U.S. Tree Planting for Carbon Sequestration (CRS Report for Congress)
| Release Date |
May 4, 2009 |
| Report Number |
R40562 |
| Report Type |
Report |
| Authors |
Ross W. Gorte, Specialist in Natural Resources Policy |
| Source Agency |
Congressional Research Service |
Summary:
Climate change is a growing concern for Congress. "Cap-and-trade" and carbon tax proposals have been suggested to limit and reduce domestic emissions of greenhouse gases, especially carbon dioxide (CO2). Most cap-and-trade proposals would establish limits on emissions from many economic sectors, while allowing "offsets"âreduced emissions or enhanced carbon sequestrationâfrom uncapped sectors, such as forestry and agriculture. Alternatively, carbon tax proposals might include tax expenditures or credits for such "offsets." In the 111th Congress, a discussion draft of possible legislation from Representatives Markey and Waxman would allow offsets for up to 2 billion metric tons of CO2 emissions (or the equivalent thereof in other greenhouse gases), divided equally between domestic and international programs. In addition, the draft includes discounting for offsetsâ1.25 offset tons are required for each ton of emission allowance. Thus, under the proposal, domestic CO2 offsets would be about 1.25 billion tons.
One of the widely discussed options for domestic CO2 offsets is tree planting. Tree planting aims to establish stands of trees that can grow for anywhere from 20 to 2,000 years, depending on the species, location, and intent of the planting. Two terms are generally used for tree planting:
reforestation, for planting trees or other activities to establish tree stands (such as assisting natural tree regeneration or preparing sites and sowing tree seeds) on areas recently cleared of forest through timber harvesting or natural disaster; and
afforestation, for planting trees on sites that have long been cleared of forests, such as crop, pasture, and brush lands.
Tree planting has greater carbon sequestration potential than other land use practices. Afforestation of crop or pasture land is estimated to have the potential to sequester between 2.2 and 9.5 metric tons of CO2 per acre per year. Reforestation is estimated at 1.1 to 7.7 metric tons of CO2 per acre per year. These estimates have a very wide range of possibilities because tree growth and forest soil carbon accumulation varies widely among species and locations.
Because of its greater sequestration potential and various aspects of measuring and monitoring performance, afforestation is a widely discussed option for providing domestic CO2 offsets. The scale and cost of an afforestation program to provide a billion tons of carbon offsets are substantial. Several additional factors should also be recognized, including natural hazards to forests, the timing of forest carbon sequestration, the impacts of significant shifts in land use, and the capacity to achieve an afforestation program of this magnitude.
