By Dr. Stephen Davis
The topic of sea level rise and its impact on south Florida landscapes is becoming commonplace in the media. This is due in part to the devastation from super storm Sandy in 2012, the increased frequency of “king tide” flood events in low-lying developed areas of south Florida, and scientific reports such as the National Climate Assessment and IPCC Assessment.
What often goes unreported is how sea level rise is affecting natural areas such as the Everglades. As a result, people are left wondering how the Everglades will respond to sea level rise and why we should continue to invest in the restoration of this massive ecosystem.
For those that haven’t been out there, the Everglades is that huge, undeveloped landscape you fly over before landing at Miami International Airport (see photo above) or Ft. Lauderdale Airport; it’s the wet-looking grassy area you drive across when going to Naples or Fort Myers.
The Everglades is the largest subtropical wetland in the United States. It is home to 67 threatened or endangered species of plants and animals. It is where you find Everglades National Park—an International Biosphere Reserve, a World Heritage Site and a designated Wetland of International Importance. It’s a one-of-a-kind place to fish, hunt, watch birds, stargaze, or just unwind.
If that isn’t compelling enough, the Everglades filters and recharges the water supply for nearly 8 million Floridians and all the agriculture, golf courses, plant nurseries, hotels and resorts in south Florida. Without it, our thriving economy could not sustain itself.
Back to sea level rise…did you know that sea level rise has already affected the Everglades and continues to change the coastline of south Florida even today? Sea levels have risen about 9 inches over the past century. We know this because one of America’s oldest operational tide gauges near Key West, Florida has given us an excellent record of sea level for 100 years.
As a result of this rise in sea level and the infiltration of salt water into freshwater habitats, coastal habitats such as mangrove forests have gradually migrated inland. We can detect this very clearly in aerial photography and satellite imagery taken over the last half of the century.
In the coastal Everglades, inches of sea level rise translate to miles of habitat change. Everglades’ wetlands dip below sea level at the coast and gradually rise as you move north at a slope of about two inches for every mile. So, for every two-inch increase in sea level, we can expect to see about a one-mile-wide strip of freshwater Everglades wetland exposed to saltwater.
Areas immediately upstream will then become more vulnerable to saltwater intrusion from storm surges that also carry mangrove seeds that become established and begin the process of habitat change. The freshwater sawgrass marshes are intolerant of salt, so they gradually give way to more saline and mangrove-dominated habitats.
We have actually accelerated the process of landward migration of mangroves by cutting off the flow of freshwater to the Everglades (see photo below). Much of the water that we now dump to tide down the Caloosahatchee and St. Lucie Rivers used to flow along the River of Grass all the way to Everglades National Park, the Gulf of Mexico and Florida Bay. By restoring the flow of freshwater, we can slow the pace of this transition, allowing for a more natural transition of habitats that give at-risk species of fish, birds, reptiles and mammals an opportunity to adjust.
By restoring the Everglades, we can slow the intrusion of saltwater into aquifers and ensure a safe and sustainable water supply for our residents and visitors, our economy and the future.