Forests are considered great storage spaces of atmospheric carbon dioxide.
According to the U.S. Environmental Protection Agency, trees rapidly store carbon dioxide during early stages of growth. As they go through their natural lifecycles, however, they progressively release carbon. The EPA estimates “that the 2008 annual net carbon flux (i.e., the excess of uptake minus release) in U.S. forests was about 792 million metric tons of carbon dioxide equivalent, which offset about 3% of U.S. energy-related (carbon dioxide) emissions.”
A new study published in the Proceedings of the National Academy of Sciences has found that sizable amounts of carbon dioxide escape via the soil to freshwater sources.
The researchers found freshwater rivers and streams transport more than 220 billion lbs of carbon each year. The new numbers indicate that current estimates of carbon storage in terrestrial landscapes may be overestimated by almost 30%.
This carbon winds up in oceans, the bottom sediment of lakes and reservoirs, or in the atmosphere as greenhouse gases, according to the researchers.
“If our goal is to use forests as a way to manage carbon stocks, we should know what is leaking into streams, rivers, and lakes,” said David Butman, study author and an assistant professor at the Univ. of Washington’s School of Environmental and Forest Sciences and in the Dept. of Civil and Environmental Engineering. “Our research suggests that in fact these landscapes might not be taking up as much carbon as we think because we’re not accounting for what’s being lost in aquatic systems.”
The researchers presented their findings at the 2015 American Geophysical Union Fall Meeting.
In the Pacific Northwest, researchers found that massive amounts of rainfall move carbon dioxide more swiftly through the land and into coastal waters compared to other regions of the U.S.
The data used for the study comes from four years worth of countrywide carbon assessment, where researchers gleaned carbon data from freshwater rivers, lakes, and reservoirs around the country.