Climate change is destroying corals in equatorial oceans

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Now and then – composition of a fossil coral reef from the Pleistocene Interglacial 125,000 years ago (above) and a living coral reef off Saudi Arabia (below). Images: FAU (fossil reef), Khaled bin Sultan Living Oceans Foundation (living reef) (composition: FAU)

Now and then – composition of a fossil coral reef from the Pleistocene Interglacial 125,000 years ago (above) and a living coral reef off Saudi Arabia (below). Images: FAU (fossil reef), Khaled bin Sultan Living Oceans Foundation (living reef) (composition: FAU)

And threatening the livelihoods of millions of people

As it gets warmer, corals move to the north and south of the equator and return in cooler temperatures. Corals retreat from their usual environments to cooler regions when water temperatures rise as a result of global warming.  This has an adverse effect on the fish population as well as on coastlines which lose their natural protection from erosion and storm damage. Millions of people will lose a vital source of livelihoods as corals decline. This conclusion was reached by an international group of researchers led by Prof. Dr. Wolfgang Kießling, Chair of Palaeoenvironmental Studies at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU). Their findings were published in the American journal ‘Proceedings of the National Academy of Sciences’ (PNAS).

The researchers investigated coral fossils from the Pleistocene around 125,000 years ago. During this time, a rapid climate change caused the global temperature to rise by 0.7 °C. This led to a massive decline in the coral species found in the waters around the equator. Only around half of the coral species found in neighbouring regions at the north or south of the equator were found directly at the equator, as the corals had moved to cooler climes, where diversity increased as a result. The greatest diversity of coral species in the interglacial period was found at the North Hemisphere. The researchers compared the migration of the coral habitat to a wave movement: corals migrate to or move away from the poles depending on whether temperatures rise or fall, taking fish and other marine life with them.

This trend  seems to be occurring again. ‘We are observing coral death close to the equator which has a number of causes including overfishing (especially using dynamite or cyanide), water pollution, construction and temperature increase,’ says FAU Researcher, Professor Kießling. ‘At the same time, the number and diversity of coral reefs are increasing in regions to the north and south of the equator.’  Researchers are particularly concerned that the temperature of the earth’s climate has increased 0.7 °C since the beginning of industrialisation which is identical to the increase in the Pleistocene period. However, fewer coral species have disappeared from the equator than during this period – currently the number of coral species is around 10 percent less than in neighbouring regions. This suggests that the greatest changes are yet to come. Forecasts also predict that a further temperature increase can be expected which will cause mass coral migration.  This is a considerable threat to the livelihoods of people living in countries surrounding the equator as fish and other marine life stay away from the region and coastlines are completely exposed to wind and waves. The researchers therefore believe that it is imperative to take this aspect into account when preparing people in the affected regions for the future.

The article ‘Equatorial decline of reef corals during the last Pleistocene interglacial’ by Wolfgang Kießling, Carl Simpson, Brian Beck, Heike Mewis and John M. Pandolfi was published in the PNAS journal (doi:10.1073/pnas.1214037110).

Further information:

Prof. Dr. Wolfgang Kießling
Phone: +49 (0)9131 85 26959