Developed through a province-wide priority-setting exercise at the 2026 Alberta Invasive Species Council Conference, this outlook highlights priority invasive species at each stage of the invasion curve. Intended as a high-level overview of invasive species in Alberta, it showcases emerging threats, established invaders, and management priorities across the different stages of invasion.
The Invasion Curve
Investing in Action at the Right Time
The invasion curve illustrates how management priorities change as an invasive species progresses from introduction to widespread establishment. It helps guide decisions about where resources and efforts can have the greatest impact.
The earlier we act, the greater the return on investment.
When an invasive species is not yet established, prevention offers the most effective and cost-efficient opportunity to avoid future impacts. If a species is detected early, rapid response and eradication may still be achievable. As invasive species become more established and spread across the landscape, management shifts toward containment, impact reduction, and protecting high-value assets.
The invasion curve highlights an important reality: invasive species management is not just about responding to problems after they occur. Strategic investments in prevention, early detection, and rapid response can significantly reduce long-term environmental, social, and economic impacts. By understanding where a species falls along the invasion curve, we can prioritize actions that deliver the greatest benefit and make the best use of available resources.
Invasive Mussels
Zebra mussels (Dreissena polymorpha), quagga mussels
(Dreissena rostriformis bugensis) and golden mussels
(Limnoperna fortunei)
Invasion Stage: Prevention
Why this species matters: Zebra, quagga, and golden mussels can clog water infrastructure, damage boats and shorelines, and disrupt aquatic ecosystems. In Alberta, an infestation could cost tens of millions of dollars annually while affecting irrigation, drinking water supplies, recreation, fisheries, and native species.
What makes them so invasive: Invasive mussels reproduce prolifically. A single zebra mussel can produce up to one million eggs in a season, allowing populations to grow rapidly. Adults readily attach to hard surfaces, while microscopic eggs and larvae can go undetected in water, helping them colonize new environments and establish quickly.
Pathways of Introduction and Spread: Adult mussels attached to boats and equipment, and microscopic larvae carried in standing water inside boats, ballast tanks, live wells, bilges, and other water-holding compartments, can be transported between waterbodies.
Economic impacts: Threaten irrigation systems, drinking water infrastructure, recreation, and fisheries, with potential costs of tens of millions of dollars annually in Alberta.
Ecological impacts: Alter aquatic ecosystems by disrupting food webs and outcompeting native species.
What can Albertans do? Clean, Drain, Dry boats and gear, stop at inspection stations, and report suspected invasive mussels.
Regulatory Status: Fisheries (Alberta) Act: Prohibited
Species Prevalence – Not detected
Rats
Rats (Rattus norvegicus)
Invasion Stage: Prevention
Why this species matters: Rats can damage crops, contaminate food supplies, spread disease, and cause significant economic losses. Alberta is one of the few jurisdictions in the world that has successfully remained rat-free. Alberta's rat-free status protects agriculture, communities, infrastructure, and public health from a costly invasive pest.
What makes it so invasive? Rats mature quickly, produce multiple litters each year, and can rapidly establish new populations. Their ability to thrive wherever food, water, and shelter are available makes them one of the world's most successful invasive mammals.
Pathways of Introduction and Spread: Hitchhike in vehicles, cargo, feed, grain shipments, and farm equipment.
Economic impacts: Damage crops, livestock feed, buildings, equipment, and stored food, and can spread diseases that threaten human, livestock, pet, and wildlife health.
Ecological impacts: Can prey on native wildlife, birds, and eggs while competing with native species for food and habitat.
What can Albertans do? Report suspected rat sightings immediately and secure potential food and shelter sources around homes and farms.
Regulatory Status: Agricultural Pests Act: Pest
Species Prevalence: Not Established in Alberta
(occasional isolated detections are rapidly eliminated)
Emerald Ash Borer
Emerald Ash Borer (Agrilus planipennis)
Invasion Stage: Prevention
Why this species matters: Emerald ash borer is an invasive beetle that kills ash trees by feeding beneath the bark and disrupting the tree's ability to move water and nutrients. Once established, it can destroy entire ash populations in a matter of years. Ash trees are a common feature of Alberta's urban forests, parks, shelterbelts, and communities. An infestation could result in the loss of millions of trees and significant costs for municipalities, homeowners, and businesses.
What Makes It So Invasive? Emerald ash borer larvae spend most of their lives feeding beneath the bark, often going undetected until trees are severely damaged and nearby trees have already been infested.
Pathways of Introduction and Spread: Primarily spread through the movement of infested firewood, nursery stock, logs, and wood products.
Economic impacts: Tree removal, replacement, and management costs can reach millions of dollars for municipalities, property owners, and businesses.
Ecological impacts: Causes widespread loss of ash trees, reducing urban canopy cover, wildlife habitat, biodiversity, and ecosystem services.
What can Albertans do? Buy firewood where you burn it, don't move firewood, and report suspected infestations.
Regulatory Status: Plant Protection Act (Canada): CFIA-regulated quarantine pest
Agricultural Pests Act (Alberta): Pest
Species Prevalence: Not detected in Alberta
EDDMapS Emerald Ash Borer Reports:
Rush Skeletonweed
Rush Skeletonweed (Chondrilla juncea)
Invasion Stage: Prevention
Why this species matters: Rush skeletonweed is a deep-rooted invasive plant that can invade rangelands, pastures, and cropland, reducing forage production and competing with desirable vegetation. Once established, rush skeletonweed is difficult to control and can reduce agricultural productivity, increase management costs, and degrade native grassland ecosystems.
What Makes It So Invasive? Its extensive root system allows it to survive drought, resist control efforts, and regenerate from small root fragments.
Pathways of Introduction and Spread: Spreads through wind-blown seed and can be moved in contaminated hay, seed, soil, gravel, vehicles, and equipment.
Economic impacts: Can reduce forage and crop production while increasing weed management costs for landowners and producers.
Ecological impacts: Outcompetes native grasses and wildflowers, reducing biodiversity and degrading grassland habitat.
What can Albertans do? Use certified weed-free forage when available, review seed certificates, clean vehicles and outdoor equipment, and report suspected sightings early.
Outreach Campaign:
Regulatory Status: Weed Control Act: Prohibited Noxious
Species Prevalence: Not detected
EDDMapS Rush Skeletonweed Reports:
Wild Boar
Wild Boar (Sus scrofa)
Invasion Stage: Eradication
Why this species matters: Wild boar are highly adaptable invasive animals that damage crops, wetlands, and native habitats while posing risks to livestock and wildlife. Wild boar can cause significant agricultural and environmental damage, spread disease, and are one of the most difficult invasive mammals to eliminate once populations become established.
What Makes It So Invasive? A sow can produce multiple litters per year with several piglets per litter, allowing populations to grow rapidly. Combined with their adaptability, ability to thrive in a wide range of habitats, and lack of natural predators, this makes wild boar one of the world's most successful invasive mammals.
Pathways of Introduction and Spread: Escaped or intentionally released domestic wild boar that establish and expand into new areas.
Economic impacts: Damage crops, fences, pasture, stored feed, and agricultural infrastructure while increasing management costs for landowners.
Ecological impacts: Root up soil, damage wetlands, displace wildlife, spread invasive plants, and degrade native habitat.
What can Albertans do? Report sightings immediately and avoid actions that may spread or disperse wild boar populations.
Regulatory Status: Agricultural Pests Act: Pest
Species Prevalence: Localized Populations Present
EDDMapS Wild Boar reports:
Knotweeds
Knotweeds (Reynoutria spp.) Japanese Knotweed (Reynoutria japonica), Giant Knotweed (Reynoutria sachalinensis), Bohemian Knotweed (Reynoutria × bohemica)
Invasion Stage: Eradication
Why this species matters: Knotweeds are aggressive invasive plants that form dense stands, crowd out native vegetation, and can damage infrastructure through their extensive underground root systems. Once established, knotweeds are extremely difficult and expensive to remove, threatening ecosystems, roadsides, riverbanks, and built infrastructure.
What Makes Them So Invasive: Extensive underground rhizomes can spread several metres from the parent plant and regenerate from tiny fragments.
Pathways of Introduction and Spread: Spreads through root and stem fragments moved in soil, fill, gravel, floodwaters, yard waste, and equipment.
Economic impacts: Can damage roads, retaining walls, drainage systems, and other infrastructure while increasing management and restoration costs.
Ecological impacts: Forms dense monocultures that displace native plants, reduce biodiversity, and alter riparian habitats.
What can Albertans do? Choose native and non-invasive plants for your yard, never dump yard waste in natural areas, put invasive species in the black bin, never the compost and report knotweed infestations early.
Regulatory Status: Weed Control Act: Prohibited Noxious
Species Prevalence: Isolated detections
EDDMapS Japanese Knotweed Reports:
Source: Invasive Species Centre
Prussian Carp
Prussian carp (Carassius gibelio)
Invasion Stage: Containment
Why this species matters: Prussian carp is an invasive fish that spreads rapidly through connected waterways and can disrupt aquatic ecosystems by competing with native fish and degrading habitat. Alberta was the first place in North America where Prussian carp was discovered. Since then, this invasive fish has spread into multiple Alberta watersheds and into Saskatchewan, threatening native fish and aquatic ecosystems through its rapid reproduction.
What Makes It So Invasive? Female Prussian carp can reproduce through cloning, allowing populations to establish even when few individuals are present. They can also spawn up to three times per year, enabling populations to grow and spread rapidly.
Pathways of Introduction and Spread: Unauthorized fish releases and movement through connected waterways.
Economic impacts: Increases management and monitoring costs for fisheries and aquatic ecosystems.
Ecological impacts: Competes with native fish, increases water turbidity, and alters aquatic habitats.
What can Albertans do? Never move or release live fish or aquarium plants and pets into the wild—it is illegal in Alberta and can spread invasive species to new waterbodies. Report sightings of Prussian carp
Regulatory Status: Unregulated
Species Prevalence: Expanding range; established regionally
EDDMaps Reports
Whirling Disease
Source: Government of Alberta
Whirling Disease (Myxobolus cerebralis)
Invasion Stage: Containment
Why this species matters: First detected in Alberta in 2016, whirling disease is caused by a microscopic parasite that threatens trout, salmon, and whitefish populations. It can reduce fish survival, impact recreational fisheries, and spread easily between waterbodies on contaminated gear and equipment.
What Makes It So Invasive? The parasite is invisible to the naked eye and can be moved between waterbodies in mud, water, fish, and contaminated gear and equipment.
Pathways of Introduction and Spread: Spread through infected fish, contaminated mud, water, equipment, and aquatic gear moved between waterbodies.
Economic impacts: Threatens recreational fisheries, tourism, and fishery management programs.
Ecological impacts: Causes deformities and mortality in trout, salmon, and whitefish, reducing fish populations and affecting aquatic ecosystems.
What can Albertans do? Remove all mud and debris from gear, avoid felt-soled waders and other porous equipment, when possible, thoroughly clean and dry gear before visiting another waterbody, and never move fish or water between waterbodies. Follow the decontamination protocol for more details.
Regulatory Status: Unregulated
Species Prevalence: Established regionally
Source: Government of Alberta
Source: Government of Alberta
Source: Montana State University
Downy Brome
Downy Brome (aka cheatgrass) (Bromus tectorum)
Invasion Stage: Containment
Why this species matters: Downy brome is one of the most widespread invasive grasses in western North America. It alters ecosystems by outcompeting native vegetation and increasing the frequency of wildfire.
What Makes It So Invasive? Known as cheatgrass for a reason—it germinates earlier than many native plants, giving it a head start in capturing water, nutrients, and space.
Pathways of Introduction and Spread: Spread by seed through contaminated forage, vehicles, equipment, animals, soil movement, and wind.
Economic impacts: Reduces forage production, increases management costs, and can contribute to wildfire suppression and restoration expenses.
Ecological impacts: Displaces native plants, reduces biodiversity, and increases wildfire frequency and intensity in grassland ecosystems.
What can Albertans do? Use certified weed-free forage when available, review seed certificates for contaminates, clean boots, vehicles, and equipment before moving between sites.
Regulatory Status: Weed Control Act: Noxious
Species Prevalence: Established Regionally
EDDMapS Reports
Source: Invasive Species Council of BC
Oxeye Daisy
Oxeye Daisy (Leucanthemum vulgare)
Invasion Stage: Containment
Why this species matters: Often mistaken for a harmless wildflower, oxeye daisy can spread aggressively through pastures, roadsides, and natural areas. Dense infestations reduce forage production, displace native plants, and lower biodiversity.
What Makes It So Invasive? Its attractive flowers disguise an aggressive invader that can quickly dominate landscapes and crowd out native species.
Pathways of Introduction and Spread: Spread through seed, contaminated forage, soil movement, vehicles, equipment, and ornamental plantings.
Economic impacts: Reduces forage quality and productivity in pastures and haylands, increasing management costs for landowners.
Ecological impacts: Forms dense stands that displace native plants and reduce biodiversity in grasslands and natural areas.
What can Albertans do? Clean your outdoor gear, Choose native plants for landscaping, avoid planting invasive ornamentals, always put invasive plants in the black bin, never the compost, and report new infestations before they spread.
Regulatory Status: Weed Control Act: Noxious
Species Prevalence: Not detected; Isolated detections; expanding range; established regionally; widespread across Alberta.
EDDMapS Reports
Kochia
Kochia (Bassia scoparia)
Invasion Stage: Widespread
Why this specie matters: Kochia is one of Alberta's most challenging invasive plants to manage. It reduces crop yields, competes with desirable vegetation, and continues to spread despite ongoing control efforts, increasing costs for producers and land managers.
What Makes It So Invasive? Spreads its seeds by tumbling across the landscape and has evolved resistance to multiple herbicides, making it difficult to control.
Pathways of Introduction and Spread: Spreads by seed through wind, vehicles, equipment, contaminated seed, and its characteristic tumbling growth habit.
Economic impacts: Reduces crop yields and increases weed management costs through additional herbicide applications and control measures.
Ecological impacts: Competes with native and desirable vegetation, particularly in disturbed habitats and grasslands.
What can Albertans do? PlayCleanGo - Clean outdoor equipment between sites, use integrated weed management practices to reduce spread, identify and control infestations early on.
Regulatory Status: Unregulated
Species Prevalence: Widespread across Alberta.
Source: MD of Greenview
EDDMapS Reports
Canada Thistle
Canada Thistle (Cirsium arvense)
Invasion Stage: Widespread
Why this specie matters: Canada thistle is one of Alberta's most widespread invasive plants. Dense infestations reduce forage production, crowd out desirable and native vegetation, increase management costs, and its sharp spines can be a nuisance for livestock, wildlife, and people.
What Makes It So Invasive? An extensive root system can spread metres underground and produce new shoots, allowing infestations to expand and recover from control efforts.
Pathways of Introduction and Spread: Spreads through wind-blown seed, root fragments, contaminated soil, forage, equipment, vehicles, and water.
Economic impacts: Reduces forage production and crop yields while increasing weed management costs for producers and landowners.
Ecological impacts: Forms dense patches that displace native plants and reduce biodiversity in grasslands and natural areas.
What can Albertans do? Outreach campaign: PlayCleanGo
Regulatory Status: Weed Control Act: Noxious
Species Prevalence: Widespread across Alberta.
EDDMapS Reports
Invasive Species Impacts:
Estimated annual cost to Alberta's economy
of documented species extinctions have involved invasive species
Estimated global cost in 2019
Rate at which global costs have increased since 1970
Early action pays off. Prevention costs far less than managing established invasions. Delayed action has already added more than US$1 trillion in costs worldwide.
Sources:
Alberta Invasive Species Council (2022) Update to the Costs of Invasive Species in Alberta.
Cuthbert, R. N., et al. (2022). Biological invasion costs reveal insufficient proactive management worldwide. Science of the Total Environment, 819, 153404. Elsevier.
IPBES (2023). Thematic Assessment Report on Invasive Alien Species and their Control of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Roy, H. E., et al. (eds.). IPBES secretariat, Bonn, Germany.