Invasive Species Expanding Their Ranges 100x Faster Than Native Species, Study Finds

Native species are struggling to keep pace with invasive species in range expansion, which is important for adaptation and survival, a new study has found.

According to researchers, species need to be able to shift at least 3.25 kilometers per year to keep up with climate change. However, they found that native species are only moving at an average rate of around 1.74 kilometers per year.

In general, invasive species are spreading 100 times faster than native plants and animals, and even some that seem more sedentary are moving at least three times faster than native species, according to the study, published in the journal Annual Reviews of Ecology, Evolution and Systematics.

“We’ve known for a long time that native species aren’t moving nearly fast enough, but there are still some that are able to keep up,” Bethany Bradley, lead author and professor of environmental conservation at University of Massachusetts Amherst, told EcoWatch. “We hadn’t necessarily looked at non-native species specifically as a group of whether they were able to keep up or not. I think this analysis basically says that not only are non-native species really able to keep up, but the reason behind it is because we’re moving them around. They’re non-native species for a reason — because humans are moving them.”

The study revealed that invasive species were moving at a rate of around 35 kilometers per year without human actions. But when factoring in the ways humans contribute to the spread of invasive species, the shift can happen at a rate of around 1,883 kilometers per year, or around 1,000 times faster than native plants and animals.

To compare how human actions drove range expansion, the researchers analyzed data for 249 native species, 242 non-native species, and 192 non-native species introduced through human actions. For example, shipping containers or ships can spread invasive species, and the pets people keep can contribute to invasive species growth. Even hiking can contribute to spreading invasive plant seeds.

One challenge is a lack of regulations on invasive species. As Bradley explained, it can take a long time to establish policies that restrict the spread of invasive species through human actions, so these species can continue their expansion as humans continue moving them.

On the other hand, Bradley said that native species will actually need human intervention to help them adapt to climate change and the competition from non-native species.

“If we want native species to survive, then we have to choose there, too. We have to make an active choice to try to help,” Bradley told EcoWatch. “This is called assisted migration or managed relocation of trying to allow for native species to shift their ranges actively with climate change. That requires our help.”

Bradley recommended for gardeners to “not only think about native species so that you avoid introducing invasive species, but also think about native species because our gardens can serve as stepping stones to help those populations survive climate change,” and suggested using tools like Lady Bird Johnson Wildflower Center’s native plant website and the Missouri Botanical Garden website for finding native plants.

In a previous study, Bradley and colleagues found that horticulture, including plant nurseries, was contributing to the spread of invasive plant species. Bradley noted that while nurseries were not setting out to spread invasive species, some popular ornamental plants sold in nurseries can contribute to their rapid spread. 

As part of that study, the researchers compiled a list of regionally invasive plant species as well as alternative, native options to raise public awareness. 

For example, the list noted that pampas grass (Cortaderia selloana) is an invasive species that can outcompete native plants and disrupt wetland habitats. For those in the northeastern U.S. who want a similar look in their garden, the list recommended planting golden feather grass (Sorghastrum nutans) as a native alternative.

To help prevent the spread of invasive species other than plants, Bradley recommended people who enjoy boating to thoroughly wash their boats to minimize spreading aquatic invasive species and for people who keep pets like snakes, fish and lizards to prevent those pets from getting loose or avoid releasing them into the environment.

The U.S. Department of Agriculture has an interactive map resource on invasive species information and news by state for the public. In the U.S., some of the most invasive species include emerald ash borers, hemlock woolly adelgid, wild boars and domesticated cats.