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Non-native species can have unexpected benefits

Over the past half a century, scientific awareness of non-native species – often called “invasive species” – has increased substantially, to the point where anyone with a “green conscience” has heard of them and their negative impacts. However, according to a new study led by Brown University, the long-standing biases against these species have hindered the acknowledgement and understanding of some of their benefits.

“Positive impacts of non-native species are often explained as serendipitous surprises – the sort of thing that people might expect to happen every once in a while, in special circumstances,” said study lead author Dov Sax, a professor of Environment and Society, and of Ecology, Evolution and Organismal Biology at Brown. “Our new paper argues that the positive impacts of non-native species are neither unexpected nor rare, but instead common, important, and often of large magnitude.”

“We want to provide a framework for the way that scientists can think about non-native species constructively going forward and explicitly document their benefits. It’s only then that we’ll be able to accurately and fully compare and contrast them in order to perform the kind of cost-benefit analyses that can be truly helpful in making policy decisions.”

While some non-native species, such as introduced pathogens and agricultural pests involve indisputably large net costs and provoke significant damage to humans and various ecosystems, most domesticated non-native species, such as wheat, tomatoes, cotton, wool, and pets like dogs or goldfish, provide large net benefits to human societies. 

By focusing on non-native species that are not directly managed by humans – so-called “wild” or “naturalized” species – Professor Sax and his colleagues found that many of these provide both costs and benefits for humans and nature.

For instance, while earthworms can negatively change forest ecosystems, they also often augment organic agriculture, significantly increasing agricultural productivity and decreasing food costs. Another example of a non-native species with major benefits is the brown trout. After reaching New Zealand, the brown trout became valued for its nutritional benefits, leading authorities to establish new environmental regulations to protect it. 

The researchers advocate to apply the same framework used to discuss the benefits of nature and biodiversity to non-native species too. “How people relate to nature, to the intrinsic value of nature, to the ecosystem services, to the provisioning of resources – these are all things that we value in native species, and there are also ways to see that non-native species are contributing to these benefits, too,” Sax explained. “It’s not like there’s some inherent trade-off: Non-natives aren’t the boogie man.” 

For instance, while non-native species can be a major cause of species extinctions, they can also contribute through their migration to regional biodiversity. Similarly, they can reduce some ecosystem functions, such as water clarity, while increasing others, like erosion control, and they can provide new valuable resources, such as fishing or hunting opportunities.

“We argue that long-standing biases against non-native species within the literature have clouded the scientific process and hampered policy advances and sound public understanding. Future research should consider both costs and benefits of non-native species,” the authors concluded.

The study is published in the journal Trends in Ecology & Evolution

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By Andrei Ionescu, Staff Writer

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