The Everglades was once an expansive subtropical ecosystem comprised of hydrologically interconnected cypress forests, sawgrass sloughs, marl prairies, and mangrove estuaries encompassing more than 3.6 million ha (Davis et al., 1994). These primary landscape features were physically defined by oligotrophic waters, low topographic relief, large spatial extent, seasonally dynamic rainfall and surface water patterns, hydrologic gradients and sheet flow, and an estuarine system (Ogden et al., 1999). These features supported great populations of wading birds with foraging ranges were tightly coupled with the dynamic hydropatterns.
The Everglades was once a single vast and well-connected expanse of floodplain that experienced unconstrained sheet flow. Over the last century, the Everglades ecosystem has been degraded by the unintended effects of water management and by spillover effects of agricultural and urban development. A vast network of canals, levees, control structures, and conservation areas was built to drain the Everglades and control floods and later the system was adjusted to store water for domestic supply and to meet agricultural and industrial needs. The largest of these projects was the Central and Southern Florida (C&SF) project constructed during the 1950s-1970s (Light and Dineen, 1994) which sought to manage the hydrology of a wetland system in which the flow quantity, timing, and distribution had been substantially altered. Unintended side effects included a loss of more than 50% of the aerial extent of the Everglades, subsidence of peat in many areas, and the creation of a highly compartmentalized flow system with excessive drying in the northern areas and in the southern area comprised of Everglades National Park. An additional unintended side effect of water management has been an impairment of water quality that has led to habitat degradation through eutrophication.
The 7 million people that inhabit southeast Florida are directly dependent on water management for flood control, water supply, irrigation, and transportation. Furthermore, congress decided that the Everglades has national significance and deserves preservation and restoration. Management of the Everglades and its resources must therefore strike a balance between the needs of the ecosystem with all societal interests; thus, an adaptive management approach is being implemented (Ogden et al., 2005). Key to the plan is the use of "best available science" and "adaptive assessment" which ensures plan flexibility to allow for modification as new information is obtained (Ogden et al., 2003). An "applied science strategy" has also been developed to incorporate science into the planning and implementation of water management (e.g., Ogden et al., 2003; Ogden et al., 2005).
Over the last four decades, a wealth of scientific knowledge has been gained about the Everglades and the south Florida natural system. This information has been synthesized into conceptual models that identify the major anthropogenic drivers and stressors, the ecological effect of these stressors, and the best biological attributes or indicators of these ecological responses for the primary landscape features of south Florida (see Ogden et al., 2005). The primary landscapes types are the Everglades ridge and slough landscape (Ogden 2005), southern marl prairies (Davis et al., 2005a), Everglades mangrove estuaries (Davis et al., 2005b), and Florida Bay (Rudnick et al., 2005). The Everglades ridge and slough conceptual model identifies the loss of sheet flow and shortened hydroperiods in some areas and ponding in others as having degraded large areas of the landscape. The underlying causes include the reduced water storage capacity of the Everglades and increased compartmentalization with levees and canals as key stressors the ridge and slough landscapes plant community composition and distribution and abundance of aquatic animals. The disruption of sheet flow is the least understood stressor (Science Coordination Team, 2003) because there is no modern day analog in which to evaluate how the higher levels of sheet flow, prevalent more than a century ago, influenced sediment and nutrient transport or how flow created and maintained the subtle topographic differences between the ground surface elevations of ridges and sloughs, as well effects on how the connectivity of sloughs affected primary and secondary production on the landscape, including supporting fish and other prey species in the quantities necessary to sustain large super colonies of wading birds.
References Cited
Davis, S. M., L. H. Gunderson, W. A. Park, J. R. Richardson, and J. E. Mattson (1994), Landscape dimension, composition, and function in a changing Everglades ecosystem. In: Davis SM, Ogden JC (eds) Everglades: The ecosystem and its restoration. St. Lucie, Delray Beach, pp 419-444.
Davis, S. M., D. L. Childers, J. J. Lorenz, H. R. Wanless, and T. E. Hopkins (2005), A conceptual model of ecological interactions in the mangrove estuaries of the Florida Everglades. Wetlands, 25, doi:10.1672/0277-5212(2005)025[0832:ACMOEI]2.0.CO;2.
Davis, S. M., E. E. Gaiser, W. F. Loftus, and A. E. Huffman (2005), Southern Marl Prairies Conceptual Ecological Model. Wetlands, 25, 821-831, doi:10.1672/0277-5212(2005)025[0821:SMPCEM]2.0.CO;2.
Light, S. S., and J.W. Dineen (1994), Water control in the Everglades: a historical perspective. In: Davis SM, Ogden JC (eds) Everglades: The ecosystem and its restoration. St. Lucie, Delray Beach, pp 47-84.
Ogden, J. C., J. Browder, J. H. Gentile, L. H. Gunderson, R. Fennema, and J. Wang (1999), Environmental management scenarios: ecological implications. Urban Ecosystems 3: pp 159-184, doi:10.1023/A:1009508718195.
Ogden, J. C., S. M. Davis, and L. A. Brandt (2003), Science for a regional ecosystem monitoring and assessment program: the Florida Everglades example. pp 135-160. In: D. E. Busch and J. C. Trexler (eds.) Monitoring Systems: Interdisciplinary Approaches for Evaluating Ecoregional Initiatives. Island Press, Washington, DC, USA.
Ogden, J. C., S. M. Davis, K. J. Jacobs, T. Barnes, and H. E. Fling (2005), The use of conceptual ecological models to guide ecosystem restoration in south Florida. Wetlands 25: pp 810-820, doi:10.1672/0277-5212(2005)025[0795:TUOCEM]2.0.CO;2.
Rudnick, D. T., P. B. Ortner, J. A. Browder, and S. M. Davis (2005), A conceptual ecological model of Florida Bay. Wetlands, 25: pp 870-883, doi:10.1672/0277-5212(2005)025[0870:ACEMOF]2.0.CO;2.
Science Coordination Team. 2003. The role of flow in the Everglades ridge and slough landscape. South Florida Ecosystem Restoration Working Group. http://sofia.usgs.gov/publications/papers/sct_flows/index.html. Accessed 1 Dec 2005.
U.S. Department of the Interior, U.S. Geological Survey
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