Tree-islands of Florida's Everglades are natural havens for the some of the most spectacular of the swampland's residents—alligators, panthers and rare birds. But five millennia ago, they may have been home to a very different community, as sites where prehistoric humans settled—and dumped their garbage.
Tree-islands have long been a curiosity of the Everglades, where they punctuate the flat marshy landscape as circular areas of raise ground. Here trees have taken root, alligators nest and a diverse range of other wildlife take refuge. Research has found that the islands owe much of their long-term resilience to a layer of hardened limey rock. It was initially thought that the islands simply formed on natural protrusions of this carbonate bedrock.
Now, excavation and analysis, by a team that includes paleoecologists, has shown that underneath the rock is more soil—and layers of human refuse, which are known as middens. These layers contained discarded food remains, including bones, charcoal fragments, and broken pieces of clay pots, as well as shell tools. It is now thought that the accumulation of this material over hundreds of years built up the land, and provided the high ground that the trees subsequently colonized.
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This garbage-tip evidence is interpreted positively by geologists as it shows that human disturbance in the environment doesn't always have a negative consequence. Research also suggests how the hard carbonate cap, known as the 'perched carbonate layer', may have formed. The probing roots of the trees drew up groundwaters from the bedrock, laden with dissolved carbonates. These precipitated to form the rocky layer, together with phosphates from discarded bones.
This layer not only provides a firm footing it protects the underlying soil from periodic fires, so that plants and trees can easily regrow afterwards. However, the ecology of these man-formed islands are now under threat – from the actions of man once more. By cutting down trees, and drawing up water tables, the perched carbonate layer is at risk of being dissolved and loosened. Climate change is causing bigger hurricanes and longer rainy seasons, and today the Everglades and its tree-islands are drowning.
Tree-islands Endangered by 2017 Flooding
Recently, Florida Fish and Wildlife Conservation Commissioner Ron Bergeron, a lifelong Gladesman also known as Alligator Ron, slipped off his camouflaged snake boots Friday and, for the second time since June, slid off a dock outside his Everglades hunting camp into inky black swamp water.
This time water reached his chest. Back in June, when he summoned reporters to draw attention to flooding across the watery marshes, it only reached his waist.
“There’s not one wading bird that can land in the Everglades right now,” he said. “The Everglades is in serious condition, actual catastrophic conditions.”
An early start to the rainy season, followed by Hurricane Irma, a punishing record-breaking wet season, and an October lashing from a tropical storm have for weeks left South Florida’s water conservation areas — vast wildlife refuges used by air-boaters, hunters and nature-lovers — flooded. The Francis S. Taylor Wildlife Management Area, which covers 1,125 square miles in western Miami-Dade and Broward counties, has been shut down since mid June. Tree islands that formed thousands of years ago, and provide habitat for deer, bears, raccoons, rabbits and even a panther spotted last year, have been under water for close to 21 weeks, a period of inundation that could start to threaten their very existence.
Early November 2017's king tides might be drawing attention eastward to Miami Beach and the state’s urban coast, but Bergeron and others say it’s Florida’s wilderness where unprecedented flooding is threatening more dire problems.
“Trees are not used to being inundated for 120 days,” said Tom Reinert, the FWC’s South Florida regional director. “Trees start to die.”
50 to 60 Tree-Islands Could be Lost
10% of Total Remaining
Over the decades, flood control has gradually whittled away at the number of trees islands, leaving only about 600 in the conservation areas west of the urban coast. Now, unless water is lowered and islands dried out, even more could die, according to the South Florida Water Management District’s chief Everglades scientist Fred Sklar.
“We could lose another 50 to 60,” he said. “That’s 10 percent.”
Everglades restoration is supposed to fix the problems. But projects remain years away from being finished. So Bergeron, who has been meeting with the U.S. Corps of Army Engineers, is asking for a more immediate remedy: raise water levels in the massive canal that runs along the Tamiami Trail and dumps into Everglades National Park.
“That’s the last avenue we have,” he said.
Army Corps spokesman John Campbell said the agency does not plan to raise canal levels due to flooding concerns in neighborhoods further south.
As with all things Everglades, fixing one thing could break something else. Bergeron is pleading for a little more “shared diversity” under the current crisis. But the Corps, which since Hurricane Katrina has made flood safety a priority, has no plans on altering course, Campbell said.
“We have the authority … to raise it to 8.5 feet. However, we also have an obligation to provide flood mitigation to the 8.5-square mile community, so we’re making an operational decision not to raise the water level at this time.”
How To Flush Water Off The Peninsula
Without Wreaking Havoc
Since the beginning of the rainy season, both the Corps and the Water Management District have been working to flush water off the peninsula without wreaking havoc. To protect the aging dike around Lake Okeechobee, water was released down the St. Lucie and Caloosahatchee rivers, which regularly raises the risk of toxic algae blooms. Last month, rising lake water finally began falling, ending the releases.
But the water in the conservation areas—WCA3 west of Miami-Dade was 2.5 feet above where it should be at the end of October—has remained persistently high. That’s despite the Corps waiving most operational rules that normally prevent moving water to protect wildlife. Flood gates intended to keep nesting grounds for Cape Sable seaside sparrows dry and which should have closed Nov. 1 are still open, and water managers continue to move water into the Big Cypress National Preserve, where water is more than a half foot higher than normal.
The only option left is the L-29 canal along the Trail, Bergeron said. But raising water to 8.5 feet, which would increase flushing from the conservation areas to nearly a billion gallons a day, raises concerns about flood protection for the 8.5-square mile Las Palmas neighborhood of ranches, nurseries and homes.
The Corps is in the midst of improving flood control as part of a restoration project intended to deliver more water south into Florida Bay, where everyone agrees more water is needed. Lack of freshwater from the marshes combined with a regional drought triggered a massive seagrass die-off in 2015 that killed between 40 and 60-square miles of meadows, a hit to marine life and the bay’s lucrative sport-fishing industry.
But this year’s rainy season put a stop to the work. Last week, Bergeron said he flew over the area and found standing water only on vacant land.
Deer and Rabbits can Swim Away
Trees Don't Move
“Ninety-eight percent of the 8.5-square mile area, under all these conditions, looked, in my opinion, very good,” he said. “I do understand the Corps’ concern with safety and welfare. I do understand that,” he said. “But now that we’re in the dry season I’m hoping the Corps evaluates what I personally observed in the 8.5-square mile area to be reasonably dry.”
Without the relief, Bergeron warns prolonged flooding in the wildlife management area could trigger a repeats of high water events in 1982 and 1994, when high water caused deer to drown, starve or die from crippling hoof rot. Today, Reinert said wildlife are managed to keep populatons healthy if flooding occurs. But that won’t help the islands.
“Deer and rabbits can all swim away,” he said. “Trees don’t move.”
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