Biological Control of Invasive Species


Invasive species are a major threat to ecosystems around the world. It is estimated that 50,000 non-native species have been introduced in the United States with over one tenth escaping to become established in the wild, involving an area larger than California. While some of these introduced species are major agricultural crops that provide most of our food, many others threaten ecosystems by outcompeting and directly preying upon native species. An estimated 40% of threatened or endangered species in the United States are at risk primarily due to threats from invasive species. The costs are not solely environmental, however, as economic costs come with prevention measures, pesticide or herbicide applications, habitat restoration, and reduced productivity of ecosystems. These costs are estimated to be as high as $137 billion a year in just the United States. Once an invasive species is established typical control measures involve mechanical or chemical means to limit or even reverse the spread of the invasive. Another approach involves using biological means to control invasive species (Pimentel et al. 2000).

Biological control involves natural predators of invasive species being introduced to bring the invasive population under control. This method has the advantage of being self-sustaining and, ideally, self-regulating. Once a predator is established, it will reproduce in its new environment and prey upon the target species. However, as the target species declines, so too will the population of the introduced predator. Whereas applications of chemical treatments must be repeated year after year at some expense, biological control can be undertaken once. However, every attempt to introduce a control agent does not meet the goal of reducing or containing the target species. In addition, some control agents can have negative impacts on native species in the ecosystem, thereby hurting the very species they are meant to help protect. This has led to an increase in opposition to biological control methods in recent years.


The next pages outlines the argument for biological control. Take me there!


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