Climate Change Is Turning Trees Into Gluttons

Trees have long been known to buffer humans from the worst effects of climate change by pulling carbon dioxide from the atmosphere. Now new research shows just how much forests have been bulking up on that excess carbon. The study, recently published in the Journal Nature Communications, finds that elevated carbon dioxide levels in the atmosphere have increased wood volume — or the biomass — of forests in the United States. Although other factors like climate and pests can somewhat affect a tree’s volume, the study found that elevated carbon levels consistently led to an increase of wood volume in 10 different temperate forest groups across the country. This suggests that trees are helping to shield Earth’s ecosystem from the impacts of global warming through their rapid growth.

Over the last two decades, forests in the United States have sequestered about 700-800 million tons of carbon dioxide per year, which, according to the study, accounts for roughly 10% to 11% of the country’s total carbon dioxide emissions. While exposure to high levels of carbon dioxide can have ill effects on natural systems and infrastructure, trees have no issue gluttoning themselves on Earth’s extra supply of the greenhouse gas. To put it in perspective, if you imagine a tree as just a huge cylinder, the added volume the study finds essentially amounts to an extra tree ring. Although such growth may not be noticeable to the average person, compared to the trees of 30 years ago, modern vegetation is about 20% to 30% bigger than it used to be. If applied to the Coast Redwood forests — home to some of the largest trees in the world — even a modest percentage increase means a lot of additional carbon storage in forests. Researchers also found that even older large trees continue adding biomass as they age due to elevated carbon dioxide levels. “Forests are taking carbon out of the atmosphere at a rate of about 13% of our gross emissions,” said Brent Sohngen, co-author of the study and professor of environmental and resource economics at The Ohio State University. “While we’re putting billions of tons of carbon dioxide into the atmosphere, we’re actually taking much of it out just by letting our forests grow.”