The Central Everglades Sub-region consists of the Water Conservation Areas (WCA’s), A.R.M. Loxahatchee National Wildlife Refuge, Everglades National Park (including Florida Bay to the park boundary), western portions of the C-102 and C-103 basins, the C-113 basin, the Southern Glades, and Model Lands.

The WCA’s encompass 1,350 square miles and represent an area equivalent to about one-third of the historic Everglades landscape. This area has been protected from development but greatly modified by channelization and diking. The WCA’s are five interconnected, diked impoundments situated downslope (south) of Lake Okeechobee and immediately upslope (north) of Everglades National Park (ENP). WCA No. 1 is entirely within Loxahatchee National Wildlife Refuge (LNWR). The WCA’s are wedged between the developed Atlantic Coastal Ridge (Lower East Coast, LEC), the Everglades Agricultural Area (EAA) and Big Cypress National Preserve.

The WCA’s provide many functions. In addition to providing water to most of the remaining Everglades habitat, they also provide water control functions including water storage, water supply, and flood control. The levee system to the east prevents flood waters from inundating the principally urban LEC, while the canals provide water supply for the agricultural lands and ENP. The WCA’s enhance water supply to the LEC by recharging the Biscayne Aquifer, the primary drinking water source for the urban area, and by retarding saltwater intrusion.

All of these functions are to be accomplished in a manner beneficial to the abundant wildlife resources dependent on the system. The WCA’s contain the last remnants of the tall-sawgrass landscape, as well as the bulk of deep marshes, wet prairies, and tree island hammocks still remaining outside ENP. The WCA’s are critically important to a diverse array of wildlife resources, particularly wading birds (including the endangered wood stork), the American alligator, and the endangered snail kite. Grass shrimp, crayfish, and select fish species are well adapted to the periodic wet/dry regimens that characterize the Everglades.

LNWR preserves the largest and most pristine remaining section of the northern Everglades. It is designated as critical habitat for snail kites and as an Outstanding Florida Waters. Thousands of tree islands, sloughs, wet prairies, and sawgrass plains characterize LNWR. It contains some of the deepest peat layers left in the Everglades. LNWR is surrounded by urbanization to the east and agriculture to the west.

The non-marine southern Everglades portion of the sub-region is coincident with the freshwater and terrestrial portions of Everglades National Park (ENP) and the adjacent authorized East Everglades acquisition lands. Established in 1947, this is the first national park created to protect a threatened ecological system. It is a wetland of international importance and has been named an International Biosphere Reserve and a World Heritage Site.

The mainland portion of ENP, predominately a mosaic of flat, seasonally flooded marshes and prairies with interspersed forested islands, is dependent on alternating wet and dry seasons. It has a high biotic diversity with a unique mixture of temperate and tropical species. This includes a large number of endangered animal species and of endemic plant species with highly specific habitat requirements.

The sub-region also includes the agricultural area east of C-111 in southern Dade County that drains into C-111 from the C-102 canal west of S-194, the C-113 canal, the C-103 canal west of S-196, and the C-111E canal. This area is utilized for production of a wide variety of vegetables and tropical fruits.

The sub-region includes the portion of Florida Bay within the ENP boundaries. Florida Bay is an 850-square-mile mosaic of shallow-water banks and relatively deeper basins connected by deep narrow channels. It is dotted with hundreds of small islands or "keys" rimmed with mangroves. Until recently clear waters and lush seagrass meadows characterized the Bay.

Florida Bay is the principal inshore nursery for the offshore Tortugas pink shrimp fishery. It provides critical nursery habitat for other important recreational and commercial fishery species, such as spiny lobster, red drum, and spotted seatrout. The Bay also supports numerous protected species, including bottle nosed dolphin, sea turtles, manatees, and American crocodile. About 85 percent of Florida Bay lies within Everglades National Park; while the remainder lies within the FKNMS.

The Southern Glades and Model Lands consist of a broad southern coast marsh prairie, with a relatively narrow fringing belt along the coastline of mangrove swamps. Under natural conditions, the southern coast marsh prairie occurred in a relatively limited area in Florida, inland from the coast in an area from east of Homestead to an area between Long Pine Key and the broadening belt of mangrove swamps north of Cuthbert and West Lakes. These prairies were separated from Shark Slough and its flanking southern Everglades marsh prairies by the Miami Rockland pine ridge.

The WCA’s are integral to the restoration effort. They include the largest remaining area of undeveloped Everglades. LNRW is currently managed in a manner that emphasizes preservation of the natural habitat in order to promote wetland species health and biodiversity. The WCA’s also serve as storage areas for excess water from Lake Okeechobee and the EAA, thus providing flood control for the LEC urban area. Water stored in the WCA’s augments the LEC water supply by recharging the Biscayne Aquifer and retarding saltwater intrusion. Management of the WCA’s also controls water flow into ENP.

Water from the mainland portion of ENP flows south to provide fresh water to the Park's mangrove fringe and Florida Bay. ENP, in turn, is directly dependent on Lake Okeechobee and the Water Conservation Areas for fresh water and is subject to contaminants transported from these areas. Because it is situated so close to a major metropolitan area, ENP faces serious threats. The water that supports Everglades resources is also in demand by urban residents and the agriculture industry. These demands for water and flood control are the source of many of the present problems in ENP.

Agricultural areas within the C-111 basin drain primarily either into Taylor Slough via the L-31W canal and pump station S-332 or to the panhandle of ENP via the lower C-111. Since these areas were historically within the Taylor Slough basin, the runoff volume is important to the area’s slough hydrology. Under some conditions, flows also are discharged eastward to Biscayne Bay. These waters aid in maintaining a freshwater head which prevents salt water intrusion.

The water of Florida Bay is a mixture of freshwater runoff from the Everglades and water from the Gulf Coast that is transported around Cape Sable from the West Florida Shelf. Periodically, the reef tract is inundated by water from Florida Bay that escapes seaward through these same channels.

Inland areas of South Florida are the source of fresh water to the coastal areas. Florida Bay and South Biscayne Bay are the receiving waters for discharges from several water management canals. These serve as direct links to upstream areas and are a source of nutrient and contaminant contributions from urban and agricultural areas. Also, Dade County ground water is the primary source of drinking water for the Florida Keys; thus, wellfield contamination problems have a direct impact.

The Southern Glades and Model Lands areas receive a dominant portion of their inflows from direct rainfall. The Southern Glades area provides sheetflow across the lower C-111 and into the ENP panhandle area. The Model Lands area provides sheetflow to the lower Biscayne Bay.

Both water quality and quantity in the WCA’s have been severely impacted as a result of their location between urban and agricultural development, and the water management operations of the C&SF Project. In particular, LNWR receives the highest average annual phosphorus loadings of all other WCA’s as well as ENP. LNWR also receives higher amounts of some pesticides, the effects of which are unknown.

Since a major portion of the Kissimmee/Okeechobee and Atlantic Coastal Ridge drainage is diverted to sea for regulatory flood control, historic hydrologic flow through the WCA’s is severely reduced. The areas have been virtually isolated from the Kissimmee and Okeechobee watersheds, and the sheetflow that was a critical element in the formation and ecological structure and function of the Everglades landscape has been eliminated.

There have been major hydroperiod impacts resulting from impoundment of these areas. Channelization coupled with impoundment has increased depth and hydroperiods at the southern end of the systems, while dewatering and shortening hydroperiods in the northern end. One result is extensive invasion by exotic plants, such as melaleuca, as well as numerous exotic fish. Another is the shortening of hydroperiods and reduction in water coverage vital to successful wading bird reproduction. This is particularly critical since these units provide major rookery and foraging habitat for wading birds in normal and dry years. Because of the multiple Congressionally authorized functions that WCA No. 1 must satisfy, it is not possible to adopt a regulation schedule that is completely consistent with the purpose for which LNWR was established.

With drainage and development of the EAA, the WCA’s serve as retention/ detention systems for water storage and for input

of agricultural drainage. However, LNWR was established to mitigate the loss of Everglades lands to agriculture but has suffered, due to its location, as a support for agriculture. Chronic introduction of drainage waters with elevated concentrations of nutrients, especially phosphorus, has resulted in massive conversions of sawgrass and wet prairie communities to stands of cattails and cattail/sawgrass mixes.

In Everglades National Park, changes in the natural hydrologic cycle include water levels, surface-water inundation, and water flow. Completion of the Tamiami Trail in 1928, the first east-west road across the basin, altered and interrupted water patterns and blocked all natural sheetflow. Present flow patterns in ENP are limited and controlled by management of the WCA’s to the north, extensive agricultural and urban pumping, and drainage canals to urban areas to the north and east. Unnatural hydroperiods and hydropatterns throughout the Everglades are now typical, resulting in sharp reductions of seasonal water levels and large discharges for flood control purposes. These have been both ecologically significant and deleterious. Groundwater from the Biscayne Aquifer flows into Biscayne Bay modifying salinity and possibly carrying pollutants into the Bay waters.

The Everglades are presently subject to intense disruptions of historic geochemical processes due to human activities along its margins and, to some extent, from atmospheric transport. With the advent of intense land-use change, notably artificial drainage, cultivation within the Everglades Agricultural Area (EAA) and development of the Atlantic Coastal Ridge, phosphorus and other substances are delivered to the Everglades in quantities significantly above historic levels. One consequence of such enrichment is extensive development of cattail stands in phosphorus-enriched areas formerly dominated by sawgrass.

Changes in water quality, quantity, and distribution have had ramifications throughout the Everglades. The total number of wading birds nesting in the Big Cypress and Everglades basins has declined by more than 95 percent from peak estimates of nesting birds in the 1930s.

Understanding the relationships between a decline in wading birds and changes in hydropatterns that have resulted from water management practices will require increased study of (1) the dynamics of prey populations and (2) specific foraging strategies and patterns associated with successful nesting of wading birds. Some of the changes in aquatic communities that form the food base for wading birds are subtle and difficult to detect in the early stages until they are manifested in obvious collapses of native communities and natural processes. A good example is the recent finding of mercury at dangerous levels in fish and their predators.

Also, non-native fish have colonized natural and disturbed habitats during the past three decades. The rate at which fish have been introduced has increased since the mid-1970’s. Several introduced species of herpetofauna also occur in ENP, and colonization will likely continue.

Water management strategies have caused reduced reproductive effort, increased frequencies of nest flooding, and increased rates of juvenile mortality for the American alligator, one of the most ecologically significant of the larger vertebrates in the Everglades.

The continuing and possibly accelerating loss of species diversity of both flora and fauna from upland communities is of great concern. Invasion of the natural vegetation communities by exotic pest plants like the melaleuca and Brazilian pepper, is one of the most serious problems in ENP. Likewise, the extent of the melaleuca and Old World climbing fern in LNWR is a serious threat to the integrity of its wetland ecosystem. It is possible these and other invasive species may modify the water table and hasten extinction of native species.

Water levels required for flood protection in adjacent agricultural areas result in excessive seepage of water from the Everglades. This results in not only a loss of water from the natural system, but also significantly reduced water levels in the historic headwaters of Taylor Slough. Additionally, the seepage water into C&SF Project canals impacts the ability of the flood control system to prevent agricultural flood damages during wet conditions. Agriculture in this basin has experienced severe damages as a result of large storm events.

In Florida Bay a series of changes has become evident since 1987 that indicates acute ecosystem stress. These include:

Vast areas of hardwood hammocks have already been lost to development. Remaining stands are highly fragmented, but are critical to dispersal and movement of the white-crowned pigeon and migratory birds, as well as for protection of many rare plants and animals.

Efforts are focused on redirecting freshwater and sheetflow into northern Florida Bay; however, there is concern that measures to direct more flow to the Everglades may bring new problems to Florida Bay. These may include an increased nutrient contribution, which could cause more algal blooms, and increased contaminant input to the ecosystem, especially pesticides.

In the Southern Glades and Model Lands area, drainage, agricultural practices, invasion by exotic plants, and excessive fires have degraded the ecosystem. Major changes include: the encroachment of mangrove vegetation into areas that formerly were marsh prairies, the conversion of expansive areas of marsh prairies into thickets of willow and other shrubs, and the introduction of exotics such as Casuarina, Melaleuca, Schinus, and others.

The restoration objectives of critical importance for the Central Everglades sub-region are listed below:

• Reestablish historic pre-drainage hydrologic gradients, dynamic storage, and sheetflow.
• Reestablish rainfall-driven hydrology.
• Restore connectivity between WCA’s.
• Restore pre-drainage water quality.
• Restore pre-drainage landscape and ecological integrity.
• Control exotic plants and animals.
• Restore pre-drainage fire frequency and spatial boundary.

The restoration objectives for the non-marine portion of Everglades National Park are listed below:

The restoration objectives for the Southern Glades and Model Lands areas area listed below:

Important restoration projects in progress or proposed for the Sub-region are identified on the following pages: