Non-Native Plants Increasingly Move North Due to Climate Change, Study Finds

The orange hawkweed, native to the Alps of Austria, grows wild from gardens in many parts of Europe. Franz Essl / University of Vienna

Many plant and animal species that originate from warmer regions are able to acclimate to more northern climates as temperatures increase due to climate change.

A new study by an international team of researchers has concluded that, as climate change continues, the likelihood of alien plant species from regions nearer to the equator being introduced by humans to northern regions on the same continent increases.

When humans transplant species outside of their natural range, serious ecological consequences, such as throwing the existing ecosystem off-balance, can result, a press release from the University of Vienna said. This can lead to economic damage, estimated at $400 billion or more annually, according to the World Biodiversity Council’s 2023 report.

“The accelerating climate change will increasingly allow heat-loving alien species to settle. This can lead to significant negative consequences for biodiversity and the economy in the recipient regions,” explained Franz Essl, leader of the Division of BioInvasions, Global Change & Macroecology at the University of Vienna, in the press release.

The study, “The poleward naturalization of intracontinental alien plants,” was published in the journal Science Advances.

The research team used examples of transplanted plant and animal species from Europe, North and South America and Australia, pointing out that “alien” species that establish themselves in new areas originate from their own continent more than half the time, the press release said.

“Here, we studied naturalized (i.e., self-sustaining) intracontinental aliens using native and alien floras of 243 mainland regions in North America, South America, Europe, and Australia. We revealed that 4510 plant species had intracontinental origins, accounting for 3.9% of all plant species and 56.7% of all naturalized species in these continents,” the authors wrote in the study.

In Europe, as well as North and South America, the research team found similarities in spread patterns. In most of the cases, intracontinental spread went from regions near the equator in the direction of the poles.

“In North America and Europe, the numbers of intracontinental aliens peaked at mid-latitudes, while the proportion peaked at high latitudes in Europe,” the authors wrote.

The scientists also demonstrated that native species were moving northward naturally in increasing numbers, but were mostly being transplanted by humans.

“In this work, we were able to show that not only are native species increasingly migrating northwards, but alien species are also predominantly being spread northwards by humans,” Essl said in the press release.

In the study, the researchers looked at the role that geographical, climatic and human factors have in the spread of alien plants on the same continent. They found that spread is counteracted by strong differences in climate and long distances.

“The closer an area is to the original distribution area of a species and the more similar the climate is, the easier it is for alien species to colonize,” said Bernd Lenzner, a terrestrial ecologist at the University of Vienna, in the press release.

The scientists concluded that climate change effects will speed up the spread of alien plants within the same continent.

“These findings suggest that poleward naturalizations will accelerate, as high latitudes become suitable for more plant species due to climate change,” the authors wrote in the study.

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