A “sixth mass extinction” could be imminent in the oceans.
If the average temperature on the earth's surface rises by more than four degrees by the year 2100, a study published in the journal Science calculates that a mass extinction would be the logical consequence.
University of Washington oceanographers have combined ecophysiological properties of marine life with different climate scenarios to predict their risk of extinction.
The results show how relevant climate policy will be in the coming years: If greenhouse gas emissions can be reduced in such a way that the temperature increase does not exceed two degrees Celsius, the risk of extinction in the sea will decrease by more than 70 percent.
Polar species are particularly threatened.
With rising temperatures and falling oxygen concentrations, they lack the opportunity to migrate to new areas.
In general, the risk of extinction is highest where species live close to ecophysiological limits, ecosystems are particularly productive or oxygen levels are already low, the researchers write.
The study only examined habitat loss due to climate change and the possibility of migration to new habitats.
Ocean acidification and declining primary production could exacerbate the problems.
The researchers did not even consider environmental changes that are not directly related to climate change, such as overfishing, pollutant inputs and invasive species.
The largest mass extinction to date, which is believed to have wiped out more than 90 percent of all marine species, occurred around 252 million years ago.
At that time, volcanic eruptions had caused rapid climate changes and falling oxygen concentrations.
According to the study, it is striking that the processes that led to habitat loss were very similar to those of the past.
Marine biodiversity is already more endangered than it has been in the past ten million years.