Analysis Identifies Most Worrisome Invasive Plants that May Arrive Soon

UMass Amherst ecologists’ study will help managers prep for unwelcome visitors
Giant Reed
Giant Reed. Photo credit: Wisconsin Dept. of Natural Resources/J. Miller

AMHERST, Mass. – To help resource managers in the Northeast meet a climate change  challenge – more than 100 new invasive plant species could expand into the area – University of Massachusetts Amherst ecologists are offering a new analysis that narrows the large list down to five priority species with the greatest potential impacts.

Senior author and invasive plant ecologist Bethany Bradley says, “A hundred new species is a lot for natural resource managers to watch for, especially since these plants are totally unknown in the area now. Watch lists are critical, but really long watch lists can be overwhelming.”

“We assessed the reported ecological and socio-economic impacts of 100 species and narrowed the list down to five invasive plants that have major impacts and are known to have invaded ecosystems similar to those found in the Northeast,” she adds. “This information should help natural resource managers develop more proactive monitoring to defend our ecosystems against the incoming wave of new invasive species.”

The five are bur-chervil (Anthriscus caucalis), giant reed (Arundo donax), slender wild oat (Avena barbata), water primrose (Ludwigia grandiflora) and a wild blackberry (Rubus ulmifolius). Bradley says, “Some are now in the mid-Atlantic states, some in the Southeast, some in California, but they all have the potential to be here by 2050. Several of these species are deliberately planted as ornamentals or biofuels, so they could get here quickly,” she adds.

In previous research, Bradley and colleagues had compiled a “watch list” of 183 range-shifting invasive plants that could soon arrive to Massachusetts and the greater Northeast, 100 species in Southern New England and 83 more in Northern New England. Monitoring for invasives is costly, Bradley says, so narrowing the field makes sense for conservation budgets. Also, “from an invasive species perspective, the only time you can get a win is if you stop it early,” she adds.

First author of this study, published online in the journal Biological Invasions, is Mei Rockwell-Postel, a 2019 environmental sciences graduate who reviewed findings of more than 800 research papers for the analysis. Bradley was Rockwell-Postel’s advisor for the project and is an associate professor of environmental conservation and a co-principal investigator of the Northeast Climate Adaptation Science Center (NE CASC) at UMass Amherst.

Bradley is also a co-director of the NE CASC’s Regional Invasive Species and Climate Change (RISCC) Management Network, whose members recently surveyed natural resource managers to identify their major concerns and questions. Last year, the managers named range-shifting invasive species as one of their top priorities.

For this work, Rockwell-Postel and Bradley adapted a well-established protocol, the Environmental Impacts Classification for Alien Taxa (EICAT), to evaluate potential impacts of the 100 invasive plants that could become established now or by 2050 in New York, Massachusetts, Connecticut or Rhode Island.

The researchers scored ecological impacts on a four-point scale from “minimal concern,” to “major concern,” and evaluated whether socio-ecological impacts were present or not. Low impact means that the invader changes the behavior of another organism but does not cause its population to decline. Medium impact means the invader causes the population of a single native species to decline, and major impact means that the invader causes the populations of multiple native species to decline. They categorized 20 species as having potential high impact, 36 as medium, and 26 as low.

Bradley notes, “Although we identified 20 species as having high impact, we were able to narrow that group further by focusing on species where we had high confidence in reported impacts and they were likely to affect New England ecosystems such as forests, wetlands and grasslands,” she adds. “Those additional criteria narrowed it down to five.”

The ecologist adds, “Usually when we talk about invasive species, we’re talking about problems with no good solutions. In this case, we have an opportunity to stop some really bad invasive species before they even arrive. An important next step is to stop them from being planted. We have recently started a discussion among invasive plant councils in the Northeast about proactively listing these priority species, including representatives from  the Massachusetts Invasive Plant Advisory Group. We hope that putting this science into action will remove these potential threats to our ecosystems.”

This work was supported by the USDA Northeastern IPM Center, the Massachusetts Agricultural Experiment Station, the Massachusetts Agricultural Experiment Station and the UMass Amherst Department of Environmental Conservation, the National Science Foundation, the U.S. Geological Survey and the NE CASC.