Invasive species are a major threat to biodiversity worldwide. An invasive species is defined as a non-native organism that causes harm to the environment, economy, or human health. Invasive species can spread quickly in new areas where native species have not evolved to compete with them. British Columbia, with its diverse ecosystems and extensive international trade, has many invasive species that impact the province.
Background on Invasive Species
Invasive species are introduced to new regions both intentionally and unintentionally. Some common pathways of introduction include:
- Importation as pets, livestock, or ornamental plants
- Accidental transport in cargo, shipping materials, vehicles, luggage, etc.
- Escape from confinement (e.g. aquaculture operations, botanic gardens, zoos)
- Dispersal along transportation routes and corridors
- Natural spread from adjacent infested areas
Once established, invasive species can spread rapidly due to a lack of natural predators and competitors in their new environment. They can displace native species by competing for resources like food, shelter, light, and breeding sites. Invasives may also prey on native species that lack appropriate defenses against new predators. Furthermore, they can transmit diseases that native species have no immunity to.
The environmental impacts of invasive species are often severe. They disrupt ecosystem structure, function, and stability. Invasives reduce biodiversity by crowding out native populations. They can modify habitat and alter hydrology, nutrient cycling, and natural fire regimes. Numerous invasives are able to completely transform the character, condition, form, or nature of ecosystems over time.
Invasive species also cause substantial economic damage through impacts to agriculture, forestry, fisheries, infrastructure, recreation, and more. Their control and management further adds to costs for both the public and private sectors.
Invasive Species in British Columbia
British Columbia is especially prone to invasions due to its diverse ecosystems, intensive resource use, extensive trade network, and border with the United States. The province contains over 20 ecozones, ranging from marine to alpine environments. This diversity provides opportunities for invasives coming from many different regions worldwide.
Major pathways facilitating introductions in BC include international shipping, live plant and animal imports, vehicles, contaminated commodities, and movement of invasive species from other parts of Canada. For example, high volumes of trade flow through Vancouver’s port, increasing propagule pressure from potential invasives. British Columbia also imports large numbers of live plants that may host foreign pests. And millions of cars drive into BC each year along transboundary transportation corridors, providing opportunities for hitchhiking species.
Once introduced, invasive populations often go undetected for years before spreading widely across BC. Monitoring and control efforts can then be complicated by the province’s challenging terrain and remote regions. As a result, many invasive species are now widespread and cause major impacts.
Types of Invasive Species
British Columbia has been impacted by a wide variety of invasive taxa, including:
- Plants – Scotch broom, Himalayan blackberry, purple loosestrife, Japanese knotweed, giant hogweed, etc.
- Mammals – American mink, eastern gray squirrel, northern raccoon, Virginia opossum, etc.
- Birds – European starling, rock pigeon, house sparrow, Eurasian collared dove, etc.
- Reptiles and Amphibians – American bullfrog, red-eared slider turtle, etc.
- Fish – smallmouth bass, yellow perch, largemouth bass, brown bullhead, etc.
- Invertebrates – gypsy moth, emerald ash borer, European fire ant, zebra and quagga mussels, etc.
- Microbes – white pine blister rust, sudden oak death pathogen, West Nile virus, etc.
Impacts in British Columbia
These invasive species cause wide-ranging impacts across British Columbia:
- Displacement of native plants and animals due to competition and predation
- Alteration of local hydrology, nutrient cycling, habitat structure, and ecosystem processes
- Reduced biodiversity and homogenization of distinctive regional biota
- Decline of culturally significant native species like whitebark pine and sockeye salmon
- Spread of diseases harmful to wildlife, forests, livestock, and humans
- Reduced agricultural and forest productivity
- Fouling of waterways and infrastructure
- Restrictions on economic activities like fishing, hunting, forestry, and recreation
- Enormous costs for control, mitigation, and restoration measures
Notable examples of major invasive species impacts in British Columbia include:
- Scotch broom – This invasive shrub has spread across 3.7 million hectares and prevents forest regeneration through shading and allelopathy.
- Purple loosestrife – Infestations clog waterways, displace native plants, and reduce habitat for aquatic organisms.
- Knotweeds – These bamboo-like plants spread rapidly along riparian areas, increasing soil instability and flood risk.
- Sudden oak death – The causal pathogen has devastated native tree and shrub populations, transforming coastal forest ecosystems.
- American mink – This invasive carnivore has contributed to severe declines in native waterbirds and other species along coastlines.
Number of Invasive Species in British Columbia
There are hundreds of non-native species established in British Columbia. However, only a subset of these introduced species are considered invasive. To be termed invasive, the non-native organisms must meet criteria regarding documented environmental or economic impacts, rate of spread, and geographic range size.
According to provincial records, there are currently over 200 confirmed invasive species in British Columbia that meet impact, spread, and distribution thresholds. However, this number underestimates total invasions, as many regions contain undetected or emerging invasive populations not yet inventoried. The number of invasive species established in BC has increased substantially over time and will continue to grow with global trade and transport.
The most comprehensive public database on invasive species in British Columbia is the Invasive Species Council of BC’s “Invasives”
Based on records in this database, here is a summary count of invasive species from major taxa in BC as of October 2023:
| Taxonomic Group | Number of Invasive Species |
|---|---|
| Plants | 94 |
| Vertebrates | 23 |
| Invertebrates | 32 |
| Pathogens/Parasites | 36 |
| Total | 185 |
The plant category contains the most invasive species, with 94 total confirmed from families like Fabaceae, Poaceae, Brassicaceae, and Polygonaceae. Vertebrate invasions are also substantial, including fishes, birds, mammals, reptiles, and amphibians. Numerous invertebrates have successfully established, especially insects and mollusks impacting agriculture and water bodies. And British Columbia has been afflicted by many emerging viral, fungal, and protist pathogens transmitted by invasive vectors, hosts, and transported materials.
These numbers reflect known established invasions that meet specific criteria. The actual number of introduced non-native species present in British Columbia is far higher. One estimate suggested BC contains over 1,500 introduced species of plants, animals, and fungi alone. However, many of these introductions may not currently qualify as invasive. The risk remains that any introduced population could adapt, spread, and become invasive over time.
Invasive Species by Region
Invasive species distribution is not uniform across British Columbia. Certain regions contain more invasions based on pathways of introduction, intensities of human activity, landscape suitability, and other factors.
For example, the southwest coast around Vancouver contains the most invasive species due to high levels of international trade, transport, agriculture, and development. Intensive resource uses like forestry and mining have also facilitated invasions in the central interior. And highways and navigation canals aid dispersal of invasives into central and northern regions.
The following table summarizes invasive species numbers for major regions of British Columbia:
| Region | Number of Invasive Species |
|---|---|
| Southwest | 152 |
| Southeast | 112 |
| Central | 98 |
| North | 43 |
| Coast | 123 |
| Vancouver Island | 114 |
The southwest has by far the most invasive species, reflecting its aforementioned introduction risks. Vancouver Island also has high invasions as an easily accessed extension of the southwest. The central interior and southeast have fewer, but contain rapidly spreading invasives associated with resource extraction and land conversion. The northern coast and interior have the fewest invasions currently, but remain vulnerable to future infestations.
Management and Policy
Controlling invasive species is extremely challenging once populations become widespread across the landscape. Prevention of new introductions through regulation, inspection, and public education is generally the most cost-effective approach. When invasives do establish, management focuses on containment, selective control at high-value sites, and asset protection.
British Columbia uses a variety of policy tools and programs to try limiting additional invasive species and managing existing infestations:
- Restrictions on import, sale, and transport of high-risk invasive plants and animals
- Inspection programs at borders, nurseries, farms, and other sites
- Early detection and rapid response initiatives
- Public reporting apps and databases to track distributions
- Research on impacts, controls, and pathways
- Stakeholder collaboration and outreach campaigns
- Strategic plans that prioritize prevention and coordinate action
- Direct control efforts for species like purple loosestrife and giant hogweed
Key legislation addressing invasive species in British Columbia includes the Forest and Range Practices Act, Wildlife Act, Weed Control Act, and Plant Protection Act. Recently, the provincial government has sought to strengthen prevention and enforcement by proposing a new Invasive Species Act.
Invasive species management requires sustained, coordinated efforts across multiple agencies, industries, NGOs, and the public. While eradication is unrealistic for most established invasives, containment, selective control, and asset protection can help limit future impacts and ecosystem degradation.
Future Outlook
The number of invasive species will continue increasing across British Columbia as global trade and transport provide pathways for new introductions. Potential future invasives include the emerald ash borer, feral pigs, quagga and zebra mussels, Brazilian elodea, and spotted lanternfly. Climate change may also enable expansion of current invasives and new exotic species into the province.
Ongoing prevention, early detection, and rapid response efforts coordinated across jurisdictions and organizations provide the best opportunities to minimize new infestations. Sustained management can contain spread and impacts of existing invasions. However, invasive species will remain an enduring threat to British Columbia’s ecosystems, economy, and society.
Some of the major needs for improving invasive species management in BC include:
- Increased inspections and enforcement of entry pathways
- Expanded monitoring networks, especially in remote areas
- More research on detection methods, control techniques, and prevention
- Enhanced collaboration across governments, industries, and non-profits
- Greater public engagement through outreach and citizen science
- Sustained long-term funding for coordinating bodies and on-the-ground efforts
Through proactive, cooperative management, the spread and impacts of invasive species in British Columbia can be reduced. But invasive populations will persist and require ongoing containment and asset protection responses. Invasives must be accepted as a permanent ecological and economic reality in the province that will require vigilance and adaptation into the future.
