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REF NO.: 77

SUBJECT: Coral reefs losing ability to keep pace with rise in sea levels

DATE: June 21

Many coral reefs will be unable to keep growing fast enough to keep up with rising sea levels, leaving tropical coastlines and low-lying islands exposed to increased erosion and flooding risk, new research suggests.

An international team, including Memorial University’s Dr. Evan Edinger, a professor of geography, biology and earth sciences, compared the maximum upward growth rates of coral reefs in the Caribbean and Indian Ocean regions with predicted rates of sea-level rise and found many will be unable to keep pace.

Amount and types of coral

The growth of coral reefs is strongly influenced by the amount and types of coral living on the reef surface.

This growth is now being hampered by combinations of coral disease, deteriorating water quality and fishing pressure, along with severe impacts from coral bleaching caused by global warming.

Coral bleaching can occur when water is too warm. Corals expel the algae living in their tissues, causing them to turn white. After bleaching, some corals survive and some die.

“Two decades ago, when some reef scientists raised the question of sea-level rise as a threat to coral reefs, we reef geologists pointed to the rates of reef growth when sea level was coming back up after the last ice age, when most, but not all, reefs did just fine with rapid rates of sea level,” said Dr. Edinger.

“But now so many modern reefs in the Caribbean and Indian Oceans have such low coverage of live coral that they just can't make limestone fast enough to keep pace with rates of reef erosion and anthropogenically increased rates of sea-level rise.” 

Coral stressors

Dr. Edinger helped to design the protocol used for measuring how fast the reefs can produce limestone and helped collect and analyze the data from the Caribbean sites.

Coral cover — the proportion of reef surface covered by live stony coral — is a strong predictor of the extent to which rates of sea-level rise will exceed reef growth, and thus how much additional submergence will occur.

“We know the principle drivers of coral mortality — bleaching, diseases, eutrophication from pollution on the land and overfishing,” said Dr. Edinger. “Doing something about each of those stressors is the hard part. It’s hard, but our study is another reminder that there is no time to lose.”

The paper, published in the June 21 issue of Nature, is titled Loss of Coral Reef Growth Capacity to Track Sea-level Rise Under Climate Change.

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For further information, please contact Kelly Foss, communications advisor, Faculty of Science, at (709) 864-2019, (709) 699-3788, or kfoss@mun.ca.

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