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Response To Maclean's Editorial: An Unwelcome Invasion  



The author of “A Welcome Invasion” (view article here) suggests that not all non-native species are bad, some have unintended benefits, impacts have been small and local, and therefore we should welcome all non-native species. The logical validity of this deductive argument rests on unsound reasoning and omits readily available, verifiable evidence. The information provided in “A Welcome Invasion” is not accurate, relevant, or complete, and should be rejected as such. There is overwhelming evidence that many invasive species have had an enormous impact in Canada, an impact on wildlife, ecosystems, cities, and people. The Invasive Species Centre and its partners are working to improve Canada's ability to protect our natural resources from the environmental, economic, and social effects of invasive species and we would like to address misunderstandings in the editorial and put the discussion of this critical issue on an evidence-based footing.

It is true that not all non-native species have been invasive. However, some have caused significant, undeniable economic and environmental harm.  Invasive species aren’t just dispersing naturally from neighboring locations. Contemporary trade and transportation systems bring a super-accelerated time scale and a huge geographic scope which make today’s invasive species introduction nothing like the natural range expansion or ecosystem succession of days gone by. Policies and programs in Canada focus on species that present the greatest threat to the environment, economy, and society. A rigorous and methodical risk assessment process based on published science, data collection, and analysis helps to prioritize and allocate resources to prevent the introduction and spread of species that threaten to do the greatest harm. It’s not about panic, intolerance, animosity, or hostility. It’s about empirical evidence, solid research, and using resources where they are needed most.

There is no shortage of evidence that invasive species are harmful. Since 2007, white-nose syndrome (an alien invasive fungus) spread across eastern North America, killing thousands of little brown bats such that this once common bat is now endangered in southern and northeastern Ontario.  More than 100 years ago, chestnut blight reduced the once common American chestnut tree to a rare, stunted shrub in southern Ontario.  Dutch elm disease changed the landscape of southern Ontario by killing tens of thousands of mature, stately American elms. The most recent effects of this virulent disease are visible along the rivers, streams, and thoroughfares of central Ontario. Butternut canker has been so devastating in its effects that this formerly common tree is now endangered in Southern Ontario and private landowners are forbidden under provincial law to cut even one on their own property without adhering to the stringent requirements of the Endangered Species Act.  The Great Lakes Fishery Commission says that sea lamprey predation on valuable fish stocks was so high in the 1940s it became a key factor in the collapse of the Great Lakes ecosystem and economy that it supported; tens of thousands of jobs were lost, property values were diminished, and a way of life was forever changed for millions of people. Sea lampreys killed more than 100 million pounds of Great Lakes fish annually, five times the commercial harvest in the upper Great Lakes.

Perceived benefits of invasive species mask well-documented negative impacts. Zebra mussel invasions can result in clearer water, but they also deplete planktonic food resources for native species, take over fish spawning areas, cut the feet of beach-goers, increase toxic algal blooms, and clog water intakes lines with their dense colonies thereby affecting Great Lakes homeowners, taxpayers and utility customers to an estimated cost of U.S. $1 to 5 billion per year (Aldridge, 2006). Suffice to say, clearer water alone is not an indicator of a healthy ecosystem. According to the 2017 State of the Great Lakes Report, we are not yet winning the battle against invasive species, including zebra mussels, in the Great Lakes, and this will have very serious consequences in the long run (https://binational.net/2017/06/19/sogl-edgl-2017/).

Invasive species cause severe damage and the ecological and economic impacts are readily documented. Emerald ash borer is not an anomaly in its destruction of our natural environment. It is just the latest invasive species to cause great damage to North American cities and forests. Costs are estimated at close to $900 million to over $2 billion just to deal with Eastern Canadian urban street and backyard trees, not including natural forests, parks, and riverbank areas (McKenney et al., 2013). Cities and homeowners bear the responsibility and costs of removing, replacing, and treating their infested trees and impacts are also felt through the influence of tree cover on property values, energy savings, and pollution control. When we consider the effects of the invasive species described here, we see that biological invasions have patterns that require well-designed policy actions to manage.

Our concern at the Invasive Species Centre is with high-risk invasive species that will not bring diversity to Canada. These invasive species are adaptable, reproduce quickly, have few predators, and outcompete or kill native species. They effectively reduce diversity where it once existed and threaten our natural resources and economy.

Denialist articles that use rhetorical arguments to disregard evidence attempt to cast doubt on the scientific consensus that species introductions pose significant risks to biodiversity and ecosystems have increased exponentially over the past three decades, especially in the mainstream news. This growing phenomenon could slow development and implementation of policies designed to safeguard against invasive species spread and impact (Ricciardi and Ryan, 2017). Invasive species are a significant issue for Canadians because of the serious environmental and economic harm they cause, and for that reason, they deserve credible and balanced coverage.

We encourage readers to learn more about invasive species, their impacts, and how they can help to prevent their spread at www.invasivespeciescentre.ca. Clean, drain and dry your boat when changing water bodies, plant native species in your garden, buy or find firewood where you plan to burn it, dispose of your bait in the garbage away from shore, and let your elected officials know that invasive species issues are important to you!   


Dr. Kandyd Szuba

Board of Directors, Chair


Tracey Cooke

Executive Director