Root, Stem and Leaf,
the Wetlands’ Vital Tissues

“WHEN WE TALK ABOUT a land-loss crisis in coastal Louisiana, we’re really talking about a plant-loss crisis,” says Rex Caffey, wetlands and coastal resources specialist at Louisiana State University. “Land loss is just the inevitable consequence of losing vegetation.”

Although wetland plants may seem to lack allure, professionals like Caffey insist that they are the foundation of coastal restoration. And with good reason when you consider the significance and scope of plants’ four basic functions:

• Plants build and stabilize soil. Trapping particles of waterborne sediment among their roots, stems and leaves, plants slowly accumulate the thick mud of the marshes and keep soil from washing away. Vegetative cover protects existing soil substrates from erosion and nutrient loss, while dead and decomposing plant biomass further increases soil volume and improves soil structure.
• Plants create habitat. All organisms in the wetlands, from microbes to alligators, depend on plants or plant-eating animals for nutrition. As well as supplying food, wetland vegetation provides shelter, breeding grounds and nurseries for a profusion of marine organisms, waterfowl and terrestrial wildlife.
• Plants purify water. Plants contribute to aquatic health by absorbing large quantities of nutrients and chemicals from water and sediment. By diminishing the nutrient load and immobilizing toxins, plants reduce contamination both in groundwater and downstream.
• Plants shield infrastructure. The physical barrier of a single stem appears negligible, but thousands of acres of plants effectively absorb destructive wave energy and reduce damaging storm surge. Plants are a living shield against the sea, protecting Louisiana’s coastal infrastructure as well as its natural environment.

Lending a Hand to Nature

Because the ecosystem of Louisiana’s marshes is so destabilized, plants need help to save the wetlands. Many projects funded by the Coastal Wetlands Planning, Protection and Restoration Act (commonly known as the Breaux Act) involve engineering, such as designing water control structures to regulate tidal flow, stabilizing shorelines or directing the correct placement of dredged material to create new marshes. Even so, typically the mark of these projects’ success is the emergence of a thriving plant community.

In many instances that plant community will colonize a project area naturally; other sites benefit from humans intervening with plantings. Intervention is advantageous in places

• that could erode before natural colonization takes hold
• where there is no natural seed bank
• where water flow fails to deliver seeds or plant-generating bits of root
• in which foraging wildlife deplete the available store of plants and seeds
• where exotic plant species are likely to invade and prevent the succession of desirable plants

“Plantings can facilitate the restoration process,” says Rebecca Howard, research ecologist at the National Wetlands Research Center.“They can establish conditions that foster the wetlands’ capacity to regenerate themselves, and then let nature design and sustain their performance.”

Planning for Plants

“Think of sediment in a new CWPPRA project as lumber,” says Caffey, “and plants as the nails that hold that lumber in place. Without the nails of vegetation, the new land will collapse and be swept away.”

To make the best use of the nails, Caffey supports including plans for plants in the initial design of Breaux Act projects that require revegetation. Projects can encourage the growth of desirable species by creating conditions under which they flourish. For instance, seashore paspalum grows best at low elevations in slightly salty soil. If limited in height, ridges built from dredged material become places where paspalum readily takes hold and thrives.

Since the science of using plants for restoration purposes is relatively new, Howard cites the need for continuing research to determine what plants work best for specific locations, and why. “We want to select plants with known growth characteristics and match them to conditions at restoration sites,” she says.

For example, plants with densely clumped stems can trap fine sediment, while those with sparse stems may capture only coarser particles. One species’ bulbous root system may help aerate the soil, while another’s slowly decomposing fibrous root contributes biomass. By studying botanical attributes and selecting plants for specific restoration purposes, scientists can build on nature’s capabilities to protect and restore the wetlands.