The U.S. Geological Survey is participating in a multi-institutional effort to assess, monitor, and restore the ecosystem of South Florida. Federal, State and local agencies are collaborating to establish a firm scientific basis for land management and water policy issues. Historical changes in South Florida related to rapid population growth in the early to middle 1900's have led to significant alteration of the natural hydrocycles and water quality of Florida and Biscayne Bays. These changes have affected the salinity and nutrient supply and introduced toxic components into Biscayne Bay. The Biscayne Bay ecosystem shows increasing signs of distress: declines in fisheries, increased pollution, and dramatic changes in nearshore vegetation. Northern and central Biscayne Bay are strongly affected by the urban development associated with the growth of Miami. Southern Biscayne Bay is influenced by drainage from the Everglades, which has been altered by canals and agricultural activities. Restoration and preservation of Biscayne Bay and Biscayne National Park are dependent on a comprehensive understanding of the linkages between the hydrologic system and the bay ecosystem, and of natural versus human-induced variability of the ecosystem.

The ecosystem of Biscayne Bay includes the marginal freshwater and saltwater wetlands, intertidal communities, and marine communities. The health of each of these communities can be linked to their interaction with the hydrologic regime of South Florida. Major factors that may affect these communities are:

• The alteration and control of freshwater flow entering Biscayne Bay.
• Urbanization of Dade County, thereby increasing storm runoff and pollutants into Biscayne Bay.
• Natural and artificial changes to vegetation associated with fires and urbanization.
• Natural disasters, including hurricanes, and prolonged wet or dry seasons.