Forestry and global warming
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Impact of Global Warming on Forestry
Elevated levels of atmospheric carbon dioxide could lead to faster growth and greater levels of sequestration in the world’s forests. Barton and Jarvis (1999) found that enclosing selected spruce branches doubled the rate of photosynthesis for current-year shoots while doing nearly the same for older shoots. Though these results cannot be extrapolated to the entire ecosystem, it does demonstrate the positive response that trees can have to higher levels of CO2. (Balling 2000). More recently, the Smithsonian Environment Research Center (2010) studied the growth of Chesapeake Bay hardwoods over a 22-year period and found that growth exceeded expectations. In an accompanying press release, the authors explained that the only reasons forests could be growing faster would be increased temperature, a longer growing season, and increased levels of CO2. (Cheplick 2010).
Greenhouse Gas Emissions from Forestry
According to recent EPA statistics, forestlands sequester 863.1 million metric tons of CO2 equivalent, or 13 percent of total U.S. emissions. Forest’s levels of sequestrations far exceed the next highest carbon sink, urban trees and soil fertilization, which only sequesters 95.9 million metric tons of CO2 equivalent. All forests do not sequester the same amount of greenhouse gases. As Schroeder and Green (2001) note, “[a]fter trees are planted, carbon storage rises slowly (if at all) for a few years, then increases rapidly while the trees are growing vigorously, and gradually levels off as the forest matures.”
Sequestration
Compared to agriculture, carbon sequestration in forests has a greater potential for mitigating future climate change, but it is not without its challenges. Schroeder and Green (2001) projected that additional forestry projects could store about 14 percent of “business as usual” emissions by 2050. The costs associated with carbon sinks as a mitigation mechanism are more modest compared to the changes necessary to achieve the same result in the energy sector. Schroeder and Green report that many forest sequestration projects would cost under $3 per ton of CO2. Additionally, forest sinks protect watersheds, reduce erosion, and provide habitat for wildlife: all benefits that can be yielded regardless of the extent of climate change.
To effectively capture the benefits of forest sequestration, an international regime would need to prevent leakage, or “the impacts that are precipitated by carbon-absorbing forest projects but are external to those projects”. (Sedjo 2001). An example of such leakage would be subsidizing forest conservation in the United States, which leads to deforestation in other parts of the world to meet the same demand for paper products. Such an action would result in no net carbon reduction but would occur at significant cost.
For these reasons, the American Forest and Paper Association noted in comments to the Advanced Notice of Proposed Rulemaking on Regulating Greenhouse Gases Under the Clean Air Act that forest management should not be included in any cap and trade framework and should continue any voluntary sequestration projects exclusively in a voluntary manner. (AF&PA 2008)
References
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