Ecosystems in East store most carbon

Ecosystems in East store most carbon

INTERIOR Secretary Sally Jewell released a new report June 25 showing that each year, forests, wetlands and farms in the eastern U.S. naturally store 300 million tons of carbon — or 1.1 billion tons of carbon dioxide equivalent — which is nearly 15% of the greenhouse gas (GHG) emissions the Environmental Protection Agency estimates the country emits annually.

"Today, we are taking another step forward in our ongoing effort to bring sound science to bear as we seek to tackle a central challenge of the 21st century: a changing climate," Jewell said. "This landmark study by the U.S. Geological Survey (USGS) provides yet another reason for being good stewards of our natural landscapes, as ecosystems play a critical role in removing harmful carbon dioxide from the atmosphere that contributes to climate change."

In conjunction with the national assessment, USGS also released a new web tool that allows users to see the land- and water-based carbon storage and change in their ecosystems between 2005 and 2050 in the lower 48 states.

With this report on the eastern U.S., USGS has completed the national biological carbon assessment for ecosystems in the lower 48 states — a national inventory of the capacity of land-based and aquatic ecosystems to naturally store carbon, which Congress called for in 2007.

Altogether, the ecosystems across the lower 48 states sequester about 474 million tons of carbon a year (1.738 billion tons of carbon dioxide equivalent), which is comparable to counterbalancing nearly two years of U.S. automobile emissions, or more than 20% of the GHG emissions EPA estimates the country emits each year.

The assessment shows that the East stores more carbon than all of the rest of the lower 48 states combined — an amount that exceeds and offsets yearly U.S. automobile emissions — even though it has fewer than 40% of the land base. Under some scenarios, USGS scientists found that the rate of sequestration for the lower 48 states is projected to decline by more than 25% by 2050 due to disturbances such as wildfires, urban development and increased demand for timber products.

"What this means for the future is that ecosystems could store less carbon each year," USGS acting director Suzette Kimball said. "Biological sequestration may not be able to offset GHG emissions nearly as effectively when these ecosystems are impaired."

USGS scientists have been building the national assessment since a 2007 congressional mandate in the Energy Independence & Security Act. The first report covering the Great Plains was released in 2011, while the second report on the western U.S. was released in 2012. Reports on Alaska and Hawaii are expected to be completed in 2015.

The area studied for the eastern U.S. carbon assessment was defined by similarities in ecology and land cover. The study area extends eastward from the western edge of the Great Lakes and the Mississippi floodplains, across the Appalachian Mountains and to the coastal plains of the Atlantic Ocean and the Gulf of Mexico.

The major ecosystems USGS researchers evaluated were terrestrial — forests, wetlands, agricultural lands, shrub lands and grasslands — and aquatic — rivers, lakes, estuaries and coastal waters.

Biological carbon storage is the process by which carbon dioxide is removed from the atmosphere and stored as carbon in vegetation, soil and sediment. The USGS inventory estimates the ability of different ecosystems to store carbon now and in the future, providing information for land use and land management decisions.

The report can be found at http://pubs.usgs.gov/pp/1804.

 

Major findings

* Forests, which occupy about half of the land in the East, accounted for more than 80% of the estimated carbon sequestered in the region annually. They are the largest carbon-storing pools and have the highest rate of sequestration of the different ecosystem types.

* Wetlands, including coastal ones, which comprise only about 9% of the land cover in the region, account for nearly 13% of the region's estimated annual carbon storage. They also have the second-highest rate of sequestration of all ecosystem types.

* In contrast, carbon dioxide is emitted from the surface of inland water bodies (rivers, streams, lakes and reservoirs), equal to about 18% of the recent annual carbon sequestration rate of terrestrial ecosystems in the East.

* Agricultural areas cover about 31% of the East and account for only 4% of the region's annually sequestered carbon.

* Grasslands and shrub lands, as well as other types of land, contained just 1.1% or less of the region's carbon.

* The eastern U.S. is projected to continue to be a carbon sink (absorbs more carbon than it emits) through 2050, increasing the carbon stored by as much as 37%. However, the rate of sequestration is projected to slow by as much as 20%, primarily because of decreases in forest cover.

* The area projected to experience the most change — about 30% — is the southeastern U.S., primarily because of conversion of land from forests to agricultural and urban land.

* By 2050, coastal carbon storage could increase by 18-56%. Land use changes could increase nutrient and sediment flow from urban and agricultural lands, but this would also increase the amount of carbon stored in coastal areas.

Volume:86 Issue:26

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