Wednesday, April 11, 2007

Carbon Offset Tree Planting Can Spur Global Warming

More evidence that using carbon offsets to plant trees is a bad idea has been presented by scientists from Stanford University and Lawrence Livermore Laboratory in a paper published in the Proceedings of the National Academy of Scientists. According to a report in the Guardian the scientists found that tree planting increases warming unless it occurs within a thin strip of tropical land at the equator. The problem with planting trees elsewhere is that whereas grassy areas and snow reflect a lot of sunlight back out of the atmosphere, trees, being dark in color, absorb most of the suns rays. This soaking up of the heat overwhelms the cooling effect of absorbing the greenhouse gas carbon dioxide. In areas near the equator trees promote the formation of convective clouds which produce cooling and the overall effect of adding trees in such tropical areas is cooling.

Although it appears that planting trees outside of the tropics increases global warming the scientists by no means advocate chopping down trees in nontropical regions to combat global warming since trees have many important functions such as providing habitat for various animals and plants, protecting watersheds, etc. It therefore appears that outside of the tropics that the main goal should be to preserve the forests that we already have.


Ru said...

Bob, the valuable research work you quote takes no account of the emissive footprint of alternate land-uses and so we need to be careful about extrapolating policy decisions from it.When you plant trees (as we do) on land that was previously grazing pasture you reduce the emission of (ruminant)methane and no account is taken of this in the climatic modelling used. Also this work equates natural forest canopy with the managed woodland that offset treeplanters create. When we plant offset trees we control the mix of species, the spacing etc which affect the albedo of the resulting woodland. In general terms their work is clearly valid and important but care has to be taken lest we throw the baby out with the bath water.

Eco Interactive said...

For updated information on this study visit