Invasive Species Council of British Columbia

Why You Should Care

Butterfly bush (Buddleja davidii) This fast-growing plant has escaped gardens and now rapidly spreads into disturbed, open areas and along coastal forest edges, roadsides, and especially on sunny stream edges and riverbanks where it replaces native plants.

Butterfly bush
J. Leekie

Invasive species are plants, animals or other organisms not native to BC whose introduction and spread harms the province’s native species, economy and human health.

Most invasive species are unintentionally introduced by human activities into places outside their native habitat and, once they’re removed from natural predators and diseases they often reproduce, spread and survive better than native species.

With few limits on their populations invasive species can easily take over sensitive ecosystems permanently upsetting the balance of plant, insect, bird and other animal life.

What are their 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.
  • 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 (by six important invasive plants in BC) costing at least $65 million in 2008. With further spread, impacts would more than double to $139 million by 2020 (Source: ISCBC 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).

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 BC’s biodiversity. Many rare and endangered species are at risk from extinction due to the nature of invasive species, in particular due to the diet of invasive animals. Prevention is key to any effective management plan.

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 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

Invasive plants also impact human health and safety by obstructing sightlines and road signs along transportation corridors. Some invasive plants cause skin burns, dermatitis, and increase allergies. For example:

  • The leaves and stems of Giant hogweed contain a clear, watery, highly toxic sap that, if touched, can cause hypersensitivity to sunlight resulting in burns, blisters, and scarring of the skin
  • Scotch broom (Cytisus scoparius) commonly causes seasonal allergies and hay fever
  • Tansy ragwort (Senecio jacobaea) can be toxic to horses and livestock
  • Japanese knotweed (Fallopia japonica) obstructs sightlines

Invasive animals which cause problems include invasive rabbits which damage infrastructure in metropolitan areas of Vancouver Island. The American bullfrog and Grey squirrel populations compete for resources with their native counterparts in the Lower Mainland.

How are they introduced and spread

Invasive species are introduced and spread in a variety of ways, including:

  • As goods such as plant products, firewood, hay, or wood packaging
  • As live food imports
  • As horticultural imports
  • Through vehicles such as aircraft, commercial and recreational boats
  • In ballast water released from ships
  • By disease, spread by wildlife

Invasive plants are introduced and spread by: 

  • Unintentional dispersal by humans during activities and by nature
  • Being planted in gardens
  • Improper disposal of garden plants


Invasive plants are non-native plant species that have been introduced, either intentionally or accidentally, into the environment from other areas. Without their natural pathogens and predators, they are capable of moving aggressively into an area, and monopolizing resources such as light, nutrients, water, and space to the detriment of other species. Invasive plants threaten natural ecosystem functions, species biodiversity, food security, human health and safety, and economic development.

The ISCBC refers to invasive plants that include all species listed as noxious, invasive, or invasive in federal, provincial, or local regulations.

Commonly, native plants are species that reached their location without assistance from people. In Canada and the United States, native plants are plants that already existed here at the time of European colonization.

Exotic plants are non-native species that are introduced into a new location by human activity, either intentionally or by accident. Unlike invasive plants, exotic plants do not have negative environmental, economic, or social impacts.

No. A weed is commonly thought of as an unwanted plant in a given area, such as a vegetable garden or lawn. An invasive plant is a plant that when transplanted from its native habitat, grows aggressively, out-competing and displacing desired vegetation.

“Noxious weed” is defined in the BC Weed Control Act as:

“Noxious weeds are typically non-native plants that have been introduced to British Columbia without the insect predators and plant pathogens that help keep them in check in their native habitats. For this reason and because of their aggressive growth, these plants can be highly destructive, competitive and difficult to control. The BC Weed Control Act imposes a duty on all land occupiers to control designated noxious plants.” (

While the term “invasive plant” encompasses the same definition as “noxious weeds,” “noxious weeds” are only those defined by the BC Weed Control Act.

They harm the environment:

Invasive plants out-compete native plants, alter ecosystems, and can create an increased fire hazard.

They harm human and animal health:

Skin irritation, blisters, scarring and severe breathing problems are just some impacts on people. Toxins in some plants make them inedible or toxic to animals.

They harm the economy:

Property and crop values drop while control costs rise from treating infestations on rangelands, gardens, parks or along roadsides.

They impede recreation:

Invasive plants make trails impassable, damage fishing streams, puncture tires, and can cause skin rashes.

Yes. According to the International Union for Conservation of Nature (IUCN), invasive species are the second most significant threat to biodiversity after habitat loss. Invasive species become predators, competitors, parasites, hybridizers, and diseases to native plants and animals. They often dominate the ecosystems they invade, upsetting the natural balance that existed prior to their introduction.

However, not all exotic or introduced species are invasive; some exotic plants are beneficial. For example, most of the agricultural crops in Canada are exotic species, yet they are essential for supporting our food supply. For example, corn is a cereal grain domesticated from Mesoamerica since European contact with the Americas in the 15th and early 16th Century. Many exotic species survive without ever becoming a problem.

Globally, the cost of damage caused by invasive species has been estimated at $1.4 trillion per year – close to 5% of global economy (Global Invasive Species Programme).

Virtually all ecosystem types on the planet are affected by invasive species and they pose one of the biggest threats to biodiversity worldwide.

Globalization through increased trade, transport, travel and tourism will inevitably increase the intentional or accidental introduction of organisms to new environments, and it is widely predicted that climate change will further increase the threat posed by invasive species.

Most species have predators in their natural range that keep their population numbers in check. When new species are introduced, however, they typically come without their natural predators.

Most invasive species produce copious amounts of seed that often remain viable for great lengths of time. This seed is often bird- or wind-dispersed, allowing it to cover great distances.

Some invasives have aggressive root systems that can spread long distances from a single plant. These root systems often grow so densely that they smother the root systems of surrounding vegetation.

Some species produce chemicals in their leaves or root systems, which inhibit the growth of other plants around them. For example, diffuse knapweed (Centaurea diffusa) emits a toxin called catechin into the soil that can kill native plants.

Most invasives grow quickly and capitalize on sunlight, space, and soil, thereby “shading out” and reducing or halting the growth of native vegetation.

Most invasives thrive on disturbed soil, on and around new developments, or along transportation and utility corridors.

Seeds, above-ground runners & roots

A single invasive plant can produce thousands of seeds that spread in the wind, water and soil, hitching a ride on livestock, wildlife and people to new locations. Many invasive plants form new plants nearby with horizontal roots or runners that grow on or under the soil surface.

Improper disposal

Invasive plants are often introduced in public parks and natural areas when people improperly dispose of garden or yard waste. Plant fragments left in the soil quickly generate new growth.

Nearly all exotic plants (invasive or non-invasive) are deliberately imported for agricultural use, landscaping, and gardening. Invasive plants may be accidentally introduced along with soil, plants, and seeds. Many wildflower and birdseed mixtures contain invasive plants.

Many invasive plants start in gardens and then spread into public parks and natural areas. Common ways that invasive plants spread from gardens include improper disposal or “composting” of hanging baskets and garden waste or soil into natural areas as well as trading of ornamental plants with invasive qualities.

Invasive plants also hitch a ride through increased trade and travel, along transportation and utility corridors, as well as from recreational activities, wildlife, livestock, and pets. All citizens and industries contribute to the problem, but improved management practices and awareness will help to reduce their spread.

Invasive plants originate on other continents, neighbouring countries, or in differing ecosystems within Canada, and date back to the time when people started to travel between continents. Increased transport, trade, travel, and tourism are bringing an unprecedented number of invasive plants to Canada and into BC.

Invasive plants are everyone’s problem. They cost landowners, land managers, governments, resource management agencies, and taxpayers millions of dollars each year. Control treatments, labour, and research are the highest expenditures associated with invasive plant management.

Many invasive plants are still sold in garden centres and are not labeled as being invasive. Gardeners purchase these plants for their beauty, such as yellow flag-iris (Iris pseudacorus) for striking flowers, and giant hogweed (Heracleum mantegazzianum) for stunning foliage, flowerheads, and architectural-like stems. Both, however, have negative impacts to surrounding ecosystems and communities: yellow flag iris invades watercourses, impacting surrounding wetlands and clogging waterways, while giant hogweed produces a toxic sap that causes severe skin burns and rashes when touched. Gardeners also purchase invasive plants because they tend to grow fast and are often shade tolerant.

In partnership with the BC Landscape and Nursery Industry and others, the Invasive Species Council of BC has developed a Grow Me Instead booklet that informs gardening enthusiasts and industry professionals on horticulture’s most “unwanted” invasive plants for regions across BC while providing a variety of native and non-invasive exotic alternatives. View the Grow Me Instead booklet and “snapshot” brochure under the Resources section of this website. To order hard copies, contact the ISCBC office at 1-888-933-3722.

Mechanical methods include, hand pulling, digging, cultivating and pruning to remove or prevent seed production of invasive plants. Foraging (using goats, cows and other foragers) can reduce the growth rate of certain invasive plants in exchange for a nutritional food source.

Chemical methods include the application of various herbicides to kill or limit the spread of invasive plants.

Cultural methods include replanting or reseeding of recently treated or disturbed areas before invasive plants can become established.

Biological methods involve using natural enemies, either insect or disease causing organisms, to suppress the growth of, or kill the invasive plant without harming other non-invasive plants in the area.

Restoration and landscaping with native or non-invasive exotic plants helps to prevent the spread of invasive plant species.

Many of these control and prevention methods are used in combination, depending on the site and characteristics of the invasive plant.

Protecting native ecosystems, transportation corridors, agricultural and public lands, and even urban gardens from invasive plants requires that land managers develop an integrated approach to management. This type of approach is typically referred to as ‘Integrated Pest Management (IPM)’.

IPM is a decision making process that includes identification and inventory of invasive plant populations, assessment of the risks that they pose, development of well-informed control options that may include a number of methods, site treatment, and monitoring.

Read about the Integrated Pest Management Act.

In British Columbia, there are multiple levels of authority with jurisdiction over invasive plant management. Key legislation includes:

  1. Weed Control Act
  2. Forest and Range Practices Act
  3. Integrated Pest Management Act
  4. Community Charter

1) The Weed Control Act requires all land occupiers to control the spread of 48 provincial and/or regional noxious weeds on their land and premises, and specifies provisions for transportation, movement, and cleaning of machinery.

2) The Forest and Range Practices Act requires forest and range managers to specify and implement measures that prevent the introduction or spread of the 42 invasive plants listed under the Invasive Plants Regulation within their forest stewardship plans, woodlot licence plans, range use plans, and range stewardship plans.

3) The Integrated Pest Management Act regulates herbicide applications that may be used to control invasive plant infestations.

4) The Community Charter is enabling legislation that provides powers that municipalities may use for, among other things, invasive plant control. Authority for invasive plant control is available under either weed control powers or broad powers for the protection of the natural environment.”

In Canada, there are two key pieces of legislation pertaining to invasive plants: the Seeds Act and the Plant Protection Act defines seed as ‘any plant part of any species belonging to the plant kingdom, represented, sold, or used to grow a plant’. Therefore, grain fed to animals (e.g. birdseed) cannot be regulated under the Seeds Act and Regulations. The Seeds Act and Regulations are relevant to large-scale plantings, roadsides, landscaping, gardening, ornamentals, land reclamation, soil conservation, green cover, wildlife grazing or habitat, wetland restoration, and other similar activities.

The Plant Protection Act and Regulations aim to ‘prevent the importation, exportation, and spread of pests injurious to plants and to provide for their control and eradication and for the certification of plants and other things’. This network of jurisdictions can be very confusing to land managers, because there are often multiple agencies and governments controlling invasive plants on adjoining land parcels. To further compound the issue of overlapping agency jurisdiction, there are numerous pieces of legislation, regulation, and policy that govern invasive plant management in BC. As a result, it is often unclear to land managers which legislation is in effect and how they are to comply with that effective legislation, especially when more than one Act or Regulation is in effect.

Currently there is no federal noxious weed or invasive plant legislation that specifically regulates the import of aggressive or potentially invasive plants for landscape and garden use.

1) Through province-wide cooperation and coordination, the Invasive Species Council of BC is working to minimize the negative ecological, social, and economic impacts caused by the introduction, establishment, and spread of invasive species.

The ISCBC is a non-profit society and registered charity whose members are involved in all aspects of invasive species management. Members include technical specialists working for government and industry, regional committee coordinators, First Nations representatives, foresters, forest technologists, biologists, ranchers, horticulturists, recreation enthusiasts, gardeners, and other concerned individuals. Membership is open to everyone willing to work collaboratively. LEARN MORE.

2) There is a growing network of Regional Committees across BC that deliver localized management, outreach, and education programs. To report invasive plant sightings, get involved in local weed pull events, and learn which species are of concern in your area, as well as practical ways manage them, contact your regional invasive plant committee. Contact information can be obtained by calling 1-888-933-3722, or visit the Committees section of this website.

3) The Inter-Ministry Invasive Plant Working Group (IMIPWG) drives invasive plant policy and management for the Province. Members of the IMIPWG are comprised of: Ministry of Agriculture and Lands; Ministry of Forests and Range; Ministry of Environment; Ministry of Transportation and Infrastructure; Ministry of Energy, Mines & Petroleum Resources; Ministry of Tourism, Culture & the Arts; Ministry of Aboriginal Relations & Reconciliation; as well as representatives of the Oil & Gas Commission, and Integrated Land Management Bureau.

4) The Aboriginal Working Group is working to build partnerships between First Nations bands and councils, regional invasive plant managers and coordinators, the Invasive Species Council of BC, and key stakeholders, to improve invasive plant management on reserve lands and bordering public lands.

5) A diversity of non-profit environmental organizations (such as those involved in wildlife conservation and ecosystem restoration); gardening clubs; biologists; invasive plant specialists; industry representatives and professionals (i.e., horticulture, transportation, recreation, forestry, and utilities), and other concerned individuals.

The Canadian Food Inspection Agency (CFIA), Environment Canada (EC), Natural Resources Canada’s Canadian Forest Service (NRCAN-CFS), Fisheries and Oceans Canada (DFO), Agriculture and Agri-Food Canada (AAFC), Canada Border Services Agency (CBSA), and Parks Canada.

The Government of Canada and its Provincial/Territorial counterparts introduced An Invasive Alien Species Strategy for Canada in September 2004. This Strategy will minimize the risk of invasive species to the environment, economy, and society and protect environmental values such as biodiversity and sustainability.

The strategy includes the prevention of intentional and unintentional introductions of invasive species from other countries, or from species moved across provincial and territorial borders within Canada, or between ecosystems within a region.

Four equally important goals form the foundation of the invasive species strategy:

  • Prevent the harmful intentional and unintentional introduction of invasive species to Canada;
  • Detect and identify new invaders;
  • Respond rapidly to new invaders upon detection;
  • Manage established and spreading invaders through eradication, containment and control.

In addition, a National Invasive Species Working Group, comprised of provincial invasive plant and species councils and committees, was established in January 2009, and is now called the Canadian Council on Invasive Species (CCIS). THe CCIS works collaboratively across jurisdictional boundaries to support actions and information that can help reduce the threat and impacts of invasive species. Invasive plant and animal species groups are now working in partnership to build upon the lessons learned in each province or territory to improve public awareness.

There are an estimated 485 invasive plant species in Canada, according to the Canadian Food Inspection Agency (CFIA). The Invasive Alien Species Partnership Program states that invasive species include at least 27% of all vascular plants in Canada.

Results of the 2009 Economic Impacts of Invasive Plants in BC (Report #12) analysis indicate that without intervention, the economic damage caused by each one of the seven selected invasive species in the study was estimated to range from $1 to 20 million dollars in 2008, increasing to between $5 and 60 million by 2020 (based on 2006 Canadian dollars). The total expected damages, in the absence of any management, were estimated to be a minimum of $65 million in 2008, rising to $139 million by 2020. These values are likely underestimates as economic data were not available for all potential impacts.

Survey respondents in BC estimated spending $6,979,932 on invasive plant management in 2006, including dollars spent on operations, outreach, and coordination activities (ISCBC Report #6: 2006 Economic Impacts Baseline Report).

In the agriculture sector alone, BC farmers and ranchers lose an estimated $50 million in crop revenue, and then also pay several million dollars more for control measures, such as herbicides and cultivation (Ministry of Agriculture and Lands).

What are invasive species costing Canadians?

The estimated annual cumulative lost revenue caused by just 16 invasive species is between $13 to $35 billion in Canada, says the federal Invasive Alien Species Partnership Program. Invasive species damage to the agricultural and forestry industries results in an estimated $7.5 billion of lost revenue annually. The discovery of invasive species in Canada can also result in trade restrictions imposed by foreign countries, interrupting billions of dollars in trade.

The Canadian Food Inspection Agency (CFIA) estimates that of the 485 invasive plant species in Canada, weeds in crops and pastures alone cost approximately $2.2 billion every year.

What are invasive species costing the United States?

According to the Canadian Food Inspection Agency (CFIA), the total cost of preventative measures, control programs, and lost production due to invasive species is estimated to exceed $137 billion a year in the United States.

The global cost of tackling invasive species costs an estimated $1.4 trillion each year, 5% of the global economy, states the Global Invasive Species Programme (GISP).

See specific information on these invasive plants on the Publications page.

The level of invasiveness will vary based on the local climate and growing conditions. To find out if these invasive plants occur in your area, call 1-888-933-3722 or contact your Regional Committee.

Be part of the solution in your community, and in your own backyard. Learn about becoming a volunteer.

To find out more on what events are happening in your region, or report an invasive plant, call 1-888-933-3722 or contact your Regional Committee.

As a non-profit organization, we require funding to undertake our work. If you would like to sponsor one of our existing projects or fund research on a specific invasive species, please contact the Invasive Species Council of BC at 1-888-933-3722. Alternatively, go to the Donate page of this site for more information. Thank you to all of the funding partners who have contributed! For current funding partners, see “Funding Partners” under the “About Us” section of this website.

Call the ISCBC toll free hotline: 1-888-933-3722.

As a member of the public, you can use the “Report-a-Weed” function of the Invasive Alien Plant Program (IAPP), the web-based application module managed by the Ministry of Forests, Lands and Natural Resource Operations:

Visit Eflora, the electronic atlas of BC’s plants to see distribution maps, photos, and identification details of native and invasive plants. Visit the Community Mapping Network Invasive Species Atlas, an online tool for locating and displaying invasive plants in southwestern BC.

If you find a plant you suspect is an invasive species, you can take a picture or collect a sample plant. All occurrence reports require detailed notes including date, location (latitude/longitude or details of state, county, township, and description sufficient to relocate the site), collector (full name and contact info such as email or phone), and any additional notes the collector feels might be useful. Please contact the Royal BC Museum for assistance.



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