Invasive species can have environmental impacts by reducing native species populations, degrading ecosystems, and increasing fire risk. Click on the boxes below to learn more about the environmental impacts.
Invasive species can eat, compete against, and spread diseases to our native species. Because the natural pests or pathogens of invasive species are not present here in BC, they can spread more aggressively than native species and so easily replace them. Invaded ecosystems are generally not nearly as resilient as healthy, functioning ecosystems. Invasive species are also a major threat to species at risk.
American bullfrogs
American bullfrogs are aggressive predators that eat our native fish, birds, ducklings, reptiles, and amphibians – basically, anything they can fit in their mouths!
An American bullfrog eating a native leopard frog.
English ivy
English Ivy forms a thick blanket of plant material that physically excludes native species on the forest floor and can also climb and kill trees. It is often introduced into natural areas by people dumping garden waste such as hanging baskets.
English ivy spreading along the ground and up trees.
Orange hawkweed
Orange hawkweed is an invasive plant that can affect native grasslands, where it will outcompete and impact other species, including species at risk. Orange hawkweed spreads by seeds, rhizomes and stolons. While cutting the top growth may prevent seeds from forming, it will also stimulate the plants to spread via their rhizomes, creating a dense mat of nothing but hawkweed.
Orange hawkweed can take over grassland areas by forming dense mats that outcompete native and desirable species.
White-nose syndrome
White-nose syndrome (WNS) is a disease caused by an invasive fungus that is seriously impacting North American bat populations. Since the winter of 2006, WNS has killed over 6 million bats in eastern North America and can be spread by people visiting caves. Although it has not been detected in BC at the time of this writing, it was found in nearby Washington State in 2016. Native bats are critical to agriculture in BC, as they are all insectivorous and so help to manage insect populations. More than half of the bat species in North America are threatened or endangered, and white-nose syndrome poses a real threat to these important animals in our ecosystems.
Little brown bats with white-nose syndrome: New York.
Ecosystem degradation
Invasive species disrupt natural processes. They can alter the hydrology, erosion and sedimentation, and fire risk in an ecosystem.
Aquatic invasive species
Aquatic invasive species such as flowering rush, Eurasian watermilfoil, Brazilian elodea, and zebra/quagga mussels change the ecosystems of lakes by negatively impacting water quality and hydrology and preventing the survival of many native species.
Eurasian watermilfoil can impact water quality.
Feral pigs
Feral pigs increase erosion by disturbing soil and increasing sedimentation.
They eat native, vegetation, crops, insects and other wildlife, including species at risk and young livestock. They also compete with native animals for habitat and food. In some areas, feral pigs have also become extremely aggressive to humans, and have caused at least one death in the United States.
Feral pigs don’t just eat vegetation and insects, they can eat other wildlife, including SAR and young livestock. And they don’t just compete with native animals, but livestock too.
The majority of occurrences of feral pigs in B.C. are confirmed instances of escaped farm pigs which were subsequently recaptured or eradicated. The extent and size of any feral populations, if they exist, is not well understood.
Feral pigs cause damage by rooting and digging in soil.
Fire risk
Several invasive species can change ecosystems in a way that makes them more susceptible to fire and its impacts. Examples of such species include cheatgrass and scotch broom.
Cheatgrass
Cheatgrass is an annual grass that increases the risk and intensity of wildfires because it forms dense mats of dry material. Cheatgrass and other annual invasive grasses have contributed to an increase in the frequency and intensity of fires in the western United States.
Cheatgrass is present in BC and is spreading throughout the interior grasslands.
Scotch broom
Scotch broom forms large infestations. This can increase the fuel load in an area, as the oils in scotch broom plants are extremely flammable, and plants often have dry and dead branches on them. The presence of scotch broom therefore increases a wildfire’s intensity, making it more difficult to fight. This was experienced by BC Wildfire Service staff responding to fires near Nanaimo, BC, in 2018.
Scotch broom in bloom.Scotch broom forms dense, dry patches that increase fire risk.
