Across the globe, coastal wetland vegetation distributions are changing in response to climate change. In the southeastern United States, increased winter temperatures have resulted in poleward range expansion of mangroves into pure salt marsh habitat. Climate change-induced expansion of mangroves into salt marsh will significantly alter carbon (C) storage capacity of these wetlands, which currently store the highest average C per land area among unmanaged terrestrial ecosystems. Total ecosystem C stocks were measured along a 342 km latitudinal gradient of mangrove – to – marsh dominance in Florida. Carbon stocks were quantified through measurements of above- and belowground biomass and soil C. Interior mangrove C stocks were greater than both salt marsh and ecotonal C stocks and soil C comprised the majority of each ecosystem C component (51–98%). The wetlands investigated in this study cover 38,532 ha, and store an average of 215 Mg of C ha−1. Currently, mangroves cover 31% of the land area studied, storing 44% of the total C, whereas salt marshes occupy 68% of the wetland area and only store 55% of the C. Total conversion of salt marsh to mangrove may increase C storage by 26%, predominately due to increases in aboveground biomass.
