Walking Trees

By Betty Lipe, Extension Specialist, Pinellas County Extension

Have you ever heard of the term “walking trees”? It was inspired by the red mangrove, Rhizaphora mangle. The red mangrove grows along the water’s edge and is easily identified by its tangled, reddish roots called prop roots. These roots have earned mangroves the title “walking trees”. The mangrove appears to be standing or walking on the surface of the water.

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

White mangrove, Laguncularia racemosa, usually occupies the highest elevations farther upland than either red or black mangroves. Unlike its red or black counterparts, the white mangrove usually has no visible aerial root systems, although in the right environmental conditions, they will grow pneumatophores and prop 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 blade where the stem starts. The glands, called nectarines, excrete sugar attracting and feeding many insects.

Mangroves are one of Florida’s true natives. They thrive in salty environments because they are able to obtain fresh water from saltwater. Mangrove systems help purify the water in estuaries by filtering the runoff that flows into the estuaries from upland regions. The relationship between mangroves and their associated marine life cannot be overstated. By trapping sediment, mangroves actually stabilize the soil while the roots and vegetation help prevent shoreline erosion. The mangrove prop roots create a maze-like “nursery” beneath the water where young crabs, shrimp and small fish such as snook and mullet can swim, but the large fishes that prey on them cannot. The prop roots also provide a place for oysters, barnacles and anemones to attach while birds like the top of the trees as roosting sites. Mangroves provide a multi-tiered habitat for a diversity of wildlife.

Tampa Bay is in the northern range of the mangrove swamp ecosystem. This is due to sensitivity to freezing temperatures. Mangroves can reach a height of 80 feet, hence the name mangrove forest. Mangroves help to buffer the storm waves and winds and provide protection to inland areas. Mangroves can be naturally damaged and destroyed, but there is no doubt that the human impact has been most severe. Scientists have been able to evaluate habitat changes by analyzing aerial photographs from the 1940’s and 1950’s and comparing it to current satellite imagery and aerial photography. Frequently the changes illustrate loss of mangrove acreage, particularly in the Tampa Bay area. As one of the ten largest ports in the nation, Tampa Bay has lost over 44 percent of its coastal wetlands acreage of both mangroves and salt marshes in the last 100 years. As mangroves are removed, invasive species such as Brazilian pepper and Australian pines have taken hold, further reducing the amount of native habitat.

Today mangroves on public and private lands are protected through local ordinances because of their value to the surrounding ecosystem. For further information on laws protecting mangroves go to http://www.dep.state.fl.us/water/wetlands/

Florida 4-H youth learn about mangroves and their ecosystems through the Forest and Marine Ecology projects and competitions. For more information on the 4-H marine programs go to: http://florida4h.org/projects/marine/index.shtml. For information on the 4-H forestry program go to http://www.sfrc.ufl.edu/4h/.

References:
http://www.floridaplants.com/horticulture/mangrove.htm
http://www.sfrc.ufl.edu/4h/Black_mangrove/blacmang.htm
http://www.sfrc.ufl.edu/4h/Red_mangrove/redmangr.htm
http://www.sfrc.ufl.edu/4H/White_mangrove/whitmang.htm