INVASIVE PLANT SPECIES
Yellow Iris (Iris pseudacorus) is an invasive species in BC,
photo by Ernie Sellentin.
Report a Weed is a feature of the BC Ministry of Forests and Range Invasive Alien Plant Program aimed at reporting new occurrences of invasive plant species. Read more about their program here.
Invasive species are a part of the flora of
British Columbia. They are most often alien species that have become abundant and
widespread in the landscape to such a degree that they replace
or swamp the natural species assembly in an ecosystem, and cause
havoc with ecosystem function. There are often economic implications
associated with invasives, such as in rangeland areas where they
replace important browse plants. When an invasive species moves into an ecosystem, it can sometimes completely blanket an area.
The invasive species problem is a complex one.
Invasive plant species affect food sources for wildlife, can influence
pollinator availability, and can crowd out native species directly.
We are now seeing dramatic changes in bird populations, elk herds,
reindeer herds, and other wildlife as a result of the replacement
of native plant species by alien species. While some animal species can
adapt and feed on alien food sources, many cannot.
A comprehensive discussion on invasive plant species in the Georgia Basin, prepared by Pamela Zevit for E-Flora BC, can be found here (pdf).
WHICH SPECIES ARE CONSIDERED INVASIVE?
There is presently no single list of invasive plant species for BC, although many invasive plant councils in BC have identified the top invaders in their region. However, at E-Flora BC we have compiled a list of invasive, noxious and problem weeds for the province. These are species identified in these categories by various BC agencies and groups in the province. . Click here to view the list.
Because new and potentially invasive species continue to arrive in BC, this list will be continuously updated. We also provide a working list of species that experts feel should be prohibited in British Columbia. These include species that have already arrived here, and species that have not yet arrived, but would be significant threats if they moved into the province.
Giant Hogweed/Giant Cow Parsnip (Heracleum mantegazzianum) is an alien
species, photo by Hugh Griffith.
GENERAL DEFINITIONS: ALIEN VERSUS INVASIVE
Alien Species: An alien species is a species that occurs in a region where it is not native. Many alien species in BC are from Europe or Asia (the majority of our alien species) but some alien species have arrived here from eastern North America, or South America. Not all alien species are invasive. Many simply occupy disturbed sites, such as roadsides, and do not displace native species.
Invasive Species: Invasive species are (usually) alien species that have moved into natural ecosystems and have altered ecosystem characteristics, either through their sheer abundance or through structural changes in the system. They can change plant community composition, which ultimately affects the wildlife that can occur there.
Visit our Advanced Search page in order to call up a list of atlas pages for invasive plant species in BC. Click on "invasive" and "vascular plants " in order to produce a list.
Common Crown-vetch (Coronilla varia) is an alien species in BC,
photo by Diane Williamson.
TICKING TIME BOMBS
An introduced species can occur in an area sporadically
or innocuously for many years or decades before exploding in numbers
and sweeping through the landscape. There are many factors that
drive this, including the effects of annual or cyclical climatic
variation. Periods of drought often favour alien species reproduction
and dispersal. In addition, the longer flowering periods of many
invasives can allow more successful reproduction and dispersal.
As a result of their greater success, invasive species are fueling
massive ecosystem shifts, both in terrestrial and aquatic areas.
The implications of this are immense.
HOW DO INVASIVE SPECIES GET HERE?
Alien species arrive in BC by several pathways of introduction. They arrive as seed sources in cattle feed, they hitch a ride on
trains and other transport methods, including recreational vehicles,
they come in with horticultural imports, they arrive in ships’ ballast
and are flushed into our bays and harbours, they are used in landscaping
and 'beautification' projects, they are brought in for aquariums.
In the right conditions, they like their new home and spread quickly.
CONTROLLING INVASIVE PLANT SPECIES
Once invasive plants have arrived and spread,
the problem becomes one of control and reduction of spread. Methods
of control for invasive species range from direct hand-pulling
of plants, such as is frequently done for purple loosestrife, to
chemical control for widespread invasives such as knapweeds, to
biological control. Biological control can include the use of beetles
as predators on specific species, such as purple loosestrife. This
has had some mixed success.
Baby's Breath (Gypsophila
paniculata) is an alien species in BC,
photo by Amelie Rousseau
HOW CAN YOU HELP?
Redressing the problem of invasive species
will take the efforts of governments, scientists and individuals.
You can help in several ways:
- Help collect distribution data on the occurrence of weed species in BC. Click here to directly report new sightings of invasive plant species under the BC Ministry of Forest and Range 'Report a Weed' program.
- Become familiar with which species are invasive
in BC and in your neighbourhood. E-Flora BC provides the means
to do this.
- Use the search buttons on our Species Search page to call up the atlas pages for invasive vascular plant species. These atlas pages will provide
you with a description and illustration of the species, information
on its distribution in BC, and more;
- Remove invasive species from your garden
and do not purchase seeds or plants of invasive species. Think twice about using species such as English Ivy or Japanese knotweed in your garden or landscaping;
- Help spread the word about the serious impacts
invasive species are having on the ecosystems and rangelands. Invasive
species can be very pretty and very colourful, but they are none-the-less
unwanted intruders in our environment.
- Help remove invasive species in your local
area. Join the efforts to remove invasives that are being conducted
by groups such as the invasive plant councils of BC;
- Allow no quarter for invasives. Encourage
complete removal of invasives wherever they are found. We can
only stop this problem if we remove all of the plants so that
pollinators do not preferentially select invasive species over native species,
and so seed sources are curtailed. Removal will allow native
wildlife populations to rebalance themselves around the natural
components of their landscape, and abundances and species compositions
will shift back to a pre-invasive level;
- Encourage municipalities to adopt a "native
plant planting policy" and an "anti-invasives planting policy";
- Join the an invasive plant committee nearest you to lend your support. Encourage your
municipality to join.
Chickory (Cichorium intybus) is an alien species commonly found
along roadsides and disturbed sites,
photo by Diane Williamson