Tuesday, September 13, 2011

Coral reefs signal mass extinction

Coral reefs 'will be gone by end of the century'
They will be the first entire ecosystem to be destroyed by human activity, says top UN scientist

The Independent: Professor Peter Sale studied the Great Barrier Reef for 20 years at the University of Sydney. He currently leads a team at the United Nations University for Water, Environment and Health.

The predicted decline is mainly down to climate change and ocean acidification. [Sale's] book, Our Dying Planet... contains further alarming predictions, such as the prospect that 'we risk having no reefs that resemble those of today in as little as 30 or 40 more years...'

Coral reefs... contain a quarter of all marine species, despite covering only 0.1 per cent of the world's oceans by area, and are more diverse than the rainforests... About 180 million people live within 100km of a reef, of which some 275 million are likely to depend on the reef ecosystems for nutrition or livelihood. Fringing reefs can also help to protect low-lying islands and coastal regions from extreme weather, absorbing waves before they reach vulnerable populations.

Carbon emissions generated by human activity, especially our heavy use of fossil fuels, are the biggest cause of the anticipated rapid decline... Climate change increases ocean surface temperatures... and leads to coral bleaching, where the photosynthesising algae on which the reef-building creatures depend for energy disappear. Deprived of these for even a few weeks, the corals die. On top of this comes ocean acidification. Roughly one-third of the extra carbon dioxide we put into the atmosphere is absorbed through the ocean surface... The imbalance created makes it harder for reef organisms to retrieve the minerals needed to build their carbonaceous skeletons...

If past mass extinctions are anything to go by... reef disappearance has tended to precede wider mass extinction events... 'The losses of species that are occurring now are in every way equivalent to the mass extinctions of the past,' Professor Sale says... About 20 per cent of global coral reefs have already been lost in the past few decades... 'If we can keep CO2 concentrations below 450 parts per million we could be able to save something resembling coral reefs.'... The current atmospheric carbon dioxide concentration is about 390 parts per million, but few experts believe it will remain below 500 for long.
Image: Australia's Great Barrier Reef is the planet's largest reef system and one of the seven natural wonders of the world, but it may not survive the century. Source here.