Rapid Reductions In Greenhouse Gas Emissions Are Critical For Avoiding A Major Mass Extinction Of Ocean Species

As humanity’s greenhouse gas emissions continue to warm the world’s oceans, marine biodiversity could be on track to plummet within the next few centuries to levels not seen since the extinction of the dinosaurs, according to a study published by Princeton University researchers.

The paper’s authors modeled future marine biodiversity under different projected climate scenarios. They found that if emissions are not curbed, the extinction rate for marine species could double by around 2100.

The researchers combined existing data on marine species with models of climate change to predict how changes in habitat conditions will affect the survival of sea animals around the globe over the next few centuries. They then compared their model to the magnitude of past mass extinctions captured in the fossil record, especially to the End-Permian Extinction – Earth’s deadliest extinction event so far. The fossil record shows that more than 250 million years ago volcanic gas emissions caused ocean temperatures to increase and oxygen availability to drop, leading to a mass extinction claiming more than 80 percent of Earth’s marine species.

Water temperature and oxygen availability are two key factors that will change as the climate warms due to human activity. Tropical waters would experience the greatest loss of biodiversity, while polar species are at the highest risk of extinction, the authors reported.

Marine animals have physiological mechanisms that allow them to cope with environmental changes, but only up to a point. The researchers found that polar species are more likely to go globally extinct if climate warming occurs because they will have no suitable habitats to move to. Tropical marine species will likely fare better because they have traits that allow them to cope with the warm, low-oxygen waters of the tropics. As waters north and south of the tropics warm, these species may be able to migrate to newly suitable habitats. The equatorial ocean, however, is already so warm and low in oxygen that further increases in temperature – and an accompanying decrease in oxygen – might make it locally uninhabitable for many species.

Together with overfishing and pollution, climate change could so become the leading factor in the extinction of marine species.

“Extreme warming would lead to climate-driven extinctions that, near the end of the century, will rival all current human stressors combined,” so the study’s key result according to first author Justin Penn, a postdoctoral research associate in the Department of Geosciences.

The study found, however, that reversing greenhouse gas emissions could reduce the risk of extinction by more than 70 percent.

“The silver lining is that the future isn’t written in stone,” says Penn. “The extinction magnitude that we found depends strongly on how much carbon-dioxide we emit moving forward. There’s still enough time to change the trajectory of carbon-dioxid emissions and prevent the magnitude of warming that would cause this mass extinction.”

The paper, “Avoiding ocean mass extinction from climate warming,” is published in the journal Science.


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