Better Way to Calculate Greenhouse Gas Value of Ecosystems

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.

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.

“What some analyses miss is the potential for that forest to take up more carbon in the future,” she said.

“And they’re missing the greenhouse gas costs — the added emissions that result from intensively managing the land — that are associated with that new cropland.”

Using the new method, the researchers calculated the GHGV of a variety of ecosystem types, including mature and “re-growing” tropical, temperate and boreal forests; tropical and temperate pastures and cropland; wetlands; tropical savannas; temperate shrublands and grasslands; tundra; and deserts.

“In general, unmanaged ecosystems — those that we are leaving alone, such as a virgin forest or an abandoned farm where trees are re-growing — are going to have positive greenhouse gas values,” Anderson-Teixeira said. Managed ecosystems such as croplands or pastures generally have low or negative greenhouse gas values, she said. (See chart.)

Source: Better Way to Calculate Greenhouse Gas Value of Ecosystems – Science Daily

Date: 6 June 2010