Tropical rainforests cover 3% of the Earth’s surface but contain 40-50% of all carbon stored in the biosphere on land. Despite this vital role, researchers have revealed that tropical forests are dying at an increased rate, with consequences for biodiversity, carbon storage, and global climate.

The study led by Evan Gora, a forest ecologist at the Cary Institute of Ecosystems, has uncovered that despite deforestation, drought, higher temperatures, and fires being the leading causes of death of forests, thunderstorms, which are becoming more frequent with climate change, are an underappreciated threat.

According to Goya, trees in tropical forests are dying at a higher rate than in the past, and the composition of forests is changing too.

“That could be problematic for the future of not just tropical forests, but for the planet,” he says.

The team reanalyzed data from previous studies on tropical forest carbon stocks and uncovered that storms were at least as good as drought and temperature in explaining the patterns of tree mortality and forest carbon storage.

This highlights that despite storms’ obvious danger to people, they have been overlooked and understudied as a potential threat to tree mortality.

The researchers estimate that storms are responsible for 230-60% of tree mortality in the past.

“That number must be increasing as storm activity increases by 5 to 25% each decade,” says Gora.

The discovery promises to have a drastic effect on the Earth’s climate system models, especially after the research team incorporated storm events into the largest plot-based study of forest biomass carbon dynamics to date. That study had previously concluded that when temperatures surpass a critical threshold, tropical forests rapidly lose carbon stocks—a process now understood to be further accelerated by storm disturbances.

“But when you add storms, that relationship goes away,” said Gora. “It shows that you have to include storms, or you might not get the answers right.”

Ian McGregor, a Cary Institute Forest ecologist in Gora’s lab and coauthor of the study, says given the team’s findings, “it’s clear we need a more thorough understanding of these storms to have more accurate climate models, and thus more effective policy.”

There are good reasons why scientists have overlooked storms until now. Temperature and water stress can be monitored with meteorological stations and readily connected to long-term forest plot data. It is much harder to detect storms and track their highly localized damage. Mortality caused by thunderstorms is not easily detected via satellite, and it’s not practical for researchers on foot to survey large forested areas frequently enough to pinpoint the damage caused by a specific storm.

You can read more about the findings here.