Land-building and Stabilization by Mangroves

Covering broad areas of tropical shorelines are unique plants known as mangroves, which exhibit several structural and physiological modifications to the saline environment—especially in their root systems. Prop-roots and pneumatophores, two obvious modifications, allow mangroves to play a role in coastal geomorphology, either as land-builders or as stabilizers of substrates derived from classical sedimentation processes. Current data show that: (1) Provided with proper substrates, mangrove seedlings can be raised in the laboratory for later planting in the field, although on exposed beaches success ratios may be low. (2) Larger mangrove plants (1.0–5.0 m in height) may be transplanted with relative ease and appear to succeed with few or no mortalities resulting from the techniques used. (3) Pruning of mangroves appears to be a successful method of mangrove control, allowing their utilization for stabilization around housing developments. (4) Fossil evidence for mangroves as shoreline developers is suggested by the discovery of a fossil mangrove reef off the Miami, Florida, coast. However, submergence of near-by mangrove areas has occurred, as evidenced by sea-grass beds growing above buried peat in the bay bottom. (5) Black Mangroves may be more useful than Red Mangroves as shoreline stabilizers due to their cold-hardiness, ability to tolerate disturbed substrates, and rapid production of pneumatophores. (6) Insect and isopod damage to mangroves has been documented, and it has been suggested by several research workers that such damage may lead to increased erosion of coastlines in many areas of southern and central Florida. In addition, boring activities in Red Mangrove seedlings may result in decreased numbers of seedlings being available for new mangrove growth and colonization. (7) Mangroves have been suggested for use as stabilizers of substrates in conjunction with planned filling and sea wall construction.