28 May 2010

Researchers Calculate Greenhouse Gas Value Of Ecosystems

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Researchers at the University of Illinois have developed a new, more accurate method of calculating the change in greenhouse gas emissions that results from changes in land use.

The new approach, described in the journal Global Change Biology, takes into account many factors not included in previous methods, the researchers report.

There is an urgent need to accurately assess whether particular land-use projects will increase or decrease greenhouse gas emissions, said Kristina Anderson-Teixeira, a postdoctoral researcher in the Energy Biosciences Institute at Illinois and lead author of the new study. The greenhouse gas value (GHGV) of a particular site depends on qualities such as the number and size of plants; the ecosystem’s ability to take up or release greenhouse gases over time; and its vulnerability to natural disturbances, such as fire or hurricane damage, she said.

Greenhouse gases trap heat in the atmosphere and contribute to climate change. The most problematic greenhouse gases include carbon dioxide (CO2); methane (CH4), which is about 25 times more effective than CO2 at trapping heat but persists in the atmosphere for much less time; and nitrous oxide (N2O), an undesirable byproduct of crop fertilization.

The new approach accounts for emissions of each of these gases, expressing their net climatic effect in “carbon-dioxide equivalents,” a common currency in the carbon-trading market. This allows scientists to compare the long-term effects of clearing a forest, for example, to the costs of other greenhouse gas emissions, such as those that result from burning fossil fuels for transportation, electricity, heat or the production of biofuels.

At first glance, biofuels appear carbon-neutral because the plants absorb carbon dioxide from the atmosphere and store the carbon in their tissues as they grow, said plant biology and Energy Biosciences Institute professor Evan DeLucia, who co-wrote the paper. That carbon is released when the plants are used as fuels. These emissions are balanced by the uptake of CO2, so – in theory, at least – no new carbon is added to the atmosphere, he said.

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