The climate impact of tropical peatland degradation

Southeast Asia is a global hotspot of peatland degradation and related greenhouse gas emissions. Anthropogenic impacts, mainly associated with agricultural conversion, shift Southeast Asian peatlands from carbon sinks to significant carbon sources. Here we first describe the impacts of anthropogenic drainage on landscape-scale carbon dynamics of individual peatlands and then use an impulse‐response model of radiative forcing to quantify the climate impacts of peat-carbon losses. Whereas water-table elevation (i.e. drainage depth) determines the magnitude of CO2 emissions at the site-scale, the geometric arrangement of artificial drainage networks determines carbon losses on the landscape-scale. Among all peatland greenhouse gas fluxes, the rapid release of large quantities of CO2 with lowered water tables has the greatest impact on atmospheric radiative forcing. While peat accumulation in undisturbed peatlands produces a slowly increasing net radiative cooling, drainage, within decades, causes a shift in radiative forcing to a positive atmospheric perturbation (i.e. net warming), which can persist for centuries to millennia. The pace of this shift in radiative forcing and the magnitude and duration of the warming effect depend on the age and carbon pools of peatlands.