Wildlife and habitat damage assessment from Hurricane Charley: recommendations for recovery of the J. N. “Ding” Darling National Wildlife Refuge Complex

INTRODUCTION

Large infrequent disturbances (LIDs), such as hurricanes, fires, floods, tornados, and volcanic eruptions, leave an imprint on the ecosystem and are important ecological events (Turner and Dale, 1998). Their ecological importance to the animal and plant community, however, is not well understood, but research and our understanding has increased during the last 25 years (Literature cited and suggested reading). LIDs have a continual lasting effect from multiple events that occur over long time periods. For Florida, Ball and others (1967) estimated that 160,000 to 320,000 major hurricanes (Category 3-5) have occurred in the last 2 million years. In southern Florida, these storms occur every 20 or more years (Lugo and others, 1976). One of the most recent storms came ashore on 13 August 2004 as Category 4 Hurricane Charley at North Captiva Island and passed over much of the J. N. “Ding” Darling National Wildlife Refuge (JNDDNWR) Complex, Sanibel, FL (Caloosahatchee National Wildlife Refuge [NWR], Island Bay NWR, Matlacha Pass NWR, and Pine Island NWR). Within five weeks, a team of scientists was assembled to conduct field assessments of damage and literature searches for assisting the refuge staff with recovery. Our objectives for this research were to conduct an assessment of Hurricane Charley damage to wetlands and habitat for selected bird populations (especially mangrove forests, Mangrove Cuckoos, and Black-whiskered Vireo), waterbird rookeries (mangrove islands), impoundments (waterbirds and waterfowl), sea grass beds (manatees), and upland hardwood hammocks and ridges (threatened eastern indigo snake [Drymarchon couperi]). We also contacted potential collaborators and partners for information and possible cooperation for research on the effects of the storm.

Numerous reports exist concerning hurricane damage to tropical coastal ecosystems such as mangrove forests (Cahoon and others, 2003, Craighead and Gilbert, 1962, Doyle and others, 1995, Reimann, 1940, Roth, 1992, Smith and others, 1994, Stoddard, 1969), rain forests [Biotropica, Volumes 23(4a) and 28(4a)], freshwater swamp forests (Rybczyk and others, 1995), and hardwood hammocks (Horvitz and others, 1995, Slater and others, 1995). Hurricane impacts are complex and range from minor damage, such as defoliation, to catastrophic blow-downs of entire stands. Hurricane damage, however, is much more than impacts to vegetation (Cahoon, 2003). Elevation within coastal marshes and forests can be changed by erosion (Jackson and others, 1995), sedimentation (Risi and others, 1995), formation of tip-up mounds and pits (Titus, 1990), or by post-event subsidence and compaction (Cahoon, 2003, Cahoon and others, 2003, Smith and others, 1994). Defoliation of the vegetation causes inputs of fresh, nutrient-rich leaves into coastal waters and flooding alters the sediment salinity and nutrient regime. Both can impact nutrient fluxes and water quality (Blood and others, 1991, Jackson and others, 1995). Disturbance to the forest canopy results in changed vegetation structure including shorter stature and smaller diameter stems. Importantly, species composition is altered, which may provide conditions for undesirable species to appear or increase in abundance. Vine and liana populations may increase rapidly following the loss of canopy trees (Allen and others, 1997, Sanchez and Islebe, 1999, Schnitzer and others, 2000). This period of succession can also include invasions by exotic species (Horvitz and others, 1995, 1998). Tip up mounds and pits created when a tree topples serve as sites for colonization and regeneration for both native and exotic species (Cooper-Ellis and others, 1999, Titus, 1990). Often, differences in storm effects are found in close proximity, depending on topography, elevations, and extent of the storm (Scatena and others, 1996, Walker, 1991). Hurricane Charley produced a wide variety of damage, short-term, and long-term effects at the JNDDNWR Complex.

Refuge mission and objectives

JNDDNWR Complex joins in partnership with residents of Sanibel, Captiva Islands, Lee County, and the State of Florida to safeguard and enhance subtropical habitat for wildlife. The Complex protects and provides habitat for endangered and threatened species including the west Indian manatee (Trichechus manatus), wood stork (Myteria americana), bald eagle (Haliaeetus leucocephalus), and eastern indigo snake (Drymarchon couperi) as well as other United States Trust Species, such as Mangrove Cuckoos (Coccyzus minor) and Nearctic-Neotropical migratory birds. The refuge's staff implements management techniques to sustain natural ecosystem processes and to provide feeding, nesting, and resting habitat for shorebirds, waterbirds, waterfowl, and Nearctic-Neotropical migratory songbirds. The staff also provides high quality interpretive and environmental education programs and recreation compatible to the purpose of the refuge (United States Fish and Wildlife Service, 2004).