Twilight zone at risk from climate change

Life in the ocean’s “twilight zone” could decline dramatically due to climate change, new research suggests. The twilight zone (200m to 1,000m deep) gets very little light but is home to a wide variety of organisms and billions of tonnes of organic matter.

The new study warns that climate change could cause a 20-40% reduction in twilight zone life by the end of the century.

“Our findings suggest that significant changes may already be under way,” Dr. Crichton continued.

“Unless we rapidly reduce greenhouse gas emissions, this could lead to the disappearance or extinction of much twilight zone life within 150 years, with effects spanning millennia thereafter.

“Even a low-emissions future may have a significant impact, but that would be far less severe than medium- and high-emissions scenarios.

“Our study is a first step to finding out how vulnerable this ocean habitat may be to climate warming.”

The study’s three emissions scenarios are based on total carbon dioxide emissions after 2010. “Low” is 625 billion tonnes, “medium” is 2,500 billion tonnes, and “high” is 5,000 billion tonnes.

For context, the Global Carbon Budget (led by the University of Exeter) estimated total global carbon dioxide emissions of 40.6 billion tonnes in 2022 alone.

Emissions have been close to 40 billion tonnes every year from 2010-22, so most of the carbon dioxide (about 500 billion tonnes) for the study’s “low” scenario has already been emitted.

At the current rate, the “medium” scenario would be reached 50 years from now, and the “high” in just over a century.