Mangroves: Nature's not-so-secret weapon against rising seas

A bill sponsored by state Sen. Ileana Garcia, R-Miami, is slowly making its way through the chamber and would include tasking the Florida Department of Environmental Protection with protecting mangroves and spoil islands, as well as promoting public awareness and identifying “vulnerable properties along the coastline.” 

“Putting mangrove restoration in state statute just helps to ensure that the efforts are properly funded and the necessary resources are available, making mangrove restoration front and center,” Garcia told members of the Environment and Natural Resources Committee in early March.

The bill (SB 100) has cleared the first two of its three committees unanimously, including just last week. Garcia added a provision to make clear the bill would not preempt access to and navigation of marked channels or right-of-way of the Florida Intracoastal Waterway. 

Also in the bill is for FDEP to include the “development of living shoreline design options” for the Biscayne Bay Aquatic Preserve, located in South Florida and covering roughly 65,000 submerged acres. It’s the largest estuary in Florida. 

Here’s why mangroves are crucial: “Mangrove forests stabilize the coastline, reducing erosion from storm surges, currents, waves, and tides. The intricate root system of mangroves also makes these forests attractive to fish and other organisms seeking food and shelter from predators,” according to the National Ocean Service. 

“I think this is especially important,” said state Sen. Bobby Powell, D-West Palm Beach. “Mangroves, of course, are very important … the same thing with coral reefs and our environment in terms of natural disasters – how they help protect.” 

Living shorelines…

The idea that shorelines can be considered “living” has taken off in recent decades as an awareness of global climate change and its devastating impacts has entered the mainstream. 

But coastal restoration is nothing new to environmentalists. ‘Living shorelines’ is the phrase used to describe coastlines and shores that have natural barriers and protections cultivated along them. 

“There is evidence that living shorelines with intact natural coastal habitats (e.g., wetlands, dunes, mangroves, and coral reefs) experience less damage from severe storms and are more resilient than hardened shorelines,” the bill’s staff analysis reads. 

…and ‘hardened coasts’

The opposite of a living shoreline is one considered by ecologists as “hardened” or “armored,” Carlie Dario said. She’s a Ph.D. candidate with the University of Miami, studying "the values of perceptions" of nature-based solutions for coastal risk reduction and resilience in Florida. 

Hardened and armored coastlines are those that have infrastructure in place such as sea walls that could assist with mitigating sea water rise, but pose challenges as nature erodes their use. But native protections, such as mangrove trees, help to naturally mitigate storm surge. 

Some studies say wide mangrove forests help reduce up to 66% of wave impacts, improve water quality and provide a home to millions of organisms. Yet mangroves in Florida are often subjected to development and destruction. 

“Despite these benefits, human activities such as coastal development are responsible for destroying more mangrove forests worldwide than any other type of coastal habitat,” according to the Florida Fish and Wildlife Conservation Commission. 

There’s no one “master blueprint” for what Florida’s coastline could look with a living shoreline, Dario said. More rural North Florida coasts are different than South Florida’s urban coastlines. Shorelines must be assessed for what ecosystems they support. 

“It’s always been the default to put a wall, put a bulkhead to mitigate shoreline erosion,” Dario said. “But over time in certain parts, in front (of the bulkhead) and behind, erosion continues to happen.” 

Human behavior as part of the environment

As coastlines are developed, Floridians lose natural protections. This will continue to contribute to flooding further inland during storms and hurricanes and other impacts.  

“When you put structures, whether they’re hard or green structures, they become part of the physical environment,” Dario said. “And (they) are therefore modifying different actions between users of the coastlines.” 

In a report published by FDEP’s Florida Coastal Management Program in 2015, the authors wrote that hardened shorelines prevent the expansion of coastal habitats, threaten sea turtle and shorebird nesting sites and affect water filtration. “As (the) sea level rises, the threat of utilizing hardening shorelines to protect coastal development is expected to increase,” the report says. 

Dario said there is a movement toward what is called “hybrid” shorelines – a mixture of what’s termed gray and green infrastructure. 

Gray means human-made stormwater infrastructure such as gutters, drains and retention basins. Green means natural, or mimicking nature, according to the U.S. Environmental Protection Agency. Green infrastructure includes permeable pavement, rain gardens and urban tree canopies.  

What’s next?

About a year ago, Dario reached out to the state DEP for data illustrating hardened and living shorelines, though no report was then available. 

“It’s a major undertaking,” Dario said of rendering the information. Yet it would also provide a clear look at what areas still remain wild. 

“How can we make (this) mainstream?” she asked.