Unless Climate Change Is Curbed, Mass Extinction In Oceans Is Likely

Life in Earth’s oceans could face a mass extinction – a loss in biodiversity that could rival the planet’s past great extinctions – if climate change continues unabated, according to a new study.

The release of vast amounts of anthropogenic greenhouse gasses into the atmosphere is fundamentally changing Earth’s climate system, threatening many species with an increased risk of extinction. However, climate’s impact on global biodiversity is challenging to observe, particularly for the planet’s enormous marine menagerie.

In addition to direct human impacts, including habitat destruction, overfishing, and coastal pollution, marine species are increasingly threatened by climate-driven ocean warming and oxygen depletion. While previous mass extinction events due to global environmental changes are illustrated by the fossil record, the future of ocean life as we know it under runaway climate change remains uncertain.

Using extensive ecophysiological modeling, which weighed a species’ physiological limits with projected marine temperature and oxygen conditions, Justin Penn and Curtis Deutsch evaluated the extinction risk for marine species across climate warming scenarios.

The authors found that under “business as usual” global temperature increases, marine ecosystems planet-wide are likely to experience mass extinctions potentially rivaling the size and severity of the end-Permian extinction – the “Great Dying” – which occurred roughly 250 million years ago and led to the demise of more than two-thirds of marine animals.

Penn and Deutsch’s modeling revealed patterns in future extinction risk. While tropical oceans are expected to lose the most species under climate change, many will likely migrate to higher latitudes and more favorable conditions to survive. However, polar species are likely to go globally extinct, as their habitats will disappear from the planet entirely.

“Climate change is, in effect, walking species off the ends of the Earth,” write Malin Pinsky and Alexa Fredston in a related Perspective. However, the study also suggests, that reducing or reversing greenhouse gas emissions could reduce extinction risks by as much as 70%.

“With a coordinated approach that tackles multiple threats, ocean life as we know it has the best chance of surviving this century and beyond,” Pinsky and Fredston write.