POTENTIAL CARBON BENEFITS OF THE CONSERVATION RESERVE PROGRAM IN THE UNITED-STATES

Three scenarios of the Conservation Reserve Program (CRP) were simulat ed to project carbon (C) pools and fluxes of associated grassland and forestland for the years 1986-2035; and to evaluate the potential to o ffset greenhouse gas emissions through C sequestration. The approach w as to link land-area enrolments with grassland and forestland C densit ies to simulate C pools and fluxes over 50 years. The CRP began in 198 6 and by 1996 consisted of 16.2 x 10(6) ha cropland converted to 14.7 x 10(6) ha grassland and of 1.5 x 10(6) ha forestland. The CRP1 simula ted the likely outcome of the CRP as contracts expire in 1996 with the anticipated return of 8.7 x 10(6) ha grassland and of 0.4 x 10(6) ha forestland to crop production. The CRP2 assumed that the CRP continues with no land returning to crop production. The CRP3 was an expansion of the CRP2 to include afforestation of 4 x 10(6) ha new land. Average net annual C gains for the years 1996-2005 were <1, 12, and 16 TgC yr (-1) for CRP1, CRP2, and CRP3, respectively. Afforestation of marginal cropland as simulated under CRP3 could provide approximately 15% of t he C offset needed to attain the Climate Change Action Plan of reducin g greenhouse gas emissions to their 1990 level by the year 2000 within the United States.