Summary
As signatories to the United Nations Framework Convention on Climate Change, the U.S. submits a National Inventory Report of greenhouse gas (GHG) emissions and sinks each year, which includes GHG estimates from forest land contributed by the Forest Service and compiled by the agency’s Northern Research Station Forest Inventory and Analysis Program. In 2015, the forest land category represented an estimated offset of 11.8 percent of economy-wide GHG emissions. Since 1990, forest land area has increased by an estimated 0.15 percent per year. (These increases are due, in large part, to the conversion of abandoned croplands to forest land and reversion and expansion of trees in grassland ecosystems. There also have been losses in forest land over the past 25 years, predominately to grasslands, croplands, and settlements. The estimated net U.S. carbon flux associated with forest land conversion over the last decade is approximately zero, with gains in forest land constituting sequestration of 23 teragrams of carbon of per year and losses resulting in emissions of 23 teragrams of carbon per year. The estimated emissions constitute decades and possibly centuries of accumulated carbon within these forests, which is abruptly or gradually released to the atmosphere during land use conversion, whereas the gains in forest land only represent carbon sequestration from new growth of live biomass and the accumulation of newly dead organic matter over the 20 years since land use conversion.
