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NatureInvasive species are more useful than they say
Studies have so far focused on the negative impact of non-native species. Scientists, including from UNIGE, suggest seeing the bright side of things.
An invasive species in New Zealand, the brown trout has become very popular with anglers.
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The majority of scientific studies on non-native species, often referred to as invasive, focus on their negative impact in their new environment. The public particularly remembers the misdeeds of the zebra mussel or ragweed. An international team, made up of scientists from the American universities of Brown and Washington, as well as the University of Geneva (UNIGE), proposes to “shift the focus” and to consider the benefits that these “invaders” can also bring.
“Positive impacts of non-native species are often explained as serendipitous surprises, the kind of things people might expect to happen from time to time, under particular circumstances,” says Dov Sax, a professor in the Department of Science. Ecology, Evolution and Organic Biology from Brown University. “Our study argues that the positive impacts of non-native species are neither unexpected nor rare, but instead common, significant, and often large-scale.”
Make a cost-benefit analysis
The study, published in the journal «Trends in Ecology and Evolution», advocates using a framework developed by IPBES, an international platform for the valuation of biodiversity and its ecosystem services, which examines the benefits of biodiversity to humans and nature and applies it to non-native species . It would thus make it possible to consider “these species in a constructive way and to explicitly document their advantages”, explains the researcher. The idea is then to make a cost-benefit balance sheet to see if the contribution of a species is positive or negative.
Earthworms are cited as an example of a non-native species whose benefits are underestimated. If they can negatively alter forest ecosystems, they can also improve organic farming. A meta-analysis has indeed shown that their presence can lead to a 25% increase in agricultural productivity. The resulting lower cost of food and increased ability to feed people is a direct economic benefit.
A protected invasive species
The study also highlights the unexpected benefits of another non-native species, brown trout. Taking the example of New Zealand, she demonstrates that most of the non-native species that have invaded the country have negative consequences and therefore residents are focused on eradicating them. Yet the country has embraced the brown trout well: New Zealanders value the nutritional and recreational benefits of fishing it so much that they have established new environmental regulations to protect the species in their waters.
“The relationship people have with nature, its intrinsic value, ecosystem services, resource provisioning are all things we value in native species. There are also ways to see that non-native species contribute to these benefits,” says Martin Schlaepfer, lecturer at UNIGE’s Institute of Environmental Sciences.
For example, non-native species can be a major cause of species extinction but also contribute, through their own migration, to regional biodiversity by increasing species richness, including in Switzerland. Introduced mussel species in Swiss lakes, for example, can alter available nutrients while increasing water clarity. “We argue that long-standing biases against non-native species in the literature have clouded the scientific process but also hindered policy advances and proper public understanding. Future research should consider both the costs and benefits of non-native species,” concludes Martin Schlaepfer.