Forest Carbon Markets: Potential and Drawbacks

摘要

Forests are major carbon sinks (storehouses), and activities that alter forests can release or sequester carbon dioxide (CO2), the most common greenhouse gas (GHG). Some carbon markets have been formed under mandatory GHG reduction regimes, such as the Kyoto Protocol and various regional and state initiatives in the United States. Other markets have formed for voluntary efforts to reduce GHG emissions. Offsets, or credits for sequestering carbon or reducing emissions in unregulated sectors, are typically allowed in both mandatory and voluntary markets. Forestry activities are among the largest-volume and lowest-cost opportunities for generating offsets. Various forestry activities may be feasible for carbon offsets. Afforestation (planting trees on open sites) and reforestation (planting trees on recently cleared sites) are the activities most commonly included for offsets. Some propose that the carbon stored in long-term wood products, such as lumber and plywood, could be credited as carbon offsets, and mill wastes often substitute for fossil fuels to produce energy; however, short-term products (e.g., paper) and the biomass left in the woods after timber harvesting release carbon, making the net carbon effects uncertain. Some forest management practices also might qualify for carbon offsets; certified sustainable forest practices provide a system of assured, long-term forests, while activities to increase tree growth face many of the same concerns as long-term wood products. Finally, deforestation is a major source of GHG emissions, accounting for as much as 20% of anthropogenic emissions. Thus, avoided deforestation, especially in the tropics, potentially provides an enormous opportunity to reduce GHG emissions. However, avoided deforestation is particularly prone to leakage as well as many of the concerns about forest carbon offsets generally.