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Invasive species compete with native species for resources like space, light, water, and food. They can also directly prey on native species (in the case of invasive species like wild pigs or northern giant hornets) or carry diseases and parasites that can spread to native species. Through these activities, invasive species reduce biodiversity (the diversity of living species in an ecosystem) and can put native species at risk.

Species at risk and other native species that rely on these habitats for survival. The loss of native species, such as certain plant and tree species, can also decrease shade for forest floor plants, reduce nutrient resources for microscopic organisms, and have cascading effects in terrestrial and aquatic ecosystems. Ecosystem services are positive benefits provided to society by ecosystems (e.g. clean air provided by forests, flood and erosion control in wetlands). These services can be significantly impacted by the loss of native species and alteration of habitat.

Photos: Forest ecosystems overrun by Japanese knotweed (top) and yellow archangel (bottom).

A recent study found that municipalities and conservation authorities are estimated to spend $50.8 million per year on invasive species management in Ontario alone. Across Canada, economic costs associated with invasive species can include management (mechanical, chemical, and biological), research and monitoring programs, reduced crop yield, job losses (such as in the case of reduced forestry production), damage to infrastructure, and impacts to international trade and tariffs.

Additional economic losses caused by invasive species can include loss of ecosystem services (i.e. increasing flooding, reducing resiliency to climate change), impacts to tourism and recreation, and reduced property values (such as cottage properties overrun by zebra mussels or city lots with trees affected by emerald ash borer).

Economic costs of invasive species are much lower when funds are allocated to prevention and early detection efforts. Once an invasive species spreads, management is exponentially more expensive and less efficient.

Photos: The ISC’s 2019 Economic Impacts Study estimated that Ontario municipalities spend over $22 million annually on emerald ash borer management (top). Spotted lanternfly, not found in Canada, is a looming threat to Ontario’s billion-dollar fruit and wine industries (bottom).

Many of Canada’s beloved pastimes are at risk due to invasive species. They threaten recreational spaces and compromise outdoor activities such as hiking, swimming, fishing, boating, and visiting local parks. Examples include beaches covered in zebra mussels that can cut the feet of beach goers, waterfront taken over by invasive aquatic plants such as Phragmites and hydrilla, loss of trees in local parks due to invasive pests or pathogens, and reduced fishing opportunities resulting from species loss related to competition with/habitat alteration by aquatic invasive species.

Invasive species cause direct and indirect impacts to human health. Direct risks include contact with species such as giant hogweed, wild parsnip, and Northern giant hornet. Indirect impacts to human health include reduced outdoor opportunities, which are proven to be beneficial for mental health and well-being.

Invasive species pose significant threats to different cultures in Canada. Asian longhorned beetle is a threat to Canadian maples, an important piece of Canadian cultural identity for many. Invasive species can also impact Indigenous communities by reducing the availability of culturally-important species, such as the loss of American ginseng (impacted by garlic mustard) as a component of traditional medicine, or the loss of ash trees (impacted by emerald ash borer) as an important source of material for traditional activities like basket-making.