Corkscrew Swamp Sanctuary losing water; scientists wonder why
It started right around 2000.
Nothing had much changed before then. Even through all the decades of new houses , even as canals were sloppily dug and roads hastily built by high-pressure property salesmen, even as agriculture grew and wetlands were steadily paved over, nothing seemed to greatly change the water levels in the Audubon Corkscrew Swamp Sanctuary.
But in 2000 and 2001, the water began disappearing, researchers Shawn Clem and Mike Duever found.
Over the past 18 years, the swamp has been getting the same amount of rainfall as it always has. It fills to its capacity during the wet months.
But as soon as the rains stop during the dry season, the standing water and ponds that should be receding slowly are instead sucked away rapidly. In most recent years, the swamp has been completely dry for months.
Researchers at Corkscrew now are racing to find out what is causing the water loss, and what the dry spells mean for the future of the wildlife, environment and aquifers there, and in Collier County as a whole.
"If it's happening here, it's not the only place it's happening," Duever said. "And I think when you look at the fires we've had, even with the amount of rain we've been getting, it could be more widespread. We just have the data here to show it."
Part of what makes the Corkscrew sanctuary valuable to researchers is that Audubon has been tracking daily water levels and rainfall totals there since 1957. That trove of information dates to before Immokalee Road was built, before the canals dried out the land that would become Golden Gate Estates, and before electricity and telephone lines were brought to the Corkscrew area.
The measurements are taken at the swamp's Lettuce Lake, the site of the deepest standing water and a popular stop on the Corkscrew boardwalk. There, alligators are easy to spot, and it's not far from where increasingly rare wood storks try to nest.
Duever, a biologist, led the sanctuary's research for more than 20 years, starting in the 1970s.
Clem, a wetlands and aquatics ecologist, now leads the sanctuary's research team.
Together they mapped out the 60 years of daily water level and rainfall data from the swamp.
The numbers show there had been a stable patternbefore something upset it around the turn of the 21st century.
For at least 50 years, the standing water in the Lettuce Lake would reach its peak at about 1.2 meters deep near the end of the rainy season in October. Then the water levels would slowly fall over the winter before bottoming out in June with about .2 meters of standing water. The lakes are 4.6 meters above sea level, so when there is standing water there is also groundwater in the muck and swamps under the lakes.
Starting around 2000, the lakes still filled just about every year to their peak at 1.2 meters deep. But the water levels started drastically falling in March and the lakes were completely dry by late May or early June.
Historically, dry outs would happen periodically after a particularly dry season. But since 2000 and 2001, the swamp is drying out as a matter of course, Clem said.
No one thing changed that year, Clem said.
"We don't know what's causing it," she said. "I don't think it's one thing. My best guess is that there are four big possibilities that stressed and stressed and stressed the system until in the late '90s it hit a breaking point."
Clem and Duever believe the water loss is due to some combination of increasing human use, with more wells and more homes demanding more water; agricultural water demand; canals that are flushing water out of the system; and changing vegetation, where drier conditions are causing the thriving of more leafy plants like willow, which hold less and lose more water, encouraging drier conditions.
"We don't know the proportion that each of those may be to blame," Clem said.
The researchers are presenting their findings to other scientists and ecologists, to authorities like the South Florida Water Management District and to the public in the hope that studies can be done to find specific causes and to see whether the trend may be true outside of the boundaries of Corkscrew.
Water Management District spokesman Randy Smith said he had heard of the Corkscrew findings but declined to comment on them.
The research also has caught the eye of SeaWorld and Coca-Cola. After representatives of the two business giants took a tour of the sanctuary this spring, the companies decided to donate $100,000 to help remove willows and plant sawgrass in the hope of holding water longer.
It's becoming increasingly clear the drying out of the ancient swamp, even for just a few months a year, is threatening wildlife that has relied on it for untold centuries.
Wood storks, a threatened species that has been nesting at Corkscrew Swamp Sanctuary for at least as long as settlers first arrived and documented them, stopped regularly nesting there the same time as the water levels started changing.
The storks, which historically had successful nesting seasons in Corkscrew every other year, are now only nesting in the swamp once or twice a decade. Instead they are moving farther into the Everglades or farther north of Florida.
When water levels lower too fast, the storks either lose their food source — the fish in that water — or the trees that hold their nests are left vulnerable to predators like raccoons that climb up to steal their eggs, Clem said.
"That water brings in alligators and if you're worried about mammals like raccoons, alligators are great guardians," she said.
The swamp itself, one of the last ancient cypress strands left in Florida, with its age-old towering cypress trees, may have never been more vulnerable, Duever said.
It is built upon about 6 feet of organic soil that has been building up over centuries. When that soil dries it becomes a particularly potent fuel. If that fuel were to catch fire it would smolder like an uncontrollable mulch fire, Duever said.
"There really isn’t anyway to stop a fire when it gets into organic soils," he said. "The only thing is to wait for the water to come up again. That's my big fear. If a fire gets in, it will take the whole thing out."