Protecting ecosystems from non-native species stems from a “biological bias,” says biologist Mark Davis. Instead of dividing the world into native and non-native environments, scientists ought to judge species based on what they do, he says, not where they come from.
 
Sam Rosenzweig | December 2011 Issue
We’re used to dividing the world into native and non-native ecosystems. What’s wrong with that?
“All species were non-native at one time. How long does a species need to be at a place before it is considered native? ‘Native’ and ‘non-native’ is a dichotomous categorization [overlaid] onto what is actually an ecological continuum.”
So how should scientists be assessing species instead?
“They should focus more on the effects of species than on where they originated. Non-native species are just species. From our perspective, some are going to be helpful, some are going to cause harm and most will be relatively benign. The best example in the U.S. is the honeybee, which is not native and provides billions of dollars in economic benefits. Others, such as some introduced berry-producing shrubs, provide food for native animals or help increase the amount of nitrogen in farm soils. There are plenty of native species that cause great harm. Poison ivy and poison oak are native. The insect killing the most trees in North America at this time is the mountain pine beetle, a native species.”
What makes standing up against non-native species so popular?
“People don’t like change, especially when it happens very fast. A lot of people are opposed to the rapid globalization that is taking place. This has resulted in a revitalization of nationalism and local culture and concerted opposition to new ideas, new people and new ways of doing things. For many, the anti-non-native-species perspective represents the anti-globalization response.”
Is that harmful?
“The consequences are huge, since the nativism paradigm has distorted many conservation efforts to get rid of non-natives and restore native species to a site and resulted in a lot of money spent on what have often turned out to be largely fruitless efforts. You can garden your backyard and maintain or keep out whatever species you want, but you can’t garden nature.”
Photo: Beatrice Murch via Flickr