Hurricane Ian’s Impact on Keystone Species
Hurricane Ian has drastically affected all the habitats on Sanibel Island, with impacts on keystone species yet to be fully determined. The conservation and sustainability of several keystone species in South Florida are vastly important to other wildlife species. Keystone species have an immense effect on the natural environment and hold the ecosystem together. The loss of a keystone species would result in an intense change to the overall habitat and species diversity.
Two of most well-known keystone species in Florida are actually reptiles: the Florida gopher tortoise (Gopherus polyphemus) and the American alligator (Alligator mississipiensis). Both create habitats that benefit many other species.
Gopher tortoises, a threatened species in Florida, live in open sandy upland grasslands and ridges. Gopher tortoises dig long and sometimes deep burrows that have been documented to provide habitat for over 350 animal species throughout their range. Many of these species are completely dependent upon these burrows and would not be able to survive without them.
Many of the uplands on Sanibel were flooded over from the storm surge and burrows were totally inundated with tortoises in them. “Tortoises are accustomed to occasional flooding and although there was likely a significant loss of tortoises, it’s certain that many survived,” said SCCF Wildlife & Habitat Management Director Chris Lechowicz. “This has been verified by several people throughout the island.”
Gopher tortoises have been seen walking around looking for live grasses and sprouts of other plant species. Many plant species are beginning to regrow leaves and sprout from the ground; however many species will not be successful for a period of time due to the saltwater intrusion in the soil. Pictured here is a gopher tortoise spotted on Sanibel by Virginia Lattner.
Prior to Ian, gopher tortoises were documented to be in steep decline due to development. Their preferred habitat is unfortunately where people prefer to build housing and businesses which results in them being pushed out or relocated to other areas. The invasion of exotic plant species, such as Australian pines (Casuarina equisetifolia) and Brazilian pepper (Schinus terebinthifolius), as well as native shrubs and trees that invade open canopy grasslands due to the lack of wildfire, have greatly reduced the usable habitat for the Florida gopher tortoise.
The American alligator provides several benefits to the habitat and wildlife species. During the dry season in south Florida, they create “alligator holes” in mostly dried up wetlands that provide wet habitat for wading birds, other reptiles, and fish. The mound-like nests of alligators provide nesting areas for other egg laying vertebrates such as wading birds and turtles.
These species choose to nest in these guarded alligator nests because the female alligator will protect that mound, containing her eggs as well as other species eggs from predators such as raccoons (Procyon lotor) and coyotes (Canis latrans). Several bird species have been shown to lay eggs on small rookery islands in lakes, rivers, and other waterbodies that have healthy alligator populations. They choose to lay eggs on these islands because there is safety from predators that may try to swim across. Alligators hunt for prey in the water which helps protect bird eggs and young.
“Alligators will be affected by the saltwater intrusion on the island,” said Lechowicz. “Although alligators can tolerate saltwater for a time, they cannot live in it indefinitely. They must find freshwater areas to survive. We’re still in the rainy season, so the freshwater being added to the island from rainfall will bring down salinities in many areas and will create new freshwater puddles for wildlife to drink from.”
SCCF will continue to monitor these keystone species and will provide updates.