The doctor on Christopher Columbus’s ship reported in 1494 that mangroves in the Caribbean were “so thick that a rabbit could scarcely walk through.” Mangroves live on the edge between land and sea, forming dense thickets that act as a protective border against the forces of wind and waves. Four species grow along many low-lying coastal areas on the mainland and along island lagoons and fringes. Of these, the red mangrove and the black mangrove are most prolific. Red mangrove in excess of 30 feet high is found in tidal areas, inland lagoons, and river mouths, but always close to the sea. Its signature is its arching prop roots, which provide critical habitat and nursery grounds for many reef fish. Black mangrove grows to almost double that height. Its roots are slender, upright projectiles that grow to about 12 inches, protruding all around the mother tree. Both types of roots provide air to the tree.
Red mangroves (Rhizophora mangle) specialize in creating land—the seedpods fall into the water and take root on the sandy bottom of a shallow shoal. The roots, which can survive in seawater, then collect sediments from the water and the tree’s own dropping leaves to create soil. Once the red mangrove forest has created land, it makes way for the next mangrove in the succession process.
The black mangrove (Avicennia germinans) can actually out-compete the red mangrove at this stage, because of its ability to live in anoxic soil (without oxygen). In this way, the red mangrove appears to do itself in by creating an anoxic environment. But while the black mangrove is taking over the upland of the community, the red mangrove continues to dominate the perimeter, as it continuously creates more land from the sea. One way to identify a black mangrove forest is by the thousands of dense pneumataphores (tiny air roots) covering the ground under the trees.
Soon, burrowing organisms such as insects and crabs begin to inhabit the floor of the black mangrove forest, and the first ground covers, Salicornia and salt wart (Batis maritima) take hold—thereby aerating the soil and enabling the third and fourth mangrove species in succession to move in: the white mangrove (Laguncularia racemosa) and the gray mangrove (Conocarpus erectus), also known locally as buttonwood.
Each of the three primary mangrove species lives in a very salty environment, and each has its own special way of eliminating salt. The red mangrove concentrates the salt taken up with seawater into individual leaves, which turn bright yellow and fall into the prop roots, thereby adding organic matter to the system. The black mangrove eliminates salt from the underside of each leaf. If you pick a black mangrove leaf and lick the back, it will taste very salty. The white mangrove eliminates salt through two tiny salt pores located on the petiole (the stem that connects the leaf to the branch). If you sleep in a hammock under a white mangrove tree, you will feel drops of salty water as the tree “cries” upon you! The buttonwood also has tiny salt pores on each petiole.
Importance of Mangroves
Mangrove islands and coastal forests play an essential role in protecting Belize’s coastline from destruction during natural events such as hurricanes and tropical storms. Along with the sea grass beds, they also protect the Belize Barrier Reef by filtering sediment from river runoff before it reaches and smothers the delicate coral polyps.
However, dense mangrove forests are also home to mosquitoes and biting flies. The mud and peat beneath mangrove thickets is often malodorous with decaying plant matter and hydrogen sulfide–producing bacteria.
Many developers would like nothing better than to eliminate mangroves and replace them with sandy beaches surrounded by seawalls. But such modification to the coastline causes accelerated erosion and destruction of seaside properties, especially during severe storms.
Birds of many species use the mangrove branches for roosting and nesting sites, including swallows, redstarts, warblers, grackles, herons, egrets, osprey, kingfishers, pelicans, and roseate spoonbills. Along the seaside edge of red mangrove forests, prop roots extend into the water, creating tangled thickets unparalleled as nurseries of the sea. Juveniles of commercial fisheries, such as snapper, hogfish, and lobster, find a safe haven here. The flats around mangrove islands are famous for recreational fisheries such as bonefish and tarpon.
The three-dimensional labyrinth created by expanding red mangroves, sea grass beds, and bogues (channels of seawater flowing through the mangroves) provides the home and nursery habitat for nurse sharks, American crocodiles, dolphins, and manatees.
Here are some great opportunities to get up close to the mangroves and the wildlife they support:
Snorkeling among the red mangrove prop roots is a unique experience where you can witness the abundant marine life that grow on prop roots and live between the roots. It is within the algae, plants, corals and sponges that grow on the roots that juvenile spiny lobsters and sea horses can be found.
Destruction of mangroves is illegal in most of Belize; cutting and removal of mangroves requires a special permit and mitigation.
© Joshua Berman and Avalon Travel from Moon Belize, 9th Edition