Repelling the Invaders Might Not Be Such a Good Idea

Have you been trying to eradicate invasive, non-native plants in favor of indigenous species in your area? You might want to think again, at least if controlling erosion is part of your goal.

A recent study conducted at a coastal New Jersey state park compared the protective effects of two different species of plants in protecting the dunes: a native American beach grass, Ammophila breviligulata, and the invasive Asiatic sand sedge, Carex kobomugi, an aggressive plant that’s been present on the East Coast of the US since the 1920s and that tends to take over and beat out local vegetation.

The lead investigator, Bianca Charbonneau, a doctoral candidate at the University of Pennsylvania, has been studying coastal erosion since Hurricane Sandy in 2012. She and her team found that the two species were both present in the park but grew on separate dunes, not intermingling, which was essential for the study. Using aerial imagery and NOAA elevation data, the team compared pre- and post-storm dune crests and other variables. They found that dunes covered with American beach grass lost on average 3 meters more during a storm than those with the Asiatic sand sedge.

The ability to protect the dunes seems to depend more on the plants’ ability to trap sand, and on the nature of the root systems rather than the height of the plants, as had previously been believed. The researchers admit they do not yet know, however, how different plant species affect the formation of the dunes in the first place—whether the growth rate and shape of the dunes varies depending on what’s growing there.

So where does this leave us in terms of vegetation management strategy? “If you value the natural composition and habitats afforded by native plant diversity, you should be trying to control this invasive,” says Charbonneau. “If your priority is protecting houses on the coast, you might consider letting it lie.” The study was published in the Journal of Applied Ecology.