Alien Species.vp - IUCN

With this in mind, if the proliferation of IAS is indeed a natural response to the driving agent
of disturbance, industrial Homo sapiens, then the role of these invasions in maintaining
ecological integrity must be investigated. This line of enquiry has been severely suppressed in
the current agronomic paradigm. An exception is Walter Westman, who pioneered this concept
in his studies of the effects of pollutants on native and alien vegetation. Westman et al. (1985)
were able to demonstrate that deposition of chemicals from urban and industrial pollutants
resulted in soil changes that facilitated the growth and spread of alien species that had evolved
into pollution-resistant ecotypes. Pollution also caused the death or mutation of native
mycorrhizae fungi, and prevented formation of nitrogen fixing nodules on plant roots. The
proliferation of herbicide-resistant weed ecotypes, of course, has been well known for half a
century (Harper, 1956; Baker, 1974). In 1990, Westman suggested that in many cases, weed
species may be better adapted than specialized native species to deal with the stressful
conditions of habitat and climate change and pollution. Thus, alien species may also serve an
important role in soil binding and nutrient retention in degraded habitats that are no longer
suitable for native species (Westman, 1985, 1990).
The Native American perspective
Native American people, and perhaps all indigenous people, are especially well qualified to
understand the potential for harm that is the outcome of uncontrolled growth and expansion of
alien or non-native populations of species. While Native American people have themselves
been the victims of invasions of their homelands by the arrival of immigrants on this continent,
they have generally not viewed new plant introductions with the same alarm that western
scientists have. According to Native American herbalist Betty Hall (Shasta elder), newly
introduced plants were often welcomed, and new uses were found for them. Closely related
plants, such as the thistles in the genus Cirsium, were used as food and medicine in similar ways
across the continent, whether native or not. And Indian people are quick to notice how the birds,
butterflies, and other insects are drawn to species otherwise thought of as weeds by western
scientists. Plants that are considered weeds often have medicinal values, such as wormwood
(Artemisia sp.), mullein (Verbascum thapsus), sea fig (Carpobrotus sp.), St. John’s wort
(Hypericum perforatum), milk thistle (Silybum marianum), and blackberry (Rubus sp.), in
California. Reetha Amin (Atsugewi elder) refers to these types of plants as “healers”. She says
these plants heal people, and they heal the Earth too; that is why they grow in waste places, on
disturbed ground. If this is so, then when we kill these plants because they are not native
species, is it possible that we are causing further harm, by interrupting the natural healing
process? These plants are wild; they are self-directed. As such, they do belong to the Earth.
Ancient indigenous cultures, who have occupied areas of the North American continent for
10,000 years or more, have direct cultural experience from thousands of years of direct
interaction with the land. Many tribal people have stories dating back to time immemorial,
which carry warnings about a previous time, when people made mistakes dealing with the
environment. The stories are meant to serve as a warning to each generation, so the same
mistakes are not made again. As Winona LaDuke (Anishinabe) has stated “Natural law is preeminent”,
and failure to obey this system of law will have inescapable consequences (LaDuke,
1995).
Navajo story tellers, for example, tell of a time when plants ruled the Earth. Many of them
were harsh plants, and covered with dangerous spines. If the Earth is not cared for properly, we
are warned, this time could return. Elders, when questioned about the current sweep of prickly
invasive species showing up now in the western desert regions of their homelands, reply that
the Earth is responding to the damage that unsustainable land use has brought with it (Burnside,
pers. comm.).
49
Human dimensions of invasive alien species