Alien Species.vp - IUCN

Vivian Parker
managers, relying upon traditional ecological knowledge, challenge us to look closely at the
ecosystems in which invasive plants occur, while asking what they might be telling us.
We recognize the role that humans have played in disrupting the balance of nature, and that
humans must also play a role in restoring the balance. Policy makers and resource managers
must shift the focus of their attention from treatment of the symptoms of ecosystem disorder, to
identifying and preventing the causes of plant invasions. Invasive plants are one of the
symptoms of an altered biological trajectory resulting from unsustainable resource extraction
and industrialization of the planet. We must take actions that will restore the balance to
ecosystems that are threatened by the loss of native biodiversity.
The ecological perspective (all things are connected) bears great similarity to the Native
American concept of relationship (all things are related). This perspective is necessary for
successful long-term restoration of native ecosystems. However, an agronomic bias – which
focuses on the negative impact of IAS on agriculture – currently dominates research on
invasive plants, severely limiting lines of enquiry into the broader causes and prevention of
alien plant invasions. An ecological approach to control of invasive plants requires that the
many interactions between species be investigated. For example, evidence for the beneficial
effects that invasive species may be having in stressed ecosystems has largely been ignored.
The agronomic bias also imposes a value-laden language upon alien species, and may
institutionalize the conceptual paradigm that certain plants and animals are bad or even evil.
Colonizing invasive plants have been characterized as “aggressive,” “choking,” “stealing,”
“corrupting,” “harmful,” “destructive,” and guilty even of “deliberate takeover” (e.g., USDI,
USDA, 1999). With the understanding that all life is sacred, we do not think that such
characterizations are helpful, and we believe that adherence to this paradigm may result in
further harm to the planet.
The purpose of this paper is to focus attention on the causes of plant invasions, and threats to
native plant habitats. I will discuss the role of invasive plants in plant community development
and evolution of new species, and present evidence that contradicts widely-held assumptions
about the effects of invasive plants, particularly in regards to competition. These assumptions
have been used to justify use of destructive herbicides. It is my hope that the issues addressed in
this paper may provide a starting point for developing a new paradigm, based on ecology and
respect for life, rather than on economics.
The complex nature of invasions and global change
Generalizing across all taxa, without distinguishing between their various life histories and
habitats, is misleading and should be avoided. I provide some examples below.
Differences between plant invasions and other types of invasions
The great differences between the life histories of plants, animals and pathogens make it
inappropriate to generalize across all taxa in regard to invasive species. This is an important
distinction. For example, the lumping together of invasive life forms, and the subsequent
assignment of their economic costs, is unscientific and has left open the potential for misuse of
these figures by special interest groups. Reports such as Pimentel et al. (1999) and OTA (1993)
combined diverse taxa and effects in order to arrive at aggregate economic costs of invasive
species. The Pimentel report included such costs as lost work time for workers who had been
bitten by dogs ($85 million per year), and the costs of AIDS infections ($6 billion), although
dogs and AIDS bear little direct relationship to the true issues of invasive species and biological
diversity on the planet. In the OTA report, fully 96% of the costs calculated were due to 62% of
the species, which were all insects and agricultural pests. Since agriculture itself is a primary
threat to the biodiversity of the planet (e.g., Ehrlich and Ehrlich, 1981), one could theorize that
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