Dead trees keep a surprising amount of carbon out of the atmosphere when they fall into streams, a new study from the Gund Institute for Environment at the University of Vermont finds.
Trees take climate-warming carbon dioxide out of the atmosphere as they grow, trapping it in their wood.
“One of the ways that we can look to help remove some of that [carbon] from the atmosphere is through what we call natural climate solutions — and that is basically using ecosystems, using nature, to store more carbon on the landscape and therefore pull some out of the atmosphere,” said author William Keeton, a professor of forest ecology and forestry at UVM and director of the Gund Institute’s Carbon Dynamics Laboratory.
Pulling carbon out of the atmosphere at an increasingly rapid rate is a critical tool for avoiding the worst impacts of climate change, alongside reducing climate-warming emissions from burning fossil fuels.
Vermont’s forests are still recovering from being largely clear-cut in the 19th and early 20th centuries, and researchers at UVM say that means they have an exceptional potential to store vast amounts of carbon as they age.
When trees fall or die, they continue to trap carbon — especially if they fall in a place where they may decompose more slowly, like streams. Older forests tend to have larger downed trees, which means more stored carbon.
Protecting forests and allowing trees to grow bigger and older is widely viewed as an important climate solution.
And while many studies have looked at the carbon stored in dead trees on the ground, fewer have examined the carbon stored by wood that falls into rivers, streams and lakes.
Ph.D. candidate and lead author Stephen Peters-Collaer wanted to help close that gap in the research.
To do this, the researchers studied the amount of carbon stored in streams in old growth forests in the Adirondacks in New York, and in streams in younger forests in New Hampshire’s Hubbard Brook Experimental Forest. They measured the length and thickness of logs in a particular stretch of stream, and then ran some math based on previous studies to calculate how much carbon was stored in each piece of wood, and tallied the total for that stretch.
“From our study, we found that the amount of carbon stored in wood in streams, as forests on the landscape age towards an old-growth condition, we can expect that to increase four to five times,” Peters-Collaer said.
Small headwater streams store an exceptional amount of this dead wood and make up 70% of the river miles in the United States.
From our study, we found that the amount of carbon stored in wood in streams, as forests on the landscape age towards an old-growth condition, we can expect that to increase four to five times.Stephen Peters-Collaer, Ph.D. candidate and lead author
Keeton says this finding suggests Vermont and other Northeastern states would do well to bolster protections for small streams and for the land right around them, called inner riparian zones — something policymakers in the Chesapeake Bay region have pursued.
“That inner zone must be strictly protected and basically off-limits for logging,” Keeton said. “We don’t have anything like that up here in northern New England. We don’t have anything like that in Vermont.”
Keeton says carbon offset markets, which pay landowners to store carbon on their lands, would also do well to consider the carbon stored in protected streams — something few if any do now.
Lastly, Peters-Collaer says this study offers useful information for forest landowners in Vermont.
“There are a lot of landowners across the region that are interested in using their land as a natural climate solution, whether that’s through management or through passively letting the forest age,” he said. “I think this provides potentially an area for landowners to think about carbon storage on their landscape that previously wasn’t really counted.”
