SCIENCE: Climate Change Is Stifling Forests Across the Western US

Higher temperatures and drought are having a big effect on trees in the western U.S. and it's affecting their growth and their ability to absorb carbon from our atmosphere. The eastern U.S. is seeing a different story. Here's the new research.

(Photo: Western forests. Credit:  USDA Northwest Climate Hub)

Climate Change Is Stifling Forests Across the Western U.S.

The findings suggest forests may struggle to store carbon, an important bulwark against rising temperatures 

01/15/24 , Dave Levitan, The Messenger

Forests in the western United States are struggling in the face of rising temperatures and extended drought, a study published on Monday, Jan. 15, 2024 finds. The results are bad news for trees and for us — the forests act as a carbon sink, but the trees may be losing their ability to store greenhouse gases.

It's a paradox that more carbon dioxide in the atmosphere can, in some cases, juice plant and tree growth, but the negative effects of the climate change that comes with more greenhouse gases outweigh the benefits of extra plant fuel.

The researchers, led by Aaron Hogan of the University of Florida, used data from the U.S. Forest Service to examine trends in forest health between 1999 and 2020. In total, they analyzed more than 113,000 measurements across the country's forests.

They found that in the eastern part of the country, where warming has been relatively mild and precipitation has increased, forests have shown slightly accelerated growth over the past two decades. But in the West, the opposite was true, with a marked slowdown in forest productivity.

Extreme events like wildfires have played a role, but the researchers said the decline in forest productivity can't be fully explained by trees dying. Rather, the trees seem to be growing more slowly thanks to drought, rising temperatures and a lack of rain.

WHY TREES ARE IMPORTANT: Globally, forests sequester around 25% of carbon emissions each year — maintaining them is critical to staving off catastrophic global warming.

"Our study suggests that future projections of climate and sea-level rise may be too optimistic because, in reality, ecosystems are likely to store less carbon in the future," said Jeremy Lichstein, also of the University of Florida and the study's senior author, in a press release.

"Less ecosystem carbon storage means more carbon in the atmosphere and therefore more warming and accelerating climate change."

The research comes hot on the heels of another study that found that thousands of tropical tree species are at risk of extinction. And other recent research has suggested that the massive boreal forests of Canada, Russia and the rest of the far north may be shrinking.

As with many studies of increasing climate impacts, the take-home message is simple.