Invasive Species Really Don't Belong Here

In September my brother and I drove through 12 ecozones from the Forest/Savannah Transition in Wisconsin through Tall Grasslands to the Western Short Grasslands in Colorado, my first time to see the American Prairie. For decades, I had read about conservationists’ efforts to restore its ecological integrity. At Blue Mounds State Park in Minnesota, we walked along a ridge at sunrise, saw bison in Northern Short Grasslands, and then stopped at the park office to chat with two conservation officers.

They described a 20-year long campaign against weeds in their bison range, but mentioned misgivings. They gave me a copy of an article about researcher Mark Davis of Macalester College, St. Paul. His research shows that exotic species often fit well into native ecosystems and contribute to ecosystem function and biodiversity.

Of course, some exotics are fine (e.g., exotic game birds and honeybees), but many are seriously ruinous to terrestrial or aquatic ecosystems or agriculture. Here in British Columbia, ranchers spend millions of dollars trying to limit the spread and reduce the density of knapweeds, for example, and farmers work hard to keep alien weeds out of their crops, as they do in Minnesota. Our aquatic biologists have likewise spent a small fortune trying to limit the growth of damaging aliens, such as the milfoil that fouls beaches in the Okanagan. But, although I have enjoyed hunting chukars and ring-necked pheasants in North America, it was much more of a thrill to see chukars in their native habitats in the Hashemite Kingdom of Jordan and ring-necked pheasants in the Peoples’ Republic of China. Clearly, aesthetics and values are valid components of the debate, if there is one. Some species just don’t belong here.

I agree with Davis that scientists have become more sanguine about the issue and it is usually non-specialists who have such an anti-invasive fervour. I don’t mind their zeal. In 1994, when I published the first comprehensive analysis of invasive species in this province , there was virtually no government or public attention to the damage caused by invasives. Now there are new laws to restrict importation and government staff, stakeholder committees, and citizens’ groups in every region that sponsor research, conduct campaigns to limit the spread of invasives, and mobilize volunteers to eradicate infestations in certain situations. This is all good for the environment.

Leaving Minnesota, we drove through South Dakota, Nebraska, and Colorado, stopping at state parks and National Grasslands all along the way. We saw pronghorn antelope, more bison, desert cottontails, prairie dogs, and other prairie wildlife in four more short-grass ecozones. Without conservation efforts like those at Blue Mounds State Park, these would have been degraded habitats empty of wildlife.

References
Harding, L.E, P.R. Newroth, R. Smith, M. Waldichuk, P. Lambert and B. Smiley, 1994. Exotic species in British Columbia. In: L.E. Harding and E. McCullum (eds.), 1994. Biodiversity in British Columbia: our changing environment. Environment Canada, Delta, B.C. p. 159-223.
DAVIS, M. 2003. Biotic globalization: does competition from introduced species threaten biodiversity? Bioscience 53:481-489.
World Wildlife Fund 2000, Terrestrial Ecoregions