In recent years, there have always been disturbing news: the acute threat of the huge and actually strictly protected barrier reef off the Australian east coast, for example, which is decimated by recurring marine heat waves and pollution. But the entire dynamics of coral death in the tropical and subtropical oceans are now visible for the first time through the most comprehensive inventory of the international scientific network Global Coral Reef Monitoring Network. The data set, evaluated by more than 300 marine scientists, takes into account the development of around 12,000 coral areas in 73 countries – a total of more than two million individual observations.
Joachim Müller-Jung Editor in the Feuilleton, responsible for the department “Nature and Science”. Follow I follow
The research network has been regularly monitoring the health of corals since 1978, but researchers have never observed such an acceleration as that since the last report “Status of Coral Reefs of the World” was published 13 years ago. Their conclusion: between 2009 and 2018 alone, an estimated 14 percent of tropical reef corals disappeared – approximately 11,700 square kilometers. This corresponds approximately to the coral area of Australia.
In the same period, the area with strong algae growth has increased by a fifth. No coincidence: where the colorful coral animals with their symbiotic algae can no longer survive, especially species-rich biotopes for fish, crustaceans and other living creatures disappear. While coral reefs cover only 0.2 percent of the world’s seabed, they host about a quarter of the diversity of marine organisms. Since they still live near the coast, they provide the food and livelihood for millions of people. According to estimates cited in the report, coral reefs provide “ecosystem services” to people each year with a market value of $2.7 trillion. The diving and tourism industry alone accounts for 36 billion dollars, while the estimated six million fishermen in the coral-rich waters on the coasts earn six billion dollars.
The most important cause are heat waves
The corals in South Asia and the Pacific, around the Arabian Peninsula, as well as the corals off the coast of Australia are particularly badly affected by the mass extinction. In some countries, destructive fishing with dynamite is still a reason for large-scale coral losses. However, the most important cause is now the irregularly recurring heat waves, which can lead to bleaching of the corals and ultimately to the death of the reefs. In 1998, an exceptionally hot year in the world, which was particularly marked in the tropics by the climate anomaly El Niño, eight percent of all reefs had died in one fell swoop. Especially the Indian Ocean, East Asia and the Caribbean were massively affected by this mass bleaching.