Warmer water devastates Great Barrier Reef's seabirds

Is the article below a sign of growing realism? The scientists quoted attribute warming to changes in sea currents, not anything in the atmosphere. And they talk of climate "fluctuations" rather than warming. But you would not know that if you just read the headline and the first sentence. Even the Australian media are faithful to the one true religion


GLOBAL warming has been blamed for dramatic declines in seabird populations on the Great Barrier Reef and surrounding waters. Tens of thousands of seabirds are failing to breed because warmer water from more frequent and intense El Nino events means there is insufficient food to raise their young, according to research compiled by the Great Barrier Reef Marine Park Authority. Warm water near the surface forces fish, plankton and other prey into deeper water, where it cannot be reached by seabirds.



The research forms the basis of a report commissioned by the marine park authority and the Queensland Environment Protection Agency to address the impact of climate change on seabirds, and obtained by The Australian under freedom of information laws. "Recent analyses at key sites have revealed significant declines in populations of some of the most common seabird species, which raises concerns regarding the threatening processes acting on these populations," says the report, prepared by C&R Consulting.

The report, Seabirds and Shorebirds in the Great Barrier Reef World Heritage Area in a Changing Climate, says the reef is home to between 1.3 and 1.7million seabirds and half the world's population of several species. The results of research by Bradley Congdon and five other seabird experts working for the marine park authority have been published in another report, Climate Change and the Great Barrier Reef: A Vulnerability Assessment. The authors concluded that recent climate fluctuations were having significant detrimental impacts on seabird populations.

The two reports paint a grim picture of the predicament for seabirds. In the Coral Sea, populations of great and least frigatebirds declined by 6-7 per cent annually between 1992 and 2004. Despite a return to more favourable conditions since the severe El Nino event of 1997-98, populations have not recovered. On Raine Island, in the northern barrier reef, populations of at least 10 of the 14 breeding seabird species have been falling. Numbers of common noddies have fallen by 96 per cent, sooty terns by 84 per cent, bridled terns by 69 per cent, and red-footed boobies by 68 per cent.

The park authority's vulnerability assessment report says there is no evidence of significant human interference or habitat loss on Raine Island, indicating "depletion of marine food stocks linked to changing climate" as the cause. On the Swain Reefs, in the southern reef, the number of brown booby nests has dropped from 350 in 1975 to less than 30 since 2000. "The declining trend was consistent throughout the region and was not simply a consequence of inter-seasonal migration between islands," the report says.

On Heron Island, the black noddy population had been rising since early last century, but the number of active nests fell from about 70,000 to 30,000 between 1996 and 2000, with mass mortality of adults and chicks in the El Nino year of 1998.

In 2002, another year of abnormally high sea surface temperatures, almost none of the huge numbers of wedge-tailed shearwaters that normally nest annually on Heron Island succeeded in raising young. Off Heron in 2003, a 1C increase in sea surface temperature reduced feeding frequency by shearwaters from one night in two to one night in five. In 2006, a similar rise in water temperature resulted in the number of daily meals fed to the chicks of black noddies falling from three to one-half.

Negative impacts on seabird populations were recorded in all parts of the barrier reef, in virtually all species, and in nearly all components of reproductive biology. Timing of breeding, year-to-year recruitment, number of breeding pairs, annual hatching, chick growth and adult survival were all affected.

Source

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