„UN Climate Change Conference sets the course for the International Coral Reef Symposium 2020 in Bremen“

The UN Climate Change Conference will be held in Poland until 14 December. Its results will also have a major impact on the future of tropical coral reefs, says Christian Wild. The scientist acts as conference chairman of the International Coral Reef Symposium in Bremen, planned for July 2020.

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 of the oceans. Stony corals, which form reefs, react very sensitively to these environmental impacts. Ocean warming often triggers the dreaded coral bleaching, while ocean acidification impedes the formation of reef structures from lime by the corals. High CO2 emissions therefore pose two different threats to tropical coral reefs, which may eventually lead to the loss of these important ecosystems in the near future. We are therefore observing very closely what will be decided in Katowice. The UN Climate Change Conference (COP24) sets the course for the International Coral Reef Symposium (ICRS) 2020 in Bremen.

At the 2015 Paris Climate Change Conference, the goal was formulated to limit global warming to 1.5 degrees Celsius. In Katowice, it is now a question of binding details on implementation. Assuming we do not reach this level. What could this mean for tropical coral reefs?

Coral reefs will already have major problems if the ocean is warmed by 1.5 degrees Celsius. Many coral species start to bleach already then and often they die as a direct consequence of the bleaching. Any increase in ocean temperature beyond that will only exacerbate the problem.

During the Jurassic geological age, at the time of the dinosaurs some 150 million years ago, large parts of Europe were a tropical shallow sea with large, healthy coral reefs. At that time, the CO2 concentration of the atmosphere was about five times higher than it is today, and the Earth’s poles were ice-free due to the warm climate. So, why do a few degrees higher in average temperature mean such a great threat today?

According to all we know, the past climate changes in Earth's history have taken place over very long time scales - millions of years. Therefore, corals had enough time to adapt to the new conditions. The climate change we are currently experiencing is taking place at a rapid pace - within a few decades. It is therefore extremely unlikely that corals will be able to adapt quickly enough.

More information:


Professor Christian Wild
Marine Ecology
Faculty of Biology/Chemistry
University of Bremen
Phone +49 421 218-63367
E-mail: christian.wildprotect me ?!uni-bremenprotect me ?!.de

Portrait of a man
Professor Christian Wild from the University of Bremen is an expert for tropical coral reefs.
White coralls with fishes in the ocean.
Coral bleaching in the Red Sea in November 2015.