The threshold rate of sea level rise determining resilience vs. non-resilience in southeast Florida coastal wetlands

Background/Question/Methods .  The simplicity of the physical environment modulating southeast Florida coastal wetland response to sea level rise provides an opportunity to determine the threshold rate or tipping point between resilience and non-resilience. This is because the ecosystem is oligotrophic, located on a stable platform and subject to minimal allochthonous sediment input. The only environmental variable that must be considered when modeling its response to the Anthropocene marine transgression is the rate of autochthonous (biogenic) sediment accretion.

Using local sediment accretion data, topography, paleoecology and chronostratigraphy a depositional model was developed to predict resilience of southeast Florida coastal wetlands to the increasing rates of sea level rise forecast to accompany global climate change.

Results/Conclusions .  Our data suggest the tipping point between a resilient (stable, with minor coastal erosion, limited habitat inundation, landward community migration) and non-resilient (submergence) response to accelerating sea level rise is a rate of 3 mm/yr. At rates exceeding this tipping point, biogenic sediment production and accumulation cannot keep pace with rising water levels. At the present rate of sea level rise (3.3 mm/yr), the southeast Florida coastal wetlands will be submerged within 150 yr or 50 yr at 10mm/yr.  

These forecasts are likely conservative, given our model assumes the tidal range is constant and not increasing with sea level rise as most predict. Furthermore, changing surface water management strategies (increasing delivery) will not be sufficient to counter salt water encroachment and thus the loss of southeast Florida coastal wetlands under conditions of accelerating sea level rise seems inevitable.