nature.com:
According to two new studies, planting forests in areas that currently don't have trees -- a process called afforestation -- can reduce the local availability of water.
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This is an excellent example of making wrong generalizations from narrowly defined and specific scientific studies.
The overall water held in an ecosystem increases with forestation. That has been shown over and over and over. Should we now throw out all of that data because these two studies show that a subset of specific indicators of water availability can decrease?
The type of trees planted would be important. Some trees are adapted for arid climes, some for places with lots of rain.
If the area has no trees, one might ask, why not? If the area is decidedly dry and hot, then the appropriate vegetation might be cactus instead of a forest. If a forest cannot thrive without human supplied irrigation, then it is not appropriate for the microclimate.
As the biosphere heats up, we may see that temperate climates move further northward in the northern hemisphere, and thus temperate forests will have to move northwards as well.
Well put, mamacat.
Of course trees use more surface water, but they also hold more surface water, cool the ground level air, reduce wind erosion and encourage more water from rain to fall.
Good points, more reasons this study is deeply flawed.
I think this research is probably flawed. Much can be done with berms, swales and other earth shaping features to dramatically increase the water captured in the ground, which potentially mitigates the problems this research describes. Google Permaculture and Earthworks to learn more about rainwater harvesting.
Another drawback I just found...plan ahead when you plant trees. If you plant heavily on the east, south and west it will block the incoming solar for you when you're ready to put in solar panels.
But deciduous shade trees by west-facing windows in warm climates are a good idea, since they soften the peak solar cooling loads in the afternoon. Just select species that exhibit broad and relatively dense branching and prune the tops if they ever get too tall.
And a whole lot of leaves to burn in the fall.
Why burn? Compost them.
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Posted: 11-11-09 08:32 AM