Global and regional fluxes of carbon from land use and land cover change 1850-2015

摘要

The net flux of carbon from land use and land cover change (LULCC) is an important term in the global carbon balance. Here we report a new estimate of annual fluxes from 1850 to 2015, updating earlier analyses with new estimates of both historical and current rates of LULCC and including emissions from draining and burning of peatlands in Southeast Asia. For most of the 186 countries included we relied on data from Food and Agriculture Organization to document changes in the areas of croplands and pastures since 1960 and changes in the areas of forests and "other land" since 1990. For earlier years we used other sources of information. We used a bookkeeping model that prescribed changes in carbon density of vegetation and soils for 20 types of ecosystems and five land uses. The total net flux attributable to LULCC over the period 1850-2015 is calculated to have been 145 +/- 16 Pg C (1 standard deviation). Most of the emissions were from the tropics (102 +/- 5.8 Pg C), generally increasing over time to a maximum of 2.10 Pg C yr(-1) in 1997. Outside the tropics emissions were roughly constant at 0.5 Pg C yr(-1) until 1940, declined to zero around 1970, and then became negative. For the most recent decade (2006-2015) global net emissions from LULCC averaged 1.11 (+/- 0.35) Pg C yr(-1), consisting of a net source from the tropics (1.41 +/- 0.17 Pg C yr(-1)), a net sink in northern midlatitudes (-0.28 +/- 0.21 Pg C yr(-1)), and carbon neutrality in southern midlatitudes.