UN Climate Change Conference sets the course for International Coral Reef Symposium in Bremen

On December 3, 2018, the UN Climate Change Conference began in Katowice, Poland. The results will also have a major impact on the future of tropical coral reefs. Global CO2 emissions pose a threat to the important ecosystem, says Professor Christian Wild in an interview with Meike Mossig at the University of Bremen. The scientist is organising the International Coral Reef Symposium in Bremen, planned for 2020. This is the first time it will be held in Europe.

© Harald Rehling/Universität Bremen

Mr. Wild, what dangers do our CO2 emissions pose for coral reefs?

The emission of CO2 and other greenhouse gases leads to warming and acidification in the ocean. Stony corals, which form reefs, react very sensitively to it. The warming often triggers the dreaded coral bleaching, while the acidification makes the formation of reef structures from lime by corals very difficult. The high level of CO2 emissions therefore poses two threats to tropical coral reefs. This could even lead to the loss of these ecosystems in the future. We are therefore keeping a very close eye on what is decided in Katowice. The 2018 UN Climate Change Conference sets the course for the 2020 International Coral Reef Symposium (ICRS) in Bremen.

At the UN Climate Change Conference in Paris in 2015, the goal was formulated of limiting global warming to 1.5 degrees Celsius. The task in Katowice is now to determine binding details on implementation. Let’s assume we don’t reach this value – what does that mean for the coral reefs?

Coral reefs will already have great problems if the sea warms up by 1.5 degrees Celsius, because many corals will then already start to bleach. Bleached corals then often die. Any increase in temperature beyond that will exacerbate the problem.

In the Jura Mountains, at the time of the dinosaurs about 150 million years ago, large parts of Europe were a shallow tropical sea with large, healthy coral reefs. At that time, the CO2 content of the atmosphere was about five times higher than today and the poles were ice-free due to the warm climate. Why does an average temperature a few degrees higher pose such a great threat today?

According to all we know, the climate changes in Earth’s history have taken place over very long periods of time – millions of years – which meant that corals had enough time to adapt to the new conditions. The climate change we are experiencing right now is happening at a rapid pace – within a few decades. It is therefore extremely unlikely that corals can adapt quickly enough.

Photo credits: Harald Rehling/Universität Bremen and ICRS 2020/Claudia Pogoreutz

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