Once again, the consequences of climate change are becoming apparent. Especially in Australia. Last summer, fires made the headlines. Now it is the corals that are suffering from the heat. The famous Great Barrier Reef is shrinking massively as the results of a new study show.
The Great Barrier Reef is well known. Although the coral reef is on the other side of the world, we all know it. Some have visited it themselves, while others know what it looks like because the collection of coral reefs is a UNESCO World Heritage Site. The Great Barrier Reef is almost a symbol of the Australian continent. Now it is in great danger. After rising temperatures fuelled fires in Australian forests, extreme temperatures are also taking their toll on the Great Barrier Reef.
The Great Barrier Reef is dwindling
Large aggregations of coral will soon no longer be a given. The existence of coral reefs is threatened worldwide. Thus, the largest contiguous collection of coral reefs on our planet off the east coast of Australia is also in danger. The so-called Great Barrier Reef is currently making sad headlines. This large, 2 000 kilometre-long cluster of over 2 900 individual coral reefs is dwindling. It was the largest contiguous collection of coral reefs in the world. In the past 25 years, the Great Barrier Reef has lost about half of its coral. According to a new study, it is irrevocably in danger.
Corals are sedentary, colony-forming cnidarians. There are numerous species. They all occur exclusively in the sea, especially in the waters of the tropical belt. Depending on their growth form, they differ between soft and hard corals. The latter form skeletons through deposits of lime. As this dead material is constantly overgrown by living tissue, coral reefs slowly develop. It takes a long time for them to reach a size of over 2 000 kilometers. This also explains the special nature of the Great Barrier Reef. It is considered a natural wonder of superlatives. As early as 1981, UNESCO declared it a World Heritage Site. In addition, the Great Barrier Reef belongs to the seven wonders of the natural world.
Now Australian researchers have discovered that the number of small, medium and large corals is drastically decreasing. Between 1996 and 2017, more than half of all corals disappeared. And this does not only affect the cnidarians on the ocean surface. The population is also dwindling in deeper waters. The heat records of 2016 and 2017 caused particularly severe damage to the Great Barrier Reef. The high temperatures of these years have fuelled the so-called coral bleaching.
Coral bleaching in the Great Barrier Reef
Coral bleaching means that the corals initially repel the unicellular algae with which they live in symbiosis. By shedding the algae, corals then lose their colour – but that is not all. If this situation continues for a long time, the corals die completely. The smaller corals in particular suffer from this phenomenon. They are less resistant. Until now, Australian researchers thought that the Great Barrier Reef was protected by its size alone. Now, however, the latest findings show that even this relatively well-protected coral reef is increasingly impaired. Experts warn of irreversible damage to this sensitive ecosystem. If global warming continues, the warming of the oceans will increase. And this is further damaging reefs like the Great Barrier Reef.
Beyond coral bleaching
It is not only the warming of the oceans that poses a threat to corals. Ocean acidification is also damaging the reefs. Since the oceans absorb part of our emissions, carbon dioxide accumulates in them. This in turn inhibits the formation of new calcareous shells. The discharge of faeces also seems to promote coral bleaching. Certain bacteria in the faeces are suspected to be the trigger. Microplastics also seem to harm reefs like the Great Barrier Reef. A laboratory study shows that some coral species are also damaged by microplastics. In addition, deep-sea fishing threatens corals. Drilling platforms for oil or gas production or underwater cables can also harm the cnidarians.
Conference in Bremen, Germany
It is undisputed that climate change is destroying coral reefs. Already, a third of the reefs have been lost. Another 40 per cent are massively threatened. Nevertheless, researchers are looking for ways to stop the death of these ecosystems. This summer, they are holding virtual discussions in Bremen. In northern Germany, there is a wealth of expertise and knowledge in marine research. This year, the University of Bremen is hosting the International Coral Reef Symposium. About 1 200 researchers from 80 nations will exchange ideas. They are looking for ways to stop the destruction of these valuable ecosystems. In the context of this conference, an important strategy paper is going to be published.
Entitled “Rebuilding Coral Reefs: A Decadal Grand Challenge”, it is addressed to decision-makers from politics, administration, business and civil society worldwide. The paper highlights the urgent need for action to protect and restore coral reefs. The strategy paper provides a summary of the most important and latest scientific and social findings. It thus provides the basis for discussions and negotiations on environmental and nature conservation, climate change and sustainable development at local and global level.
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