SUB-REGION 4. EVERGLADES AGRICULTURAL AREA
ECOLOGICAL CHARACTERISTICS:
o Highly managed landscape that includes urban areas.
o Expansive (700,000 acre) flat terrain on a tilted geologic platform (drainage implications).
o Dominated by muck soil.
o Sources of water are rainfall and Lake Okeechobee.
o Highly dissected by a reticulated canal network with an elaborate system of structures and pumps to facilitate flood control and irrigation.
o Area includes about 500,000 acres of intense agriculture, including 430,000 acres of sugarcane harvested annually and about 70,000 acres of sod, rice, and vegetables.
o Canals and flooded fields serve as habitat for wading birds and various biota, including endangered species.
o Area favors colonizing of opportunistic species.
o Area functions as a pool of nutrients, elements, and agricultural chemicals.
o Controlled annual burning of extensive areas an important component of present management.
o Soil subsidence (primarily oxidation) is occurring at the rate of 3 cm per year because of drainage.
o Land use is evolving due to soil subsidence.
o Hydroperiod is highly managed, with repeated flooding and draining.
o Dependent on other sub-regions or areas for water supply and disposal of flood waters.
o The pre-development sub-region included a pond apple swamp forest on the southern shore of Lake Okeechobee and an extensive dense, tall sawgrass plain, two vegetated landscapes that have been virtually eliminated from South Florida (Davis et al. 1994).
ECOLOGICAL RESTORATION OBJECTIVES:
o Eliminate the oxidation and subsidence of peat soils.
---Minimum: Slow peat loss through improved water management.
---Interim: Halt peat loss by maintaining saturation 60% of the time.
---Maximum: Begin re-accretion of peats within the area.
o Reduce atmospheric deposition from open burning to historic levels which resulted from natural fires.
o Develop an economically viable agricultural system that substantially reduces or eliminates subsidence of muck soils and allows for historic water flows to Everglades to the south.
o Restore representative communities of missing native plants including the pond apple swamp forest and the dense, tall sawgrass, as described in Gunderson et al. 1993.
HYDROLOGICAL RESTORATION OBJECTIVES
o Restore the modern historic hydrological linkage from Lake Okeechobee to the Water Conservation Areas by providing adequate conveyance capacity to carry the volumes of water that otherwise will be released to sea in Lake Stage Regulation. Use output from the Natural Systems Model for guidelines on historic, predrainage flow volumes and timing.
o Restore static and transient, or dynamic, water storage capacity in the EAA.
---Minimum: By a flowway or alternative means, create sufficient conveyance and transient storage within the EAA to allow the natural volumes and timings of flows through the STAs into the Everglades wetlands to the south. Develop a rain-driven formula for scheduling releases. Use a Natural System Model that includes Lake Okeechobee and the EAA and takes into account the seasonal volumes of the regulatory releases from Lake Okeechobee to the St. Lucie Canal and the Caloosahatchee River.
---Incremental: Create a sawgrass dominated flowway to provide conveyance and dynamic storage. In addition, recreate water storage capacity by developing an agricultural system that ends subsidence, e.g., by maintaining surface inundation 60% of the time to prevent further subsidence (Brooks and Lowe 1984, Lowe 1986).
---Unconstrained: Fully restore the predrainage EAA water storage and conveyance capacity and reverse subsidence, accreting organic soils.
o Deliver water from the EAA into the Water Conservation Areas that complies with Class III water quality standards and is of sufficient quality for preventing an imbalance of native flora and fauna and maintaining ecological integrity.
o Water delivered to Loxahatchee National Wildlife Refuge and the other WCAs is in compliance with the Refuge's Outstanding Florida Water designation and is in compliance with the terms of the 1991 Settlement Agreement and the 1992 Court Order.
---Minimum: Deliver water from the EAA to Lake Okeechobee that is consistent with preventing eutrophication of the Lake, and is consistent with requirements of the 1987 SWIM Act and the Lake Okeechobee SWIM Plan (South Florida Water Management District 1989).
---Incremental: Eliminate all backpumping into the Lake.
o Modify water export to facilitate re-establishing the predrainage sheetflow into the WCAs (particularly WCA3A), water delivery timing, and WCA hydroperiod, based on output from the Natural Systems Model and a rain-driven formula.
CRITICAL LINKAGES:
o Hydrologically linked to Lake Okeechobee, Water Conservation Areas, Big Cypress, Urban Areas, Everglades National Park.
o Through airshed linkages, the EAA contributes atmospheric loading of excess nutrients and contaminants to the South Florida Ecosystem.
o The EAA is an exporter of biomass (crops), nutrients (water, air and crops), and soil (crops, water).
SUCCESS CRITERIA
o Soil subsidence is halted (incremental goal) and peat is formed (unconstrained goal).
o Atmospheric deposition of contaminants (such as mercury) and nutrients is reduced.
---Minimum: No increases beyond current levels, or beyond levels with significant ecological effects.
---Unconstrained: No greater than maritime background depositions.
o Export of nutrients, peat soil constituents, and contaminants by drainage water is reduced.
---Minimum: Water delivered to the Refuge is in compliance with the Refuge's OFW designation and the terms of the 1991 Settlement Agreement and the 1992 Court Order. Water delivered to the Refuge and the other WCAs is in compliance with Class III water quality standards and is adequate for preventing an imbalance in native flora and fauna, and is adequate for maintaining ecological integrity.
---Incremental: Reduce concentrations toward settlement agreement figures.
o Nutrient loading from the EAA into Lake Okeechobee does not contribute to eutrophication of the Lake, as defined by lake inflow monitoring and the requirements of the SWIM Act of 1987 and the adopted Lake Okeechobee SWIM Plan (South Florida Water Management District 1989).
---Minimum: Desired macrophyte and periphyton communities return to parts of WCAs where they have been changed.
o EAA water storage capacity is increased.
---Minimum: Capability to make the water deliveries scheduled by the rain-driven formula based on Natural System Model.
o The predrainage sheetflow into WCA3A from the EAA is re-established, as defined by output from the Natural Systems Model.
o WCA hydroperiod and water delivery timing approximates the modern historic condition as defined by output from the Natural Systems Model.
o Mercury levels in wildlife populations are reduced to levels that exhibit no symptomatic effects on animal behavior, reproduction, survival, etc.
o Mercury levels in freshwater fish, alligators, frogs, turtles, and birds do not exceed EPA and Florida screening criteria for protection of human health.
