It is already known that global warming poses a threat to marine animals. An international team led by Canadian researcher Daniel Boyce has now supported this assessment with the help of a new global climate risk index.
Accordingly, if the worst-case scenario of the Intergovernmental Panel on Climate Change (SSP5-8.5) occurs by the end of 2100, there is a high risk for around 87 percent of the almost 25,000 marine species under consideration that they will not be able to survive in their current habitat. More than half of the species would then be endangered on nine percent of the sea surface, especially in coastal regions with high biodiversity such as the Caribbean or Indonesia. There is a risk of marine ecosystems collapsing.
The model study, now published in “Nature Climate Change”, provides a forecast for animals, plants, chromists, protozoa and bacteria that live in the upper 100 meters of the oceans. The analysis is limited to the change in temperature. According to the researchers’ findings, larger predatory species – especially those that are fished for food such as puffer fish, tuna and sharks, as well as tropical species – are most threatened.
The study also enables a regional differentiation of the risk, according to which countries of the Global South that are heavily dependent on fisheries and tropical coastal ecosystems are more severely affected. Heavy pollution is mentioned as another risk factor. The risk is estimated to be lower for polar regions.
First high-resolution estimate
However, the hydrobiologist Christian Möllmann from the University of Hamburg, who was not involved in the study, pointed out that the endangerment of the species should not necessarily be interpreted as extinction. The endangerment also includes negative influences on population size, reproduction and growth, he told the Science Media Center (SMC).
According to Möllmann, the fact that carbon emissions endanger marine animals is nothing new.
The junior research group leader Sebastian Heel from the Leibniz Center for Tropical Marine Research (ZMT) Bremen also points to the potential of individual species for migration. Tropical marine animals in particular could therefore move to other regions. “The actual risk for individual species can therefore be lower than calculated in the study,” said Heels the SMC. The study also shows no correlation between extinction risk and climate risk.
Nevertheless, the biologist classifies the results of the study as alarming: the extremely negative IPCC scenario should be treated with caution. “But the fact that even under the most optimistic scenario, over half of all species across their current range are still critically endangered by the end of the century is dramatic.”
The most important basic statements of the study would also apply regardless of the scenario chosen, such as the threat to tropical coastal ecosystems and that the benefit of emission reductions in poor countries dependent on fisheries is greater than in Europe, for example.
Deep-sea species not recorded
The zoologist Angelika Brandt from the Senckenberg Research Institute and Natural History Museum, Frankfurt/Main, complained to the SMC that the study only refers to the upper 100 meters of the oceans. Because the greater part of the habitable ocean space is the deep sea. Nevertheless, the results would reflect known patterns “that decision-makers do not seem to understand or want to understand”. In this respect, the calculation of the risk alone for the upper layer of the sea is an important approach.
The authors of the study suggest using their results to prioritize the protection of endangered marine species and ecosystems within the framework of climate-oriented strategies, for example through the repeatedly demanded goal of placing 30 percent of the sea surface under protection. However, the importance of geographic differences and the location of habitats should be taken into account.
However, zoologist Brandt reminds us that only the upper sea region is considered in the analysis. “Marine protected areas, however, are regions that contain the entire water column.” In addition, the metric used by the authors for the risk of extinction is based exclusively on Red List status. “That is weak and biased, since marine invertebrate species are systematically underrepresented in the Red List and, above all, more than 90 percent of deep-sea species are not yet known and described,” says Brandt.