News Release

REF NO.: 58

SUBJECT: Study shows immediate response to invasive species can pay off

DATE: April 30, 2019

A new study shows that invasive species can have a dramatic impact on native species, and a strong proactive response can help mitigate those impacts.
Dr. Amanda Bates is the Canada Research Chair in Marine Physiological Ecology and an associate professor in the Department of Ocean Sciences, Faculty of Science, at Memorial. She is part of an international research team that conducted the first global meta-analysis of the characteristics and size of invasive species’ impacts on native species as invaders become more abundant.

'Magnitude of these effects'
The team found that impacts depend strongly on the invader’s position in the food chain, also known as tropic level. Invasive species at higher trophic levels have the greatest impact early in the invasion.
“What surprised me most was the magnitude of these effects,” said invasion ecologist Bethany Bradley of the University of Massachusetts Amherst. “Invasive animal pests, like the emerald ash borer, or lionfish, will, on average, cut the populations of native species in half if we don’t prevent or control these invasions.”
Dr. Bates says when just a few invasive individuals higher in the food chain show up and begin eating native species, there’s an immediate sharp decline in native populations. Once they reach a higher abundance, the damage has already been done.
“Removing these species immediately will make a major difference, especially if they are top predators,” said Dr. Bates. “This has big implications for management. Early detection is critical, but if you can control the invasion at any point, it’s a win for ecosystems.”

Green crab in N.L.
For native species faced with an intruder at the same level of the food chain, competition for the same resources does not lead to a sharp initial decline, but as the number of invaders increases, native species decline in abundance and community diversity.
“Invasives reduce other species around them because they’re feeding on them, or they’re competing for space and taking up resources,” said Dr. Bates. “In Newfoundland and Labrador, the green crab not only competes with lobster and has impacted the lobster fishery, but green crabs also bury themselves in the sediment and feed on the roots of seagrasses, which can decimate seagrass beds, which are important habitat for juvenile fishes.”
The team hopes their findings will encourage governments around the world to make a stronger commitment to proactive policies designed to prevent the introduction of invasive species, as well as increased management targeting the early stages of invasion.
Dr. Bates says the research supports the huge green crab mitigation efforts being undertaken in this province.

“Our study suggests this is a fantastic strategy for managing the impacts of the green crab in our waters.”
The study, which saw team members analyze findings from 1,258 case studies from 201 research papers, was published in a paper released in the online issue of Proceedings of the National Academy of Sciences, released on April 29.

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