vivoboard September 5, 2018

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The boardwalk at Pa-hay-okee Overlook is a brief, winding path into a dreamworld in Everglades National Park. Beyond the wooden slats, an expanse of gently waving saw grass stretches to the horizon, where it meets an iron-gray sky. Hardwood tree islands — patches of higher, drier ground called hammocks — rise up from the prairie like surfacing swimmers. The rhythmic singing of cricket frogs is occasionally punctuated by the sharp call of an anhinga or a great egret.

And through this ecosystem, a vast sheet of water flows slowly southward toward the ocean.

The Everglades, nicknamed the river of grass, has endured its share of threats. Decades of human tinkering to make South Florida an oasis for residents and a profitable place for farmers and businesses has redirected water away from the wetlands. Runoff from agricultural fields bordering the national park causes perennial toxic algal blooms in Florida’s coastal estuaries.

But now, the Everglades — home to alligators and crocodiles, deer, bobcats and the Florida panther, plus a dizzying array of more than 300 bird species — is facing a far more relentless foe: rising seas.

South Florida is ground zero when it comes to sea level rise in the United States. By 2100, waters near Key West are projected to be as much as two meters above current mean sea level. Daily high tides are expected to flood many of Miami’s streets. The steady encroachment of saltwater is already changing the landscape, killing off saw grass and exposing the land to erosion.

Against this looming threat, Everglades ecologists and hydrogeologists are racing to find ways to mitigate the damage before the land is reclaimed by the ocean, irrevocably lost.

Sea level rise is a global problem, but coastal water management in South Florida faces some particular challenges, as a 2014 National Climate Assessment report noted. Growing urban centers need access to freshwater, flat topography encourages ponds of water to linger, and porous limestone aquifers are particularly vulnerable to encroaching saltwater. Storm surges occasionally drive seawater far inland, compounding the problem.

“We can’t ignore it anymore,” says Shimelis Dessu, a hydrogeologist at Florida International University in Miami. When it comes to water management needs in South Florida, ecological conservation has tended to be low on the list, compared with human and agricultural needs, Dessu says. Now, sea level rise is forcing people to think differently. “The ocean is no longer an external thing,” he says. “It’s already in the house.”

Draining the swamp

Florida’s tug-of-war over water has a long history.

In the 1800s, settlers first began draining the land to make way for agriculture and communities. Water management in the state began in earnest in 1948, when the U.S. Congress authorized the Central and Southern Florida Project for Flood Control and Other Purposes.

That project was meant to control flooding along the Kissimmee River and Lake Okeechobee, in the south-central part of the state. During the rainy months in summer and fall, the river and the broad, shallow lake often overflowed, flooding surrounding areas. The spillage would travel slowly southward across southern Florida in a broad sheet and eventually drain into Florida Bay, an open water body between the mainland and the Florida Keys. During the journey, some of the water would seep into the ground, replenishing the Biscayne Aquifer, a limestone layer that underlies much of the southeastern part of the state.

But the recurrent flooding made the land uninhabitable and farming impossible. So with Congress’ 1948 authorization, the U.S. Army Corps of Engineers built a complex system of levees, canals and reservoirs to control the floods and channel water away from farmlands south of Lake Okeechobee and from growing population centers. Three large “water conservation areas” were constructed to collect and store water during high rainfall events and release it in times of drought. The remaining wetlands — encompassing about half of their original area — were enclosed into two protected areas, Everglades National Park and Big Cypress National Preserve.

Such an intensive overhaul of South Florida’s water cycle led, perhaps inevitably, to new problems. Reducing the amount of freshwater that naturally heads south into the Everglades proved destructive to the habitats of plants and animals. Wading bird populations, for example, shrank by 90 percent over the last century. Diverting the water away from its natural overland course also meant less water was available to replenish the Biscayne Aquifer, which provides drinking water to 3 million people.

Agriculture is big business in Florida; the state’s exports total more than $4 billion each year. But fertilizer from the agricultural regions pollutes waterways feeding into Lake Okeechobee, causing algal blooms in the lake. Regulated discharges from the lake to control flooding shunt polluted water to the east, west and south, causing periodic algal blooms on the coasts and in Florida Bay.

 

Credit: A freshwater, saltwater tug-of-war is eating away at the Everglades

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