Climate change alters what’s possible in restoring Florida’s Everglades

The Everglades are a vast network of subtropical freshwater wetland and estuarine ecosystems that once spanned the length and breadth of south Florida. Fifty years of dredging and diking, starting in 1948, greatly reduced their extent, altering water flow patterns and causing widespread ecological damage.

For the past 20 years, scientists and engineers have been working on a multi-billion-dollar restoration effort designed to reclaim the Everglades’ past glory. I am a hydrologist and have worked for 25 years in south Florida. Currently I co-lead a team at the University of Maryland Center for Environmental Sciences that worked with federal and state agencies to compile a report card on the ecological health of the Everglades.

The report card revealed that not enough has been done yet to reverse the ecological damage from years of misdirected water management. Although some progress has been made toward restoration’s original goals, growing evidence of unanticipated effects from climate change and sea level rise is forcing experts to reassess what is possible.

[embedded content] Both scientific and political hurdles make ‘rehydrating’ the Everglades one of the most complex ecological restoration projects ever attempted.

Rescuing the ‘river of grass’

Advocates have been working to protect the Everglades nearly as long as developers have been dismantling it. In 1947, author and activist Marjory Stoneman Douglas published her classic book “The Everglades: River of Grass,” which warned that “The Everglades were dying,” and their loss would doom the entire region. Presciently, Douglas observed that the Everglades recharge the aquifer that supplies water to Miami and other coastal communities, making south Florida’s booming economy possible.

Douglas’ assessment spurred action to preserve this unique ecological resource, although it took decades to organize and fund a restoration effort on the scale that was needed. In the year 2000 federal and state agencies launched the Comprehensive Everglades Restoration Plan, which is designed to restore the characteristics of the water cycle in south Florida that were critical to sustaining the historical Everglades. At the same time, water managers also must maintain water supplies and flood protection for farms and communities that have been built in and around the Everglades, with more people arriving every year.

Stressed ecosystems

After nearly two decades of work, the health of the Everglades is only fair, and progress still lies in the future. That’s the conclusion of the Everglades Report Card, which was released in April 2019 after assessing a huge quantity of data collected from 2012 through 2017. Overall, it finds that “the ecosystems of the Everglades are struggling to support the plants and animals that live there and the natural services they provide to people.”

Sea level rise is increasingly a factor. About 10 years ago, scientists began seeing unsettling changes in the freshwater wetlands of Everglades National Park at Florida’s southwest tip. Holes were appearing in expansive sawgrass prairies near the coast, filled with dead vegetation and standing water. Experiments confirm that the cause is salt water infiltrating the freshwater wetlands.

Sawgrass grows on top of a thick deposit of peat. Too much saltwater can kill the plants and eat away at the peat, causing the soil surface to collapse. As seawater infiltrates vast areas of sawgrass, formerly healthy sawgrass prairie is beginning to unravel like a moth-eaten wool sweater.

Open-water ‘pothole’ ponds in a sawgrass marsh, Everglades National Park, are thought to have been formed through collapsing peat driven by saltwater intrusion. Everglades Foundation/Stephen Davis, CC BY-ND

Outpaced by rising seas

The Everglades have natural defenses against sea level rise. Dense mangrove forests along Florida’s southwest coast form a protective barrier that absorbs storm surge from hurricanes. Mangroves filter out and consolidate mud and sand churned up by hurricanes from the sea bottom, building up the coast’s elevation in pace with sea level rise.

Freshwater draining from the interior piles up behind the mangroves, creating a hydraulic barrier that prevents seawater from infiltrating inland. And freshwater wetlands keep up with sea level rise through the accumulation of undecomposed plant material and marl, a mineral-rich mud produced by algae.