Illinois Natural History Survey - University of Illinois

Illinois Under Siege

This issue of Illinois Natural History Survey Reports is devoted to a single topic--invasive species. Because we consider this topic so important and because there are many invasive species in Illinois, this issue is more than twice as large as previous ones so that we can adequately cover the topic. Even our school activities column, "The Naturalist's Apprentice," is designed to help answer the question, What is a pest?

Each new invasive species receives a moment of media attention, then fades from public notice. Such intermittent publicity masks a general pattern that should concern everyone: Because new species are introduced almost every year but we seldom are able to completely eradicate them, the total number of invasive species is increasing. Approximately one-third of the plants you are likely to see in most woodlands, wetlands, and grasslands in Illinois are non-native species. In the aquatic realm, the Great Lakes illustrate virtually every problem associated with transfers of species by humans, culminating in an altered ecosystem that no longer maintains itself but requires costly human intervention. The invasive species described in these articles are only a few of the more recent introductions that Survey scientists are seeking to control.

What is an invasive species? There are at least 4,500 known species of foreign origin that have established free-living populations in the U.S. Some of these are beneficial animals and plants that were intentionally introduced, such as cattle and wheat, and are not considered problems. There are others, however, that displace beneficial native species, carry diseases and parasites that threaten human health and the health of domesticated and native species, and cause economic damage (e.g., the zebra mussel clogs water intakes of industrial and municipal water plants). Not every species that is introduced to the U.S. survives and establishes self-maintaining populations. The terms "invasive" or "weedy" are generally used for species that out-compete and displace native species, often becoming the dominant species, not just in a numerical sense, but also in terms of altering environmental conditions. For example, dense beds of zebra mussels can use up enough oxygen in rivers to stress not only themselves but also native fishes, mussels, snails, and aquatic insects.

Invasive species, as you will learn from this issue, are an old and continuing problem in Illinois. Some species, such as purple 
loosestrife, have been around for more than a century. Others, such as the Asian longhorned beetle, arrived only this year; others, no doubt, will come in the months and years ahead. At INHS, we are constantly vigilant to detect their arrival, to study their impact both on our environment and economy, and to develop strategies to prevent introductions of new invasive species and control invaders that have already arrived, or at least limit their spread and harmful effects. Control methods for invasive species should be designed to have maximum effectiveness against targeted organisms but minimum negative impact on native species and their habitats. Integrated pest management is a comprehensive strategy used by INHS scientists that can include biological control as well as carefully timed and targeted chemical control. These methods are described in further detail in other articles in this newsletter.

Interestingly, the news about invasive species is not all bad. There are a few success stories that have resulted from cooperative efforts of INHS researchers with govermental agencies and commercial and private interests that are affected most by invasive species. (See articles on crucifer weevil, pine stem borer, and purple loosestrife for some good news.) Once we know the the basic ecology of an invasive organism, we can develop long-term control measures that can be both environmentally friendly and economically sound. The monitoring activities for invasive species at INHS as well our studies on the life histories of invaders and development of control methods will continue. We may never stop unwanted invasions but there is a realistic potential for us to keep invasions under control when they occur.

Richard Sparks, Director of the Water Resources Center at the University of Illinois

Illinois Natural History Survey

1816 South Oak Street, MC 652
Champaign, IL 61820

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