Following are excerpts from the Bulletin of the Ecological Society of America which form a dialog regarding use of the term invader in the field of ecology. The ESA Bulletin publishes "letters, longer commentaries, and philosophical and methodological items related to the science of ecology." The Ecological Society of America also publishes the journals Ecology, Ecological Monographs, and Ecological Applications. For more information, go to http://www.esa.org/.
From "Eight Ways to be a Colonizer; Two Ways to be an Invader: A Proposed Nomenclature Scheme for Invasion Ecology" by M.A. Davis and K. Thompson, ESA Bulletin 81(3), July 2000, "We believe that inconsistent and imprecise use of invasion terminology is one factor that is contributing to the ongoing difficulties of the field. . . . Depending on the author, a species in the invasion literature might be referred to as alien, exotic, invasive, nonindigenous, imported, weedy, introduced, non-native, immigrant, colonizer, native, naturalized, endemic, or indigenous [references omitted-Ed.]. In many cases, these terms are not defined, or if they are defined, they are not always defined consistently. Until a commonly accepted vocabulary is adopted by invasion ecologists, we think the field will continue to have difficulty developing reliable generalizations, partly due to misunderstandings and misinterpretations among investigators. . . Clearly, an invader is not just any newcomer, but one that has a large impact on the new environment. This impact could involve community, ecosystem, and/or economic effects."
January 2001: From "Two Ways to Be an Invader, But One is More Suitable for Ecology" by C.C. Daehler, ESA Bulletin 82(1), "Some invading species have greater ecological impacts than others, but defining invaders as those species with the largest impacts is an exercise in subjectivity that will be unlikely to contribute to clarity. For ecology, defining invader based on population growth and spread in a new region is preferable. It captures a general ecological process that can be confirmed with simple measurements, leading to greater agreement among ecologists, and greater progress in understanding invasions as ecological phenomena."
July 2001: From "Invasion Terminology: Should Ecologists Define Their Terms Differently Than Others? No, Not if We Want to be of Any Help!" by M.A. Davis and K. Thompson, ESA Bulletin 82(3), "We believe that there are compelling practical and conceptual reasons for impact to be a part of the defining criteria for an invading species. The primary practical reason is that, outside of the discipline of ecology, "invasive species" are usually explicitly defined on the basis of their impact . . . it would be counterproductive to the field and to society if ecologists were to define the terms "invader" and "invasive" differently than the rest of society, and not include "impact" as part of their definitions."
April 2002: From "Biological Invasions: Politics and the Discontinuity of Ecological Terminology" by M. Rejmanek, D.M. Richardson, et al, ESA Bulletin 83(2), "According to these authors [Davis and Thompson], invasion always implies some kind of impact, and all "invasive" taxa are harmful. There are several problems with their proposal. . . . there is much confusion, especially in the recent literature, particularly because many newcomers to the burgeoning field of invasion ecology ignore existing terminology and instead rely on the highly emotional negative connotations of the word "invasion" in relation to war and other aggressive human activities. This is especially true for the popular literature on invasions. Unfortunately, such sloppy terminology has permeated what should be authoritative documents on this topic . . . "
July 2002: From "Newcomers" Invade the Field of Invasion Ecology: Question the Field's Future" by M.A. Davis and K. Thompson, ESA Bulletin 83(3), "We developed our proposed nomenclature on the explicit recognition that some new species "have a negligible effect on the new environment, whereas some have a very large impact (Davis and Thompson 2000)." We proposed that usage of the word "invasion" be confined to those circumstances in which the newcomers have a large impact on the community, ecosystem, or economy. . . . To most readers, this argument over the usage of a couple of words must seem like a tempest in a teapot. However, there may be more at stake here than just vocabulary. . . . Invasion ecology clearly has been a hot area of research in recent years, spawning invasion journals, invasion symposia, special grant initiatives, and countless books and articles on the topic. Yet, despite all this activity, very little progress in understanding the ecology of these new introductions has been gained, beyond that which could already be acquired using existing ecological models and knowledge. We fear that, despite original good intentions, the emergence of invasion ecology as a distinct subdiscipline has hindered more than helped our efforts to understand the ecology of these new introductions (Davis et al 2001). Paradoxically, ecology may contribute more constructively to society's efforts to deal with the ecological, economic, and health problems caused by some of these new species if the field proceeds without the language and paradigms promoted in invasion ecology."
Personal communication from M.A. Davis, Nov. 2002: My feeling now is that if for some reason we continue to feel compelled to use the word ‘invader', it would make more pragmatic sense if we used the word in the way that the public and policy members have been using it, i.e., defined in terms of impact. How-ever, personally, I've come to the conclusion that both scientific research and conservation efforts would be facilitated if we dropped the native/exotic/invader paradigm and language completely and referred to species as ‘long-term residents' or ‘recently introduced species' or ‘problem species' (which can include either long-term residents or recently introduced species).
KB
Aquaphyte Contents | Aquaphyte page | Home