FORESTS, grasslands, shrublands and other ecosystems in the West sequester nearly 100 million tons of carbon each year, according to a U.S. Department of the Interior report released Dec. 5.
Carbon that is absorbed, or "sequestered," through natural processes reduces the amount of carbon dioxide in the atmosphere. DOI noted that the 100 million tons sequestered in western ecosystems is an amount equivalent to, and offsets the emissions of, more than 83 million passenger cars per year in the U.S., or nearly 5% of the Environmental Protection Agency's 2010 estimate of the nation's total greenhouse gas emissions.
"This important study confirms the major role that our natural landscapes have in absorbing carbon and helping to counterbalance the nation's carbon emissions," DOI deputy secretary David J. Hayes said.
The report, authored by U.S. Geological Survey scientists, is part of a congressionally mandated national assessment of carbon storage and sequestration capacities of ecosystems. This assessment estimates the ability of different ecosystems in the West to store carbon -- information that will be vital for science-based land use and land management decisions.
The first report on the Great Plains was released in December 2011; reports on the eastern U.S., Alaska and Hawaii will follow.
The area studied extends from the Rocky Mountains to the Pacific coastal waters and totals just more than 1 million square miles. The study's results show that, among their many other ecosystem services, these lands are immensely valuable because of their ability to store carbon.
The fine level of detail in the report means that resource managers can evaluate the effects of land management practices on carbon storage and sequestration in and near specific ecosystems, such as Yellowstone National Park, DOI said. It also could be used to understand how the rate of carbon sequestration increases as forests regrow following a large wildfire.
DOI noted that terrestrial ecosystems -- forests, wetlands, agricultural lands and grasslands -- accounted for more than 95% of the estimated total carbon sequestered in the West between 2001 and 2005.
Although the ecosystems vary widely in their potential for storing carbon now and in the future, the study found that forests are by far the largest carbon-storing pools, accounting for about 70% of the carbon stored in the West. Forests occupied 28% of the land in the West, contained the most carbon per unit of area and had the second-highest rate of sequestration of the various ecosystem types.
Wetlands had the highest rate of sequestration of all ecosystem types, but they cover less than 1% of the West, DOI added.
Grasslands and shrublands contained 23% of the region's carbon on nearly 60% of the land area in the West. Agricultural lands, which comprise about 6% of the West, contained 4.5% of the carbon stored during the same period.
The report is available online at http://pubs.usgs.gov/pp/1797.