Consensus statement on climate change and coral reefs

This comes from the 12th International Coral Reef Symposium, meeting in Cairns this week. I think the statement is largely accurate, although it exaggerates threats to corals from local factors like fishing and pollution.  The second phrase of the final sentence (in bold) is demonstrably false; “A concerted effort to preserve reefs for the future demands action at global levels, but also will benefit hugely from continued local protection.” First, there is very little effective local protection for reefs.  So I don’t know what the statement means by “continued”.  Less the 1% of the world’s reefs are even in marine reserves – few of which are fully or even partially enforced. Second, although local protection could in theory mitigate local problems, it is pretty clear that only the reduction of greenhouse gas emissions can limit the impacts of global change. Learn more about coral reefs and climate change here.

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.

One Response to “Consensus statement on climate change and coral reefs”

  1. Dave Baker says:

    Hi John,

    Just thought I would mention that there are quite a few talks/posters here that report experimental and observational evidence of lowered coral bleaching thresholds associated with increased pollution from land-based sources, corroborating such observations from Wooldridge & Done (2009) and others. So, there may be some time that can be gained by managing localized pollution inputs. However, I agree with your central message.

    Hope all is well.

    –Dave

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