Washington, DC (September 1, 2007)- A recent article in Audubon Magazine claims that Americans are on a tree-planting binge, on the premise that jamming seedlings into the ground can offset carbon pollution. In reality, the article makes ugly claims of its own, and misses the point on several levels.
In “naturally treeless habitat” selling carbon credits for cutting city trees instead of planting them would be counterproductive because:
* As they grow, trees take carbon dioxide out of the air and transform it into roots, leaves, bark, flowers, and wood. Over the lifetime of a tree, several tons of carbon dioxide are taken up.
* By providing shade and transpiring water, trees lower air temperature and, therefore, cut energy use, which reduces the production of carbon dioxide at the power plant. Lowering summertime temperatures by planting trees in cities is one way to reduce energy use and thereby reduce carbon dioxide emissions.
* Planting trees is an immediate solution. Even if we were able to switch immediately to fuel sources that do not emit carbon dioxide, the levels in the air will remain high for decades or even centuries because of the long “lifetime” of carbon dioxide. Planting a tree to shade a building is something all of us can do now.
* Tree planting projects provide myriad other social, environmental, and economic benefits that make communities better places to live.
* Putting the right tree in the right place is critical to optimizing benefits, reducing threats from invasive plant species, and minimizing conflicts with other aspects of the urban infrastructure.
* The climate effects of incremental darkening from increased tree canopy cover in higher latitudes is not relevant to cities, where asphalt, concrete, and roof surfaces account for 50 to 70% of urban areas. These impervious surfaces absorb and store more heat than trees, resulting in summertime urban heat islands. Increasing tree canopy cover is one of the most cost-effective ways to cool “hot spots” such as parking lots and wide streets.
* Tree planting and alternative GHG reduction strategies are not mutually exclusive- all have a place in reducing carbon dioxide emissions. Planting trees in cities is not a panacea to global warming. It is one of many complementary bridging strategies, and it is one that can be implemented immediately.
* Settlers planted trees in prairie towns because they needed trees to protect them from sun, snow, and rain.
Note: Thanks to Dr. Greg McPherson for his comments on this article.
Read the “Ugly As a Tree” Audubon Magazine article.