Understanding the role that living habitats play in the protection of coastal ecosystems and human communities has become increasingly important in the face of a changing climate and increased coastal development, yet we lack the predictive capacity needed for informed management. Previous, high profile studies that followed Hurricane Katrina and the 2004 Asian tsunami were based largely on correlative work that ignored heterogeneity in and dynamics of natural and human ecosystems. We have addressed this problem by developing a suite of ecosystem service models for predicting and valuing the ability of habitats (e.g., marshes, mangroves) to attenuate waves and storm surge, reduce flooding, and regulate natural processes of erosion and sedimentation that are critical to maintaining beaches. The models are process-based and consist of (1) a biophysical step (based on principles of hydrodynamics) which determines how the supply of coastal protection services varies with the extent and density of habitat, (2) a use step where demand by human communities for the coastal protection service is quantified, and (3) an economic step for valuation in monetary terms. Outputs include the avoided area of land eroded or flooded due to the presence of habitats, as well as avoided beach nourishment, damages to property, and number of people affected.  

Results/Conclusions

Our work has revealed that protection depends not only on the structure of habitats, but also on attributes of the physical environment (hydrodynamic conditions, coastal topography, coastline orientation) and the intensity and location of human use and need. Results also suggest conditions in which certain habitat types are likely to provide protection. We expect these models will aid decision and policy-makers in predicting how various drivers (e.g., restoration or loss of habitats, sea-level rise, increases in magnitude and frequency of storms) will influence the protective capacity and value of living habitats and the human communities that rely on them. As such, these models can also inform strategies for ecosystem-based climate adaptation.  As part of a scenario-assessment tool called Marine InVEST (www.naturalcapitalproject.org), our coastal protection models can be used to understand trade-offs among a suite of ecosystem services, including food from fisheries and aquaculture, wave energy, and recreation, provided by coastal and marine ecosystems.