More on Florida Mangroves

Worldwide more than 50 species of mangroves exist. Of the three species found in Florida, the red mangroves, Rhizohpora mangle, is probably the most well-known. It typically grows along the water's edge and is easily identifiable by its tangled, reddish "prop-roots" which have earned red mangroves the title, "walking trees." The red mangrove in particular appears to be standing or walking on the surface of the water.

The black mangrove, Avicennia germinans, usually occupies slightly higher elevations upland from the red mangrove and can be identified by numerous finger-like projections, called pneumatophores, that protrude from the soil around the tree's trunk.

The white mangrove, Laguncularia racemosa, usually occupies the highest elevations farther upland than either the red or black mangroves. Unlike its red and black counterparts, the white mangrove has no visible aerial roots. The easiest way to identify the white mangrove is by its leaves. They are elliptical, light yellow-green, and have two distinguishing glands at the base of the leaf where it meets the stem.

All three of the species utilize a remarkable method of propagation. Seeds sprout while still on the trees and drop into the soft bottom around the base of the trees or are transported by currents and tides to other suitable locations where they can settle into the soft bottom and grow.

Florida's mangroves are tropical species, therefore they are sensitive to extreme temperature fluctuations as well as to subfreezing temperatures. Research indicates that salinity, water temperature, tidal fluctuations, and soil also affect their growth and distribution. Mangroves are common as far north as Cedar Key on the Gulf coast and Cape Canaveral on the Atlantic coast. Black mangroves can occur farther north in Florida than the other two species, however, frequently all three species grow intermixed.

People living along the south Florida coasts benefit in many ways from mangroves. Mangrove forests protect uplands from storm winds, waves, and floods. The amount of protection provided by the mangroves, however, depends upon the width of the forest. A very narrow fringe of mangroves offers only a limited amount of protection while a wide fringe can considerable reduce wave and flood damage to landward areas enabling overflowing water to be absorbed into the expanse of forest. Mangroves can also help prevent erosion by stabilizing shorelines with their specialized root systems. Mangroves also serve to filter easturine water, maintaining water quality and clarity.

It is true that mangroves can be naturally damaged and destroyed, but there is no doubt that human impact has been most severe. As you may have read about in the seagrasses section of this document, Florida Department of Environmental Protection, Florida Marine Research Institute Scientists are studying changes in Florida's coastal habitats and are able to evaluate habitat changes by analyzing aerial photographs taken during the 1940' and 1950's and comparing them to satellite and aerial photographs taken during the 1980's. Frequently the changes they observe illustrate loss of mangrove acreage. Through researching the history of study sites, these losses can often be attributed to human activities.

Tampa Bay, located on the southwest Florida coast, has experienced considerable change. As one of the ten largest ports in the nation, Tampa Bay has lost over 44% of its coastal wetlands (mangrove and saltmarsh) acreage over the past 100 years.

The next major bay system south of Tampa Bay is Charlotte Harbor. Unlike Tampa Bay, Charlotte Harbor is one of the least urbanized eastuarine areas in Florida. However, there has been some mangrove destruction here also with Punta Gorda waterfront developments accounting for 59% of the total loss. An increase in mangrove acreage was noted in parts of the Harbor due to other changes in the system. As tidal flats were colonized by mangroves, tidal flat acreage decreased while mangrove acreage increased. Spoil islands, created as by-products of dredging, also provided suitable habitats for mangroves to grow.

A changing system was also observed on the southeast Florida coast in Lake Worth, near west Plam Beach. Lake Worth has experienced an 87% decrease in its mangrove acreage over the past 40 years. These historic mangrove forests have since been replaced by Australian pines and urbanization. The remianing 276 acres of mangroves occur in very small scattered areas and are now protected by strict regualtions.

Another study site included the Indian River from St. Lucie Inlet north to Satellite Beach. Indian River is the longest saltwater lagoon in Florida with just under 8,000 acres of mangroves. Only 1,900 acres of this is avaible as fisheries habitat, however, because of mosquito impoundments. Consequently, 76% of the existing mangrove areas are not productive to fisheries. Looking purely at fisheries benefits, 86% of the mangrove areas have been lost since the 1940's.

State and local regulations have been enacted to protect Florida's mangrove forests. Mangroves cannot be removed, pruned, or disturbed on either state or private land wihtout a premit from the Florida Department of Environmental Protection. Local laws vary, so be sure to check with officials in your area before taking action.

Mangroves are one of Florida's true natives and are part of our state's heritage. It is up to us to ensure a place in Florida's future for one of our most valuable resources...mangroves.