Fifteen years ago, there was no noticeable problem with invasive Carolina willows at Audubon’s Corkscrew Swamp Sanctuary. That changed.
Corkscrew’s marshes and prairies, once dominated by diverse grasses and sedges that provide critical habitat for a range of wildlife species from the tiny least killifish to the threatened wood stork, were becoming smaller and fewer as the thirsty Carolina willow and other woody shrubs replaced the prairies taking advantage of altered seasonal water conditions that allowed them more water and a lack of wildfire to burn them away.
The Carolina willow, almost by itself, has expanded the definition of “invasive species” to include particularly aggressive plants that are native to Florida, not just faraway exotics.
"Now, more than ever, protecting and preserving 13,450 acres within the Sanctuary is critical to the quality of life for both wildlife and surrounding communities,” said Marshall Olson, Corkscrew’s interim sanctuary director. "As development continues to creep closer to Corkscrew Swamp Sanctuary, we need healthy wetlands to protect water quality, recharge aquifers, reduce the risk of catastrophic wildfire, and hold water during big rainfall events."
Now thanks to five years of mulching, burning, and burying the willow 1,000 acres are under restoration and more are being worked on every week.
“We’re not going to ever remove all of the willow,” said Renee Wilson, senior communications coordinator for Audubon Florida. “It is a native species; however, once we get the acreage into restoration we’re much better able to manage it and keep the willow at bay.”
The willow consumes so much water in a year the amount is counted not by inches but 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 drown many of the tiny Carolina willow saplings.
Once a stand of willows is established it can easily drink dry 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 wooded forest.
And the plant is stubborn, too. 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 Carolina willow started crowding out the native freshwater wetlands in Corkscrew in about 2010 and 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 flows in and out of the sanctuary as subdivisions were built surrounding the preserve.
Audubon’s restoration approach uses three steps: mulching up the willow, using controlled burns to set small wildland fires under the watchful eyes of trained firefighters, and allowing the summer rains to drive the remaining woodchips down into the ground turning the remnants of the Carolina willow into nutrient-rich mulch far more welcome than the Carolina willow itself.
That’s allowing allow prairie grasses to regrow in pools of water where birds forage, and gators bellow. Now in places within the 13,500-acre swamp not a willow’s in sight.
Controlled prairie fires are the best way to keep the Carolina willow from re-establishing itself, so while more willow is mulched up in the future, the firefighters will be overseeing set fires until, someday, all that will be left, where there are supposed to be wet prairies, are wet prairies.
“The 1,000 acres are now under restoration,” Wilson said. “They will continue to be maintained into perpetuity.”
Corkscrew Swamp Sanctuary, at 375 Sanctuary Road in Naples, is open from 8 a.m. to 1 p.m. and parkgoers are guaranteed at least two hours to gander at the grandeur. Tickets are available online, and adult admission is $17, admission for children ages 6 to 14 is $6, and free for ages 5 and under.
Environmental reporting for WGCU is funded in part by VoLo Foundation, a non-profit with a mission to accelerate change and global impact by supporting science-based climate solutions, enhancing education, and improving health.
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