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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 [1] 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 [2], 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 [3] 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