INVASIVE PLANT SPECIES

Yellow Iris (Iris pseudacorus) is an invasive species in BC, photo by Ernie Sellentin.

by
Brian Klinkenberg

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, alien and noxious weeds for the province, and this information is provided on the atlas page for each species. Click here to view the list. Species on this list have been identified by various BC agencies and groups as invasive species, noxious species, and problematic alien species. Because new and potentially invasive species continue to arrive in BC, this list will be continuously updated, and 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 move 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.

Watch how alien and invasive species spread in the province. Visit our animated maps.

Visit our species search page in order to view 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 byDiane 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 introducton. 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.

Aquilegia sp. (columbine), photo by Diane Williamson. Columbines easily set seed
that spread invasively in the garden.

SOLUTIONS

In British Columbia, invasive species are being taken seriously by ecologists, government agencies, and NGO's. In 2005, an Invasive Plant Council for BC was launched under the umbrella of the Fraser River Coalition. This group is tackling the issue in several ways, including public awareness campaigns aimed at discouraging the use of invaders, assessment of legislation that can prohibit import of invasives or require the removal of invasives, and encouragement of research that will aid in combating the problem. Stopping the flow of invasive species or potential invasive species will be an important step.

One key first step in invasive species management is easy access to information on invasives species, their distribution, change in distribution over time, and control methods. Since the founding of the Invasive Plant Council of BC, several regional invasive plant councils have been formed to tackle local invasions. They provide information on invasive species, and include the Northwest Invasive Plant Council, the Greater Vancouver Invasive Plant Council, and others.

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?-- NO QUARTER

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. View the E-Flora list of Invasive, Alien and Noxious Weeds of BC . 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. Tell your neighbour why they are not a good idea;
• 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

Some global invasive species

Parthenium hysterophorus (Santa Maria feverfew) invasive in Kenya

BC Invasive plant committees

Invasive Plant Council of BC
Coastal Invasive Plant Committee
Greater Vancouver Invasive Plant Council

Key LINKS

Weeds BC

A list of noxious weeds in BC

BC Weed Legislation

Invasive Plant Alert, Ministry of Agriculture, Food and Fisheries