Invasive Carolina willow becoming a problem at the Corkscrew Swamp Sanctuary
Growing ever-closer to the public area in the 13,500-acre Corkscrew Swamp Sanctuary is a forest of extremely thirsty, ecosystem-changing, shape-shifting, pollen-producing Carolina willows that have invaded the wet prairies.
Way up high, standing atop an observation deck built at the edge of a pristine Old Florida swamp, the quality of the view is contingent on which way you look.
Behind the tower, there is a boardwalk that disappears in a darkened forest where the canopy is thick, the air cool, and the water shallow. Songbirds tweet, alligators bellow, butterflies flitter, woodpeckers peck, and 500-year-old cypress trees grow. Slowly. It is a picture of environmental health.
In front of the tower, the scene is wildly different. Growing ever-closer to the pristine swamp is a forest of extremely thirsty, ecosystem-changing, shape-shifting, pollen-producing Carolina willows that have invaded the wet prairies in the 13,500-acre Corkscrew Swamp Sanctuary.
The Carolina willow is selfish, and it’s a lousy neighbor. The plant, which can also grow as a bush either before or after it’s a tree, sends a shallow root system into the soaked soil, and takes a never-ending gulp. Long, serrated, spear-shaped leaves sprout out from branches and criss-cross one another, denying animals access to wet prairies that provide excellent foraging, and a place to cool off.
“We have had a native plant, the Carolina willow, take over many of our wetlands,” said Audubon Florida’s Lisa Korte, who is the director of the sanctuary. “Rather than having these very open wetlands, you’ve got a physical barrier where wading birds are not able to get in.”
The willow is among the plants and animals native to Florida that are expanding the definition of “invasive species.” The Department of Agriculture says a plant or animal (or fungus or bacteria or seed or egg) is invasive if it will likely cause harm to the environment, the economy, or human health.
The Carolina willow meets each of those criteria.
The willow consumes so much water in a year the amount is counted by depth, like a large puddle, and an average tree can suck up one or two feet — more if stressed — to a point where it lowers the water level in a wet prairie and diminishes its flow. In turn, those changes increase the number of tiny willow saplings that will grow into mature bushes or trees because the process is no longer controlled naturally by flooding rains in the summer that smother the tiny saplings.
Once a stand of willows becomes more substantial it can easily drain a wetland, and common sense would dictate that should be the end of a plant known for being a water hog. But the Carolina willow can adapt to not only survive drought, but thrive, and begin a sort of terraforming that can turn an herbaceous wetland into a forest.
If a wildfire burns up a Carolina willow tree, or a homeowner cuts it down, it will grow back - as a bushy, squat shrub. Thickets of willows can block access to waterways, choke streams, and contribute to saltwater intrusion.
The plant is not recommended for use around the house as they are often laden with pests such as tent caterpillars, leaf beetles, aphids, willow sawfly, and various twig borers. The willow is rather susceptible to disease like blight, powdery mildew, leaf spots, crown gall, and cankers.
The willow’s wood tends to crack in winds and heavy rains, dropping leaves, twigs and branches as litter that must be cleaned up. In humans, the willow’s pollen can cause a severe allergic reaction.
One of the only positive uses of the Carolina willow is that its grey bark with scattered warts has long been chewed on for its aspirin-like pain relief. The trunk of the tree has been particularly suited for building prosthetics, along with crates, and wooden utensils. Horticulturalists say the willow’s shallow, expansive root system makes it good for erosion control in places with lots of water and full sun. However, horticulturists recommend surveying the surrounding erosion control area for willow saplings as the plant “moves” by releasing its tiny, hairy seeds to the wind.
Korte thinks the Carolina willow, which did not grow in the sanctuary until about 15 years ago, was able to establish there due to a combination of climate change-induced alterations in seasonal rainfall patterns including stronger and more frequent storms, and diverted water flow in and out of the sanctuary as subdivisions were built surrounding the preserve.
Perhaps even more important was the decline in the time-worn practice of allowing natural and controlled wildfires to burn, which clears the land naturally while fostering healthy regrowth. Blazing forest fires are not something people who just bought a new home along a woody sanctuary wanted to see as the residences started being built in the 1960s and 1970s.
“Prior to that, people would just burn anytime, all the time. You know, the ranchers. People did what they needed to do,” Korte said. “In the ‘70s, ‘80s and ‘90s, there started to be protocols and you had to get a permit to burn and notify your neighbors, the authorities. Now we are trying to catch up with that.”
For now, the sanctuary’s land managers are eradicating the willows with heavy machines and commercial wood chippers, digging up the plants and shredding them. With its roots ripped from the ground and in tiny pieces, the plant is washed down into the soil like a natural mulch.
Dozens of invasive species also have taken up residence inside the sanctuary’s 13,500 acres. including the South America giant apple snail, which can grow to the size of a baseball, will eat anything, and lays gooey pink eggs on whatever sticks out of the water in a swamp. Once the snail has chewed through all the plants in a swamp or wet prairie it will move onto dry land to continue feasting. The snail also poses a threat to human health as it can carry rat lungworm, a parasite that can make people who eat the snail – a popular delicacy in Taiwan -- sick and occasionally cause meningitis.
The sanctuary is also dealing with melaleuca, a tree native to Australia that grows prolifically throughout the Everglades and crowds out native vegetation, the Brazilian pepper tree, which produces a dense canopy that starves other plants of sunlight, and air potato, a vine from Asia that can grow up to six inches a day and smothers native vegetation.
“We don’t have pythons, I can tell you that,” said Renee Wilson, a spokeswoman at the sanctuary. “Although our staff has attended training on how to identify them and catch them, if necessary.”
The Fish & Wildlife Foundation of Florida says more than 500 invasive species now call the Sunshine State home. At least 374 of them have been discovered in Collier County; in Lee County, more than 425 have been found.
Most of Corkscrew Swamp Sanctuary is off-limits to the public, but part that is includes a 2.25-mile long raised boardwalk, which allows visitors to stroll above the swamp for hours, take pictures, and revel in the plethora of plants and animals.
The Corkscrew Swamp Sanctuary, 375 Sanctuary Rd. in Naples, is open from 8 a.m. to 3 p.m. every day of the year, although the last visitors are admitted at 1 p.m. so there will be two hours available to stroll through the preserve. General admission is $17, $10 for full-time college students, $6 for children 6-14 years old. Children under 6 years old are free. Tickets must be purchased online here.
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