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Invasive Species — Villains, Saviors or
Something in Between?
by Jessica Sprajcar,
(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.
