The persistent negative view of non-native species that has dominated conservation and ecological restoration activities in theUnited Statesin recent decades has its roots in the early 1980s, when a group of ecologists interested in species introductions developed a new subdiscipline of ecology now known as invasion biology. For the next 10 to 15 years, most ecologists referred to all nonnative species as “invaders” (Mack 1985, Mooney and Drake 1989). But by framing the redistribution of species as biological pollution by invasives, ecologists presented more than just scientific findings to the public and policymakers: They also promoted a valuebased and prescriptive conservation agenda — stating, in effect, that all non-native species should be eradicated (Temple 1990). That agenda still dominates many conservation initiatives today.
I believe the use of invasion terminology has created a bias against non-native species in general. The introduction of new species to a geographic area could be thought of as “species additions” or the “global mixing of species,” terms that are unaccompanied by any value-laden message. Framed this way, the issue of non-native species might elicit management approaches and policies beyond control and eradication.
Without question, some non-native pathogens, insects, plants, and animals are “invasive” in that they cause great harm. Most non-native species, however, are not invasive or harmful, but are simply species additions to a particular region without substantial undesirable effects, despite common belief to the contrary. For example, non-native plants growing in eastern North American forests such as garlic mustard, buckthorn, and honeysuckle are commonly described as the cause for declines of native forest wildflowers. However, increasing numbers of recent scientific studies are concluding that the new plant species are not responsible for these declines (Nuzzo et al. 2009, Rooney and Rogers 2011). Instead, the declines are believed to be more often caused by other factors, including the introduction of earthworms (which alter the litter-soil environment) and exploding abundances of white-tailed deer (which eat many native wildflowers) (Nuzzo et al. 2009).
Why were non-native plants so quickly declared invasive and the enemy of native plants? One reason was mistakenly assuming a causal relationship between two events happening at the same time (the decline of native plants and the increase in non-native plants). Another was that messages from invasion biologists had led land managers and the public to expect negative effects of non-native species.
A Shift in Perceptions
The general public has never had much of a say as to whether non-native plants should be declared harmful or not. Rather, they have been told at the outset that these plants (e.g., garlic mustard, buckthorn, etc.) are invaders “infesting” our forests and threatening native biodiversity, and that control and eradication efforts—often requiring public tax dollars — need to be undertaken to reduce their abundance.
Times are changing, however. More citizens are beginning to question the value-based messages regarding non-native species and the costs associated with eradication. One example: In October 2012, a conference titled “Rethinking ‘invasive species’: Environmentalism gone awry?” will occur in Washington, D.C. I’ve been invited to speak at this event, which is sponsored by Fearless Fund, an organization formed to encourage environmental activism and advance the education and physical, social, cultural, health, and economic well-being of local communities.
By reexamining the underlying assumptions and motivations behind the broad campaign against non-native species, the conference hopes to explore creative rather than destructive responses to changes in our environment. By doing so, it will help citizens gain some say in how to assess the harm or worth of newly introduced species, and the strategies developed to manage them. Some public interest groups are already active in this respect. East Bay Pesticide Alert, for example, is an organization in California formed to contest the extensive use of pesticides to control non-native plant and insect species.
Public participation in the valuation of and response to non-native species could ultimately result in more effective land management and conservation policy by ensuring that society’s scarce financial and human resources are allocated to projects and programs that best embody and promote the values and priorities of the citizens.
Mark Davis is a DeWitt Wallace Professor of Biology at Macalester College in St. Paul, Minnesota.