To the Editor: On Marlene Condon


In the March issue Susan Roth and William Hamersky responded to Marlene Condon’s article “Ecologists Recognizing Value of Alien Plants,” in which Ms. Condon reported that more and more ecologists are taking a more nuanced approach to native and nonnative plants.

Ms. Condon is correct. In the 1980s and ’90s ecologists defined invading species as any nonnative species that was found outside its traditional range.  Today, ecologists define invasive species as just those nonnative species that are causing harm to human health, the economy, or the ecology of their new environment. These species represent a minority of nonnative species. In some environments the nonnative species are often the only species that can thrive there, for example in many urban settings.

Ms. Condon is correct that some ecologists and land managers still view native and nonnative species in a black and white perspective and pursue an agenda-driven science. I was disappointed that Roth and Hamersky adopted such a personally hostile and condescending tone in their reply to Ms. Condon.  Such a vindictive response is hardly going to lead to constructive conversations about nonnative species. And constructive conversations are what are dearly needed. Fortunately, they are taking place in some venues. The U.S. Fish and Wildlife Service is one place where resource managers now recognize that some nonnative species can actually enhance habitat restoration and rehabilitation efforts.

I encourage more conversations about native and nonnative species. But emotional responses that deny any credibility whatsoever to opposing views are not going to be constructive.

Mark Davis
DeWitt Wallace Professor of Biology at Macalester College, St. Paul, MN


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