Proposed mitigation work on Fish Slough in conjunction with the National Audubon Society's Kissimmee Prairie Sanctuary INTRODUCTION The National Audubon Society owns and manages the 7,677 Ordway Whittell Kissimmee Prairie Sanctuary in Okeechobee County. This Sanctuary holds some of the highest quality dry prairie habitat left in the State and hosts many listed species of animals, especially those dependent on prairies. Dry prairies presently are poorly represented in conservation holdings and are rapidly being converted to improved pastures, citrus or row crops, creating concern for the long-term persistence of this ecotype. The Kissimmee Prairie Sanctuary is specifically dedicated to conservation of this ecosystem and its components, but drainage problems are preventing the Sanctuary from fulfilling its goals. This mitigation project would increase the area of the Sanctuary by about 600 acres, but more importantly, will restore proper drainage to about 5,000 acres of Sanctuary. PRESENT CONDITIONS In an average year, rainwater on the Sanctuary exceeds evapo transpiration by 10-15 inches. Because of an underlying hardpan soil layer, almost all of this water flows off the Sanctuary, historically to the south through Fish Slough and to the west through Sevenmile Slough (Figure J). Due to legal agreements and activities of neighbors, water no longer exits through Fish Slough and instead is impounded by the Military Grade on the southern border of the Sanctuary. Much of this impounded water now "backs" across the Sanctuary to the northwest, exiting down Sevenmile Slough (Figure 2). The result is increased hydroperiods in Fish Slough through impoundment, and Sevenmile Slough through extra flow. The headwaters of Fish Slough, upstream of the Military Grade, cover about 8,000 acres. About 2,000 acres of the Sanctuary are in this drainage, but because the impounded water is forced to flow to other parts of the Sanctuary, about 5,000 acres of the Sanctuary are directly affected by increased hydroperiod. The most greatly affected wetlands have changed from their historic sand-bottomed, largely open (Hypericum ringed ponds) conditions, to muck-bottomed, vegetation-choked (especially Pontaderia and Sagittaria) conditions. The adjacent uplands have succeeded from grasslands to brush dominated systems. The changes in uplands and
wetlands are exasperated by the interruption in fire regimes caused by increased wetness. South Aorida experienced wet years in 1994 and 1995 which has magnified the effects of the lack of drainage. Oak trees have died from flcxxling in many areas on the Sanctuary, as have saw palmettos. The Federally endangered Grasshopper Sparrow inhabits the Sanctuary's upland prairies that were so flooded in 1995 that no successful reproduction occurred. Other species certainly are being impacted as well. PROPOSED MITIGATION ACTION The Kissimmee Prairie Sanctuary can restore its historic and natural water flows by purchasing about 600 acres of land (Figure 3) between the Military Grade (where the impounding presently occurs) and Fish Slough (where drainage needs to occur). Water then could be released through this area, restoring the proper hydrology to the rest of the Sanctuary. In addition to restoring natural hydrology to the Sanctuary, the newly purchased area could have considerable restoration work performed through modifying the Military Grade for proper water control, filling ditches and restoring wetlands on the purchased area, and perhaps replacing improved pastures with native grasslands ( extent of activities depends on funding). The landowner of the tract in question is interested in selling thf? land for our mitigation needs. The area was permitted for citrus in 1992 ( and not converted to date) and five vegetation and land use categories were identified by Milleson Environmental Consulting, Inc., including: 342 acres of improved pasture; 115 acres of native/transitional grassland; 23 acres of palmetto prairie; 47 acres of oak hammock; and 77 acres of freshwater marsh. The marsh acreage was interpreted "legally" and an ecological assessment yields closer to 200 acres of wetlands. The National Audubon Society has experience in restoration work, with 4 projects in progress ( and one project finished) on the Sanctuary at this time. We could supervise the project ourselves, or cooperate with appropriate parties. Additionally, Sevenmile Slough is on a tract of land that the State is in the process of acquiring for a State Preserve (the 47,000 acre Latt-Maxcy property) and this proposed mitigation project will help restore a more natural hydrology for that area.