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Repelling the Invaders Might Not Be Such a Good Idea

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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.

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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. EC_bug_web

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  1. The first question this article should have answered is “Why do we need to stabilize sand dunes?” The ecology of sand dunes tend to be complex and dependent on sand dunes changing frequently. I suspect that if you consider whether or not removing invasive species from sand dunes from an ecological perspective, removing invasive species makes good sense. Unfortunately, the article does not consider the ecological perspective.

  2. There are increasing studies showing our attempts at controlling invasives are backfiring. Pesticides are the “go to” control due to the cost of other methods, but the large scale use of these products is producing more and more superweeds. Plus there is mounting evidence of the soil microbiome being significantly changed by this approach.

    Several studies suggest that “nature will find a way” if you give the ecosystem (including the microbiome) adequate time to respond. I’ve seen this on a small scale in fields where common mullein was the invasive. The local prairie dog colonies began dining on the mullein, but then someone had to rush in and “fix” the problem with a heavy dose of pesticide.

    Nature works on a different time scale than our “do it now” mentality accepts.

    If you truly want to limit invasives perhaps the place to start is by curbing industrial farming monocultures and subdivisions. Or perhaps doing sufficient science to better understand the system dynamics.

    Rising sea levels in coming years will most likely challenge any native species – so do we continue a flawed invasive control plan, or take the time/money to understand all the factors?

  3. Usually I agree with your blog, but do not agree with your comments about preferring an invasive plant to stem erosion. That was the philosophy when the old Soil Conservation Service promoted the use of plants such as Russian olive and Multiflora rose, which have since become a scourge and decreased the diversity of many of our native ecosystems. Why purposefully introduce invasives when we can only temporarily save beachfront homes in the face of climate change and rising sea levels?

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