Mangroves of the Sebastian Shoreline — Sebastian, Florida

Three species of mangrove grow along the Indian River Lagoon shoreline at Sebastian: red, black and white. The Florida Department of Environmental Protection lists all three, along with seagrasses, among the plants of the Indian River-Malabar to Vero Beach Aquatic Preserve, the state preserve that covers the lagoon off Sebastian between Brevard and Indian River counties. Each species takes a different position on the shore, and the zonation can be read from a boat or a lagoon-side trail near Sebastian.

According to FDEP, the red mangrove typically grows along the water edge and is easily identified by its tangled, reddish roots called prop roots. The black mangrove usually occupies slightly higher elevations upland from the red mangrove and is identified by finger-like projections called pneumatophores that rise from the soil around its trunk. The white mangrove occupies the highest elevations and has no visible aerial roots; its elliptical, light yellow green leaves carry two glands at the base of the blade. FDEP notes that all three frequently grow intermixed, which is the pattern along much of the lagoon shore in Indian River County.

The 1986 state management plan for the aquatic preserve described the pattern that still frames the Sebastian area: mangrove trees fringe the shoreline of the barrier island and, to a lesser extent, the mainland and perimeters of the spoil islands. The spoil islands, built from dredge material when the Intracoastal Waterway was cut, are now ringed by mangroves even where their interiors are dominated by exotic trees, according to FDEP, which states that the shallow edges of the islands in the Indian River Lagoon have been colonized by mangrove forest, salt marsh and seagrass beds.

Several public sites near Sebastian sit in or beside mangrove habitat. The FDEP Coastal Access Guide for Indian River County describes the Lagoon Greenway as crossing over 3 miles of coastal plain, maritime hammock and mangrove forest. Pelican Island National Wildlife Refuge, whose public use areas sit on the Historic Jungle Trail 3.3 miles south of Sebastian Inlet, lists mangroves among the plants of its upland habitat, and its Centennial Trail passes restored wetland and tidal mangrove communities, according to the U.S. Fish and Wildlife Service. Across the lagoon, Coconut Point at Sebastian Inlet State Park is the site of the newest mangrove planting.

Mangroves are tropical plants, and Sebastian sits within the stretch of Florida coast where cold sets their limit. FDEP states that Florida mangroves are sensitive to subfreezing temperatures and are common as far north as St. Augustine on the Atlantic coast, and that black mangroves can occur farther north in Florida than the other two species. The UF/IFAS publication on mangrove range expansion reports that stands of black mangroves can be found as far north as the St. Augustine inlet, and that black and red mangroves have expanded their range as winter temperatures have increased.

The change is measurable on the coast north of the Indian River County line. FDEP reports that aerial images from 1984 to 2011 show the Florida Atlantic coast gained more than 3,000 acres of mangroves, that all of the increase occurred north of Palm Beach County, and that the acreage between Cape Canaveral and St. Augustine doubled, much of it at the expense of salt marsh. The lagoon at Sebastian lies south of that stretch, where FDEP and the 1986 management plan already documented established mangrove fringes on the barrier island and spoil islands.

Mangrove trimming in Sebastian is governed by state law. Section 403.9324 of the Florida Statutes makes the Mangrove Trimming and Preservation Act (sections 403.9321 to 403.9333), and the rules of any local government that receives delegated authority, the sole regulations for trimming and alteration of mangroves in Florida. As of June 2026, the FDEP delegation list names Miami-Dade County, Broward County, Hillsborough County, Pinellas County, the Town of Jupiter Island, the City of Sanibel and Sarasota County. Indian River County and the City of Sebastian are not on that list, so FDEP administers the rules for the Sebastian shoreline.

The homeowner exemption in section 403.9326 allows trimming of a riparian mangrove fringe without a permit when the mangroves do not exceed 10 feet in pretrimmed height and are not trimmed so that any mangrove is reduced to less than 6 feet, measured from the substrate. The exemption applies to property with a shoreline of 150 feet or less; on a longer Sebastian shoreline, no more than 65 percent of the mangroves may be trimmed under it. No herbicide or chemical may be used to remove foliage.

Taller trees on the Indian River Lagoon shore require a professional mangrove trimmer. Under the same statute a professional may trim mangroves up to 24 feet in pretrimmed height, again not below 6 feet, and trees 16 feet or taller must be trimmed in stages so that no more than 25 percent of the foliage is removed annually. Trimming outside these exemptions requires a general or individual permit from FDEP under section 403.9327 and the sections that follow. Inside the aquatic preserve, the 1986 management plan set a stricter policy: prohibit the trimming or removal of mangroves and other natural shoreline vegetation, except for legally authorized projects and under local mangrove protection ordinances.

The best documented planting is at Pelican Island itself. The U.S. Fish and Wildlife Service reports that the island was 5.5 acres in 1903, began eroding around 1943, and by 2000 was less than half its original size. A shoreline enhancement project completed in 2001 installed a 165-foot oyster shell wave break and planted smooth cordgrass and mangroves along the island shore to encourage sediment accretion, building the island back up over time.

Volunteers carried the work to the surrounding shore. The NOAA Restoration Center records that from 2002 to 2004 the Marine Resources Council, with FDEP, restored approximately 230 acres of shoreline through invasive species removal and native mangrove planting at sites in the San Sebastian River State Buffer Preserve, Sebastian Inlet State Park and Pelican Island National Wildlife Refuge. Community volunteers planted 5,284 native mangroves along the shoreline of the Indian River Lagoon.

The Marine Resources Council still grows mangroves locally. The Environmental Learning Center described an October 25, 2025 Sebastian Mangrove Workshop that focused on growing red mangroves at the council nursery in Sebastian for shoreline habitat projects in the lagoon. In September 2026 the Sebastian Inlet District reported that 22 reef arch structures were installed along approximately 200 feet of eroded shoreline at Coconut Point, on the south side of Sebastian Inlet State Park, with up to 90 mangrove plants to follow, funded through a $95,000 state cost-share grant.

FDEP describes mangroves as nursery areas for fish, crustaceans and shellfish and as food sources for species including snook, snapper, tarpon, sheepshead, red drum, oyster and shrimp, all part of the Indian River Lagoon fishery off Sebastian. Their branches serve as rookeries for coastal birds such as brown pelicans, the namesake birds of Pelican Island. FDEP also states that mangroves help prevent erosion by stabilizing shorelines with their root systems and help maintain water clarity, which is the reasoning behind the living shoreline at Coconut Point.