Climate change is threatening marine animals, and a study is now taking a closer look at species and regions. Things are not looking good in the tropics in particular, even if the two-degree target is reached.
Fish and seafood are essential for survival for around ten percent of the world’s population. Around 800 million people, mainly in developing countries, live from fishing, production, processing and sale. But climate change is threatening most of the animal species that live in the top 100 meters of the sea. Without ambitious climate policies, marine ecosystems could collapse, threatening the food security of poorer countries that depend on fisheries. That’s the bottom line of a new study by an international research team.
The risks of climate change for marine animals are generally known. However, the new study breaks down the threat to marine ecosystems more clearly by species and region than previous studies. The team, led by Canadian Daniel Boyce, developed a “Climate Risk Index” that indicates how much marine life in different regions would be affected by warming waters. Other factors that are also changing due to climate change, such as acidification or the loss of oxygen in the water, were not taken into account. The study has now been published in the journal “Nature Climate Change”.
Already today, warming is rapidly changing ecosystems. This can be seen, among other things, in the fact that the occurrence of marine life is changing. Species such as bluefin tuna, which are normally found around the Mediterranean, are now also appearing in the Arctic, while others are migrating from the tropics. “These—and many other—changes are set to intensify,” comment Boyce and his co-author Derektitsor. This will affect virtually all living things in the sea – “from bacteria to whales”. Another risk factor is pollution, especially in coastal regions.
Boyce’s team determined the climate risk for almost 25,000 marine species. They analyzed three factors. First, how exposed is an animal species to changes caused by climate change? Second, how sensitive is she to these changes? Third. How good is the species at adapting?
The scientists used the most optimistic and the most pessimistic forecast of the Intergovernmental Panel on Climate Change (IPCC) for global warming. It was found that even if the two-degree limit of the Paris Agreement is observed, around 55 percent of the species considered will be endangered in around half of their range on average by the year 2100. In the pessimistic scenario, it becomes even more dramatic. Then 87 percent of the species are endangered, in 85 percent of the respective area. The tropical coastal ecosystems are generally particularly affected, while the risk is lower for polar regions.
The experts emphasize the resulting danger for food security, because fished species are particularly endangered by climate change in developing countries that are heavily dependent on fisheries. They therefore emphasize how important it is to comply with the two-degree limit from this point of view as well. In addition, the results of the study could be used to identify regions where the establishment of marine protected areas would be most beneficial. At the international level, the goal of protecting 30 percent of the surface of the oceans is being discussed. The World Biodiversity Council will discuss this in December.
Reacting to the new study, other experts emphasized that the identified “endangered” species do not necessarily mean that they are extinct. The biologist Sebastian Ferse from the Leibniz Center for Tropical Marine Research (ZMT) in Bremen pointed out that tropical marine animals in particular could move to other, less warm regions. “The actual risk for individual species can therefore be lower than calculated in the study,” he said. Nevertheless, the results are alarming. “The fact that even under the most optimistic scenario, more than half of all species across their current range are still critically endangered by the end of the century is dramatic.”
The zoology professor Angelika Brandt from the Frankfurt Senckenberg Research Institute and Natural History Museum pointed out that the study is mainly about marine species that are interesting for fisheries, “not so much about marine biodiversity per se”. The largest part of the habitable space of the oceans is the deep sea, which is explicitly not considered in this study.
