Human activities such as dredging and careless boating are threatening South Florida’s mangroves and seagrass

ship grounded in Florida Keys National Marine Sanctuary

Despite the valuable role that mangroves and seagrass play in the Florida Keys ecosystem, these plants are facing one particularly large threat: Us.

In the Florida Keys, human development is the greatest threat to mangrove communities. Since the 1950s, more than 60 percent of mangroves in Monroe County have been destroyed for development. Activities such as dredging, using herbicides, and increasing waste water runoff have destroyed thousands of acres of mangrove habitat.

Propellers have scarred virtually every seagrass bed in South Florida, with over 30,000 acres of seagrass damaged by light, moderate, and heavy scarring. When a boat’s propeller hits seagrass, it fragments the seagrass bed. This can severely restrict the movement of animals living in needed habitat, leaving barren areas where fish and other critters once flourished.

Given the importance of mangroves and their continued destruction, the Mangrove Trimming and Preservation Act was passed in 1996, making it illegal to remove, destroy, or damage mangroves in the State of Florida. The law also calls upon the use of certified, professional mangrove trimmers to ensure that these trees are properly maintained. Mangroves have also been designated a species of special concern.

To reduce the chances of damaging seagrass communities, boaters should be familiar with local waters where you plan to boat, stay in deep water and marked channels, wear polarized lenses to read the water, and use up-to-date nautical charts. If you find yourself in water that is too shallow, you should immediately stop, turn your motor off, and trim your motor up to prevent further damage. Wait for high tide and carefully walk your vessel out to deeper water or call for help.


Did You Know?

Damaging seagrass with your boat's propeller will fragment the grass bed and severely restrict the movement of marine wildlife in needed habitat. This can create barren areas where fish and others once flourished.

And consider that a moment's carelessness can quickly impair this precious resource – a propeller scar cut into seagrass today can be around in seven years or longer.