Cultivating Remedies to Stem Wetland Loss

“PLANTING VEGETATION IN LOUISIANA’S wetlands is hard work,” declares Ron Boustany, biologist with the Natural Resources Conservation Service. “Keeping an eye out for alligators, you wade through murky water and sink up to your knees to dig hole after hole in soft, bottomless mud.”

And there’s no assurance the hard work will pay off: a single high tide or unexpected storm can undo entire plantings.

Despite the difficulties, many scientists are convinced of the value of plantings and are experimenting with ways to overcome their drawbacks. Currently the entire process, from propagating stock through root division to setting out each plant by hand, is time-consuming and labor-intensive. However, some innovative ideas for expanding the use of this restoration tool are in the works.

Looking for Natural Answers

“Aerial seeding is the easiest, fastest, most costeffective method of planting large areas of wetlands,” says Mike Materne, plant specialist at Louisiana State University’s Agricultural Center. “It’s really the only alternative we have to planting by hand.”

Unfortunately, aerial planting has a major drawback— many wetland plants produce few viable seeds, multiplying instead through rhizome division or root spread. Consequently, Materne and other scientists at the Ag Center are developing strains of native plants that promise both a high seed yield and a greater rate of germination. They are also looking for characteristics conducive to mechanical harvesting, and analyzing issues such as optimal temperature and moisture levels for winter seed storage.

But Materne isn’t limiting himself to seed. “We’re exploiting the plants’ own strong suit: vegetative propagation. We’re chopping the underground stem into small fragments for aerial distribution. This could be a way to get vegetation to large areas of wetlands that are inaccessible by boat or foot.”

Submersed Vegetation Takes Root on Mats

Having done his share of digging in knee-deep water, Ron Boustany went back to the lab to search for other planting methods. In a recent study he grew submersed aquatic plant seedlings on biodegradable mats in a greenhouse. He then transplanted the seedlings by pinning the mats to the bottom of marsh ponds.

“The mats provided a durable but temporary substrate,” Boustany says. “They helped young plants withstand the destructive forces of wind and wave. Also, the mats seemed to bolster natural colonization by providing stability for additional species. As we learn how best to site the mats — how deep, how far from shore — we expect to increase the resulting plant cover.”

Benefits Increase with Choices

Although the plants are natural, wide-scale plantings are not natural elements in the environment. Observers caution that, even as their successes are emerging, plantings may also be deleteriously affecting the ecosystems they are targeted to save.

Materne acknowledges the concern. “An area planted in a single species is artificial,” he says. “As we see the widespread use of Vermilion cordgrass in restoration, we’re realizing the benefit of planting multiple cordgrass strains. If one proves susceptible to changing conditions— drought, say, or a new insect pest — there would be other, more resistant strains to maintain the plant community. The collapse of one strain would not jeopardize the entire marsh.”

More varied plantings could also alleviate fears of genetic dilution, the possibility that a single cultivar crossbreeding with wild strains could diminish the entire species’ genetic diversity. Using multiple strains might instead enrich the species’ genetic mix, while planting a blend, or suite, of different species could enhance an ecosystem’s stability and resiliency.

With Louisiana’s imperiled wetlands at stake, the quest for optimal plants and the best planting techniques is urgent. “Changes happen quickly in the wetlands,” Materne says, “and we’re helping plants keep pace. Drawing on the Ag Center’s decades of agronomic experience, we’re developing plants that will become the key element in coastal restoration.”