FLAMINGO, FLORIDA - Grabbing a clump of vegetation to steady herself, Tiffany Troxler gingerly slides her feet along the makeshift boardwalk as she ventures out into the marsh. The boards sag, dipping her up to her knees in the tea-colored water.
"This is the treacherous part," the Florida International University researcher says. "The water levels are up."
To a layman, this patch of brown-green sawgrass and button mangrove deep inside Everglades National Park looks healthy enough, but Troxler knows trouble lurks just beneath the murky surface. She points to a clump of grass: Beneath the water line, the soil has retreated about a foot, leaving the pale root mass exposed. It is evidence that the thick mat of peat supporting this ecosystem is collapsing - and research suggests encroaching sea water is to blame.
"You can think about these soils as your bank account," says Troxler, associate director of FIU's Sea Level Solutions Center. "In the condition that this marsh is right now, the outlook is not good."
Formed roughly 5,000 years ago, during a time of sea level rise, the Everglades once comprised an area twice the size of New Jersey. But over the course of just the last century, about half of the Everglades' original footprint has been lost - plowed under or paved over, never to be recovered, so long as South Florida's 8 million human inhabitants claim it for their homes, livelihoods and recreation.
The glades have been sapped by canals and dams that remapped the landscape and altered animal habitats, polluted by upstream agricultural areas, transformed by invasive species. And now, rising sea levels - this time, caused by man - threaten to undo what it took nature millennia to build.
What the Army Corps of Engineers calls a "highly managed system," others have sardonically labeled a "Disney Everglades."
Nearly two decades and $4 billion into the Comprehensive Everglades Restoration Plan, an ambitious federal-state program adopted in 2000, new data about the pace of climate change have called into question how much of the Everglades can ever be restored.
"I tend to think that everything can be saved," says Fred Sklar of the South Florida Water Management District, which monitors and runs much of the Everglades' infrastructure. "Restored is another question."
Draining the swamp
Today, we understand that natural systems like the untouched Everglades provide enormous benefits - water filtration, nurseries for fish and other wildlife, protection from storm surges, even carbon sequestration. But to 19th-century Floridians, all that water - and the mosquitoes and reptiles it harbored - represented an impediment to progress.
And so when Florida became a state in 1845, one of the Legislature's first acts was to pass a resolution asking Congress to survey the "wholly valueless" Everglades "with a view to their reclamation."
Beginning in earnest during the 1880s, a host of entities set about draining the swamp. They dug canals carrying nutrient-laden water that altered the salinity of coastal estuaries and caused toxic algae blooms. They seeded the wetlands from the air with a thirsty, paper-barked Australian tree called melaleuca. The vast custard apple forest that girded the lake's southern shore was torched. And peat soils that had accumulated over thousands of years dried up and blew away, causing the ground to shrink 6 feet in some places.
And still, the tinkering continued.
It was an event in 1928 that, as much as any, altered the Everglades' course. That year, a hurricane overwhelmed a dike at Lake Okeechobee - the Everglades' 730-square-mile "liquid heart" - causing a deluge that killed 3,000 people. The resulting 143-mile, 30-foot-high Herbert Hoover Dike now nearly completely surrounds the lake, permanently severing its connection to the park.
Scientists estimate that more than 650 billion gallons of fresh water a year once flowed south into what is now the national park. Today, that flow is about 280 billion gallons.
Now, some of the same canals and levees and pumps that helped drain the Everglades are being used to try to save them. Alongside the Everglades Agricultural Area, the 700,000-acre checkerboard of sugar cane and winter vegetable fields south of Lake Okeechobee, huge tracts are being converted to store and clean water for use when and where it is needed.
Perhaps the biggest step toward that end so far is the re-engineering of Tamiami Trail, the east-west highway that essentially has acted as a dike through the heart of the Everglades since the 1920s. Since 2013, workers have elevated 3.3 miles of the roadway, allowing water to flow freely into Shark River Slough, historically the deepest and wettest part of the Everglades.
"We're starting to see the vegetation respond, and we're getting more of those marsh grasses, more of those open water sloughs," says Stephen Davis, a senior ecologist with the Everglades Foundation. "I'm very confident that we can restore this ecosystem. And by restoration, I mean enhancing the functionality of what remains."
In 2015, the Corps submitted its most recent report to Congress, estimating the total cost of restoration at $16 billion - about twice the original projection. Three years later, panel of the National Academies of Sciences, Engineering, and Medicine urged a sweeping reassessment of the projects in the pipeline, warning that the current work is lagging behind the pace of climate change and could take 65 years to complete at the current funding levels.
When the restoration plan was adopted in 2000, its authors were anticipating seas to rise only 6 inches by 2050. They've since already risen 5 inches.
Earlier this year, an interagency group that includes the Corps of Engineers and the National Park Service issued its latest Everglades status report, writing that "the region's ecosystems are degraded and the anticipated ecological benefits of restoration are still to be realized."
Still, there are at least some hopeful signs.
Scientists poking through the bellies of wood storks, an "indicator species" for Everglades restoration, have found evidence that they are feasting on the non-native African jewelfish. And the endangered Everglades snail kite is showing a fondness for an exotic species of the mollusk, another latecomer to the region.
Perhaps the most encouraging development of all is the ongoing $578 million project to restore 40 square miles of the Kissimmee River Basin. Since the demolition of some of the dams, a portion of the river has found its old channel. The wetlands are returning, and so is the wildlife.
Whatever the final price tag, William Nuttle, a consultant with the University of Maryland's Center for Environmental Science who began his career in the marshlands of South Florida, notes that humans created this "hybrid ecosystem." Thus, he says, it's up to humans to maintain it - for nature's sake, and for our own.
"We started in South Florida by declaring war on the ecosystem," Nuttle says. "It's not restoration that we're paying for; it's restitution."
This Associated Press series was produced in partnership with the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.
EDITOR'S NOTE: Heroic efforts to revive ecosystems and save species are being waged worldwide, aimed at reversing some of humankind's most destructive effects on the planet. "What Can Be Saved?," a weekly AP series, chronicles the ordinary people and scientists fighting for change against enormous odds - and forging paths that others may follow.