Problems With Planting Forests
Many policymakers have embraced planting forests as one way to combat the buildup of carbon dioxide in the atmosphere, but a new study suggests this may be a poor strategy for minimizing greenhouse gases because fast-growing trees such as evergreens take a high toll on water and soil resources.
The international team of researchers, who examined more than two dozen plantations in Brazil, Belgium, South Africa, the United States and elsewhere, concluded that planting forests sometimes harmed local streams and damaged the soil. Thirteen percent of the streams they examined dried up completely for at least one year after plantations, many of which featured evergreens, had grown five to 10 years in the area.
"Trees use more water than just about anything else -- grasslands, croplands, shrub lands," said Robert B. Johnson, a Duke University biology professor at the Nicholas School of the Environment, one of the authors of the paper in Friday's issue of journal Science.
The trees they studied -- especially pine and eucalyptus -- also changed the acidity and salinity of the soil by soaking up calcium, nitrogen and potassium while releasing sodium, Johnson said in an interview last week.
The findings raise questions about the wisdom of planting trees to soak up carbon dioxide emissions from cars, power plants and other industrial sources, he said: "It's not a single good-bad story. We have policies that focus strictly on carbon. That's something we should reconsider, the other effects on the environment that putting on these carbon binders have."
-- Juliet Eilperin
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