Some deforestation may offset Global Warming

Agence France-Presse writes

Planting new trees in snow-covered northern regions may actually contribute to global warming as they have the counter-effect of tropical forests, according to a study out Monday.

While rainforests cool the planet by absorbing carbon dioxide and producing clouds that reflect sunlight, the dark canopy of Canadian, Scandinavian and Siberian forests catches sunrays that would be reflected back to space by the snow, the study said.

The study, published Monday in the online edition of the Proceedings of the National Academy of Sciences, found that reforestation projects in the tropics would help mitigate global warming but would be "counterproductive" in high latitudes.

"Our study shows that only tropical rainforests are strongly beneficial in helping slow down global warming," Govindasamy Bala, who led the research, said in a statement.

"It is a win-win situation in the tropics because trees in the tropics, in addition to absorbing carbon dioxide, promote convective clouds that help to cool the planet," he said.

"In other locations, the warming from the albedo effect (sunlight absorption) either cancels or exceeds the net cooling from the other two effects," said Bala, an atmospheric scientist at the Lawrence Livermore National Laboratory.

Reseachers used a three-dimensional computer simulation to study the effects of large-scale deforestation and look at the positive and negative effects of tree cover at different latitudes.

"When it comes to rehabilitating forests to fight global warming, carbon dioxide might be only half of the story; we also have to account for whether they help to reflect sunlight by producing clouds, or help to absorb it by shading snowy tundra," said study co-author Ken Caldeira.

However, the authors did not endorse deforestation of the boreal forests as a measure against global warming.

"Preservation of ecosystems is a primary goal of preventing global warming, and the destruction of ecosystems to prevent global warming would be a counterproductive and perverse strategy," said Caldeira, of the Carnegie Institution.

Researchers from Stanford University in California and Universite Montpellier II in France contribute to the study.

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