Florida is currently the fourth most populous state in the U.S., with an estimated 17.3 million residents (U.S. Department of Commerce, 2006). Between 1999 and 2003, Florida led the nation with 607,000 building permits issued for residential single-family and multi-family dwelling units (National Oceanographic and Atmospheric Administration, 2004). More than three quarters of Florida’s population growth and resulting development has occurred within its 35 coastal counties (Florida Department of Community Affairs, 1996; National Oceanic and Atmospheric Administration, 2004).
Figure. John’s Pass Area, Pinellas County, Florida.
Florida’s coastal population growth and urban development have been driven in part by the creation of the Intracoastal Waterway System (ICW) to facilitate vessel navigation. During the late 1800’s to the 1960’s, the channelization of Florida’s shallow bays and estuaries attracted commerce and the development of waterfront communities upon what was once submerged land and tidal wetlands. Dredge material from access channels and canals were deemed the easiest way to create home sites from “worthless swampland” (Antonini et al., 2002).
Canal systems, originally dredged to create land for homes, have become de-facto transportation systems linking tens of thousands of residential boat docks to the ICW and to deeper water in the Atlantic Ocean and Gulf of Mexico. Naturally occurring deeper channels, dredged waterways, and canal systems are also preferred by manatees as migratory routes and travel corridors to feeding areas and, in the case of residential canal systems, as “safe havens” and important sources of freshwater discharge (Lee County Division of Natural Resources, 2004). These natural and human created conditions contribute to a greater chance of collisions between manatees and boats—a significant cause of manatee deaths in Florida.
Figure. Redfish Point Area, Lee county: Pre-development (1949) and Post-development (1999).
Runoff and Pollution
Impacts to manatees from coastal development include degradation of habitat that sustains them (Sargent et al., 1995). Nutrient- and pollution-rich effluent from mining and agricultural operations, roads, parking lots, and lawns has led to a deterioration of water quality and, subsequently, to a reduction in the extent and health of mangroves and seagrass beds (Livingston, 1990). In addition, the alteration of wetlands by dredge and fill operations, channelization of rivers and streams, and other changes to freshwater flow also threaten the habitat that manatees rely on for survival.