Glades Anatomy: Ridge and slough degradation in Everglades National Park, 1900 to present

The Florida Everglades have experienced substantial changes over the 20th century due to natural climate variability and human management. Federally mandated restoration of the Everglades is aimed at restoring historic hydrology and landscape ridge-and-slough patterning. Paleoecological data can provide key insights into historic vegetation and hydrology, and consequently, restoration targets.  Here we present paleoecological evidence from four sites along historic Shark River Slough, the central waterflow path in Everglades National Park.  These data indicate loss of deep water sloughs and replacement by sawgrass ridges, starting in the early 20th Century.  We integrated these data into a modeling framework in order to (1) use fossil seed profiles to test models predicting long-term sawgrass/slough dynamics given a priori assumptions about water management and (2) use the model and data to inverse-calculate the timing and magnitude of human management effects on water levels.  Data from the Florida Coastal Everglades LTER program were used to calibrate model equations relating hydrology, sawgrass biomass and soil accretion.  We found that predicted seed profiles agreed to within 1 standard deviation of observed values (R²=0.51 - 0.90). Modeled and observed profiles reflect increased sawgrass biomass coincident with the timing of the Tamiami Trail construction (ca. 1930). In our second approach, the model and data were used to inverse-calculate water management effects and the results indicated a step decrease in water depths (by ~30 cm) in the 1930s and a smaller decrease (~5-10 cm) in the 1950s.  While this first-generation is simple in its mechanistic detail, it demonstrates the usefulness of paleo-ecological proxies in testing ecosystem models in refining our understanding of historic hydrology, a critical performance measure for Everglades restoration.