Marine life is in serious trouble if ocean oxygen levels continue to plummet. A new report by the International Union for Conservation of Nature (IUCN) reveals that ocean oxygen levels have decreased by about 2 percent since the middle of the 20th century, and continued deoxygenation will put wildlife and human survival in danger.

The report, which involved work from 67 scientists in 17 countries, was released Saturday at the COP25 UN Climate Change Conference in Madrid.

“Urgent global action to overcome and reverse the effects of ocean deoxygenation is needed,” said Minna Eps, director of the IUCN Global Marine and Polar Program. “Decisions taken at the ongoing climate conference will determine whether our ocean continues to sustain a rich variety of life, or whether habitable, oxygen-rich marine areas are increasingly, progressively and irrevocably lost.”

Related: IPCC landmark report warns about the state of the oceans, polar ice content and the climate crisis

Both the climate crisis and nutrient pollution cause ocean deoxygenation. Nutrient pollution includes nitrogen from fossil fuels and run-off from agriculture and sewage. This depletes oxygen by encouraging too much algae growth.

However, scientists have recently realized that rising ocean temperatures are also lowering ocean oxygen levels. Scientists say that these higher temperatures are probably responsible for about half of the oxygen loss in the ocean’s top 1,000 meters, which is the highest in biodiversity. While reversing nutrient pollution is relatively easy, reversing oxygen loss from climate change isn’t.

“To curb ocean oxygen loss alongside the other disastrous impacts of climate change, world leaders must commit to immediate and substantial emission cuts,” Dr. Grethel Aguilar, acting director general of IUCN, said in a tweet.

Larger fish that require more energy, such as tuna, sharks and marlins, are especially threatened by dropping ocean oxygen levels. Changing oxygen levels have already pushed them closer to the surface, where they face greater risk of overfishing. Recent massive fish die-offs may also be caused by oxygen loss. Scientists predict that lowered ocean oxygen may have far-reaching effects, such as changing the Earth’s phosphorus and nitrogen cycles on land.

+ IUCN

Via EcoWatch

Image via Jeremy Bishop