REGIONAL APPROACH TO HYDROLOGIC-ECOLOGIC RESTORATION OF THE SOUTH FLORIDA ECOSYSTEM

INTRODUCTION

This section is an overall characterization of the regional South Florida Ecosystem as it was prior to drainage and development and as it is today with the problems that drainage and development entailed. An overall restoration goal for the system is stated, followed by restoration guidelines and overarching objectives for system restoration. The themes stated in these introductory paragraphs will be repeated often in the subsection treatments that follow in the main body of the report. The problems and potential solutions identified in subregions apply to the entire system; the problems can only be be solved by a regional approach. An important lesson from history is that, in this ecosystem, any successful restoration plan developed must encompass the whole regional system, not geographic areas in isolation.

The fundamental tenet of South Florida restoration is that hydrologic restoration is a necessary starting point for ecological restoration. Water built the South Florida Ecosystem. Water management changes are seriously damaging this Ecosystem. And restoration begins with the reinstatement of the natural distribution of water in space and time. The spatial extent of the hydrologically restored area is critical to ecological restoration, as will be explained below. Water quality improvement must be an integral part of all hydrologic restoration. The focus is on the wetlands because the greater part of the predrainage South Florida Ecosystem was wet.

Management of the hydrologic system affects land use and is constrained by land use considerations. The treatment of land use is an important factor in restoration planning. Furthermore, supportive land use planning and permitting is essential to the success of the restoration effort. In recognition of this fact, the Interagency Task Force listed the following as one of its main coordinated management objectives:

Support development of a comprehensive wetland permit mitigation strategy for South Florida that furthers ecosystem restoration.

Environmentally sound land-use planning and development, as well as hydrologic improvements, will be necessary for restoration success. Although it may place some constraints on land use, the restoration program will reduce constraints on economic expansion by increasing the overall water supply and improving the quality of life.

Presently, urban and economic growth is not sustainable and agriculture is not sustainable, given the artificially created limitation of water in South Florida, as well as the loss of organic soils. By addressing these problems, this restoration plan provides for more sustainable economic opportunities while at the same time improving the sustainability of natural ecosystems.

SIGNIFICANCE OF RESTORATION

The South Florida Ecosystem is of national and international significance for its support of wildlife and fish. Over half the United States population of Wood Storks winter in this ecosystem and, during drought years, most are found within the Water Conservation Areas and Everglades National Park (Bancroft et al. 1992, Everglades National Park unpublished data). The area appears equally important to the U.S. population of White Ibises, with over 100,000 individuals feeding within the Everglades-Big Cypress Area during late winter (Hoffman et al. 1990, Everglades National Park unpublished data). Some stay to nest in South Florida, but most migrate north to breed. South Florida is an important staging area for many migratory birds, including Glossy Ibises, Peregrine Falcons, and Swallow-tailed Kites, on their routes between breeding and wintering grounds. The estuaries of South Florida are used as nursery areas for numerous species found on the Florida Keys Reef Tract and throughout the Gulf. Lemon and Black-tipped Sharks enter the bays, especially Florida Bay, to pup. The estuaries are important nursery grounds for pink shrimp and gray snapper, which, as adults, range as far as the Dry Tortugas. Sea turtles nest on the area's beaches, and young turtles use the inshore areas as nursery grounds. The Florida Keys Reef Tract is the only living coral reef in the continental United States. The continued degradation of the South Florida ecosystem threatens the future of these species.

A human population of roughly 4 million resides in South Florida. Quality of life is strongly affected by the condition of natural systems of the region that provide many services to urban communities. These services should include adequate supplies of clean water, clean air, aesthetically pleasing natural landscapes, and an interesting diversity of wildlife and fishery resources.

Tourism is a major industry in South Florida. Recreational fishing and diving are significant to the overall economy of south Florida, both directly and through their stimulation of tourism. For example, recreational activities and tourism account for 50% of the total employment in Monroe County, which consists mainly of the Florida Keys. Recreational fishing contributes about $77 million to the economy, while diving contributes about $354 million to the Florida Keys alone. Everglades National Park and other wetland scenic areas are other large tourist magnets. The future of this part of the tourism industry is directly tied to the condition of the South Florida Ecosystem.

Clearly, restoration of the South Florida Ecosystem means improvement in local quality of life and the regional economy.

DESCRIPTION OF THE NATURAL SYSTEM

The South Florida Ecosystem encompasses an area of approximately 28,000 km² comprising at least 11 major physiographic provinces, including the Everglades, the Big Cypress, Lake Okeechobee, Florida Bay, Biscayne Bay, the Florida Reef Tract, nearshore coastal waters, the Atlantic Coastal Ridge, the Florida Keys, the Immokalee Rise, and the Kissimmee River Valley. The system is dominated by the watersheds of the Kissimmee River, Lake Okeechobee, and the Everglades. The system functions as an interconnected mosaic of wetlands, uplands, coastal areas, and marine areas. Wetlands dominated the predrainage landscape. Prior to drainage, wetlands covered most of central and southern Florida (Fig. 1). The Everglades region was characterized by an extremely low gradient (2.8 cm/km), yet heterogenous, landscape mosaic sculpted by 5000 years' evolution of hydrologic and biologic forces on a Pleistocene limestone platform. Our best template for the predrainage hydrologic structure and elevations is the 1850-era military map (Ives 1856), which defines the "predrainage" system discussed in this report (Fig. 2).

Fundamental Characteristics of the Predrainage System

 Predrainage landscapes consisted of swamp forest; sawgrass plains; mosaics of sawgrass, tree islands, and ponds; marl-forming prairies dominated by periphyton; wet prairies dominated by Eleocharis and Nymphaea, cypress strands, pine flatwoods, pine rocklands, tropical hardwood hammocks, and xeric hammocks dominated by oaks. The natural seascapes of South Florida consisted of shallow seagrass beds, riverine and fringe mangrove forests, intertidal flats, coral reefs, hard bottom communities, mud banks, and shallow, open inshore waters. These were all interconnected on a topographic gradient that ranged from about 20 ft at Lake Okeechobee to below sea level at Florida Bay.  The predrainage wetland ecosystems of South Florida had three essential characteristics:

1. a hydrologic regime that featured dynamic storage and sheet flow,
2. large spatial scale, and
3. heterogeneity in habitat.

Dynamic Storage and Sheet Flow

 The structure contributing to dynamic storage included the very shallow elevation gradient, the vast expanses of emergent vegetation, the thick peat substrates, sand hills, and highly permeable limestones. The water masses were constantly progressing downslope but so slowly that, in effect, water was banked during one season to use in another. Transport varied between structural elements from on the order of months to years.  Throughout the system, groundwater seepage, driven by hydraulic gradients, provided the base flow of creeks, rivers, and possibly even surface runoff across the mangrove zone. Base flow is the river or stream flow provided entirely by seepage from groundwater sources. For example, in the Kissimmee River in the upper part of the watershed, prior to drainage and channelization, 80% of annual river flow was base flow (Burns 1975, Burns and Taylor 1979).  The all-important extended hydroperiods of the natural system depended more on the large dynamic storage capacity and delayed flow-through that were natural hydrologic features of this system than on the immediate effects of rainfall. Because of the dynamic storage and slow rate of water flow throughout the natural system, wet season rainfall kept the wetlands flooded and maintained freshwater flow to the estuaries well into the dry season. The carry-over effect of the enormous dynamic storage capacity of the natural system was so great that a year of high rainfall maintained surface water in wetlands and freshwater flow to estuaries even into one (Walters et al. 1992), Fennema et al. 1994) or more (Browder 1976) subsequent drought years. The dynamic storage made wetlands and estuaries less vulnerable to South Florida's spatially and temporally variable rainfall.

Large Spatial Scale

The vastness of the predrainage wetland extent made it possible for the natural ecosystem to (1) support genetically viable numbers and subpopulations of species with large feeding ranges or narrow habitat requirements, (2) provide the aquatic production to support large numbers of higher vertebrate animals in a naturally nutrient-poor environment, and (3) sustain habitat diversity through natural disturbance. Population resiliency is undoubtedly proportional to the area of these wetlands because habitat diversity, the amount of seasonal refugia, and the number of dispersal options are proportional to wetland area.

In the predrainage era, the nutrients that were the basis of primary production were derived principally from rainfall. The nutrients in water entering from upstream were scrubbed by the vegetation and soils and not available downstream. Sheet flow enhanced the uptake of nutrients from the water column. The periphyton community, made up of microscopic algae, not only assimilated available nutrients from the water column but also created an environment that precipitated phosphorus, along with calcium carbonate, into the substrate. The system was extremely oligotrophic, given the nutrient loading, spread over the entire areal extent. During seasonal dry-down, topographic depressions (e.g., alligator holes) became areas of concentrated aquatic biomass, producing localized feeding opportunities for large carnivores, including wading birds. The higher vegetation, as well as the periphyton, had adaptations for surviving under low nutrient conditions (Davis 1990).

Heterogeneity in Habitat

Habitat heterogeneity maintained by micro-topographic features, small-scale climatic variation, and natural disturbances such as freezes, fire, and storms, acting on the large spatial scale of the wetlands, was a major contributor to biotic diversity and the persistence of populations. The mosaic of habitat types and water depths provided the spatial framework for the production and survival of animals under a wide seasonal and annual range of hydrologic conditions. The vegetative landscape resulting from this vast, low relief, low gradient landform was a diverse mosaic of plant communities. These communities varied in extent from patches on the order of tens of meters to areas approaching physiographic provinces. The larger expanses had more long term resiliency than the patches. Large spaces were necessary to maintain resiliency under conditions that changed on scales from seasons to decades. To some extent, maps from the 1800s, when compared with maps of the 1980s, reveal large scale persistence of landscape patterns, even in the face of major anthropogenic disturbance.

Relationships with Spatial and Temporal Variation

The diverse and large number of aquatic biota that these systems once supported are maintained by the complex annual and long-term hydrologic patterns of the natural system, as expressed in wet-dry cycles, drying and flooding rates, surface water and water depth patterns, annual hydroperiods, flow volumes, and, at the coast, salinity and mixing patterns. For most animals, annual patterns of production, dispersal, and survival were seasonally regulated by the annual periodicity of wet-dry cycles and by the rates of drying and flooding. Primary and secondary production, including that in the key periphyton communities, depended on depth and duration of surface water.

The production of food for consumption by larger predators was largely a function of surface water area and flooding duration during the annual wet period. Food availability was then determined by the amount of forage produced and the rate and degree that it became concentrated into a smaller space during the annual dry season. The distribution and persistence of large animal populations was further influenced by the seasonal patterns of surface water distributions and, in the coastal wetlands and estuaries, salinity patterns, superimposed over major habitat, or plant community, patterns. For example, large, historic wading bird nesting colonies were once clustered in wetlands adjacent to estuaries, presumably because the prey base for these birds was greatest and most reliable at the estuarine/freshwater interface.

Colonial wading birds were extremely abundant in predrainage South Florida and were conspicuously present even into the 1960s and, to a lesser extent, the 1970s. Wood Storks, White Ibis, Great and Snowy Egrets, and other species nested in vast numbers in mangrove swamps along the southern rim of the Everglades and at various interior locations, particularly Corkscrew Swamp in southwest Florida and along the Kissimmee. Other large predators such as alligator, panther, and bear were common. Fish such as snook, tarpon, sea trout, and red drum were abundant in the estuaries. The Florida Reef Tract supported a healthy living coral reef and a rich diversity of associated fish and other organisms, including snappers, groupers, and spiny lobster.

Relationships with Spatial and Temporal Variation in the Estuaries

The estuaries of South Florida had salinities naturally ranging from about 18 ppt to 36 ppt or slightly greater and lower salinities (0-18 ppt) in the mangrove zone. These estuaries were naturally well mixed, rather than stratified. They had horizontal salinity gradients, with salinities increasing in an offshore direction and a lower salinity range throughout the estuary during the wet season. Parts of the more enclosed estuaries may have infrequently experienced salinities of between 36 and 40 ppt during the dry season. The estuaries received freshwater across a broad front, flowing across the mangrove zone, as well as from creeks and rivers, which provided some freshwater inflow throughout the year.

Salinities shifted gradually from high flow to low flow conditions because of the enormous dynamic storage capacity of the upstream system. Shallow, oligotrophic waters promoted the growth of seagrass beds, which supported a resident fauna and the juveniles of many species that spawn offshore but depend upon estuarine nursery grounds. The proproots of mangroves lining the estuaries and tidal creeks also provided habitat for estuarine life. Schooling coastal migratory species such as Spanish mackerel, bluefish, and pompano entered the estuaries during higher salinity times of the year.

Natural resources in the estuaries and on the reef tract supported recreational and commercial fisheries. A major fishery for pink shrimp, based on nursery grounds in or near Florida Bay, became established in the Dry Tortugas. A lucrative charter and guide-boat trade and other tourist-related water-dependent industries developed, particularly in the Florida Keys.

THE ALTERED SYSTEM

Water quality as well as water quantity problems for the natural systems of the Everglades and South Florida estuaries resulted from the man-made changes in the hydrology of the watershed. These changes began before the turn of the century with dredging by Hamilton Disston that channelized the Caloosahatchee River and connected it to Lake Okeechobee. Changes in the hydrologic structure of South Florida culminated in the creation and implementation of the Central and Southern Florida Project in 1948. The enabling legislation gave the U.S. Army Corps of Engineers the responsibility for construction and oversight of water management structures throughout the Kissimmee-Okeechobee-Everglades basin. The State created the Central and Southern Florida Flood Control District in 1949, which has since become the South Florida Water Management District (SFWMD). Project purposes were (1) flood control, (2) drainage, (3) water supply (municipal, industrial and agricultural), (4) protection against salt water intrusion, (5) preservation of fish and wildlife resources in the Everglades, (6) water supply to Everglades National Park, and (7) recreation and navigation. Initial focus was on flood control, drainage, and water supply. Flood control made possible massive land use changes that decreased the land available for water storage and recharge.

Population Growth

A rapidly expanding population that now exceeds 4 million developed in South Florida, mainly in upland areas such as the southeast coastal ridge but also in the wetlands. This presence, with all its needs and demands, has further changed the South Florida Ecosystem. In addition to hydrologic alterations, the changes include an increasing water demand by agricultural and urban uses, although the water supply has been decreased by the conversion of land to agricultural and urban uses and by the shunting to the coast of freshwater that previously was stored in the wetlands, in the soils, and in the aquifers. Other changes include water treatment and quality problems, and the introduction of non-native plants and animals, some species of which have invasively moved onto remaining open lands, including natural-area parks.

Soil Subsidence

The intensive drainage and associated agriculture south of Lake Okeechobee (the Everglades Agricultural Area, or EAA) caused a tremendous loss of organic soil, which continues today. The compaction and oxidation of organic soils in the agricultural lands south of the Lake was one of the first observed environmentally destructive effects of the large-scale drainage. In most areas, five or more feet of organic soil had been lost by 1984 (Stephens 1984). A recent calculated rate of loss is 3 cm per year. The maximum thickness of this soil was only 12-14 ft initially, and the soil is underlain by limestone. The process of oxidative loss of soil continues today, although the process has been slowed in some locations by reflooding fallow fields and maintaining a high water table.

Soil loss of such magnitude has had many impacts on Everglades hydrology and ecology. The elevation gradient from the upper to the central Everglades has been greatly affected by the soil loss. The loss of elevation has meant a loss of the hydraulic head that once drove water south. The movement of water from north to south now requires pumpage and the pumpage effort necessary to move water continues to increase with time as the soils continue to subside. The soil loss has also meant a loss of water storage capacity, which has meant a reduction in the ability of the area to absorb water and mediate seasonal and longterm variations in rainfall.

The problems caused by soil loss are magnified by the enormous spatial extent over which the loss has occurred. In fact, the loss is not confined to the EAA but actually extends into the northern parts of Water Conservation Areas 1 and 3A, where additional soil loss has occurred due to the diversion of water around these areas and even to the EAA to support agriculture.

Water Quality Implications of Soil Loss

The combination of soil loss in the Everglades Agricultural Area, routing water around the EAA, water demand by the EAA, and materials leaching out of the EAA has caused downstream impacts, many of which have only recently been recognized. The loss of soil may have resulted in the concentration of compounds and minerals such as phosphorus in the remaining soil. It seems likely that soil loss has --or soon will-- proceed to the point at which the binding capacity of remaining soil becomes saturated and, with additional loss, the extremely concentrated compounds and minerals will be released into waters that flow downstream. This problem, in conjunction with the application of pesticides and other chemicals for at least 50 years poses a potential ecological threat. The high concentrations of mercury found in largemouth bass, alligators, panthers, and other top predators demonstrates how contaminants have, in fact, concentrated in aquatic food chains.

The well fields of eastcoast cities are supplied with water from Lake Okeechobee and the Everglades through major canals traversing the Everglades Agricultural Area. Discoloration of the water is evidence of the presence of dissolved organic carbons that are precursors to trihalomethanes formed in the chlorination treatment process for drinking water. In an EPA study, the Miami Preston-Hialeah well field was found to have one of the highest concentrations of trihalomethanes in U.S. drinking water supplies. Trihalomethanes are known cancer causing agents. Dade County water treatment plants have switched to the use of a chloramine-based purifying process, but there may be public health concerns with byproducts of this process also.

Everglades waters were naturally clear. The organic soils in the EAA and elsewhere that are oxidating due to drainage are the obvious source of the dissolved organic compounds that are causing problems in water treatment. In fact, concentrations of low molecular weight dissolved organic compounds decrease dramatically with distance south from the EAA (R. Jones, Florida International University, pers. comm.).

Nutrient Enrichment and Contamination

Accompanying the drainage and development of much of the South Florida wetland system, the increased rates of runoff into and through the system, and the diminished hydroperiods in remnant wetlands has been the introduction or transport of water-borne eutrophication-causing nutrients, contaminants such as mercury and other toxins, and introduced, invasive, non-native species, into remnant wetlands. Nutrient-laden agricultural runoff water has resulted in altered macrophyte and algal communities with diminished support capacities as food chain bases and habitats.

Elevated concentrations of chlorinated hydrocarbon pesticides or their derivatives (e.g., DDE) have been found in the tissues of Great Egrets and other wading birds from Water Conservation Area 1 (M. Mafei, unpublished data).

Mercury Contamination

High levels of mercury in fish and wildlife throughout much of the South Florida wetlands represents a particularly alarming ecological threat. Roughly one million acres of the Everglades are under health advisories recommending that anglers completely avoid consumption of largemouth bass and several other species of fish (Lambou et al. 1991). Mercury body burdens in largemouth bass collected in the Everglades were higher than in those taken at SuperFund sites noted for mercury contamination (D. Scheidt, EPA, Athens, Georgia, pers. comm.). Alligators harvested from the Water Conservation Areas cannot be sold for human consumption because of elevated mercury levels in their tissue. In 1989 a Florida panther died from mercury toxicosis (Lambou et al.). Mercury is suspected as the causative agent in the deaths of two other panthers. Analyses of racoons, a major prey organism of panthers, from certain areas of South Florida revealed very high concentrations of mercury in liver and muscle tissue (Lambou et al).

Fragmentation of Landscapes and Habitat

The South Florida Ecosystem is now highly fragmented with diminished habitat diversity. Four major wetland landscapes are reduced to remnants: the cypress strands fringing the western side of Atlantic coastal ridge, the pondapple forest/swamp on the southern shore of Lake Okeechobee, the tall sawgrass plain of the now Everglades Agricultural Area, and the biologically important peripheral wet prairies in southeastern Dade County (Davis et al. 1994).

On the eastcoast ridge, most of natural areas have been replaced by urban development. Only 10% of the former rockland pinelands and 10% of the tropical hardwood hammocks persist. Both are seriously stressed by a combination of lowering of the water table and invasion by introduced species, which makes them much more vulnerable to natural disasters such as hurricanes.

Compartmentalization of much of the remaining Everglades fragmented the system by creating a series of poorly connected wetlands. Similarly, urbanization fragmented the upland systems. The former role of these now diminished systems in regulating both the hydrology and ecology of the South Florida ecosystem no doubt was enormous; yet now the urban area exerts a stress on both the water supplies and water storage capacity of the ecosystem.

Loss of Wetland Area

Roughly 50% of the predrainage wetland area has been lost to agricultural, industrial, and residential development (Fig. 3). In particular, the critical peripheral, or short hydroperiod, wetlands on the eastern side of the Everglades have been diminished. Loss of wetland area has significantly reduced the landscape heterogeneity, habitat options, and long-term population survival for vertebrate species with large spatial requirements. Wading birds, snail kites, and panthers, for instance, have become increasingly stressed by the fragmentation and loss of habitat. Decreasing the spatial extent of South Florida wetlands has reduced the solar collector area that becomes transformed into aquatic productivity. Reducing topographic heterogeneity at regional and local scales has narrowed survival options. By any measure of species richness, there has been a drastic erosion of the biodiversity of the South Florida ecosystem.

Accompanying the decrease in wetland area has been a loss of wetland function, sheetflow, and base flow through water management, which produced a significant change in volume and timing of water flow and overland flow patterns across wetlands and into the estuaries of South Florida. The Everglades and other wetland systems of South Florida were naturally flowing, or lotic, systems that not only covered greater area but also had longer periods of inundation and more sustained outflows to estuaries than exist today under managed conditions.

The Kissimmee-Lake Okeechobee-Everglades basin has been compartmentalized by impoundment of Lake Okeechobee, drainage of the Everglades Agricultural Area, and construction of levees around both the EAA and the Water Conservation Areas. This compartmentalization, plus the channelization of the Kissimmee River and construction of a network of major canals from Lake Okeechobee to the coast, has almost eliminated the wetland- and estuarine-sustaining sheet flow characteristic of the natural system. Now water conveyance networks capture much of the rainfall that the system receives during the wet season and deliver freshwater to the estuaries in huge pulses that drastically lower salinities, stressing estuarine life and lowering estuarine productivity. Wetland productivity is lost as well, as the elimination of large volumes of fresh water from the system results in shorter hydroperiods and lower wetland carrying capacity. Lost, during the dry season, are the important delayed flows originating mainly from wet season rainfall throughout the system, including the dense sawgrass plain that formerly covered the present Everglades Agricultural Area. Lost also are the base flows that, in the natural system, sustained the estuaries during the dry season, extending the period of salinities ranging from 18-24 ppt.

Uncoupling of Wetlands and Estuaries from Rainfall

Water supply releases and regulatory releases involved in the management of stage levels in Lake Okeechobee, the Water Conservation Areas, and the East Everglades, have decoupled water flows from rainfall. Flows to the Everglades from Lake Okeechobee have shifted from primarily wet season flows in response to rainfall to dry season flows in response to urban and agricultural water demands. Impoundment of water in the Water Conservation Areas and diversion of surface water flows to the Atlantic coast, combined with groundwater and levee seepage losses eastward in the modified system, have significantly reduced flows to the southern Everglades, shortening hydroperiods in this area. These changes have resulted in larger intraannual flow variations.

Large volumes of rainwater are drained to sea annually that did not occur historically because of the loss of wetland area and reduction in dynamic storage capacity in remaining wetlands. This diversion of water eastward results in a loss of several hundred thousand acre feet per year to sea.

The reduction in flow from upstream has reduced the maximum area covered by water each year and the duration of flooding. Peak flows are higher following major rain events and flow rates decline more abruptly following the end of the wet season than in the natural system. Channelization and impoundment have disrupted the annual pattern of rising and falling water depths in the remaining wetlands of South Florida. In particular, the effects of dry season rainfall have been aggravated by increases in the depth and duration of reversals in natural drydown process--causing a rainfall event to have a greater disruptive effect on the concentration of secondary production upon which the whole system depends.

Altered Hydroperiods

One result of the changes is that hydroperiods are reduced in most South Florida wetlands compared to pre-drainage conditions. In most South Florida landscapes, development has accelerated the rate of runoff, resulting in sporadic water flow and increased frequency and spatial extent of wetland drying.

Reduced hydroperiods in wetlands appear to adversely affect aquatic production at all levels of the food chain. Surface water refugia to support populations of aquatic fauna and their predators during drought are smaller and fewer and are relocated and subdivided in the currently-managed system compared with the predrainage system.

In a few areas, such as the southern parts of the Water Conservation Areas, channelization, coupled with impoundment, has increased depth and hydroperiod. Resulting regulation water releases from the Water Conservation Areas have caused unseasonable flooding of alligator nesting sites in Everglades National Park, causing nest failure. In addition, these releases have disrupted wading bird nesting, which depends upon concentrated food supplies.

Encouragement of Invasive Introduced Species

Invasive, non-native plant species introduced by man are changing the South Florida landscape and affecting hydrologic conditions and ecosystem function. Prolific non-native animal species are changing animal community structure. Water management has encouraged the spread of these invasive species. The canal networks of the managed system provide a type of deep-water refugia that may cause a completely different community composition--particularly in the predatory fish community--than in the natural system. Furthermore, the water conveyance system may be a conduit for the dispersal of invasive introduced species. Canals also serve as artificial conduits for the transport of waterborne substances such as nutrients. Probably the most important way that water control structures encourage invasive introduced species is by creating spaces where conditions are more favorable to various introduced species than to natives. For instance, altered hydrologic regimes within remnant wetlands have increased their vulnerability to invasion by Melaleuca.

Loss of Hydraulic Head and Recharge Value

One effect of drainage was to drastically lower the water table and increase water table recession rates on the eastcoast ridge. This had a major effect on water flow to both the interior wetlands and the estuaries. It also affected the plant communities of the ridge, the salt/fresh interface, and water supply.

Changes in Fire Regimes

The role of fire may have changed from one of increasing habitat diversity in the natural system to reducing diversity in the current managed system because of altered seasonal burning patterns accompanied by overdrying of wetlands. Fragmentation has interfered with the ability of fire to maintain natural mosaics. Fire patterns have also changed because of prescribed burning, a practice that dampens the annual and interannual variability in the number and severity of fires. Man's tendency to replace natural variations and extremes in disturbances like fire with a regular schedule of variation can lead to loss of biological diversity because species tend to be adapted to natural variations in environmental conditions. Any regularization of physical driving forces may favor some species over others and affect species composition.

Lost Wetland Function Greater than Lost Wetland Area

While South Florida wetlands have been reduced by one half, wading bird populations have been reduced to less than 10% of their former size. This suggests either (1) that the particular wetlands that were lost were especially critical to wading bird feeding and nesting success and/or (2) that the remaining wetlands are so degraded that their carrying capacity for wading birds is only 20% of what it was formerly. The estuarine system serves as a foraging ground for many of the wading birds and loss of estuarine feeding opportunities may also have decreased the carrying capacity of the South Florida Ecosystem for wading birds.

Estuarine Impacts

Water management has resulted in more short duration, high volume water flow to estuaries and less life-sustaining base flows to estuaries. Regulatory releases to control lake and groundwater levels according to prescribed flood-preventive formulae result in pulses of fresh water entering estuaries, causing rapid, drastic decreases in salinity that stress estuarine organisms. In addition, water flows have been diverted from one receiving basin to another, changing the longterm salinity regimes in both systems. As a result of both diversion and the increased runoff rate, Florida Bay receives less water flow than it did historically and salinities greatly exceeding oceanic concentrations are widespread and chronic. Hypersaline conditions in Florida Bay are extreme, frequently reaching 50 ppt over large areas, with known maxima of 70 ppt during severe drought. Biscayne Bay sometimes exhibits abnormal negative, or reverse, salinity gradients, with hypersaline conditions inshore. On the other hand, salinities in Manatee Bay have dropped from 36 ppt to 0 ppt in a matter of hours due to abrupt regulatory releases from the South Dade Conveyance System. This occurrence is particularly disruptive to Manatee Bay because the bay ordinarily experiences extremely high salinities because of loss of natural freshwater inflow. The same is true in northeastern Florida Bay.

Long-term changes in freshwater inflow rates to many South Florida estuaries have shifted salinity zones upstream or downstream from where they originally prevailed each season. As a result, areas within the optimum salinity ranges for various species may no longer coincide with structural features of the estuary that favor the growth and survival of the species. In addition, salinity gradients may have become more spatially compressed (steeper), providing less overall area within some salinity zones and less opportunity to overlap with favorable structural habitat. The shifts in salinity zones and changes in area within various salinity ranges may have reduced the optimum habitat available to each species and even have altogether eliminated the habitat of some species in an estuary. Therefore, changes in freshwater flow have had spatially related consequences for estuarine, as well as wetland, habitat.

Declines in Estuarine and Reef Resources

The fisheries productivity of South Florida marine waters and estuaries is dependent upon habitat quality and quantity. One measure of habitat carrying capacity is recruitment, which is reported as the abundance of age 0 or age 1 fish. Given this, fisheries productivity is directly related to habitat productivity. Decreased fisheries productivity may be reflected by declines in catches and catch rates, although these declines are complicated by fisheries regulations, which reduce total catches (e.g., spotted seatrout, gray snapper, snook). Productivity of spiny lobster, as indicated from recruitment, is habitat-limited to the extent that sponge density is adequate. The impact of the recently documented and continuing sponge die-off on lobster productivity has not yet been observed but is likely to be observed via declines in catches and catch rates in the near future. Landings in the valuable Tortugas pink shrimp fishery, dependent upon Florida Bay nursery grounds, have declined sharply since the mid 1980s. Long-term catch rates, standardized for vessel power increases, declined from the 1960s through the 1970s. Catch rates (unstandardized) declined precipitously beginning in the mid 1980s (Browder 1985).

Fish displaying abnormal dorsal fins and misaligned scales are common in North Biscayne Bay (Browder et al. 1993) and also are present in the St. Lucie Inlet and the lower Indian River (Kandrashoff pers. comm.). The same abnormalities have been seen in at least 10 species. The multiple species occurrence of the abnormalities suggests that something common to the environment of all of the species is causing the problem.

On the reef tract, coral bleaching, coral diseases, including black band disease, and a decline in coral cover and recruitment are some indications of a declining reef community. DDE and other chlorinated hydrocarbons have recently been found in coral reef tissue (Skinner and Japp 1986).

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.

RESTORATION GOALS

The idealized goal for the natural areas of South Florida is to restore to predrainage conditions the landscape-scale hydrologic and ecologic structure and function in order to reinstate ecosystem integrity and sustainable biodiversity. The goal is an ecosystem that is resilient to both chronic stresses and catastrophic events with as little human intervention as possible.

The overall restoration goal for the South Florida Ecosystem is to establish a healthy, sustainable ecosystem that includes man and his activities.

SYSTEM-WIDE OBJECTIVES

• Maximize the spatial extent and landscape heterogeneity of the system to recover its ecological structure and function. Prevent further wetland loss, recover undeveloped degraded wetlands, and restore landscape elements that have been lost to development.
• Restore the natural hydrologic structure and function of the system.
  1. Restore sheet flow throughout the system.
  2. Restore strong hydrologic linkages between areas.
  3. Restore the natural dynamic water storage capacity of the system.
  4. Restore the natural fundamental relationship of ground and surface water levels and water flow with rainfall.
  5. Restore the natural quantity, timing, location, and quality of freshwater flow throughout the system and into estuaries.
• Gradually decompartmentalize the Water Conservation Areas to reinstate sheet flow from WCA1 through WCA3. This measure may make it easier to move water from Lake Okeechobee into the Water Conservation Areas.
• Recover populations of threatened and endangered species.
• Restore natural biological diversity.
• Reestablish natural vegetation and periphyton communities spatially and compositionally, particularly where they have been lost or altered as a result of man-caused impacts (e.g., nutrient pollution, hydroperiod change, altered fire regimes).
• Reduce the dependence of urban and agricultural areas on water supplies in Lake Okeechobee, the Everglades, and the Big Cypress.
• Restore natural rates of productivity throughout the Ecosystem.
• Reestablish sustainable breeding wading bird populations and colonies.
• Halt and reverse the invasion of South Florida ecosystem by exotic plants and animals.
• Prevent point and non-point airborne or waterborne pollution, including contaminants, excessive nutrients, sediments, and thermal pollutants.
• Reestablish the corridors for movements, dispersion, and interactions of vegetation and animals.
• Increase the hard coral cover on Florida Keys reefs.
• Restore natural estuarine and coastal productivity and fisheries.
• Link agricultural and urban growth management with ecosystem management.
• Restore a system that is self-maintaining with minimum human intervention.
• Restore the sustainability of systems of man and nature in south Florida that support cities, farms, and industries in an environment of clean air and water and abundant natural resources.

RESTORATION APPROACH

The recommended approach is inspired by Davis and Ogden (1994), but has been greatly expanded. The conceptual foundation of the restoration approach should be the following:

1. The fact that spatial extent is a critical aspect of the South Florida Ecosystem indicates that the reduction in ecosystem size and compartmentalization of the remaining systems are trends that must be reversed. Fragmentation results in erosion of biodiversity and must be corrected by restoring connections between biotic communities.
2. The importance of hydrology to almost every aspect of ecosystem function--in the annual pulse of wet and dry cycles and stochastic deviations as they relate to disturbance--mandates the development, for wetlands and estuaries, of rainfall-based water delivery plans with built-in dynamic storage and delays. The plans should provide formulas derived from present and future natural system hydrology models that will (a) restore predrainage sheet flow volumes and distributions in time and space, (b) restore predrainage depth patterns, and (c) mimic predrainage hydroperiods, including extended periods of flooding.
3. The role of natural disturbances such as drought and fire in maintaining ecosystem heterogeneity suggests a restoration guideline of allowing environmental fluctuations and extremes to occur or function as they would have in the natural system.
4. The detrimental role of human-derived inputs of nutrients, contaminants, and other materials to this fragile ecosystem demands a restoration guideline of significantly reducing or eliminating anthropogenic inputs of harmful materials into the airsheds and watersheds of the ecosystem.
5. The importance of spatial salinity gradients--maintained and positioned by freshwater inflows--in providing nursery and other supportive habitat in coastal wetlands and estuaries requires that restoration include creation of more natural volume, timing, and locations of freshwater inflows to restore historic salinity structure.
6. Recognition that alterations in water depths and hydroperiods have created conditions conducive to invasion by introduced species suggests that natural hydroperiods and water depths should be reestablished to promote control of invasive introduced species.
7. Recognition of the continuity of ground and surface water that is somewhat unique to the South Florida region demands that water table levels be raised to restore more natural flows to both wetlands and estuaries.
8. Given the historic, predrainage role of massive sheetflows emanating from the upper reaches of the Everglades watershed in structuring and integrating the physical and biotic landscape of the South Florida Ecosystem, it is imperative to reestablish sheetflow conveyance on the system's historic north-south gradient. It must emanate from the top down and be massive enough to restore historic water volume transport in time and space. Restoring sheetflow on a large scale is vital to restoring the natural volume and timing of freshwater flow to estuaries, as well as to freshwater wetlands.
9. Implications of soil subsidence on restoration are that some of the important structure of the natural hydrologic system, including the dynamic storage and hydraulic head provided by the former soils and their associated marshes, no longer exist. In the short term, their function will somehow have to be engineered. It may be possible, in the long term, to reinstate some of the natural structure by creating conditions that promote the accretion of organic soils.
10. The lifespan of agriculture in the EAA is finite because of the present advanced state of soil subsidence (Stephens 1984). This, coupled with the disruption to the entire hydrologic system and regional-wide ecology of South Florida caused by maintenance of a drained area in the middle of the watershed, suggests that every effort should be taken for public acquisition of property in the EAA as various parcels are abandoned by agriculture. It is critical to longterm ecological restoration of South Florida to eventually recover or reconstitute the natural hydrologic function of the area.
11. The impact of agriculture/horticulture on the system suggests that agricultural practices should be encouraged that decrease the application and airborne and waterborne export of nutrients and contaminants (e.g., use of native rangeland as opposed to improved pasture, onsite water retention, use of water tolerant strains of sugar cane, organic farming, development and use of sterile cultivars of ornamental non-native species, use of native plants in landscaping).
12. Urban water consumption and contamination of ground and surface waters affects the availability of clean water to south Florida wetlands and estuaries. There is a major need to encourage conservation in water use and improved techniques for treating and reusing urban waste water and stormwater runoff.
13. Areas that presently serve the ecosystem should not be relinquished in setting boundaries in the present restoration process. Rather than degrade functioning systems, it is better to upgrade degraded systems.

DEFINITION OF RESTORATION AREA

This section attempts to define the area on which hydrologic restoration should take place in order to obtain ecosystem restoration. Risk is inherent in any restoration process, particularly one of the scope of an entire region, which is what is needed here. Three alternative land areas for restoring the hydrologic system are prescribed. The "unconstrained", which recognizes and accepts the economic and social structure of South Florida but makes repairs to the hydrologic system even on developed urban lands, provides the greatest chance of success in restoring the South Florida Ecosystem. The "minimum" involves the most risk because it minimally addresses losses of wetlands, hydrologic function, and habitat heterogeneity. In between are many possible increments that can increase the success potential of the restoration effort, one of which is outlined in this document.

How Much Land is Enough?

The question of how much land is enough for successful restoration is an important consideration. The public purchased large expanses of land that became Everglades National Park and the Big Cypress with the intention of preserving natural ecosystems. As is detailed in the "The Altered System" section, these protected lands, large as they are, are not large enough to preserve the ecosystem. This is because functions the natural ecosystem depends upon are provided by lands outside the preserves; those supporting functions have been altered. In defining the minimum area for restoration in this case we recognize the risk of defining too small an area to provide all the essential elements required for a functioning ecosystem and ecosystem restoration. One should recognize that the probability of ecosystem restoration success is related to the areal extent and degree of hydrologic restoration and, therefore, the more area the better.

The three characteristics of the natural system that gave it resiliency and sustainability were dynamic storage and sheet flow, large spatial extent, and heterogeneity in habitat. These essential characteristics must be kept in mind in defining the required area for restoration.

Minimum

This prescription of minimum area is based on the best scientific information available to the Study Group regarding a hydrologically restorable unit that would result in a sustainable ecosystem. As more information becomes available, this area may need to be increased. This is, afterall, the first step in an adaptive management process, and the need for iterative improvements in both concepts and quantitative information applies here.

The minimum, or constrained, size of the area to be restored by redesign of the Central and Southern Florida Project starts with (1) all existing public lands (Fig. 5), (2) associated estuaries, (3) the Florida Reef Tract, and (4) any additional lands required to restore the above lands and waters. This assumes public acquisition is already underway for such critical areas as the Frog Pond, the Rocky Glades, the "8 1/2 Square Mile Area", the "Model Land" area, the "Triangle Area", and other lands in the Taylor Slough watershed and C-111 area of the extreme southeastern Everglades. This also assumes inclusion as public lands of the Stormwater Treatment Areas (STAs) identified in the settlement of the 1991 lawsuit (U.S. vs. South Florida Water Management District and the Florida Department of Environmental Regulation) and that all water quality requirements of the 1991 lawsuit will be met.

As a starting point, the public lands may represent a critical mass for restoring, by major engineering feats, some hydrologic functions that will be beneficial to wetlands and estuaries. However, other lands undoubtedly will need to be acquired to obtain adequate dynamic storage, remnant landscapes, and greater spatial extent and heterogeneity of wetlands. These acquisitions will reduce the risk of failing to recover wading bird and endangered species populations as well as the natural biological diversity of the system. Short hydroperiod wetlands, for example, are underrepresented in the current public holdings and are essential to wading bird recruitment. These lands are particularly needed to restore full wetland function.

Restoration of the South Florida Ecosystem cannot stop with wetlands and estuaries. The present and authorized public lands do not alone provide all the hydrologic functions needed to restore the South Florida Ecosystem. Both ecosystem health and quality of life are deteriorating in South Florida urban areas. Diminished and compromised water supplies, public health issues related to fish consumption, and air pollution are growing concerns. The entire South Florida ecosystem, including the places where people work and live, has to be restored to ecological health. Acquisition of additional strategically located lands and modification of water management affecting other non-public lands may be necessary.

Specifically, land acquisitions related to restoration should be for the following objectives: (1) recreate strong hydrologic linkages between systems, (2) restore adequate water catchment and storage, (3) expand the spatial extent and heterogeneity of the system, (4) restore critical landscape elements that have been lost or diminished, (5) provide buffering between natural and developed areas, (6) provide water quality enhancement, and (7) secure critical remaining groundwater recharge capability. A prescription for land selection is given with some conceptual boundaries (Figs. 6-8).

Given the criteria listed above, public acquisition of the lands will greatly improve the chances of restoration success, as well as the level of restoration achieved. These areas should be evaluated for aquisition now:

Landscape Remnants

Several landscapes that have been lost or greatly diminished have been identified. Restoration should include areas that still contain these landscapes or are suitable for the reestablishment of these landscapes. These include:

• Cypress strands on eastern boundary of Everglades, mainly in Palm Beach County.
• Short hydroperiod wetlands on the eastern side of the Everglades (Palm Beach, Broward, and Dade Counties).
• Suitable lands for restoring pondapple forests and dense sawgrass plain landscapes (Palm Beach County).

Hydrologic Linkages and Dynamic Storage and Sheet Flow

It may be necessary to acquire land in the EAA to increase the conveyance capacity between Lake Okeechobee and the Water Conservation Areas and to increase water storage capacity in the system. The present conveyance system apparently is not adequate since thousands of acre feet of water are discharged to sea each year through the St. Lucie and Caloosahatchee Rivers, to the detriment of receiving estuaries. In water years 1983-1992, the average annual discharge from Lake Okeechobee to the Caloosahatchee was about 350,000 acre ft., ranging between 76,000-1,500,000 acre ft. Net discharges from Lake Okeechobee to the St. Lucie Canal occurred in 6 of the 10 water years, 1983-1992, amounting, to a 10-yr average annual discharge. of 267,000 acre ft, ranging between 3,000-1,000,000 acre ft. Recapturing a large portion of this water for freshwater wetlands and discharge downstream to Florida Bay in a natural rain-driven pattern is absolutely critical to the restoration effort.

It may be possible to use engineering to achieve the conveyence function. For instance, design alternatives include (1) canal enlargement, (2) an aquaduct, and (3) the flowway concept. The flowway, however, is the most ecologically advantageous way to move water from Lake Okeechobee to the Water Conservation Areas through the EAA because it reestablishes some of the hydrologic functions of sheet flow and dynamic storage. Furthermore the flowway, acting like a marsh, would provide water quality improvement to the Lake waters. These are critical functions that would not be provided by the canal enlargement or aquaduct options. The concept of a flowway is presented in Figure 7.

If land acquisition is necessary, the precise location and quantity of land will depend on surveys, modeling results, and engineering designs. The flowway should be capable of conveying the regulatory releases of the Lake, plus any agricultural runoff. Land acquisition could be accomplished in a phased way, by acquiring agricultural land as soil oxidation forces it out of agricultural production. A cross-section of the EAA showing topsoil and solid substrate elevations projected through the year 2000 (Stephens 1984) suggests that organic soils in the part of the EAA between the Miami and the North New Rivers may soon be too thin for conventional farming. Much of the southern part of this area (The Holey Land and the Ruttenberger Tract) is already in public ownership. This area also contains a major component of the 35,000 acres of Stormwater Treatment Areas (STAs) provided in the settlement agreement (U.S. vs. South Florida Water Management District and the Florida Department of Environmental Regulation).

Catchment and Recharge

Several important natural catchment groundwater recharge areas have been identified that currently are not fully protected from development. These are important to providing water storage to make the system more resilient to seasonal and long term droughts. These areas also serve other important biological functions, as will be described. The Okaloacoochee Slough and the Corkscrew Regional Watershed are located in close proximity to each other on the Immokalee Rise in northern Collier County and function jointly in support of the biodiversity of the southwest Florida region.

Okaloacoochee Slough, besides being a catchment and recharge area, is important to the long term survival of the Sandhill Crane, the Florida Panther, and wading birds, including the Wood Stork. It is a major foraging area for nesting wading birds, providing sustained forage throughout most of their nesting seasons (Browder 1983). The area was identified as a critical corridor area for the panther, given the projected citrus development in the Immokalee Rise area (Mazzotti et al. 1992).

The Corkscrew Regional Ecosystem, as defined by the South Florida Water Management District (Mazzotti et al. 1992), is another important area hydrologically and ecologically. It is a major nesting site for Wood Storks. Part of this area already is publicly owned or owned and managed by the National Audubon Society.

The southern (south of SR 84 [Alligator Alley]) Golden Gate Estates area of the western Big Cypress is a degraded wetland that was a short hydroperiod scrub cypress and marl wet prairie before it was drained by a series of canals. As a natural system it provided sheet flow to the mangrove swamps and estuaries of the Ten Thousand Islands. The Golden Gate Estates area should be restored as part of the effort to restore sheet flow to Faka Union Bay and adjacent areas of the Ten Thousand Islands.

Sheet Flow

Restoration of the predrainage delta of the Kissimmee River and littoral system of Lake Okeechobee would mean both improved water quality (by water flow through marshes) and improved fishery recruitment (through restoration of nursery grounds). Restoration of the following two areas would make this possible.

Paradise Run area, as defined by USFWS (1993) and shown in Figure 6 (the southern part of parcel number 2).

Segment of Indian Prairie immediately adjacent to the Lake Okeechobee Dike, as defined by USFWS (1993) and shown in Figure 6 (parcel number 3).

Elimination of a segment of the northwest section of the Herbert Hoover Dike would be required to restore the predrainage delta.

Ecological Health for Urban Areas

The eastcoast ridge is a groundwater recharge area that, prior to drainage, contributed water to the Everglades, as well as coastal estuaries. Not only has much of this important function been destroyed by drainage, but urban water needs increase water consumption. Important restoration objectives are to partially restore recharge function and decrease urban consumptive use by (1) decreasing groundwater recession rates along the coastal ridge caused by drainage to canals, (2) promoting conservation in water consumption, (3) and establishing reliable means of conserving locally generated runoff and improving its water quality.

A system of buffer zones should be established at the urban east coast-Water Conservation Area interface that extends from the northern boundary of Water Conservation Area 1 southward through southern Dade County. A major role of these buffer zones would be to protect existing natural areas such as the Water Conservation Areas and Everglades National Park from the impacts of urban and agricultural development along the eastcoast ridge. Parts of the buffer strip should be restored as wetlands with natural functions, including water quality improvement. Portions could be water storage reservoirs that would serve to increase water storage capacity in the system and decrease export of wet season excess freshwater to the coast. The buffer area would also serve to recharge the aquifer and urban well fields.

Incremental

A flowway from Lake Okeechobee to the Water Conservation Areas has been identified as an option of the minimum plan. A flowway supporting a tall, dense, sawgrass landscape is an ecologically valuable incremental improvement in restoration design. This vital vegatative component of the predrainage landscape was lost to development and drainage. It is important that the flowway mimic the predrainage function of dynamic storage and sheet flow conveyance facilitated by that landscape. Thus the flow way would provide large conveyance capability, sheet flow, dynamic storage, increased areal extent and heterogeneity of wetlands, and wildlife corridors--all of which are vital to restoring wildlife populations and biodiversity.

A parallel effort should attempt to reduce agricultural runoff and the demand for water from outside the EAA. As part of the "incremental scenario", it is imperative to institute "best management practices" and other agricultural practices in the Everglades Agricultural Area that are compatible with proximity to a large, oligotrophic natural ecosystem. These would include measures that minimize water quality impacts and accommodate the water storage and conveyance needs of the natural system. These include (1) water management practices that retard or halt soil subsidence, (2) development of crops tolerant to extended hydroperiods (elevated water tables), (3) on site detention to reduce both nutrient outflows and water demand, and (4) farming practices that reduce the application and waterborne and airborne export of contaminants and nutrients.

Several studies have demonstrated that large wetland expanses and heterogeneity in timing and period of water coverage were important characteristics of the South Florida ecosystem that greatly influenced its functioning (Fleming et al., In press; Davis et al. 1994; Loftus et al., 1986). Over half of the original wetlands of South Florida have been eliminated, which impedes the restoration effort. For this reason, restoration should include the purchase and subsequent restoration of critical, strategically located, remaining undeveloped wetlands in South Florida, regardless of present condition and regardless of the presence of introduced, non-native plants. In this context, critical wetlands are defined as those that help meet the six objectives listed in the "Minimum" section above. Although full restoration of the natural plant communities on the eastcoast ridge will not be possible due to urbanization, partial restoration through water management modifications will be attempted. This restoration effort will expand on the ideas presented in the "minimum" scenario above.

The buffer zone areas addressed in the "minimum" scenario should be expanded in increments to provide the maximum possible--preferably continuous--protection for natural areas, water catchment, storage of urban storm water, and wetland water quality treatment.

Unconstrained

Unconstrained restoration means return of all former wetlands in current agricultural land uses, including the entire Everglades Agricultural Area, to full wetland ecosystem function. It would mean aquisition or regulatory easements for all remaining undeveloped wetland in South Florida. It suggests no further development of remaining natural lands in South Florida. This is not to discourage new development but rather to redirect urban development efforts to lands within the outer boundaries of currently developed units. Developed lands that are identified through the adaptive process as being critical to restoration would undergo a process that would allow their return to their natural ecosystem function.

IMPLICATIONS OF RESTORATION FOR AGRICULTURE

Agriculture is an important part of South Florida in terms of landuse, the economy, and life style. The future of agriculture in South Florida is threatened by a number of factors, including, on the one hand, urban development, and, on the other, the oxidation of organic soils. While restoration may mean the reclamation for nature of a small part of the extensive former wetlands now used for agriculture, it can also mean the salvation of the soils that will support future crop production. Restoration could provide the water supply to support crop production during the winter dry season. It could also mean the protection from freezes once provided by proximity to large areas of surface water. Once taken for granted in at least some areas, this protection is now almost absent.

This restoration program encourages a sustainable agriculture, which can only be accomplished by abating the massive soil oxidation occurring because of drainage. Restoration would hope to achieve a balance of natural, urban, and agricultural landscapes. There is a place for sustainable, ecologically compatible agriculture in a restored South Florida. If some problems can be curtailed, then, in some areas, agricultural uses are more compatible with natural area management than urban uses. An agricultural restoration plan and program should be part of the overall South Florida Ecosystem restoration program.

REGIONAL RESTORATION SUCCESS CRITERIA

The goal of restoration is a healthy, functioning ecosystem, not, in particular, to increase the production of any one species. Certain individual species, such as fishery species and wading birds, are used as success criteria here and throughout this document because time series of information are available mainly for these species. Their use as success measures is valid because they are widely accepted indices of the general health and productivity of the ecosystem. Holistic measures are more difficult to acquire and time series of this type of information are less available. The small amount of information of this type will be used.

• Reinstatement throughout the system of natural hydroperiods and sheet flow, as approximated by natural system models.
• Reestablishment of predrainage wading bird nesting colony locations and timing of nesting.
• No further wetland losses.
• Degraded wetlands restored.
• Wetland use permits stipulate requirements for enhanced hydrologic connectivity, water quality, and water storage in the South Florida wetland landscape.
• Improved recruitment of fishery and nonfishery species.
• Increased fish abundance and reinstatement of species in pre-disturbance locations.
• Reduction in body burdens of mercury in largemouth bass, alligators, panthers, and other top carnivores.
• Reduction in concentrations of known contaminants in canal surface sediments at locations SFWMD has been monitoring.
• Native landscape diversity increasing.
• Native faunal diversity increasing.
• Reduction in the prevalence of deformed fish in the estuaries.
• Reappearance of missing vegetative landscapes.
• Expanses of nutrient tolerant and exotic plant species reduced or eliminated.
• Periphyton community taxonomic composition characteristic of oligotrophic, natural hydroperiod systems.
• Increases in the populations of threatened and endangered species.