Wild Notes Spring 2010 edition
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Summer 2010

*You can also download the entire issue in PDF form.

Cosmo the flying squirrel

 


You can also download the entire issue in printable PDF form

Invasive Species — Villains, Saviors or
Something in Between?
by Jessica Sprajcar,
Conservation Program Manager for the Pennsyvlania
Department of Conservation and Natural Resources

multiflora rose bush
Multiflora rose was promoted for agricultural fence rows,
but it spread throughout the state.

(Photo: James Miller, US Forest Service)

 

Open up the pages of any conservation related publication and you are likely to see an article or two discussing the threats posed by invasive species. There are entire conferences devoted to the subject. The Wild Resource Conservation Program even has a documentary film on the topic. Invasives are everywhere, both literally and figuratively. You might think that something so ubiquitous would be well understood, but for invasives that isn't always the case. The sheer variety of invasive species makes it a challenge to quantify their impact on the environment and economy. For instance, there is no agreed upon count of how many different species of invasives there are in the United States.

At www.invasivespeciesinfo.gov they list 123 species, but their list does not include species that have already become established, meaning that they are common in the landscape, breeding and self-sustaining. Multiflora rose is a well-known example of this; take a walk through any forest in Pennsylvania and you are bound to see these prolific
shrubs.

DCNR's list of invasive plants includes more than 60 species, a handful of which are not included on the federal list. Part of the difference in lists stems from the fact that the definition of invasives is value-based; it all depends on what benefits you reap from the environment. For instance, if you are managing your land for timber and an exotic plant hinders the growth of your trees, you might consider that exotic to be invasive. Yet womeone else who manages their land for ornamental flowers and shrubs might deliberately plant that exotic because it adds to the aesthetics of their landscape. Competing ideas of what the “natural environment” should look like leads to differing opinions on what is considered an invasive.

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Pennsylvania Wild Resource Program