CO2 efflux from tropical peat swamp substrates was measured under three different land uses (selectively logged forest, recently burned and cleared forest, and agriculture) in Jambi Province, eastern Sumatra over a six-month period that incorporated parts of both the major wet and dry seasons. Clearance of peat swamp forest and cultivation led to increased emissions: mean CO2 effluxes ranged from 2.59 ± 0.22 µmolCO2 m-2 sec-1 for peat beneath selectively logged forest to 4.44 ± 1.16 µmolCO2 m-2 sec-1 beneath recently burned and cleared forest to 5.58 ± 1.34 µmolCO2 m-2 sec-1 beneath settled agriculture. Mean CO2 effluxes were significantly correlated with soil temperature at 20 cm depth (Q10 = 2.5) and water-table position. We combined SPOT satellite and CO2 efflux data to establish that the conversion of selectively logged forest to agricultural land has led to a substantial increase in annual emissions of CO2-C in the study area. © 2006, The Society of Wetland Scientists.