Thanks to warming climates and habitat destruction, ‘invasive species’ narratives have begun to shift
As human activity continues to heat the planet and destroy wildlife habitat, plants and animals are responding based on their genetic makeup and ability to adapt to changed environments. Some are losing ground, ending up on ever-growing species at risk lists, or disappearing altogether. Others are gaining ground, surviving alongside us, or even benefiting from the habitat modification we have caused – raccoons, for example.
science writer Fred Pearce’s remarks that “most losers are rare, endangered and endemic species, while most winners are common, generalist and invasive species – rats, mosquitoes, water hyacinths, etc.”
“Assisted evolution” initiatives aim to help wildlife species at risk adapt to their changing environments more quickly than normally allowed by generally slow evolutionary processes. In Australia, a program aims to help big bilby, an endangered marsupial, learn to avoid predation by intruders in their ecoregion – feral cats and foxes introduced by British colonizers.
The cats have successfully adapted to their new environment and are not going anywhere. A team of researchers has changed the standard conservation measure of building fences to keep cats out, bringing cats into bilby’s fenced shelters instead. This helps bilbies learn to avoid, a skill they need to survive in the wild.
Invasive species have long been recognized as the main threats to native plants and animals. WWF Living Planet Report Canada 2020 identifies them as a major cause of wildlife decline here. But since plant and animal species around the world have started to change range in response to global warming and habitat destruction, narratives about invasive species have also begun to change.
In the past, conservationists viewed them negatively. Various eradication initiatives have been put in place depending on the government’s capacity to manage the landscape, the threat invasive species pose to endangered species or economic enterprises, bloom levels and ease of eradication. (Think zebra mussels and purple loosestrife.)
Now, there is a good chance that species moving into new areas will leave warming and degrading habitats and would benefit from human stewardship. How should we respond? Should we differentiate between these “invasive” ecosystems as climate or habitat exiles and those that human travelers have transported to new places?
Some scientists argue for such differentiation. University of Vienna conservation biologist Franz Essl and colleagues propose that species moving or expanding their range in response to human-caused environmental changes should be classified as “neo-indigenous” species, rather than “invasive species”, and that management guidelines reflect this distinction.
To some extent, science supports a distinction, as species that move on their own are more likely to follow their natural counterparts than a species that, say, arrives in the hull of a ship.
Some scientists have proposed that the most logical way to determine how to manage an invasive species is to assess whether its presence has an overall positive or negative impact on the ecosystem. Like Mark Davis, a professor at Macalester College, writes, “Whether because of climate or because people move them, species should be assessed on their own effects and not on whether they are native or new native or non-native or non-native displaced by humans. ”
However, the effects of species on ecosystems are not unique and consensus on ecological impacts does not always exist. This can lead to ideological differences in which some conservationists advance species eradication while others champion stewardship. As an author Sonia Shah writes, “In California, wildlife officials attempted to exterminate cordgrass, introduced to the West from salt marshes on the Atlantic and Gulf coasts of Mexico, despite the fact that it provided breeding sites. ‘Feeding and Nesting Site for Endangered California Rails.’
Ultimately, human hubris drove many plants and animals to extinction. It is also hubris to try to “manage” species that have moved to new areas based on our somewhat subjective analyzes of whether they are doing more harm or good.
It is clear that science alone cannot dictate the way forward. We need to integrate other inputs, such as foresight, precaution and indigenous knowledge when overseeing programs to limit or support wildlife populations on land and in water. If we are not careful enough to think through these complex issues, wildlife management will only be guided by the economic value that humans place on certain plant and animal species over others.
The species most in need of better management is ours.
Written with input from Rachel Plotkin, Boreal Project Manager, David Suzuki Foundation. Learn more about davidsuzuki.org.