Seeing the Forest for the Trees

Science  23 Dec 2005:
Vol. 310, Issue 5756, pp. 1865c
DOI: 10.1126/science.310.5756.1865c

Tree plantations are a potentially valuable tool for slowing the increase of carbon dioxide concentrations in the atmosphere, but they also can affect the water and soil resources on which they depend. Jackson et al. (p. 1944) analyze these often-neglected effects, using a combination of field research, regional economic and climate modeling, and more than 600 already-published observations, to show that afforestation can dramatically reduce water availability, as well as salinize and acidify the surrounding soil. They find that tree plantations caused nearby streams to dry up in more than one-tenth of the cases studied, and that stream flow was reduced by half, on average. These findings should help illuminate the costs of carbon sequestration by afforestation, rather than only their benefits.

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