NASA

A satellite view of the Mississippi River shows a mosaic of riverbank land-use patterns.

Rivers and streams in the United States are releasing a lot more CO2 into the atmosphere than scientists previously thought, according to a new study by scientists at Yale. In fact, American waterways are discharging the gas into the atmosphere at a rate of 100 million metric tons per year, an amount equal to a car burning 40 billion gallons of gas, researchers say.

The study, conducted by David Butman and Peter Raymond of the Yale School of Forestry and Environmental Studies, looked at water chemistry data from more than 4,000 rivers and streams. The authors say identifying this significant source of CO2 could change the way scientists model the movement of carbon through ecosystems and the atmosphere.

“These rivers breathe a lot of carbon,” said Butman in a press release from the National Science Foundation, one of the study’s funders. “They are a source of carbon dioxide, just like we breathe out carbon dioxide and like smokestacks emit carbon dioxide.”

The study is published in the current issue of Nature Geoscience.