In this case study, approaches were examined for jointly meeting objectives in biodiversity conservation and coastal hazard mitigation. Planning and management for these objectives has typically occurred separately. The Panhandle Coast of Florida was examined because it has abundant and diverse wetlands, and the hazards from tropical storms and hurricanes have significant impacts on human communities and biodiversity.
The Overlay approach (Case 1) involved a simple overlay of spatial data representing risk and vulnerability to coastal hazards with information on coastal wetlands that could mitigate some of these hazards. The risk data included storm surge and flooding. Demographic variables such as age, income levels, and number of mobile homes were used to identify socially vulnerable communities. The salt marsh, oyster reefs, and seagrasses within five miles of the socially vulnerable communities at high risk from coastal hazards were identified as wetlands with high potential value for mitigation of hazards.
The Marxan approach (Case 2) advanced Case 1 by taking the wetlands identified with potential mitigation value and adding biodiversity information from a Florida Estuarine/Marine Biodiversity Assessment. Three Marxan scenarios were developed:
- Goals were set at 30 percent of existing distribution for only the biodiversity targets. No information was included on coastal wetlands with mitigation value. This is a typical single objective (biodiversity conservation) analysis.
- Goals were set at 30 percent of existing distribution for the coastal wetlands with potential mitigation value and the biodiversity targets.
- goals were set at 100 percent for the coastal wetlands with potential mitigation value and 30 percent for the biodiversity targets. A 100 percent goal indicates that the wetlands with mitigation value were 'locked' in to the analysis and the set of results had to include all of these wetlands.
Results and Implications
There are opportunities and approaches for combining biodiversity conservation and coastal hazard mitigation objectives. The Overlay approach (Case 1) represents a straightforward method for recognizing that wetlands have value for both conserving biodiversity and mitigating coastal hazards. The identification of wetlands within five miles of the most at risk and vulnerable human communities may provide a buffer for some of the effects of storm surge and flooding. At the same time these existing wetlands also harbor biodiversity that can be jointly conserved. Only a small fraction of the total wetlands in the Panhandle (<20 percent) are identified in this analysis, which places a priority on a particular set of wetlands. In this analysis, an emphasis is placed on meeting the hazard mitigation objective, the conservation of biodiversity is a secondary objective.
The Marxan approach (Case 2) expands on the methods in Case 1 to more fully meet both objectives. When goals are set at 30 percent for both biodiversity targets and coastal wetlands with mitigation value, the result is only slightly different (2 percent) in the total area (i.e., efficiency) than when only the biodiversity targets are examined. This result is also more spatially efficient (by greater than 36 percent) than when the wetlands with potential mitigation value are locked in to the analysis. These results suggest that there might be good opportunities to efficiently meet biodiversity conservation and hazard mitigation objectives.
These cases illustrate approaches, which it is expected will be modified and improved. There are many opportunities to enhance these analyses by:
- identifying other hazard mitigation variables (e.g., the location of critical service or business infrastructure)
- identifying wetlands with the greatest hazard mitigation value
- changing goals for biodiversity conservation and hazard mitigation (primary management priority may be given to hazard mitigation and then secondary priority to biodiversity conservation)
These cases provide a base for advancing marine ecosystem-based management by illustrating that objectives can be combined transparently and efficiently.