Peatland is a significant storage of carbon and nitrogen on the earth's surface. This paper reviews the impacts of changes in water table level and mineral nitrogen associated with human activities on greenhouse gases emissions in tropical peatland and northern boreal and temperate peatland, and evaluates the optimal water table level to minimize greenhouse gases emissions. CH4 emission increased significantly with the rise of ground water table level above -20 cm, and larger in northern peatland with plant mediated CH4 emission than tropical peatland with plant mediated oxygen supply. However, forest disturbance by fire in tropical peatland increased CH4 flux to the similar level in northern peatlands (8.3 mg C m(-2) h(-1)) due to stagnant surface water associated with the peat subsidence. On the other hand, CO2 and N2O emissions were significantly lager in tropical peatland than in northern peatland especially due to nitrogen fertilization. CO2 and N2O emissions increased with falling ground water table level below -40 to -80 cm (19 Mg C ha(-1) y(-1) for CO2 and 700 kg N ha(-1) y(-1) for N2O). Total global warming potential was significantly low in the ground water table level from -20 and -40 cm.