Invasive species are plant, animal and insect species that are not native to our region. They tend to grow rapidly and form monocultures while out-competing native species.
Second only to habitat loss, invasive plants and animals have been identified as the most significant threat to biodiversity. Invasive plants can alter water flow and lead to erosion or a reduction in available water, create and increase fire hazards, damage roads and other built structures, contain substances that are toxic to humans and animals, and reduce crop yields.
Much of the spread of invasives happens unintentionally, primarily by human activities:
- Purchasing and planting invasives, dumping garden debris into parks, ditches or wild areas
- Moving firewood, hay, or wood packaging
- Discharging ballast water from ships
- Transporting planes and boats from one region to another
Economic Impacts
The economic impact of invasive species in Canada is significant. According to Environment Canada:
- The estimated annual cumulative lost revenue caused by just 16 invasive species is between $13 to $35 billion. (Source: Colautti, Bailey, van Overdijk, Amundsen and MacIssac, “Characterised and Projected Costs of Nonindigenous Species in Canada”, Biological Invasions 8, 45-59, quoted in Environment Canada, An invasive alien species strategy for Canada, 2004)
- Invasive species that damage the agricultural and forestry industries result in an estimated $7.5 billion of lost revenue annually. (Source: Dawson, “Plant Quarantine: Preventing the Introduction and Spread of Alien Species Harmful to Plants”, in National Resources Canada, Alien Invaders in Canada’s Waters, Wetlands, and Forests, pp. 243-251, referenced in Colautti, Bailey, van Overdijk, Amundsen and MacIssac, “Characterised and Projected Costs of Nonindigenous Species in Canada”, Biological Invasions 8, 45-59
The extent of economic costs of invasive species in BC is currently unknown and requires further research. In BC, invasive plants (not including other species) cause:
- An estimated combined damage (seven important invasive plants in BC) of at least $65 million in 2008. With further spread, impacts would more than double to $139 million by 2020 (Source: Invasive Plant Council of BC Report: Economic Impacts of Invasive Plants in British Columbia).
- Estimated crop losses in BC agriculture industry of over $50 million annually. Species such as knapweed infest rangelands and reduce forage quality. Many other species out-compete desired species in cultivated fields (Source: BC Ministry of Agriculture, Food and Fisheries. 1998. Integrated weed management—an introductory manual).
- Increased maintenance costs to public parks and private property, devaluing real estate. For example, due to the explosion of leafy spurge (Euphorbia esula), Manitoba has experienced a $30 million reduction in land values (Source: Invasive Alien Plants in Canada Summary Report by the Canadian Food Inspection Agency (CFIA).
Environmental Impacts
Invasive species can alter habitats and disrupt essential ecosystem functions. Invasive plants specifically displace native vegetation through competition for water, nutrients, and space. Once established, invasive plants can:
- reduce soil productivity
- impact water quality and quantity
- degrade range resources and wildlife habitat
- threaten biodiversity
- alter natural fire regimes
- introduce diseases
Invasive species threaten biodiversity and many rare and endangered species are at risk of extinction from non-native invasions of invasive plants and other species. Invasive species can disrupt the natural migrations of wildlife since their habitat, without prevention or intense and costly management, can be damaged or destroyed – with the impacts often irreversible to the local ecosystem.
In BC, invasive species are frequently identified as top threats to species at risk. According to a research report funded by the Invasive Species Council of BC and Fisheries and Oceans Canada, habitat degradation and alteration, competition and predation are the most common mechanisms by which invasive species impact species at risk. Prevention is key to any effective management plan.
Societal Impacts
When established in crops or natural areas, invasive species can result in:
- lost income
- reduced water quality and quantity (increased erosion and sedimentation)
- reduced property values
- damage to private property and infrastructure
- loss of traditional food and medicinal plants
- reduced land and water recreational opportunities
- increased control and management costs
- export and import trade restrictions imposed
J. Samanek, State Phytosanitary Administration, Bugwood.org
Invasive plants also impact human health and safety by obstructing sightlines and road signs along transportation corridors, causing skin burns and dermatitis, and increasing allergies. For example:
- the leaves and stems of Giant Hogweed (Heracleum mantegazzianum), an escaped ornamental, contain a clear, watery, highly toxic sap that, if touched, can cause hypersensitivity to sunlight resulting in burns, blisters, and scarring of the skin. WorkSafe BC has issued a Toxic Plant Warning for this plant, and many efforts are being made in BC and across Canada to raise awareness of Giant Hogweed.
- Scotch Broom (Cytisus scoparius) causes seasonal allergies and hay fever;
- Tansy Ragwort (Senecio jacobaea) can be toxic to horses and livestock;
- Japanese Knotweed (Reynoutria japonica) obstructs sightlines