Embracing Invasive Species


We’ve talked a lot on this website and in Erosion Control magazine about invasive species, from kudzu to the salt cedar beetle. Sometimes non-native species are introduced into an ecosystem deliberately: as ornamental plants, or vegetation used to shore up eroding hillsides, or animals and insects used as biological controls to eradicate other undesirable species. Usually, though, we think of non-native species as a negative. Many revegetation projects, especially those on federal lands, specify the use of native seeds, often requiring them to be collected from a very specific and narrow geographical area.

An article coming up in the October issue of Stormwater magazine follows the efforts of land managers in Minnesota to remove invasive plants from riparian buffer zones, using methods ranging from teams of human volunteers to herds of goats. The author of that article, David Richardson, recounts in passing how members of the American Acclimatization Society in the 1800s released many species native to Europe into American parks and wilderness areas, hoping to re-create Old World habitats on a new continent. One man, in fact, set himself the goal of bringing every species of bird mentioned in the works of Shakespeare to North America, resulting, among other things, in today’s nuisance population of more than 200 million non-native starlings.

There’s another way to look at the spread of species to new habitats, however, one that advocates taking advantage of the newcomers when and where we can. A recent study, for example, showed that the root systems of invasive plants growing on coastal dunes in New Jersey were helping to anchor the dunes and protect homes and other infrastructure behind them. A book published last month makes a stronger case for acceptance of non-natives. In Inheritors of the Earth: How Nature Is Thriving in an Age of Extinction, biologist Chris D. Thomas argues that there are some success stories we should be paying attention to: species that are thriving in ecosystems in which they didn’t evolve. Yes, they might sometimes be outcompeting the native species in those ecosystems, he acknowledges, but that’s not always the case, and if they’re contributing in some way to the niches in which they now live, why fight it?

“Rather than swim against the tide of ecological and evolutionary change,” he writes, “we should remember that the old was once new. The story of life is one of diversification and renewal—successful genes and species win the game. It is time for the ecological, conservation and environmental movement—of which I am a life-long member—to throw off the shackles of a pessimism-laden, loss-only view of the world.” Even though humans have caused or accelerated many of the changes—converting forests to farmland, carrying animals with us as we move from continent to continent—he maintains that we should “be appreciative of the biological beneficiaries of the human-altered environment, while remaining cognizant of the many human-caused losses.”

Do you agree with his view of the spread of non-native plants and animals? Given the long history of extinction both before and after humans arrived on the scene—“Some species don’t make it,” he notes. “Yet, it is equally clear that there are always survivors, and they persist and then thrive by moving across the surface of the Earth to places that area hospitable to them, and by evolving new capabilities”—do you think we put too much emphasis on conservation? Chime in below in the comments. EC_bug_web

  • Steve Chafin.

    I’m still trying to get an answer on how much sea level has risen since 1992. No one has been able to answer that question, even though you are advertising webinars on the subject.

  • Larry Schmidt.

    This article is missing the mark by miles in my opinion. There are certainly examples of benign and sometimes beneficial non-native or EXOTICS. Having said that, the same is seldom the case for invasive species. Cheat grass is a good example of an invasive that offers no benefit while changing the intermountain west into a fire desert. Those non-native plants that are not classed as invasive might be worthy of further discussion. As to embracing invasive species, as the saying goes,”there is no right way to do the wrong thing !”

  • Kent Watson, PLA, FASLA.

    One of the last courses I took in undergraduate school as I worked towards my BLA degree was Plant Ecology. This one course did more to convince me of the complexity of our natural systems than anything I had learned before. In my own practice, therefore, I always place a high priority of the use of native plants to the extent possible, which is a key component to assuring that my design fits its context within the natural setting. In other words, I’m always attempting to “Design With Nature.” There are, however, circumstances where so-called “exotic” plants have to be used because they will do better in a particular setting. Then with advice from my more plant-savvy colleagues I make sure that my plant choices are not invasive and will stay within the confines of my design.

  • Mary McAllister.

    I have read Chris Thomas’s book and I agree with most of what he says. His is not the first book to defend “novel ecosystems.” His predecessors were Mark Davis, Emma Marris, Ken Thompson, Fred Pearce, and Tao Orion.
    These books have one theme in common: “invasive” plants are not the cause of the loss of native plants or the environmental damage they are accused of causing. They are a symptom of the changes in the environment caused by human activities. The most universal change is climate change, to which the non-native plants are adapted, but the native plants they have replaced are not.
    It is pointless to try to eradicate non-native plants unless we reverse the underlying causes of their competitive advantage, such as higher temperatures and drought. And Tao Orion’s book adds another reason why we should not be trying to eradicate non-native plants: the pesticides being used to eradicate them are doing far more damage to the environment than the plants themselves.

  • Fritzi cohen.

    Thank you Mary McAllister. I know first hand about the hypocrisy that surrounds the subject of what is non-native and invasive, and I unfortunately have been victimized by the pesticides that are inevitably used—all in Willapa Bay Washington. And by the way I love my butterfly bush.

  • Bill Lucas.

    Interesting. Here in the mid-Atlantic, the real problem behind the invasive exotics per is the deer that eat all of the shade adapted native understory, so no regeneration. This has been wiped out for decades, so there is no forest structure or young trees to emerge. So when the overstory dies out, invasive vines that deer don’t eat take over. This has created kudzu like barrens of tearthumb, porcelainberry, oriental bittersweet, all of whom thrive in the unshaded ground. As for their removal, herbicides are your friend. But only after physical removal, in order to get all the remnants that shoot up from the roots left behind.

    As for stormwater facilities that are ostensibly maintained, I see little benefit in the “native only” mantra. My expertise is nutrient removal in bioretention systems, and I can assure you that fountain grass is one of the most effective plants for that out there. But it is “not native”, so many jurisdictions’ blanket requirement for natives precludes its use. Even though right next door it is part of the foundation plantings. Go figure. Purists have no credibility in an impure world. Whatever works and makes things better with no adverse impacts is good by me.

  • David Speidel.

    First the topic of invasive plants, animals or even micro as they affect the original in our I bleive needs to be viewed from your groups perspective. The strongest advoces are not conservationist, but preservationists. As I understand the term and perurpose of conservation is as a economic term. Conservation defines the best How and When of a resource use. It ould be apetty to have aspeices become extent and worse if humanity’s action or inaction was the cause. But that is preservation and not conservation of useful resources. Would that mean if a species was not useful should not care. No not al all, but need to recognize we are fortunate to live in a society that has the luxury to spend resources on preservation. However that effort should not be at the expense of our society. How clever we are to find the balance should be the mission of conservationists.


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