Stay in the know about wildlife, water quality, and ecosystems on Sanibel and Captiva Islands and in Southwest Florida

Wildlife Adapting to Changes in Habitat

April 15, 2023
Nature Center Aerial 2023 1800

One of the most unique aspects of Sanibel Island is its freshwater system that supports rich species diversity. Hurricane Ian’s storm surge inundated most, if not all, of the freshwater bodies on the island, which has significantly affected most freshwater species.

“The changes in Sanibel’s uplands, wetlands, and transitional areas after Hurricane Ian will force wildlife to adapt, if possible, to sustain their island existence,” said Wildlife & Habitat Management Director Chris Lechowicz.

Pre-hurricane, the island’s freshwater bodies had salinities of 0-3 practical salinity units (PSU), which were recorded at 11-33 PSU post-hurricane. For comparison, pure seawater is 35 PSU.

Various species of invertebrates, fish, amphibians, and reptiles that depend upon freshwater will respond to the changes in different ways, Lechowicz said. Many species can withstand brackish conditions, such as mosquitofish (Gambusia affinis) and Florida red-bellied turtles (Pseudemys nelsoni), for long periods of time. However, some freshwater gamefish — bluegill (Lepomis macrochilus), largemouth bass (Micropterus salmoides), and pig frogs (Lithobates grylio) — withstand moderate levels of salinity for only a short time.

Saltwater putting stress on species

“The long, dry season and lack of significant rainfall until the summer will put high stress on these species and may cause one or more species to fade from the island,” Lechowicz said.

Much of the island’s uplands also took on saltwater. Gopher tortoise (Gopherus polyphemus) burrows, except for those in the highest areas, were flooded out. However, many tortoises have either begun to excavate their old burrows or dig new ones. The barrage of saltwater in the hammocks and grasslands either killed or weakened shrubs and hardwood trees with low salt tolerances. Fortunately, many native grasses have a saltwater tolerance, which is apparent now as many grasses have started to grow back.

Cabbage palms (Sabal palmetto) appear to be one of the most resilient plant species to the storm surge, despite several areas where these palms didn’t make it due to prolonged saltwater.

The quantity of dead vegetation, primarily from trees and shrubs, is unprecedented on Sanibel because the island hadn’t hosted such quantities of high canopy coverage in its known history.

“Historically, Sanibel was primarily an open-canopy grassland that dried out seasonally and burned in wildfires, and native wildlife adapted to this habitat,” Lechowicz said. “Now, wildlife are trying to acclimate to habitat created by an immense biomass of dead vegetation.”


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