australian scientists that says south-east Australia has become "a global warming hot spot" and the threat to coral reefs is growing.

Climate change has made the ocean more acidic and bleached corals, it says, and seaweeds, phytoplankton, zooplankton and fish have moved south. The migration has also been caused by warming waters and a strengthening of the currents off the east coast of Australia since the 1950s.

"There is now striking evidence of extensive southward movements of tropical species in south-east Australia, declines in abundance of many temperate species, and the first signs of the effect of ocean acidification on marine species with shells," said the report released last week.

The report, by a group of scientists led by Australia's Commonwealth Scientific and Industrial Research Organisation, provides a snapshot based on the leading scientific papers from the past three years.

It found sea surface temperatures had increased by 1 deg C over the last century. The east coast of Tasmania and parts of Western Australia had the highest rises.

"The rate of temperature rise in Australian waters has accelerated since the mid-20th century," the report said. "Sea levels are rising around Australia, with fastest rates currently in northern Australia."

Professor David Booth, a marine ecologist at the University of Technology, Sydney, said tropical fish have been moving towards Tasmania for 30 or 40 years but sped up in the past 10 years.

"In this case, the rapidity of the change is probably fairly unprecedented," he said, noting that it is putting fisheries at risk.

In a further worrying sign, sea forests around Tasmania, made up of giant kelp, have shrunk by 95 per cent and were officially listed as endangered by the federal government last week. The forests, which rise as high as 25m off the ocean seabed, provide a crucial habitat for a range of species, including the black lip abalone and southern rock lobster.

Environment Minister Tony Burke said: "Giant kelp forests are being progressively lost due to a warming of the sea surface temperature caused by climate change, invasive species and changing land use and coastal activities that contribute to increased sedimentation and run-off and biodiversity loss."

Along the Great Barrier Reef, damage has become so severe that scientists have proposed "last resort" measures such as protecting it with shade cloths.

A paper published this week in the journal Nature Climate Change said the pace of global warming is unparalleled in 300 million years. One of its authors, Professor Ove Hoegh-Guldberg from the University of Queensland, said the shade cloths anchored with ropes float on the water surface to protect the corals from sunlight.

"We are recommending looking at these technologies because at the current rate of warming, we may need to use them in 20 or 30 years," he told The Straits Times.

"We should test them now and see which ones work. Shading is not a strategy that can be used across hundreds of kilometres of the reef. But it might - at a local level - be able to influence how many corals die."

Scientists have been increasingly worried about the long-term threat of climate change and rising water temperatures to the Great Barrier Reef - an iconic stretch of about 2,600km of coral formations and marine life off Australia's east coast that attracts about two million visitors each year.

Prof Hoegh-Guldberg warned that the shade cloths may be useful for protecting small patches of coral but it will not "save the Great Barrier Reef" as a whole.

Background story

Climate change is...

Worsening ocean acidification
Increasing the thermal bleaching of coral reefs
Driving seaweeds, phytoplankton, zooplankton and fish southwards
Harming the sea forests around Tasmania
Reducing the population of sea snakes
Changing turtle breeding habits