Gross CO2 fluxes from land-use change: implications for reducing global emissions and increasing sinks

Daniel deB Richter Jr(dagger 1) & RA Houghton(2) The role of land use in the global carbon cycle involves both CO2 sources (e.g., as forest land is converted to agricultural uses) and CO2 sinks (as vegetation regrows following land disturbance). While land-use change contributions to the carbon cycle have been mainly evaluated using net emissions of CO2, we estimated gross emissions and gross sinks of CO2 from land-use change via global and regional simulations with a widely used carbon cycle model. Gross fluxes are large; for example, the gross CO2 sources from land-use change amount to 4.3 PgC year(1) or more than 55% of emissions from fossil fuel combustion and cement manufacture. The airborne fraction is therefore estimated to be approximately 34% of total CO2 emissions (i.e., fossil fuel plus land-use). Since land-use conversions and abandonment differ regionally, gross sources and sinks provide strong support for extensive land protection and land-use management strategies to reduce atmospheric CO2.