DEFINITION OF RESTORATION AND THE ADAPTIVE PROCESS
Definition
Restoration can be viewed as the reconstitution of a pre-existing ecological condition, or range of conditions, of a prior period. The conceptual target of restoration of South Florida's wetlands and estuaries is predrainage South Florida, as defined, for topography and hydrology, by the 1858 military map (Fig. 2) and, for vegetative cover, by the map of natural vegetation prepared by Davis (1943), as expanded to include southwest Florida and the Kissimmee River Valley (Fig 1). The large spatial scale of the pre-drainage south Florida wetlands was key to the long-term maintenance of the region's ecological functions and components. The irreversible loss of a significant portion of wetland area, as well as the almost complete urbanization of the east coast ridge, a major groundwater recharge area, make the restoration target only approachable. What one can hope to recapture is essential hydrologic and landscape characteristics that were critical to a sustained and healthy South Florida ecosystem.
Man is a recognized as a part of the system to be restored, and what is sought is a partnership between man and nature in developing a healthy economy within a fragile, but highly supportive ecosystem. Sustainable ecosystems integrating economic and ecologic processes is the restoration target for the overall South Florida Ecosystem.
Rationale for Hydrologic Restoration
Hydrologic restoration is a necessary beginning to ecological restoration. Other restoration efforts that undoubtedly will be necessary include reduction in both waterborne and airborne inputs of plant nutrients and contaminants, control of invasive introduced species, and reestablishment of natural corridors in uplands and wetlands for native biotic dispersal and diversity. Hydrologic restoration may enhance the effectiveness of other restoration measures. The restoration approach will require an adaptive process, consisting of three, overlapping components: (1) to restore both the areal extent of the system, as well as its hydrological integrity in order to recover sustainable biotic populations; (2) to adjust the hydrological restoration objectives in order to maximize ecological restoration; and (3) to establish a comprehensive, regional monitoring program to measure hydrological and ecological responses to the hydrologic restoration programs, which are referred to as success criteria. In this document, these are discussed in the context of alternative minimum, incremental, and maximum (unconstrained) areas to be covered by restoration.
The basic assumption of restoration in the South Florida Ecosystem is that hydrologic restoration, in all of its facets, will lead to ecological restoration. Certainly the hydrology of the current system can be changed in the direction of its predrainage wetland character. However, the changes in the heterogeneity of habitats and their relative coverage in remaining, restorable lands may require additional restoration efforts. One must accept the fact that much of the structure, composition, and dynamics of the resulting landscape will result from the self-designing emergent properties of the system itself. The challenge to management is to understand these new system trajectories and to guide them toward the goal of ecosystem health and sustainability. It may be necessary, in later analysis, to design enhancement projects to support recovery of some elements of the system.
Use of Models, Rain-driven Formulae, and Adaptive Management
The restoration process will require a new generation of ecological study tools to monitor, model, and assess the results of restoration. These will build upon the natural system models of hydrology. A coupling between the hydrologic models and future models of water quality, ecology, and plant and animal populations will allow examination of differences between predrainage and present-day conditions. These models should be developed at several scales, spanning the range from regional landscape models to models of constituent ecosystems and communities (see Appendix I). These models must have scientific credibility and acceptability by the scientific community.
Restoration will be guided by natural systems hydrologic models that will be used in conjunction with models of present-day hydrologic conditions. Quantitative measures of hydrological and ecological changes in the South Florida Ecosystem from pre-drainage times to the present are lacking, although paleoecological research and yet undiscovered historical records may someday provide some information. Meanwhile, the best guide for examining changes in the spatial extent and hydrological conditions of the current system with an unmanaged system will be the family of Natural System Models (NSM's), coupled with a series of spatially explicit simulation models of species or guilds at the landscape level. The natural system hydrologic models are corollaries of present system hydrologic models that have been calibrated using present data. To prepare the natural systems model versions, canals, levees, and control structures have been removed from the model. Comparisons of NSM results with present model results, given the same rainfall conditions, allow both qualitative and quantitative assessments to be made of changes in stages, duration of flooding, spatial extent of flooding, and other related parameters. For instance, they produce output that show the spatial distribution of hydroperiods under the two conditions, natural (predrainage) and present (Fig. 4). Observation of results of these scenarios vividly show how man has changed the South Florida landscape with dikes, dredges, and canals.
A natural system model (NSM) (Fennema et al. 1994) that parallels the model used by the South Florida Water Management District for routing and planning (SFWMM), shows that hydroperiods were much longer almost everywhere in the system prior to drainage. The NSM results provide hydrologic restoration guidelines. The agencies that are responsible for land and estuarine management should be jointly involved in the development of these models.
A means is needed to translate the output of the Natural System Model into a schedule of water deliveries in relation to rainfall at various locations throughout the landscape. A rain-driven formula is currently being used by the South Florida Water Management District to schedule a more natural volume and timing of water delivery to Everglades National Park from the upstream Water Conservation Area in relation to rainfall. The present formula is based on a regression of water flow rates (measured data from the 1950s) on rainfall, lagged several weeks to approximate the natural delay caused by storage in the system. Similar formulas based on output from the Natural System Model of Fennema et al. (1994) would provide improved scheduling for water releases. The Natural System Model intrinsically encorporates the delay provided by the dynamic storage in the system.
The natural system models can also be used for quantitative perspective on how to restore a more natural volume and timing of water flow to South Florida estuaries. A method for this process is stated in Appendix II.
Ecosystem-level modeling of the biota most be coupled with the results of the NSM's and of the various hydrological alternatives to understand the responses of the biotic communities. Several types of ecological models are being developed for use in evaluations in the South Florida ecosystem. An innovative modeling approach is being developed for use in south Florida jointly by the NPS, NBS, and the University of Tennessee/Oak Ridge National Laboratory. This approach uses a series of integrated simulation models of major trophic groups, coupled through a spatially explicit landscape that uses elevations, vegetation cover, and hydrologic inputs. Several of these models are being created for the Everglades/Big Cypress region.
These models must be used in concert with monitoring programs. These models must be designed to accept calibrating inputs, to suggest monitoring strategies, and to evaluate management alternatives. Monitoring programs will include broad-scale landscape characterization, water quality and quantity measures, and natural resources (e.g., wading bird populations, fisheries, snail kites, vegetation communities, and contaminants in air, water, sediments, and biota).
Modeling and monitoring, along with research, are part of the iterative adaptive management process. Adaptive management means the iterative use of models, research, and monitoring in conjunction with management to revise, improve, and fine tune management procedures. Structural elements of the hydrologic system must be flexible in order to apply the adaptive management approach. Also essential to the process is flexibility in policy and agendas, both ecological and political.
Structures versus No Structures
Potential hydrologic restoration approaches, as far as the South Florida Ecosystem is concerned, lie within the two extremes from completely removing all water control structures, including canals and levees, to adding more structures or modifying existing structures or their operation to recreate hydrologic conditions that approximate natural conditions, despite constraints imposed by loss of both wetlands and uplands. Removing structures has the advantage of reestablishing natural patterns of wetland continuity, sheet flow, and animal movements and of reducing conduits for invasions by invasive introduced species and pollutants. However, it may not be possible to restore predrainage water flow rates, timing, and spatial patterns by this approach in today's system of reduced water storage capacity and wetland and recharge area. Retaining and modifying existing water control structures and possibly adding new structures has the advantage of providing flexibility to adjust water management operations based on measured responses from the system in an adaptive management framework. Adding structure also may have unforeseen undesirable effects on the restoration process, unless innovative designs could reduce the negative aspects of structures. Determination of the most appropriate approach to use will have to be on a case by case basis and must consider ecological costs and benefits of each approach.
