What is the Real Impact of Invasive Species?

Posted Feb 24, 2009 by Bob Ewing
Invasive species are one of the top causes of biological diversity loss worldwide and significantly impact cultural diversity.
Invasive species are generally considered to be a major threat to ecosystem diversity. A recent study shows that invasive species also significantly impact cultural diversity.
The study was published in the latest issue of the journal Environmental Conservation and has provoked heated debate within the scientific community.
The study reviews 70 case studies across the globe and outlines the myriad, often unpredictable impacts of invasive species on cultural systems.
It took authors Dr. Jeanine Pfeiffer, Research Director for Social Sciences at Earthwatch Institute and Dr. Robert Voeks, Geography Professor at California State University Fullerton, five years to complete.
“Prior to being published, this review provoked debate from both biological and cultural scientists,” said Pfeiffer.
“Most biologists assume invasive species are inherently bad and overlook cultural ties, while cultural scientists have downplayed the ecological impacts of invasive species. Neither side has fully recognized the complexities involved.”
The researchers, at first, expected to find only negative impacts from invasive species, assuming they were as detrimental to cultural systems as they are to ecological systems.
“In reality the exact nature of the impact of an invasive species depends on many factors, most of which haven’t been systematically studied,” Pfeiffer said.
Pfeiffer and Voeks divided biological invasions into three categories, depending on whether the society dealing with invasive species suffers a gain, a loss, or a change in cultural traditions.
“Nearly all plant and animal introductions over the past 500 years were carried out by humans,” said Voeks, including some now considered state flowers and state birds.
Invasive species can help displaced cultures to survive. For communities like West African descendents in Latin America or Asian immigrants in the United States, exotic species used in food, rituals, and medicine (such as verbena, fennel, or castor bean) enable key cultural traditions to continue in their new homelands.
The impact of invasive species has been mostly negative for many tribes in California. Plant invaders such as star thistle and Himalayan blackberry have led to the loss of basketry and wild-harvested food species on ancestral gathering sites. Toxic pesticides used to control invasive species on public lands have also had negative health impacts on basket-weavers, hunters, and other tribal members who still live off the land.
Some traditional cultures adapt to invasive species, as was the case for the Sioux, who used introduced horses to hunt bison.
There are also situations where invasive species have mixed impacts, such as the pig in Hawaii, or rainbow trout in the Western US. A voracious destroyer of fragile native ecosystems, roasted pig remains a favored part of Hawaiian luaus.
In states such as California, Colorado, and New Mexico, the practice of artificially stocking predatory trout in lakes and streams threatens countless species of native fish and amphibians with extinction. Yet sport fishing industries have also helped urban and suburban residents appreciate nature.
“We hope our study can lead to greater incorporation of cultural considerations in research, management, and policy decisions relating to invasive species,” says Pfeiffer.
“We can’t afford to be culturally ignorant any longer.”