Soils as sources and sinks of greenhouse gases

intact peatlands and from rice agriculture; asN20 from unmanaged and managed soils; and as CO2 from land-use change. Methane emissions attributable to other wetlands add another 1.6-3.8 Gt CO2 equivalents. From a global standpoint, N20 from unmanaged soils and CH 4 from peatlands and other wetlands make soils naturally net greenhouse gas emitters. In addition, the storage of carbon in soils and the fluxes of CH 4 and N20 have been changed by anthropogenic effects towards emission rates 52 to 72 % above those under natural conditions before the dawn of intensive agriculture and land-use change. Land-use changes on mineral soils induced most of the recorded losses of soil organic matter (SOM), but there is evidence that proper agricultural management of soil resources is able to recover some of these losses and to maintain soil functions. However, the discrep-ancy between so-called 'sequestration potentials ' and the measures already adopted is amazingly large. Globally, only about 5 % of the cropped areas is managed according to practices uch as no tillage or organic farming. The contribution f soil loss by erosion, desertification a d sealing to global oxidative SOM losses is uncertain; however, in the case of soil erosion, it is considered to be a major factor in global SOM decline. Mitigatio