Sea rise could wipe out coastal nesting grounds for endangered Everglades sparrow within decades
A secretive Everglades sparrow at the center of some of the most contentious debate over restoring the vast wetlands is facing an ever more dire threat: sea rise.
A new study that modeled both rising sea levels and restoration efforts to move more water into Everglades National Park concluded that in just 50 years, the endangered Cape Sable seaside sparrow could likely disappear from coastal nesting grounds.
Researchers with the U.S. Geological Survey put the odds of finding sparrows in the prairies just inside South Florida’s watery wilderness then at less than 10%.
Meanwhile, an inland area that could become a refuge for the birds and holds the second highest amount of nesting will likely be too wet under ongoing restoration work.
“Restoration planning to date has been happening in isolation,” said USGS research ecologist and lead author Stephanie Romanach. “Now as decision makers [and] natural resource managers are starting to ask questions about what conditions are going to be like under climate change and sea level rise, those two conversations would really benefit from an intersection.”
Time to find an answer is also running out, she said.
“Conditions are changing really quickly on the ground,” she said. “We see conditions changing year to year. So we don't really have a long time.”
The tiny sparrow was added to the endangered species list in 1967, fifty years after it was first discovered on Cape Sable and two decades after the park was created amid mounting evidence that the canals, levees and roads clearing the way for development in South Florida were ruining what was left of the pristine Everglades.
Today, fewer than 2,500 sparrows remain, down from a high of about 6,600 counted in the 1980s.
The birds live and nest in marle prairies in the Everglades and Big Cypress, where the rocky grasslands have a slightly higher elevation among the wetlands. Sparrows build their nests in grasses about a half foot off the ground, high enough to escape summer rains that flood the prairie and keep predators away. Such precise nesting requirements helped make the sparrow a perfect measure for restoring historic water flow across the prairies that dry out in spring and fill with wildflowers and orchids.
“If you get the water right, the sparrow will come back. If the sparrow comes back, it's because you've got the water right,” Stuart Pimm, a Duke University conservation ecologist and an expert in extinction science, told WLRN after the last sparrow count. “Those things are intertwined inextricably.”
But so far, water management has failed to save the birds and may have even altered what had once been considered prime sparrow habitat west of Shark River Slough. During the last count in 2021, no sparrows were found in the area.
New water operations started by the U.S. Army Corps of Engineers in September 2020 aim to improve nesting grounds elsewhere. It’s not clear what will happen to the western areas.
Pimm worries the plan oversimplifies historic water patterns by moving water from the western side of the vast water conservation area north of the park directly south without balancing historic patterns.
“It's important to be aware of the larger issue. This is a national park. It's a wetland national park. And water management decisions have massively destroyed habitat in that part of the park,” he said. “That's alarming and it's worrying in all sorts of ways. What does it say for our ability to manage national parks properly?”
The new USGS findings also make clear that sea rise needs to be factored into decisions.
To get a better understanding of what the future will look like, the USGS model looked at both sea level rise and restoration plans for water management. Researchers focused on coastal habitat near Florida Bay expected to be hardest hit by sea rise. Sea level rise has already climbed about six inches in just the last 30 years.
With the coastal area expected to have less than a 10% chance for nesting, that puts more pressure on remaining nesting grounds, Romanach said.
One of those areas, just over 22,000 acres along the eastern edge of Shark River Slough, now has the second highest count of sparrows. But water operations will bring more water, Romanach said.
“As a result, it is likely to become less suitable for sparrows,” she said. “But because of its geographic position and being away from the coast a bit and already having the second highest sparrow population, it could be an interesting one to focus on for providing a refuge for seafarers from sea level rise and climate change.”
If the sparrows are to survive, management decisions need to consider how sea level rise is altering those historical landscapes where sparrows nested, she said.
“Sparrows can't nest in mangroves. And so where is this ecosystem going? What is the trajectory?” she said. “We're right now doing a lot of plumbing. We're directing water. What are we aiming for, considering climate change?”
The findings also highlight the difficulty in balancing restoration with protecting a host of endangered species found in the park.
When sparrow habitat was designated in the 1970s, nearly 200,000 acres was protected, including the area west of Shark River. At the time, scientists worried the designation left out too many areas. But after conservationists sued to have the areas expanded, the U.S. Fish and Wildlife Service instead cut the size down to just over 84,000 acres in 2007.
The area west of Shark River, the most controversial because keeping water out of the area sometimes caused flooding on tree islands to the north, was omitted. Wildlife managers said geologic testing showed the area had been sawgrass marsh. Construction of the Tamiami Trail that dammed up water created the prairie.