Abstract
Freshwater wetlands provide many benefits to humans and wildlife including: natural stormwater management, wildlife refugia during the dry-season, habitat for federally threatened and endangered species, increased water quality for human consumption, decreased nutrient loads entering Biscayne and Florida Bay, recreation, and nursery grounds for important recreational and commercial fisheries. Due to their wide reaching benefits wetlands are managed by federal, state and local government agencies in order to avoid, minimize, reduce and replace their functions through a federal policy of a no-net-loss in wetland acreage and function. The act of replacing wetland acreage and functions is defined as as “compensatory mitigation”. Very few studies if any have been completed that show how effective Miami-Dade County is at replacing the acreage and functions of permitted freshwater wetlands and therefore is the scope of this study. Using data from the class IV wetlands database, 621 permits from 1983-2008 were analyzed to determine overall trends in the amount of wetland acres permitted, and the location and types of compensatory mitigation. In addition, six compensatory mitigation projects were assessed using the Uniform Mitigation Assessment Method (UMAM) in order to offer suggestions on how to improve the replacement of wetland functions. Approximately 14,000 acres of freshwater wetlands were impacted from 1983-2008, but 26,300 were permitted as compensatory mitigation. Based on these findings Miami-Dade County is meeting the federal no-net-loss of acreage policy. Further analysis suggests however that further research is needed to determine if Miami-Dade County is meeting a no-net-loss of wetland function. Despite this, data revealed that 77% of the projects assessed in this study occurred at a mitigation bank or other Regional Offsite Mitigation Area, while only 6% occurred at the impact site or within the boundaries of the project. Out of the 77% of off-site mitigation projects approximately 48% of them mitigated for impacts in the northern part of the County by using mitigation banks in southern portions of the County. As a result of this trend, local functions like fish and wildlife habitat and local water quality may not be mitigated for since compensatory mitigation occurs in ecologically disconnected areas from the impact site. Moreover, approximately 39% of the projects assessed in the study were mitigated for in a different watershed. Under the current wetland management approach an increase in local watershed functions can be increased by permitting more on-site mitigation or by developing ROMA’s that can compensate for local watershed impacts. Furthermore, the no-net-loss policy itself relies on compensatory mitigation or the creation of wetlands that can be risky. Future wetland management should focus on determining a defined core area of wetlands that must be protected within Miami-Dade County’s two main watersheds to ensure the sustainability of wetland benefits to Miami-Dade County.