CHEYENNE, Wyo. (AP) — A new study estimates that western U.S. ecosystems — from the Rocky Mountains to the Pacific Northwest rain forests and the Sonoran desert — absorb and contain as much atmospheric carbon every year as the annual emissions of more than 83 million passenger cars.
That's the equivalent of nearly 5 percent of annual U.S. greenhouse gas emissions, helping to offset the pollution that contributes to climate change, the Interior Department said Thursday.
"This kind of groundbreaking science not only will help us be more effective stewards of our lands, but it also helps reveal how our forests, wetlands and rangelands in the West — and throughout the nation — are positively impacting the carbon cycle," Deputy Interior Secretary David J. Hayes said in a news release.
The Interior Department study authored by U.S. Geological Survey scientists is part of a congressionally mandated national assessment of how ecosystems capture and contain carbon from the atmosphere.
The scientists examined ecosystems covering just over 1 million square miles including the Rocky Mountains and Sierra Nevada Mountains, Mojave and Sonoran deserts, Great Basin, and Pacific Northwest forests.
A similar report on ecosystems in the Great Plains region came out last year. Upcoming reports will focus on the eastern United States, Alaska and Hawaii.
The latest study shows the value of Western ecosystems in part because of their ability to remove carbon buildup in the atmosphere, Interior said.
"This report contains 12 original chapters of new science that will enable land managers to track and calculate carbon storage and greenhouse gas fluxes over time for the American West's varied ecosystems," said USGS Director Marcia McNutt.
"With more than 300 references of the latest work relevant to how biological systems cycle carbon, this report is a scientific tour de force."
Land managers will be able to analyze how specific areas store carbon over time. For example, carbon storage might increase with the regrowth of a forest burned down by a wildfire, according to Interior.
The study found that forests, which cover 28 percent of the land in the West, account for about 70 percent of the carbon stored in the region. Wetlands had the highest rate of carbon storage but cover less than 1 percent of the West.
Grasslands and shrub lands cover nearly 60 percent of the West and accounted for 23 percent of the carbon stored in the region between 2001 and 2005. Agricultural lands, which cover about 6 percent of the West, contain 4.5 percent of the carbon stored during the same period.