Open borders, free trade, population growth, and wealth are all serious drivers for the spread of invasive species. Image credit: Kecko/Flickr
The open borders of the European Union, it is argued, makes the natural shift of people—from places with few jobs to those with more opportunities—a simpler prospect. Plant and animal species, of course, have never been bound by the political confines of national borders, but new research has shown that increases in human populations and the spread of wealth may be powerful driving forces in the spread of invasive species.Susan Shirley, a research assistant in the Department of Forest Ecosystems and Society at Oregon State University, explained:
Regional patterns of species invasions are complex, and there is still unexplained variation, likely due to local scale differences in several of the ecological factors...but invasive species are in large part an international trade issue, and this is an important problem we have not yet come to grips with. Next to population density, the closest correlation is to long-standing wealth, not more recent increases in income or economic activity.
This pattern has been observed in the countries of the former Soviet Union. When the Iron Curtain was drawn, it prevented travel, trade, and communication between the two halves of Europe. In almost 40 years of isolation, the number of introduced bird species in Eastern Europe increased decreased from 11 to merely five. Meanwhile, in the globally connected countries of Western Europe, the number increased from 36 to 54.
In fact, in a recent study authored by Shirley, population growth and wealth capital emerged as the most significant drivers for the spread of invasive species—beating climate change, geography, and land cover, the importance of which has been overestimated in past studies.
Shirley and her team explained in the report that:
The overwhelming effect of human factors, wealth and demography, found for several taxonomic groups translates to human activities responsible for enhancing biological invasions.
The problem that emerges from this realization is a serious one for conservationists. If the introduction of invasive species is driven by wealth, population growth, and international trade, how can this often destructive process be controlled without hampering development?
As the study points out, "nations do not have a good track record in forsaking future economic prosperity for environmental benefits." Because of this, pinpointing specific mechanisms of invasion is essential. Once this is done, monitoring will have to be improved. Legislation and limits on exports and imports will be needed. Both of these approaches, of course, will be costly.
But for now, Shirley and her team are focused on the first step: Identifying the key drivers of the spread of invasive species.