Marsh and Prairie Restoration

Study Conducted by Audubon Reveals Canal Operations are Drying Corkscrew Swamp Sanctuary

Over-drying has significant implications for wildlife, plant communities, and vulnerability to catastrophic wildfire.

NAPLES, FL -- A study conducted by Audubon’s Corkscrew Swamp Sanctuary in Naples, Florida, recently concluded that ground water levels have dropped substantially over the past two decades primarily due to canals and weirs downstream of the Sanctuary. Lower water levels contribute directly to Wood Stork nesting failures and reduce the water recharge and wildfire protection benefits provided by the protected wetlands within the Sanctuary. Overdrainage also contributes to poor downstream water quality and red tide events.

“Witnessing the impacts on this world-class wetland, and especially the decline of our treasured Wood Stork colony, has been heartbreaking,” said Shawn Clem, PhD, who is the director of research for the Sanctuary. “We saw Wood Stork nesting patterns change and knew there was an explanation, but changes in hydrology can be difficult to see, especially considering the variability in our rainfall within each year and between years,” she added.

While agricultural and public water supply withdrawals were demonstrated to have some negative impacts on water levels at the Sanctuary, the new model showed that flood control systems downstream have clearly had the greatest impact.

On Southwest Florida’s flat landscape, water normally moves slowly through swamps like Corkscrew. But canals operated to drain water during rainfall events from low-lying communities downstream have also had the effect of pulling water faster out of this increasingly vulnerable wetland of international significance.

Sixty years of daily surface water measurements demonstrated that since the mid-2000s, the Sanctuary has been substantially drier in the dry season (winter/spring) than it was in previous decades. Analyses by Audubon scientists have shown that the wetlands are drying out to a greater extent, with water levels remaining below ground for longer intervals, despite no change in rainfall patterns.

In addition to water level monitoring, Sanctuary staff have also observed impacts to Wood Stork nesting. Wood Storks are highly dependent upon the availability of fish throughout the December through May nesting season. The over-drying observed at Corkscrew Swamp Sanctuary, coupled with the regional loss of the wetlands that are critical for wading bird foraging, has led to failed Wood Stork nesting efforts at the Sanctuary for most of the past 15 years.

Last year, Sanctuary staff contracted Water Science Associates to conduct the modeling study with funding assistance from the South Florida Water Management District’s Big Cypress Basin. The model provides unique insight on the relative impact of a number of human water use and management operations on wetlands, with findings that can be applied throughout our region, and beyond. It also provides recommendations on additional data collection and modeling that are needed to develop a mitigation plan that would restore the Sanctuary’s hydrology. Next steps include further collaboration with the Big Cypress Basin, the South Florida Water Management District, local governments, and all Audubon’s landowning neighbors in order to ensure adequate flood protection while re-establishing wetland function, clean water supplies, favorable conditions for Wood Stork nesting, and wildfire resilience.

“Wetlands protect us from flooding in hurricanes, fires in droughts, and absorb algae bloom-fueling nutrients before they reach the coast,” said Lisa Korte, PhD, Corkscrew Swamp Sanctuary Director. “Corkscrew Swamp Sanctuary is a bellwether for all of Florida’s wetlands. Our quality of life and prosperity depend on protecting and restoring these important resources.”

The Sanctuary’s wetlands are a critical source of aquifer recharge and overland sheetflow into the Imperial and Cocohatchee Rivers that feed Estero Bay’s estuaries (Florida’s first Aquatic Preserve) and the Wiggins Pass Estuary, a designated Outstanding Florida Water. As the heart of the Corkscrew Regional Ecosystem Watershed (CREW), the Sanctuary also contributes clean water downstream to the Gordon River and Naples Bay.  In addition, the forested wetlands have tremendous wet season water storage and cleansing capacity and reduce the risk of catastrophic dry season wildfires.

Learn more about the study.

Audubon’s Corkscrew Swamp Sanctuary, recognized as a Wetland of International Importance by the Ramsar convention and a Wetland of Distinction by the Society of Wetland Scientists, has been an Audubon-protected site for more than 100 years. It includes over 13,000 acres, including the world’s largest remaining, old-growth bald cypress forest. An estimated 100,000 visitors annually explore the Sanctuary’s 2.25 miles of boardwalk through ancient forest and marsh habitat. 

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