What are their impacts in BC?

Invasive species are impacting British Columbia in the following ways:

Economic
Environmental
Social

Economic Impacts

Spotted Knapweed infestation. Photo: Barb Stewart

Globally, invasive alien species are one of the five most important direct drivers of biodiversity loss and change in ecosystem services. —Millennium Ecosystem Assessment, 2005

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.
• Invasive species that damage the agricultural and forestry industries results in an estimated $7.5 billion of lost revenue annually. 

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 (six 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: ISC 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

Purple loosestrife is an aquatic invasive plant that can produce 2.5 million seeds annually, displacing native species and threatening wildlife habitat.

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 from 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.  Prevention is key to any effective management plan!

Societal Impacts

Himalayan balsam infestation on private property. Photo: J. Hallworth

As native plant communities are replaced by invasive plant infestations, biodiversity declines and habitats change. These impacts are often irreversible and restoration can be extremely difficult, if not impossible; therefore, preventing their establishment and spread is key!

When established in crops or natural areas, invasive plants and/or species can result in: 

• lost income
• reduced water quality and quantity (increased erosion and sedimentation)
• reduced property values
• damage to private property and infrastructure
• and loss of traditional food and medicinal plants
• reduced land and water recreational opportunities
• increased control and management costs
• export and import trade restrictions imposed

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 (Fallopia japonica) obstructs sightlines

The impacts of invasive species requires further study in BC. Problems with invasive rabbits on Vancouver Island in metropolitan areas and their destruction to infrastructure, and the American Bull-frog and Grey Squirrel populations competing for resources with their native counterparts in the Lower Mainland are just some examples of invasive species causing damage in BC. Visit the Most “Unwanted” Invasive Organisms section to learn more.