We’ve undoubtedly transformed the earth through the extensive use of fossil fuels, but uncertain are the longterm effects that climate change will bring with it. An important—and most certainly overlooked—side effect of warmer climates is the advance of invasive species.
These species take advantage of warmer temperatures to spread beyond their natural habitats—opportunists in every sense of the word. Dr. Rowan Sage, a professor at the University of Toronto, works with invasive plants. He is currently researching the spread of kudzu and cheatgrass, two species that were intentionally introduced to the United States.
Kudzu, native to eastern Asia, was introduced in 1876 as a forage crop and ornamental plant. Farmers in the 1930s were encouraged to plant kudzu to reduce soil erosion, but under ideal climate conditions in the southwestern United States, the plant grew out of control and was officially named a pest weed in 1953. Normally, this pest weed would not be able to grow for long in Canada’s harsh climate. However, due to warmer winters and longer summers, kudzu is quickly becoming a potential threat.
Sage studies plant physiology and mechanisms of plant response to global climate change. More specifically, he looks at the mechanisms affecting productivity, competition, and species distribution.
“We’ve been studying kudzu to identify the physiological controls on its distribution and to ask a question: will it be a serious pest in Canada in the very near future? Will the climate warming that we’ve experienced and we will experience allow the kudzu to establish here?” he said.
After monitoring kudzu on a rooftop greenhouse at U of T’s Earth Science Centre, Sage found the plants did not die until late December. Due to increasing atmospheric CO2 levels, as well as increasing nutrient deposition from agricultural fertilizers, the kudzu plant has responded well to human activities across urban landscapes.
Kudzu is becoming more aggressive as it rapidly responds to changes in the global climate. In North America, kudzu is not subject to its native land’s usual biological controls, such as the predatory insects that prevent uncontrolled proliferation. It can overtake trees and fields, eroding entire forests and conquering established ecosystems by outcompeting native plant species.
Kudzu continues to climb northwards into the Mohawk River Valley in New York and is predicted to reach southern Canada within 10 to 15 years. A warmer winter in the Niagara region could jeopardize the state of its wineries, the area’s biggest agricultural enterprise.
As it turns out, geography has a lot to do with the problem of invasive plants.
“In Eastern Canada, we’re lucky because we have some significant geographical barriers—the great lakes and the St. Lawrence River,” said Sage. But, “because of the high level of commerce we have, there is an excellent probability it will come over the border, so you have to take more stringent measures.”
Cheatgrass is another invasive plant, spreading in western parts of North America, including British Columbia. It is interfering with winter wheat and other crops.
Fine, feathery, and brown, cheatgrass competes for moisture with other plant species by maturing quickly in the spring. In turn, this plant dries up quickly and becomes a fuel source for wildfires. Left uncontrolled, these fires can wipe out other vegetation and also pose a threat to rural communities.
The potency of pests increases in foreign environments where they become “super-invaders,” suppressing all native vegetation and resulting in an ecosystem collapse. Water and atmospheric quality decrease, dust and particulates are suspended in the air, and soil terrain becomes more susceptible to erosion.
Benefits of preventional measures easily outweigh the cost of dealing with invasive species once they arrive. With frequent commercial trading between the U.S. and Canada, monitoring the cross-border movement of invasive species becomes crucial.
“California has a very strict quarantine system in place,” Sage said. “At all the entry points on the highways, there are quarantine stations where you have to stop and declare anything you might have that’s a problem, mostly fruits and vegetable—so everybody there knows you can’t take certain things in.”
Canada has a program addressing this issue, but its aim is elsewhere:
“It’s more focused on keeping stuff out from Europe and Asia than it is dealing with what might be lurking out in the U.S.,” said Sage.
Critics say areas with problematic plant species should enforce more rigid quarantine measures. Border controls should also have stricter policies for importing soils and checking construction equipment, which can bring in unwanted plant seeds. The public should be made aware of the appearance of the invasive species and how to avoid their spread.
“Our hope, with this work, is that the Canadian government will institute more severe controls on kudzu and many other invasive species that are potentially moving up from the south,” said Sage.
But the professor appeared grim about the odds against plants such as kudzu and cheatgrass.
“Once you can actually see global warming, it’s probably too late— same with bio-invasives.”
