Tuesday, December 18, 2012

Carbon sequestration by Western US ecosystem has surprising numbers

Forests, grasslands and shrublands in the Western US, including Arizona,  sequester nearly 100 million tons of carbon each year, an amount equivalent to counterbalancing the emissions of about 83 million passenger cars a year in the United States, according to a new USGS report.   The USGS notes that "carbon that is absorbed or 'sequestered' through natural processes reduces the amount of carbon dioxide (CO2) in the atmosphere."   [Right, image credit USGS]

Some of the more interesting conclusions in the report are  forests are by far the largest carbon-storing pools, accounting for about 70% of the carbon stored recently in the West, even though forests cover only about 28% of the land area, making them the sinks that contain the most carbon per unit area.

Wildfires contribute volumes of greenhouse gases equal to 13% of the carbon sequestration rate of the western ecosystems, but surprisingly, water bodies, especially churned up, fast moving water, contributes CO2 equal to more than 30% of the annual sequestration rate of the region.   So, the recent high flow release of water from Lake Powell to rebuild sand bars and beaches apparently perversely added more CO2 to the atmosphere.

The report says  forest harvesting produces nearly 13 million tons of carbon per year) but agricultural harvesting generates more than 20 million tons of carbon per year.  Presumably, new growth trees and crops replace that lost sequestration potential.

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