How Archaeologists Are Rescuing Miami's History From the Rising Sea

A few more feet of water would flood 16,000 archaeological sites across Florida.

Dead palm trees on a beach
Egmont Key, which has lost half its area to sea-level rise, was the site of a forced relocation of the Seminole people by the U.S. Army. (Steve Nesius / Reuters)

MIAMI—When Hurricane Irma sprinted toward Miami–Dade County, Jeff Ransom couldn’t sleep. He wasn’t just worried about gusts shattering windows, or sheets of rain drowning highways—that’s far from unusual near his home in Broward County, where extreme weather verges on routine, and patches of US-1 are regularly submerged.

Ransom, the county archaeologist, was preoccupied with an oak tree and its 350-year-old roots. If the tree capsized with enough intensity, he worried, the flailing roots could dislodge human remains.

On a blazing blue morning in early November, weeks after the storm, we trek to the site of the Tequesta Native American burial mound that kept Ransom awake.

“All night long, I was just thinking about that oak tree flipping over,” he says. “The big roots are growing right into the burial mound. That would’ve just blown human bone everywhere.”

Irma’s winds shaved canopies off the trees at the Deering Estate, a historic homestead that contains the burial mound and other fossil sites and is managed by the Miami-Dade County Department of Parks, Recreation and Open Space. Under those bald branches, growth was rapid as vines and chutes—nourished by seaweed deposits—scrambled for sunlight. The result has been a second spring: bright, young leaves, greedy for purchase among the gumbo-limbo and strangler figs. Ransom knocks a path for us with a machete, which he carries slung in a holster. Two thwacks splinter the Brazilian pepper branches—but that’s only because the machete is dull, he tells me. Usually, a single smack is enough to slice straight through, like butter.

Ransom is 52, with a GI Joe jawbone and black aviator sunglasses. At one point, these vanish into the carpet of leaf litter, gone shaggier since the storm, and Ransom spends a few minutes poking around for them beneath the slashed fronds before remembering that he has a nearly identical backup pair.

The burial ground was—is—fine. The oak’s trunk is sturdy and thick; the roots are sunk deep into the soil. We sit for a moment on benches nearby, guzzling water in the shade while Ransom uses his machete’s blunted edge to scrape burrs off his pants and shoes.

The storm didn’t bear down on the city with all its might: In general, southeast Florida was spared the breadth of damage that forecasters had conjured. A half-mile of mangroves buffered the Cutler Midden, another archaeological site on the Deering Estate, against damage wrought by crashing waves. Ancient shell tools and pottery fragments survived intact.

Irma could have bitten harder. But in isolated pockets, the storm was ravenous. We pass fragments of a historic boardwalk, which the archaeologists had laboriously documented and annotated. The structure “had been chunked up” in the storm, explains Mallory Fenn, the public-archaeology coordinator at the southeast/southwest Florida branch of the Florida Public-Archaeology Network (FPAN). The network is a project of the University of West Florida; the southeast/southwest division operates out of Florida Atlantic University.

Fenn’s earrings are made from gator teeth, and the boardwalk looks masticated and spit out, its component parts hardly visible. An orange-and-white barrier marches across the crumpled walkway, as if it wasn’t patently clear that there’s trouble ahead.

* * *

Before I fly down to Miami to trail her and Ransom through the swamp, Sara Ayers-Rigsby sends me a packing list. Ayers-Rigsby is the southeast/southwest regional director of FPAN, and the trunk of her car is stocked with supplies, from bug netting to single-serving bags of pretzels. She’ll have ample bug spray and sunscreen to share, she writes, but I’ll want to wear long sleeves, long pants, and the most waterproof boots I’ve got. We’ll be wading into the height of the king tides; the water might rise up to our knees. Heat and mugginess can have a scrambling effect. Ayers-Rigsby later describes it as “brain-meltingly hot.”

“The weather in South Florida is inhospitable,” she warns.

Writ broadly, that’s precisely the problem. Numerous projections forecast a future of extreme weather and persistent flooding that is incompatible with many elements of life as it’s known on the peninsula. Of all of the U.S. states, Florida is the most vulnerable to sea-level rise, and Miami-Dade is at particular risk.

As the plane drifts toward descent, water is everywhere: in green-blue pools that reach for the horizon, in mud-colored eddies, in staid intercoastals studded with white yachts. From the air, many of these basins look overfull, ready to spill with the slightest top-off.

Sooner or later, the water will swallow the shoreline. When it comes to the magnitude, severity, and timetable, there are shades and gradations of apocalyptic hues. In 2015, a working group comprised of officials from across southeast Florida set out to get on the same page about the threats and to strategize about mitigation efforts. Their projection draws from local tide measurements and is aligned with estimates from the U.S. Army Corps of Engineers and the National Oceanic and Atmospheric Administration. By 2030, they anticipate a sea-level rise of 6 to 10 inches from a 1992 baseline; they predict a rise of up to 26 inches by 2060, and 61 inches by 2100.

Even if the water doesn’t crawl quite that high, damage could still be widespread and devastating. Twenty-five percent of land in Miami-Dade County sits less than three feet above current sea level, according to the World Resources Institute. Ten percent is nearly flush with the sea.

And if water does splash to the maximum level, the results could be cataclysmic. In a recent report, the real-estate company Zillow estimated that, if the sea level were to rise by six feet, 24 percent of Miami’s housing stock would be drenched.

Troublingly for Ransom and Ayers-Rigsby, a sea-level rise of just half that height could destroy as many as 16,095 archaeological sites across the state. As the terrain goes soggier or washes away, how do you protect objects embedded in it?

“You can’t wrap an archaeological site in bubble wrap and put it on a high shelf,” Ayers-Rigsby told me via phone soon before Irma swept past. Some sites can be stabilized or buffered with mangroves or oyster beds, but when it comes to safeguarding them from the pummeling rain or surging waves of a hurricane-strength storm, options are limited. “Other than building a massive construction around it,” Ayers-Rigsby said, “there’s not that much you can do.”

Among officials in Miami-Dade, “there’s no sugarcoating or backtracking” about the threat of climate change, Ransom tells me. Its consequences play out in real time, in flooded streets and waterlogged basements, and voters throw their weight behind mitigation efforts at the polls. After his landslide victory in this month’s elections, the incoming City of Miami Mayor Francis Suarez told the local ABC affiliate that “Miami should be and must be the most resilient city in the world.” That same day, voters approved a bond measure that directed $192 million to pumps, walls, drains, and other projects to keep the city drier. Meanwhile, Ransom, Ayers-Rigsby, and their colleagues work to keep thousands of years of history from being lost to the sea.

* * *

If you wonder what archaeology Florida can boast of, you’d hardly be the first. In a carpool from the airport, I told two Australian businessmen what had brought me to the city. They cocked their heads. Miami, to them, evoked beaches, surgically altered bodies, and hefty Cuban sandwiches. What else was there?

I recount this to Ayers-Rigsby while we sit on a choked concrete freeway, inching from Fort Lauderdale to Biscayne Bay. She groans and slumps her head toward the steering wheel. Ayers-Rigsby, 34, relocated to Florida from the mid-Atlantic, and is now somewhat evangelical about the region’s overlooked merits. Around her neck, she wears a pendant with the state’s silhouette.

For as long as people and creatures have inhabited present-day Florida, they’ve been shedding traces of their lives. Fenn says the flitting snowbirds and rotating crop of transplants can be afflicted with a virulent case of historical amnesia. But the scattered sites testify to millennia before the shores were dotted with high-rises fashioned from glass and steel.

The Cutler Fossil Site is a watering hole into which all manner of Pleistocene beasts toppled. Sandwiched between the limestone layers of the sinkhole, some 16 feet above the current sea level of nearby Biscayne Bay, were bones of dire wolves, mastodons, camels, llamas, saber-toothed tigers, and the American lion. Though the site is protected, the city has sprawled around it in the intervening 10,000 years. Looking down into the ancient pit from the ridge, you can hear the rumble of nearby cars. But the site is hidden and sheltered from the road and the water, protected by its isolation and its elevation.

Other sites sit more uneasily with the present. In the late 1990s, archaeologists discovered a circle of postholes cut into the limestone bedrock at the mouth of the Miami River. Carbon dating of wood fragments helped identify the site as the home of a structure built nearly 2,000 years ago by the Tequesta Indians. “People have been partying in Miami for thousands of years,” Fenn jokes, as she shows me around the site. Archaeologists, Native activists, and a galvanized public sparred with a developer, who had purchased the property as the future site of luxury condos. (A flurry of controversy swirled at the time, when some scholars wondered whether the pattern was, more simply, the drain site for a septic system. Archaeology magazine solicited input from other archaeologists, scholars, and a master septic-tank contractor, the latter of whom summarily dismissed the possibility.)

The Miami Circle was designated a National Historic Landmark in 2009. Today, the site is a grassy expanse shaded by towering condos and hotels that have sprung up around it, overlooking cruise ships and cargo freight lumbering in the distance. It’s a rare green space in a vertiginous corner of the city—and that means it sometimes becomes a place for dogs to lift their legs. A fluffy white dog squats nearby as Fenn describes working on an archaeological site just across the narrow river, where archaeologists unearthed additional Tequesta artifacts in 2014 in the prospective footprint of a massive mixed-use development. These excavations are a trippy mash-up of the ancient and the dizzyingly modern. “When you look down, you think it’s the 1850s, with a sifter and a trowel,” she says. “Then you look up and see skyscrapers, and the Metromover going by.”

During Irma, water breached the walls just below the Miami Circle site. It rushed onto the grass, carrying palm fronds washed in from the river. Fenn, who lives nearby, “ran out pretty much the second we were allowed to be outside” to check in on it. The water soon receded, leaving no apparent damage. This particular spot, loaded with infill, has been shored up to withstand exactly this type of barrage.

Other sites, which lack these preventive measures, are more vulnerable. But studying them can reveal important data about the rising sea—and how long scholars have to hatch a plan.

* * *

Ransom and Ayers-Rigsby pick through a dense thicket and a floor carpeted with spiky bromeliads. They know what they’re looking for—orange-capped rebar that they sank into the bank of the Oleta River—but Irma blew down the trees onto which they’d tied yellow ribbon to help them identify the sites at a distance. Those orange markers have been coated with dirt.

This squishy portion of the riverbank is the site of a prehistoric midden containing traces of shell tools, pottery, and other daily items that would have been used by Native American tribes who lived on the shore.

“If any site is going to erode, it’s going to be this one,” Ransom says, sloshing through the muck.

The midden, or ancient trash heap, is nearly flush with the water level, which makes this site an ideal candidate for tracking inundation and water rise before and after storm events and king tides. By obtaining a baseline measurement and a set of comparisons, the archaeologists can document both accumulation and erosion—noting which events seem to pile more sediment on the top of the site, and which strip it, ultimately threatening to haul the artifacts out to sea.

The notion of using this area as a proxy for fluctuations in the water level dates back decades. In the late 1970s and early ’80s, when he was working as the country archaeologist, Robert Carr found evidence of ancient charcoal buried about two feet below the surface. Since a fire needs to be dry, Carr reasoned that that portion of the site was once above water. At the time, climate change “certainly wasn’t on anybody’s radar” in the archaeology community, he tells me via phone. There was “no particular movement or focus going on.” Carr advocated for using soil inundation, radiocarbon dating, and water levels as firm evidence for past and future variations. His work laid the foundation for what Ransom and Ayers-Rigby are doing.

On a recent afternoon, the mangrove roots are flecked with odd pieces of very modern garbage: foggy glass bottles, a boogie board speckled with barnacles, a black DVD case, a wrinkled bag of Ruffles chips. These aren’t the signs of someone sneaking in to use the forest as a dump, Ayers-Rigsby says—the refuse has been carried in on waves.

She and Ransom slog through the sucking mud, brushing biting ants from their backs and shoulders, to measure the distance from the rebar to the waterline. They jot down the measurements in a yellow notebook, its pages warped by wetness. In some spots, the sediment is piled higher than it was the last time they measured, before Irma blew in. That accumulation suggests that the water level breached a good chunk of the shoreline during the storm, Ransom says.

Carr explains that’s not unequivocally dangerous—there’s not yet sufficient clarity about whether inundation is an impediment to preserving sites in the same way that erosion is. Conceivably, he says, a site “could be better preserved underwater than it is above ground, if sea-level rise is gradual, not a result of pounding waves hitting shoreline and tearing up and removing soils.”

Through her work at FPAN, Ayers-Rigsby has also helped recruit a team of citizen scientists to fan out across the state and conduct regular monitoring of at-risk sites. Inspired by a U.K. program, Scotland’s Coastal Heritage at Risk, the Heritage Monitoring Scouts, a brigade more than 200 people strong, survey publicly accessible sites—not the more sensitive ones, like unmarked burial grounds—and upload their impressions onto a website form. They look out for signs of flooding, erosion, or wave action, or any artifacts that may have been dredged to the surface, and flag any places that need urgent attention.

Sixty-two-year-old volunteer Paula Streeter surveys the shell midden on Calusa Island, a dot of land off the state’s southwest coast once inhabited by Calusa Indians. Streeter has a wide-ranging background—her resume includes “a zillion, million, trillion things,” she tells me via phone. Since retiring from the city clerk’s office, she’s begun assisting archaeologists. “I only started this,” she says via phone. “It was the most amazing thing in my life, and it only happened two years ago.”

Already, the Calusa shoreline is being eaten by waves and wind action, Streeter says. Artifacts are surfacing in the midden, relics of the tribe’s use of shells for tools and weapons—but the average beachgoer might not notice them. “If you’ve been trained, you know that’s an ancient form of a hammer made from a whelk shell or a horse conch,” Streeter says.

The Calusa Island site is only accessible via boat or kayak—“you can’t just zip out there,” Streeter says. Before the recent hurricanes and king tides, the team intended to survey once a month. (The site is also monitored by researchers from the University of Florida.) When toppled trees exposed these artifacts, the team upped the frequency to once per week—and instead of leaving all of the artifacts in situ, the volunteers diagram the original locations and bag some of them, so they’re not tugged out to sea. Heritage Monitoring Scouts use rebar installations to measure the distance from the midden edge to the beach. Even without their precise computations, it’s easy to see the effect of the waves and wind in exposed roots and a dramatically angled ledge of sand.

Some of these sites contain clues to enriching or correcting the historical record. One example is the dwindling island of Egmont Key, off of the Tampa coast.

A few years ago, the U.S. Army Corps of Engineers reached out to the Seminole to ask about the dwindling island. It was eroding heavily—shrunk to 280 acres, half of its size—and they were wondering whether to replenish it with sand. Was the tribe interested in preserving it?

The imminent threat to the landmass was the impetus to uncover the site’s history. With his colleagues, Paul Backhouse, the director of the Ah-Tah-Thi-Ki Museum and tribal historic-preservation officer for the Seminole Tribe of Florida, pursued some research and learned that, during skirmishes with the U.S. Army in the mid-1800s, the island functioned as a detainment site for Seminoles who were caught evading the ships deployed to remove them out west. Judging by contemporary accounts, conditions were grim: There were no sources of fresh water, and the captives were trapped.

The island sits no more than six feet above sea level. Did the tribe want to keep it above the waves? Among the Seminole community, “the overwhelming response was yes,” Backhouse says via phone. Archaeologically, there was much to learn from the site and the 19th-century artifacts that accumulated there—but it could also function as a place of catharsis and education. “Youth can come and remember the struggle their ancestors went through to remain in Florida,” Backhouse says. “This history is a hidden history—it’s not one that’s in any of the textbooks, because it’s an embarrassment to normal American history.”

Egmont Key is on the front lines. With enough elevation or distance from foot traffic, many other sites will be safe for a relatively long time, by virtue of staying dry or hidden. But as the sea creeps higher, choices will have to be made.

* * *

This fall has been an expensive one at the Deering Estate. Hurricane Irma and the October king tides packed a double punch, explains Jennifer Tisthammer, the estate’s director.

During that first king tide, storm surge swamped the service road with ankle-deep water and flooded the back lawn, where many of the estate’s special events take place. Irma’s gales ripped off 80 percent of the tree canopy; 6,000 cubic yards of seaweed washed ashore. Tisthammer’s long-term vision is to raise the back lawn—but in the meantime, the staff looked for prophylactic measures to mitigate the aesthetics and promote drainage. Sod is best, Tisthammer says, but white rock looks better than soggy, brown grass. When the staff spread out truckloads of drain rock and sand, the puddles that had been taking weeks to drain were siphoned off within a few days.

Even if the fully underwater future is far off on the horizon, the king tides offer a regular reminder—and a kind of trial run. On a page devoted to king tides and climate change, the Environmental Protection Agency notes, “Sea-level rise will make today’s king tides become the future’s everyday tides.”

Places like the Deering Estate are already factoring preventative and adaptive strategies into line items on the budget. “You’re gonna have some loss,” Tisthammer says. “Do you put $3 million into something you know will eventually go under, or allocate it differently?”

The kind of data that Ayers-Rigsby and Ransom are collecting can be used to inform broader city planning and budgeting—and this December, Miami-Dade and three surrounding counties are taking archaeological sites into account, adding provisions to the updated action plan from the Southeast Florida Regional Climate-Change Compact. The document isn’t binding, but it encourages local officials to work with historic-preservation specialists to map and rank at-risk sites; to appeal to FEMA, local emergency-management offices, and other agencies for financial resources; and to implement sustainable preservation tactics such as planting mangroves and cordgrass, or “hard armoring” sites with rocks or concrete. These strategies aren’t without drawbacks. “Hard methods may negatively impact sites by the weight and shifting of large rocks, not to mention the cost of acquiring and moving these to remote places,” Ransom says.

The solution is also not as simple as plucking artifacts from the ground and shuttling them to museum collections, where they might be preserved behind plexiglass vitrines. For the Seminole tribe, as for many other indigenous groups, Backhouse says the prevailing philosophy is that items discarded over the centuries should be left in place. He acknowledges that this mantra of noting objects, “working around them, planning around them, and not thinking of those objects as just research vehicles” might “go completely against the grain of what most people think archaeology is.” But Ayers-Rigsby and Ransom likewise consider excavation to be something of a last resort.

In the Seminole culture, Backhouse says, there’s a difference between something being upturned by an earthquake, versus pulled to the surface by human hands. The underlying philosophy is seeking harmony and balance with nature, he says—and “indigenous cultures don’t have an idea that nature’s always nice.”

Last spring, my colleague Linda Poon reported that the vast majority of states lacked any mention of historic resources in their disaster-management plans. Up until this point, that’s been the case in Miami-Dade, says Ayers-Rigsby. “One of the reasons I was so happy we had some language put into the draft of the Climate Action Fund was just to get it on people’s radar,” she adds. “Before, it was not even included at all at any level.” There’s momentum in this direction: Earlier this fall, the city of Annapolis, Maryland, hosted a conference called Keeping History Above Water, dedicated to solutions for historic preservation and cultural resources. In August, Backhouse and the Seminole tribe participated in the Tidally United Summit, cosponsored with FPAN and the Florida International University Global Indigenous Forum, which focused on the relationship between climate science and historic resources.

Meanwhile, Ayers-Rigsby is sensitive to the emergent, unfolding toll that storms and flooding can wreak on people and property. “You have to put the human aspect in the present first,” she says. You have to prioritize people’s safety and people’s livelihoods. Archaeology and historic resources are obviously necessarily secondary to that, but they should still be discussed.”

It’s painful enough to put a price tag on property—homes, cars, neighborhoods—that we will lose in the reckoning with the waves. And it can be an uphill battle to nudge residents and officials toward the level of abstraction required to dwell in the realm of forecasts and best guesses. “A risk in the future feels a lot less scary than a risk that’s presented right now,” the risk-perception expert David Ropeik told my colleague Laura Bliss in 2015. Even in Florida, where volatile weather is undeniable, it requires a few mental acrobatics to tumble toward an understanding of the sites that are at stake—sometimes literally below the surface.

But if the goal of archaeology is to preserve and interpret the past for the future, there’s plenty of work to be done—careful and quick, down in the muck and in legislative offices—before traces of that past slip away. In those strata are testaments to lives lived, forgotten, and remembered over the course of millennia: a record of what it has meant to be human.

No matter what they do, Ayers-Rigsby says, the time capsule will be incomplete. “Some things will be lost forever.”

This post appears courtesy of CityLab.