Sunday, July 15, 2012

Conservation Biology: Coral reefs in trouble

Sad realism  in a NY Times story on the future of coral reefs.

Consensus Statement on Climate Change and Coral Reefs from the recent International Coral Reef Symposium.

The international Coral Reef Science Community calls on all governments to ensure the future of coral reefs, through global action to reduce the emissions of carbon dioxide and other greenhouse gases, and via improved local protection of coral reefs. Coral reefs are important ecosystems of ecological, economic and cultural value yet they are in decline worldwide due to human activities. Land-based sources of pollution, sedimentation, overfishing and climate change are the major threats, and all of them are expected to increase in severity.

Changes already observed over the last century:

Approximately 25-30% of the world’s coral reefs are already severely degraded by local impacts from land and by over-harvesting.
The surface of the world’s oceans has warmed by 0.7°C, resulting in unprecedented coral bleaching and mortality events.
The acidity of the ocean’s surface has increased due to increased atmospheric CO2.
Sea-level has risen on average by 18cm.
By the end of this century:

CO2 emissions at the current rate will warm sea surface temperatures by at least 2-3°C, raise sea-level by as much as 1.7 meters, reduce ocean pH from 8.1 to less than 7.9, and increase storm frequency and/or intensity. This combined change in temperature and ocean chemistry has not occurred since the last reef crisis 55 million years ago.
Other stresses faced by corals and reefs:

Coral reef death also occurs because of a set of local problems including excess sedimentation, pollution, habitat destruction, and overfishing.
These problems reduce coral growth and vitality, making it more difficult for corals to survive climate changes.
Future impacts on coral reefs:

Most corals will face water temperatures above their current tolerance.
Most reefs will experience higher acidification, impairing calcification of corals and reef growth.
Rising sea levels will be accompanied by disruption of human communities, increased sedimentation impacts and increased levels of wave damage.
Together, this combination of climate-related stressors represents an unprecedented challenge for the future of coral reefs and to the services they provide to people.
Across the globe, these problems cause a loss of reef resources of enormous economic and cultural value. A concerted effort to preserve reefs for the future demands action at global levels, but also will benefit hugely from continued local protection.

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