Rivers and streams in the U.S. release substantially more carbon into the atmosphere than previously assumed, a new study finds. According to the study, published in the journal Nature Geoscience, a significant amount of carbon absorbed by plants and trees ends up in waterways before ultimately being released into the atmosphere. Using geospatial data to model the movement of carbon dioxide from more than 4,000 rivers and streams across the U.S., researchers calculated that the CO2 emitted from waterways is roughly the same as burning 40 billion gallons of gasoline. “These rivers breathe a lot of carbon,” said David Butman of the Yale School of Forestry & Environmental Studies and co-author of the study. According to researchers, the findings should alter the way scientists model how carbon is cycled at regional and global levels.