We have a real SOS: Save Our Shorelines

A red mangrove grows in the Intracoastal Waterway.

October 28, 2023

Living shorelines incorporate plants and other natural elements to stabilize shorelines, increase and reinforce coastal resilience and provide habitat for fisheries. These shorelines are not only beautiful, they benefit the environment by buffering floodwater, reducing erosion, storing carbon, purifying water, increasing biodiversity and providing wildlife habitat.

As they improve fisheries, they also promote recreation. Living shorelines have proven to perform far better during major storms than hardened shorelines. They also cost far less to establish and maintain.

By 2025, it is estimated that 33% of all shorelines in the United States will be hardened with bulkheads or other materials that interrupt natural shoreline processes. Sadly, these structures decrease fisheries’ habitats and foraging habitat for wading birds, prevent natural marsh migration and degrade water quality by eliminating runoff filtration of pollutants and excess nutrients entering the ocean, lakes and estuaries. As waves break on them with nowhere to go and they also create seaward erosion.

On the north end of Palm Beach, just north of the cut, there is a long stretch along the Intracoastal Waterway that is crying out for the implementation of a living shoreline. Decades ago, long swaths of sansevieria were planted along this coast, perhaps to stabilize the incline. Sadly, this was not a wise choice of plant material. Sansevieria, also known as mother-in-law’s tongue, is native to South Africa and listed as a category 2 invasive in Palm Beach.

Sansevieria, an invasive species from South Africa, has taken over a stretch of Intracoastal shoreline.

Spreading by underground rhizomes, this plant has taken over vast swatches of this once-beautiful coastal expanse and it is ripping up the bike path wherever it comes in contact with it. It is not a particularly attractive plant to begin with, but to further aggravate matters, this is regularly pruned with a hedge trimmer, leaving the flattened, chopped tops uneven and unsightly (hideous might be a more appropriate term).

Planting mangroves is the most effective and efficient way to establish a living shoreline. Red, white, and black mangroves, all native to Florida, contribute to the overall health of our waterways by filtering water through their root systems. The resulting ecosystem traps and cycles organic materials and important nutrients, providing food for fish and thousands of marine species. These roots also provide attachment surfaces for marine organisms that filter water through their bodies and trap and cycle nutrients, restoring water quality and clarity.

Mangrove branches serve as rookeries, providing essential nesting areas for such beautiful coastal species as egrets, herons, kingfishers, pelicans and roseate spoonbills. Additionally, mangroves sequester two to four times more carbon than mature tropical rain forests; they actually store more carbon than any tree on earth and contain the highest carbon density of all terrestrial ecosystems.

This red mangrove in the Intracoastal has already trapped some trash in the water.

Planting mangroves along this stretch of the Intracoastal would greatly improve the aesthetic of the area while stabilizing the shore, protecting the coastline from heavy winds and storm surge and improving water quality and marine life habitat. Happily, a few red mangroves have already arrived. Volunteers and the Country Club are working with members of the Palm Beach Garden Club and town officials to establish many more.

Of the three native mangrove species, red mangrove (Rhizophora mangle) is probably the most readily identifiable, with its tangled maze of prop roots growing directly in and along the water’s edge. These roots make the mangroves appear to be standing on the water’s surface, earning them the moniker of “walking trees.” A bit further up the coastline, you’ll find black mangroves (Avicennia germinans), which are identified by the many stick- or finger-like projections (pneumatophores) emerging from the soil around the base of the plant. These projections allow the tree’s roots to breathe when submerged in water; they also collect silt and debris during flooding, which helps to control soil erosion.

Black mangroves are so called for the color of the trunk and heartwood. The evergreen leaves often have a whitish tinge from salt crystal secretions. Like their red mangrove neighbors, black mangroves form dense thickets with their tangled roots. They are, however, more tree-like in appearance than the shorter red mangroves, and can be used as shade trees in upland plantings. Their blossoms produce an excellent honey.

The black mangrove is more tree-like than its red cousin, and can serve as shade trees in upland plantings.

The white mangrove (Laguncularia racemose) is often found with red and black mangroves, growing slightly further inland, but with a similar massive root system to stabilize soil and control erosion. The tiny white flowers are fragrant and attract numerous insects and pollinators, which in turn provide food for the many birds and wildlife that find refuge in the trunks and branches. All mangroves reproduce by propagules that germinate on the tree and then fall, taking root in the water or muddy soil below.

The final plant in the living shoreline succession is buttonwood (Conocarpus erectus), which has green and silver forms. These handsome, slow-growing trees are salt-, wind- and drought-tolerant, making them invaluable for coastal plantings slightly inland from mangroves. Their open spreading canopies make them wonderful shade trees as well as important wind and flood barriers. They can be pruned into formal hedges or left as beautiful architectural specimens.

Mangroves and buttonwoods, working together with seagrass beds and reefs, form the keystone of healthy coastal ecosystems. The trees trap and hold sediment and pollutants that would otherwise wash out to sea. Seagrass beds trap additional silt and mud that might smother outer reefs while providing food for manatees and other marine life. The reefs in turn protect seagrass beds and mangroves from damaging ocean waves.

The relationship between mangroves, marine life and water quality cannot be overemphasized and it is past time that we acknowledge the remarkably diverse ecosystems they create. We in Palm Beach should appreciate these vital plants as part of our state heritage, as well as one of our most valuable natural resources.

-Kim Frisbie

Original article on the Palm Beach Daily News is HERE.