Going dry: Extended water loss in Collier swamp worries researchers

If there’s one defining feature of a swamp, it’s water, and researchers at Audubon’s Corkscrew Swamp Sanctuary northeast of Naples have noticed periods of extended water loss in the wetlands there.

The sanctuary is home to the “largest remaining old-growth bald cypress swamp in the world,” according to a 2019 hydrology report, and long dry periods could shift the ecology of the wetland leaving wood stork and other wildlife populations without the habitat they need.

“It’s not a question of the volume (of water), it just has to do with how we’re drying and where that water is going,” said Shawn Clem, director of research at the sanctuary and lead author of the 2019 report.

Now the sanctuary is partnering with a local basin board to model the potential cause or combination of causes. The outcome of the models will help researchers work toward solving the water loss.

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The wood storks at the sanctuary are an important ecological indicator, Clem said, and any declines would speak to the changing ecosystem.

“For wading birds, wood storks are more particular in feeding habits and have high energy demands,” she said. “So if you have an ecosystem that can meet the needs of the wood stork, it’s also meeting needs of a whole suite of species, and I think that would trickle up to other animals.”

Declines of wood stork populations happened around same time the developments started pushing east in Collier County, she said. As more people come to the area, there’s a greater strain on the water and more flood control is needed to prevent flooding.

Clem and fellow researcher Mike Duever looked at 60 years’ worth of hydrology data and noticed extended water level decreases between the dry seasons of the ‘90s and ‘00s.

“In the data, our wet season hasn’t changed that much. The change is in the dry seasons,” Clem said. “From June to (the end of wet season), things now look similar to what they did back in ‘60s. The change is in late December, early January and that’s when we are losing water much more quickly than we did historically.”

While several issues could be a factor in the changing water levels, land development, water management and shifting vegetation are at the focus of the next step for finding potential solutions.

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In a partnership project with the South Florida Water Management District’s Big Cypress Basin, Clem said the sanctuary is working on a modeling study to determine what cause or combination of causes is drying out the swamp.

“I think what the board wants to do is get additional modeling to understand what, if anything, is going on,” said Charlette Roman, chair of the Big Cypress Basin Board. “Once the results of that modeling are complete, then that would lead us to what actions we could go on to from there.”

The basin had considered the changing hydrology prior to Clem and Duever’s report to them in 2018, said Lisa Koehler, administrator of the basin. Staff at Big Cypress Basin wanted to make sure its canal systems weren’t affecting the sanctuary’s water levels. She said the canal systems are too far south to influence the sanctuary.

"Corkscrew Swamp Sanctuary is so critical to the success of the wood stork, so I'm really excited the basin board was in support of moving this forward," Roman said.

Another potential cause in the long dry periods affecting the swamp could be the shift from grassy vegetation to larger, thirstier woody vegetation.

“Little plants with low roots get burned in dry season, those kinds of plants don’t pump a lot of water from deep in the water table,” said Brad Cornell, policy associate for Audubon of the Western Everglades and Audubon Florida. “If those are succeeded by the Carolina willow and wax myrtle and woody vegetation, those deeper roots suck more water out of ground and (shift) it into the atmosphere.”

The sanctuary has used several grants to restore about 600 acres by using a large machine to remove and mulch the willows. And so far, it has helped.

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“We saw like 1,000 black belly whistling ducks,” Cornell said of the restored area. “We know it works, but it’s very expensive.”

For now, Clem and water managers in Southwest Florida are awaiting the modeling results due out this fall, but where Corkscrew has been able to document the receding waters for decades, the rest of the region should be paying attention, Cornell said.

"The reality is that even if we keep our sanctuary in pristine condition, we are at the mercy of what people do on the land all around us," he said. "It’s the principle of watersheds that is at play here. It's very difficult for us to manage our part of the watershed without coordination with neighbors."  

Karl Schneider is an environment reporter. Follow him on Facebook and Twitter: @karlstartswithk, email him at kschneider@gannett.com