When the ecosystem models are linked with economic models, results show that projected increases in productivity may not lead to increases in harvest at the national scale, because the market responds to many different factors besides timber growth. The models project some redistribution of harvest among regions, which would in turn lead to some changes in fiber types and the ownership of lands from which wood is harvested. Harvested timber will add to a growing pool of carbon in wood products. Byproducts from timber production, which are burned for energy, reduce the combustion of fossil fuels that adds long-stored carbon back into the atmosphere. Retrospective applications of the models have explored uptake and release of carbon by forests and forest products.
Results suggest that U.S. forests are currently a net sink for carbon.
Increases in biomass on U.S. forest lands over the last 40 years are estimated to have added 281 million metric tons per year of stored carbon, enough to offset 25 percent of U.S. emissions for the period. The integrated models are currently undergoing extensive revisions in preparation for another round of projections based on updated forest inventory data, new climate projections, and developments in modeling techniques. This exercise has helped the model developers understand the strengths and weaknesses in representing key ecosystems processes, and will facilitate analytical review of uncertainty in projections of vegetation change. Forest Management to Offset CO2 Emissions Opportunities to increase carbon storage above the expected baseline have been identified and are beginning to influence landowner decisions. Studies have shown that CO2 emissions can be effectively offset by sequestering additional carbon at various steps in the life cycle of wood growth, harvest, use, and disposal.