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Seeing the forest and the trees helps cut atmospheric carbon dioxide

February 13, 2009

Addressing carbon on land is essential for stabilizing greenhouse gas concentrations

CHICAGO - Putting a price tag on carbon dioxide emitted by different land use practices could dramatically change the way that land is used - forests become increasingly valuable for storing carbon and overall carbon emissions reductions become cheaper, according to research presented today at the annual meeting of the American Association for the Advancement of Science.

"Without valuing the carbon in land, we risk losing large swaths of unmanaged ecosystems to agricultural crops and biofuels," said speaker Leon Clarke of the Joint Global Change Research Institute in College Park, Md., a collaboration between the Department of Energy's Pacific Northwest National Laboratory in Richland, Wash., and the University of Maryland.

Most analyses of future global carbon dioxide output mainly consider carbon emissions from fossil fuels and industrial processes, or otherwise include only parts of the global carbon cycle. Some studies predict dramatic changes in how people use land as they cut down trees to grow food and bioenergy crops. This study is the first to value carbon in all natural and human systems.

The scientists found that addressing the land-based carbon is essential for stabilizing greenhouse gases at low levels. Overall, land contains 2,000 billion tons of carbon, compared to the 750 billion tons in the atmosphere. In addition, forests hold more carbon than grazing does. Converting land from forest to food or bioenergy crops releases carbon into the atmosphere. Conversely, turning agricultural land back into forests tucks carbon away on land, reducing it in the atmosphere.

In today's talk, JGCRI economist Clarke showed that including terrestrial carbon changes the carbon dioxide dynamics and costs of managing greenhouse gas emissions. When all carbon emissions-fossil fuel, industrial and land-use change emissions-are included in a global management plan regardless of their origin, deforestation slows and could reverse, managers place limits on the expansion of biofuels production, and emission control becomes cheaper.

Their analysis also found that emissions from land use changes were heavily influenced by how well crops grew.

"That means to limit atmospheric carbon dioxide concentrations, improving technology for growing crops is potentially as important as energy technologies such as carbon capture and storage," said Clarke.

The analysis by PNNL scientists at JGCRI explores what could happen to global economies and environments as biofuels become an important part of energy production. They included carbon dioxide emissions from energy, the atmosphere, land use, and terrestrial sources. The results offer insights into how to best incorporate biofuels into our global economy.

DOE/Pacific Northwest National Laboratory