The casting of ‘invasives’ as ecological villains has long been backed by scientific and political consensus. Yet as species increasingly move into unfamiliar regions, a favouritism towards natives is growing harder to defend. The traditional approach of trying to stop invasions and eradicate successful invaders isn’t just costly and often ineffective. It may be entirely the wrong approach, if we’re concerned about the environment. While some invasive species are truly harmful and need to be fought, others are a healthy ecological response – they’re part of how the biosphere is adapting to humanity’s environmental impact.

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At present, invasive species are not assessed in the same way as native ones. Placed side by side, these treatments reveal a set of double standards. First, native species are presumed innocent, while alien species are presumed dangerous. Second, we are told to learn to live with the former, while eradication is treated as the default response to the latter. But these assumptions don’t seem to be grounded in data. They function instead as prior judgments that shape how evidence is gathered, interpreted and presented. In this sense, ecological nativism is not a scientific discovery, it’s a rigged result we arrive at because we look only for data that will confirm our prejudices.

A healthy ecosystem is healthy because of the complex web of interactions between its participants. These interactions are called ecological ‘functions’. Bees and butterflies pollinate; pollination is an ecological function. Fungi decompose dead wood; decomposition is a function. Plants produce organic compounds through photosynthesis; biologists call this function ‘primary production’. Ecosystems thrive when these functions are performed by the diversity of organisms and processes within them. The first nativist double standard involves calling a function harmful when an alien species performs it, even though the same function would be seen as beneficial when performed by a native species.

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I'm not denying that wildlife can cause serious harms to ecosystems as well as to human health and livelihoods. For example, in conservation circles recently, I’ve been hearing a lot about a species running rampant in parts of Africa, destroying the crops that subsistence farmers depend on, turning healthy forests into expanses of dust, and threatening to attack people, forcing villagers to hide in their homes when they could otherwise be working and socialising. You might not know about all these harms, but I’m certain you’re familiar with this highly destructive animal: the African elephant.

What are we to do about this menace, which threatens so many people, crops and ecosystems over much of the continent? If I suggested a solution that involved killing off elephants in large numbers, you’d probably be appalled, as you should be. Current thinking in conservation science is that human-wildlife conflict should preferably be solved not through eradicating organisms that come into conflict with humans, but by finding means of coexistence.

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When a harmful species is a native species, like African elephants in Africa, people will go to great lengths to peacefully coexist. When a harmful species is an alien, however, the standard response is to eradicate with prejudice.

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Rather than asking whether pythons prey on native species, we should consider a different question: are pythons keeping their prey species in check in ways that lead to healthier ecosystems?

In otherwords, Invasiveness is an analog measurement taken in context within an ecosystem, not a label that can be applied categorically in a yes/no fashion.