Sources of atmospheric methane in the south Florida environment

Abstract

Direct measurement of methane (CH 4 ) flux from wetland ecosystems of south Florida demonstrates that freshwater wet prairies and inundated sawgrass marsh are the dominant sources of atmospheric CH 4 in the region. Fluctuations in soil moisture are an important environmental factor controlling both seasonal and interannual fluctuations in CH 4 emissions from undisturbed wetlands. Land use estimates for 1900 and 1973 were used to calculate regional CH 4 flux. Human settlement in south Florida has modified wetland sources of CH 4 , reducing the natural prairies and marsh sources by 37%. During the same period, impoundments and disturbed wetlands were created which produce CH 4 at rates approximately 50% higher than the natural wetlands they replaced. Preliminary estimates of urban and ruminant sources of CH 4 based on extrapolation from literature data indicate these sources may now contribute approximately 23% of the total regional source. We estimate that the integrated effects of urban and agricultural development in south Florida between 1900 and 1973 resulted in a 26% enhancement in CH 4 flux to the troposphere.