Florida’s Ongoing Struggle with Non-Native Water Hyacinth

The Sunshine State continues controversial spraying of herbicides like glyphosate to combat the aquatic weed.

As rivers go in the United States, the St. Johns is a rarity. From its headwaters near Vero Beach to its mouth at the Atlantic Ocean 310-miles downstream, it is entirely confined within the borders of Florida and runs in the opposite direction of most large rivers, from south to north. And it’s slow, dropping only an inch per mile, making it one of the laziest rivers in North America.

photo of water hyacinth
Water hyacinth was first introduced to the St. Johns in the late 1890s by an admirer who wanted to beautify the river. The quick-growing plant spread through much of the river, and eventually to most of Florida's waterways. Photo by UF/IFAS by Marisol Amador.

The river can be insufferably hot, windless, and buggy in summer, so it’s much more enjoyable to explore in the winter months, which I did recently on a small sailboat. With every mile, the river’s appearance and that of the surrounding landscape altered as we passed through everything from swamps and marshes to dense forests of moss-covered live oaks and the buttressed trunks of stately cypress trees to downtown Jacksonville. Many of these were the same views that American naturalist William Bartram had as he explored the river in 1774.

Since pre-colonial times, the tannin-dyed waters of the St. Johns have always been used for transportation. Its wide and slow-moving expanse bisects the state and earned it the name Welaka, or “river of lakes,” by the Timucua Indians. Until creation of the railroads, it was the primary method to travel in Florida, and was used to transport goods to market and deliver mail. As people headed inland to develop farms and cattle ranches, towns sprang up along the riverbank, supplied by regular visits from steamboats.

Tawny water hid the many manatees we passed. The large aquatic mammals only revealed themselves through plumes of water as they pumped their flukes like Olympic swimmers. And as we progressed southward past sleepy river towns the salinity diminished until somewhere near Georgetown the river water became completely fresh.

And that’s where I first saw them: large green mats of water hyacinth spread out on the banks like giant picnic blankets. The hyacinth appeared to favor small coves and creeks that adjoined the river. We noticed more than a few fishermen who parked their speedboats nearby, casting lures for prize bass that shelter in the dark underneath these invasive plants. After a night at anchor, we headed out at dawn across the second-largest lake in Florida, through which the St. Johns river passes. Lake George is wide, shallow, and almost twelve-miles across; all around us rafts of water hyacinth dotted the water.

Native to the Amazon River, this class I prohibited aquatic plant was introduced to the river around 1890 by an admirer who loved its attractive purple flower and wanted to “beautify” the waterway. It was a bad idea: Within a few years, its prolific growth completely clogged sections of the river, displacing native species. The dense mats blocked light from penetrating the water, shading out submersed plants, reducing oxygen production, and promoting the breeding of mosquitos. Boats attempting to power through a large mat can foul their propellers and become stranded. Within a few years of its introduction, alarmed by reports from panicked skippers and lumber companies that used the river to transport wood that sections of the river were impassible, Congress authorized the Army Corps of Engineers to use “any means necessary” to clear the noxious weed and free the river for commercial transportation.

Still, the “weed from hell,” as it’s sometimes referred to, has spread to most of Florida’s lakes and 33 other states. Hundreds of millions of dollars have been spent trying to control it and other nonnative plants via application of herbicides and mechanical harvesting. These control efforts proved largely unsuccessful until the 1940s, when, with the discovery of synthetic herbicides, managers found more success.

photo of water hyacinth
Florida relies in large part on synthetic herbicides to manage water hyacinth, despite concerns about the impacts of this widespread application of chemicals to the states rivers and lakes. Photo by UF/IFAS by Marisol Amador.

The use of these herbicides, which include glyphosate, has not been without controversy. Fishing enthusiasts and environmentalists have long pointed to the potential impacts of the state’s spraying program, including pollution of state waterways, impacts on other plants and animals, and the accumulation of decomposing plant matter.

“It’s destroying all our habitat,” Bryan Heaberlin, a Lake Helen bass fisherman, told The Daytona Beach News Journal. “You can throw a dart at any lake in the state of Florida with a ramp on it and there will be some guy with a poison boat showing up and spraying it every so often.”

The Florida Fish and Wildlife Conservation Commission (FWC), which is tasked with managing invasive plants and administering the state’s longstanding aquatic plant management program, in January decided to take a pause from herbicide treatments as they went on a “listening tour” around the state to collect comments from various stakeholder groups. (The US Army Corps of Engineers, which does more spraying than the FWC, did not suspend its program.)

They sure got an earful. At these well-attended meetings attendees questioned the efficacy and safety of herbicide use on the water hyacinth, the qualifications of the vendors who applied the chemicals, and the effects on marine life, native plants, and habitat. Many felt that the FWC was over-applying herbicides without considering viable alternatives like biological control, and noted that the long term effects of some of the chemicals were not known. Still others were distressed that if herbicide application wasn’t reinstituted posthaste, their lake would become unusable.

And while most people — concerned citizens and managers alike — would prefer mechanical harvesting as a control measure, the machines scoop up only half an acre of the non-native plants per day, and the plants, which have one of the highest growth rates on earth, can sometimes grow faster than they can be removed.

Since the listening tour, the FWC has resumed its spraying program but has directed its staff to make changes in its habitat management plans, which include: improving timing of herbicide-based invasive aquatic plant treatments each year; exploring new methods and technologies to oversee and increase accountability of aquatic plant control contractors; exploring ways to better integrate and increase the strategic use of mechanical aquatic plant harvesting; and developing pilot projects to explore better plant management tools.

“Invasive plants are a serious threat to Florida’s waterbodies, and we know from history that they can cause considerable harm in a short amount of time. We are resuming our management program with a commitment to these enhancements,” FWC Executive Director Eric Sutton said in a statement.

Some environmental groups are apprehensive about the decision to continue spraying.

“We definitely have concerns about the spraying and management of these [hyacinth] plants, because one of our top issues that we’ve been trying to tackle for two decades now is the growing threat of toxic green algae in the river,” says Lisa Rinamen, director of St. Johns Riverkeeper, which advocates for protection and restoration of the St. Johns river. “When you spray the hyacinth they die, they drop down, and they add more nutrient pollution to a river that already has too much nutrient pollution.”

The FWC has acknowledged their Gordian knot of a problem. They maintain that research and decades of experience show herbicide use on invasive aquatic plants achieves the best results, and that doing nothing isn’t an option — the state’s rivers would become unnavigable and native plants would be further displaced. But they say they will attempt to find the balance that manages the system in a way that pleases all diverse user groups of Florida.

What you can do to help stop the spread of invasive plants:

Before leaving a boat ramp, carefully inspect your trailer and boat for aquatic weeds. Many plant species can grow back from even tiny fragments, thereby infesting new water bodies.

Never transplant aquatic vegetation without first contacting a Fish and Wildlife Conservation Commission aquatic biologist in your state.

Never empty the contents of your home aquarium into the wild. Many aquarium plants are imported from around the world and could become a nuisance weed in your state waters.

In you live in Florida, report new infestations of nonnative species such as water hyacinth and hydrilla to the Fish and Wildlife Conservation Commission’s regional biologist in your area.

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