Marking the merits of mangroves

Author:  Kate Gooderham
Want some effective and affordable protection for your coast? If you’re in the right clime, consider planting some mangroves.

marine mongrovesRecent research published in Hydrobiologica looked at the coastal protection attributes for the east central Florida coast – specifically the Merritt Island Wildlife Refuge, which also houses the Kennedy Space Center (NASA helped fund the study, appropriately).

The two main protection systems studied were salt marshes and mangroves – two primary components in the natural protection efforts covered broadly under the “living shorelines” rubric. The findings were remarkable for a number of reasons:

  • Mangroves provided 800% more coastal protection than salt marshes.
  • Mangroves were also much better (470%) at erosion control than salt marshes.
  • A healthy mangrove fringe/forest can reduce the height on incoming waves by 90%.
  • Mangrove habitat at the Merritt Island Refuge would provide $4.9 million more in coastal protection than manmade barriers.
  • Looking at all natural coastal protection options now in place in the U.S., the study estimated they offer an estimated $23.2 billion per year of protection against economic and human losses from major storm events.

Around the world, the importance of mangroves for coastal protection is more critical. The U.S. ranks 15th in total mangrove forest (605 square miles), while the top nation overall for mangroves (Indonesia) has more than 9,000 square miles of mangrove forest. These salt-tolerant trees provide valuable habitat along with vital shore protection and stabilization.

That’s an impressive amount of good news. What’s the downside?

For one, mangroves are only viable in tropical or subtropical zones due to their sensitivity to temperature. For the United States, that limits them to Florida and some portions of the Gulf coast. However, as ocean water temperatures rise, mangroves are starting to establish themselves further north on the coast – one of the motivations for this study.

Salt marshes, however, don’t face such limits and are capable of existing along low-energy coasts in far cooler areas. While their protective value may not be that of a mangrove fringe, marshes still create an impressive coastal buffer, natural habitat and agent for accretion.

Both mangroves and salt marshes have fallen prey to human activities in the past. Whether filled to create developable lands, ditched to fight mosquitoes or eliminated to enhance water access and sightlines for adjacent upland properties, thousands of acres of mangroves and marshes were lost before regulators and coastal managers finally realized the myriad values offered by such “soft” shorelines.

One should hope that understanding the many attributes they offer, and the increasing need for natural solutions as our shorelines change, will promote the rise and expansion of both mangroves and marshes. Certainly studies such as this help to make a very co