Azara Blog: Planting trees in high latitude regions might do nothing for carbon emissions

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Date published: 2006/12/18

The BBC says:

Planting forests to combat global warming may be a waste of time, especially if those trees are at high latitudes, new research suggests.

Scientists say the benefits that come from trees reducing atmospheric carbon dioxide can be outweighed by their capacity to trap heat near the ground.

Computer modelling indicates that trees only really work to cool the planet if they are planted in the tropics.
"What we have found is in the so-called mid-latitude region where the United States is located and majority of European countries are located, the climate benefits of planting will be nearly zero," said ecologist Govindasamy Bala of Lawrence Livermore National Laboratory.

"[In] the seasonally snow-covered regions [at even higher latitudes], planting new trees could be actually counter-productive," he told BBC News.
"Our study shows that tropical forests are very beneficial to the climate because they take up carbon and increase cloudiness, which in turn helps cool the planet," explained Dr Bala.
The further you move from the equator, though, these gains are eroded; and the team's modelling predicts that planting more trees in mid- and high-latitude locations could lead to a net warming of a few degrees by the year 2100.

"The darkening of the surface by new forest canopies in the high-latitude boreal regions allows absorption of more sunlight that helps to warm the surface," Dr Bala said.

"In fact, planting more trees in high latitudes could be counterproductive from a climate perspective."

The study finds little or no climate benefit when trees are planted in temperate regions.

The scientists warn that many schemes designed to offset emissions of carbon by planting trees may not be appropriate.

It is well known (or at least believed) that tropical forests do more for the planet than temperate ones. This particular study should (as always) be taken with a pinch of salt because it is just a modelling exercise. And the way this is being publicised is possibly going to do more harm than good. Are they really suggesting that temperate forests should be cut down? Sure, if you had to choose between cutting down a temperate forest and cutting down a tropical one, you might well opt for the former. But otherwise they are falling into the classic trap of looking at one thing in isolation. On the other hand, it is useful if occasionally someone reminds the American and European conservationists who are so keen on protecting their own forests (which generally means that more tropical forests are indeed cut down) that they are quite possibly doing global harm (not that they care about that of course, it is their own backyard they most care about).

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