E&ENews PM Thursday, December 22, 2005 -- 4:30 PM
CLIMATE
Study explores downside of using trees to sequester carbon
Lauren Morello, E&ENews PM reporter
Planting trees to offset warming caused by greenhouse gas emissions carries hidden environmental costs, a new study has found.
Large tracts of trees grown to sequester carbon can severely deplete stream flow and draw key nutrients from soil, while increasing salinity and acidity, according to researchers at Duke University. Those effects could outweigh some common benefits of such plantings, like decreased erosion and pesticide run-off.The group combined climate modeling, economic analyses and field studies of tree stands to investigate the effects of afforestation. Their paper will be published tomorrow in the journal Science.
Among their key findings: Tree plantations decreased nearby stream flow by an average of 38 percent, with the effect growing more pronounced as the plantings aged. Thirteen percent of streams dried up completely for at least one year. And climate modeling suggests that, in the United States, tree plantings decrease precipitation in most areas, further reshaping a region's hydrological profile.
"The message of the paper is quite simple: The trees use more water," said lead author Robert Jackson of Duke's Nicholas School of the Environment. "It doesn't matter where you are geographically -- tropics, temperates -- and it doesn't matter what you plant, whether it's a cropland or a grassland or a shrubland."