Saltwater encroachment and prediction of future ecosystem response to the Anthropocene Marine Transgression, Southeast Saline Everglades, Florida

Separating the effects of anthropogenic changes in freshwater delivery from that of sea level rise on the rate of salt water encroachment in the low relief Southeast Saline Everglades is important for understanding how the Anthropocene Marine Transgression might be best managed. We use stratigraphic and paleoecologic methods to calculate rates of salt water encroachment and biogenic sediment accumulation in the Southeast Saline Everglades. Our results suggest that sea level rise during the last century was accompanied by salt water encroachment, which is ultimately controlled by the elevation of high tide and varied by a factor of 14.8 in the five watersheds studied. These differences are attributed primarily to differences in freshwater delivery. The delivery of freshwater mitigated salt water encroachment in only one of the five watersheds. This difference is attributed to sufficient freshwater delivery to maintain a plant community with more rapid rate of sediment accumulation than other sites. Under conditions of diminishing freshwater availability and increasing rate of sea level rise, our data suggest that little can be done at a scale large enough to prevent loss of the Southeast Saline Everglades within the next 50–200 years.