DePaul University
Environmental Science Program and Public Policy Studies Program
Illinois Invaded:
Ecology, Impacts and Policy Approaches to Illinois Invasive Species Problem

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Introduction

Biological species are restricted in their spatial distribution. One of the central functions of ecological as a scientific discipline is to explain the causes of this restricted distribution, tracing these restrictions to abiotic (climate, nutrient limitations) and biological causes (competition, predation). Though there are a few species with an almost global distribution, most are restricted to particular biomes, and generally to portions within those biomes. Although the most prevalent hypotheses we have concerning the speciation process posits that new species evolve in small isolated populations and that the new species expand their range subsequently (invading them in a very real sense), the term invasive species as we will use it here refers to a range expansion assisted passively or actively by people.
The phenomenon of invasive species is not a new one. The transportation of biological populations beyond their original range by humans is an inevitable consequence of the process of transportation itself. Species associated with people invariably hitch rides from even the most antique mode of transportation - boats, wagons, human migrations on foot. One can image that even in Paleolithic times creature associated with people: endo- and ecto-parasites, seeds passively accompanying migrating humans made it to the New World. The Neolithic revolution would have accelerated the process - humanity would have deliberately introduced its domesticate species, plants and animals, wherever they went. And alongside these deliberate introductions would be those companion species that thrived in the agriculturalists fields, and flourished in their bodies (including a whole menagerie of microbes that became endemic in the burgeoning human population - crowd diseases often acquired from the very animals people domesticated).
Although the phenomenon is not a new one, there has been an intensification of invasion in modern times. Globalization, a term for processes that have both economic and cultural ramifications, has intensified since the end of WWII, and the world has become more densely interconnected. In the form of liberal free-trade policies globalization has been advocated by a number of international institutions. However, the advocacy of a policy that promotes material exchanges between far-flung parts of the world has inevitable repercussion for biological invasion. Therefore any policy developments to curb invasions will impose restrictions of trade. Crafting policy for dealing with invasion therefore is in conflict with other policies that have powerful backing. It is essential that policy development in this area proceeds with the best possible science, and is armed with informed cost-benefit analyses.

This webpage evaluates the invasion problem from both a science and a policy perspective.

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