Seasonally inundated areas cover large areas of the Amazon basin and are important components of the ecology, hydrology and biogeochemistry of the basin because they modify riverine discharges and chemical composition and are significant sources of greenhouse gases to the atmosphere. Recent advances in active and passive microwave remote sensing are providing regional information on temporal changes in inundation and aquatic vegetation. Combination of remotely estimates of inundation with extensive measurements of dissolved carbon dioxide for the central Amazon indicates that evasion to the atmosphere of carbon dioxide is about ten times the fluvial export of organic carbon by the Amazon River. The organic carbon fueling the evasion appears to be largely derived from riparian and floodplain vegetation, illustrating the importance of terrestrial-aquatic-atmospheric exchanges. Further, the evasion of carbon dioxide and methane from Amazon wetlands appears to balance much of the uptake of carbon dioxide by terrestrial vegetation.