Frequently Asked Questions regarding invasive species:

ffffWhat are invasive species?
Invasive species are species that are not native to our region, This means they were not in the Sea to Sky region pre-European contact. They arrived here through human activities from other areas of North America or from other continents. Not all non-native species are invasive though. A non-native species is considered invasive only if it negatively impacts the environment, society or economy. Invasives tend to grow rapidly and spread quickly. Because these species did not evolve here, natural controls that kept them in check in their native habitat (such as insects, viruses, fungi, predators, etc) do not exist here, so the invasives are able to grow and spread rapidly.
ffffWhat happens if we just leave them alone?
Invasive species are not native to our region, grow and spread rapidly, and are hard to get rid of. The following are some specific threats caused by their spread.

Invasive species can…

  • Outcompete our native species and decrease biodiversity
  • alter water flow and lead to erosion and/or less available water
  • create and increase fire hazards
  • damage roads, foundations, and other infrastructure
  • reduce crop yields and available forage for farm animals
  • choke out recreational trails and areas
  • decrease property values
  • decrease available habitat for medicinal and wild edible plants important to first nations culture
  • degrade fish and wildlife habitat
  • burn, sting, or poison humans and animals
  • block sightlines along roads and railways

Invasive species are the second most significant cause of species extinction worldwide, after habitat destruction. Their impact is severe and often irreversible if left alone.

ffffHow do invasive plants spread?

  • Intentional introduction as garden ornamental, medicinal plant, or food crop- many invasive plants got their start in someone’s garden. Most were exotics brought from other parts of the world where they had native predators and diseases to keep them in check. Plants can easily escape gardens and cross fences through seed dispersal, or by intentional planting in wild areas. Some nurseries still sell invasive plants -ask your local nursery if it is Plantwise.
  • Improper disposal of garden waste – although it might seem like a good idea to “recycle” your garden debris into a natural area, what you’re really doing is introducing plants that can smother, choke and otherwise ruin parks, greenways and other greenspaces needed by wildlife and people. Plant fragments and seeds in garden waste can easily take root and grow after having been dumped in a natural area. Dispose of invasive yard waste in the invasive species bin at your local transfer station or landfill
  • .Dispersal by direct growth – many invasive plants are rapid-growing and fast-spreading. English ivy, for example, can spread up to 4.5 metres in a single year. These plants can creep under fences or out of planters, spreading into nearby habitat and onwards from there.
  • Dispersal by seed – many invasive plants are prolific seed producers. One purple loosestrife plant, for example, can produce 3 million seeds! These can then be dispersed by water, people, animals, vehicles, etc. to new areas.
  • Transport of earth from one area to another -fill soil and truck ballast often contains invasive seeds or plants. Once moved to a new area, the plants grow and spread into natural areas.
  • On the hulls of boats – water infested with invasive mussels can contaminate new lakes when vessels are moved between them.

ffffWhy use chemical herbicides?

Extremely aggressive and destructive invasive species like Japanese  Knotweed require chemical control as it is the only method that can manage the spread faster than the spread itself.

When does the risk of losing a riparian or natural area to destruction from invasive species outweigh the risk from potential herbicide contamination? As a society, we need to weigh all the risks and develop best management practices. Like a doctor prescribing medical narcotics to heal a patient when “plenty of rest and fluids” aren’t enough, the selective use of herbicide is one of the crucial tools used for controlling species such as Japanese knotweed.

In considering the potential direct effects of any chemical on any biological organism, it is necessary to take into account two fundamental principles of toxicology:

  1. All chemicals (e.g. caffeine, alcohol, nicotine, glyphosate, sodium chloride [table salt]) are toxic, but some are more toxic than others;
  2. The degree to which a toxicological effect is expressed depends on exposure or dose, both in terms of the actual amount, and the time frame over which it occurs. As an analogy, think of the difference in effect resulting from consuming several glasses of alcohol in an hour versus the same amount over an entire day.

Chemical control options include stem injection, cut and fill, and backpack foliar spray.

Read more about SSISC’s herbicide control methods.

ffffWhy do people buy invasive plants?
Invasive plants can be pretty, but the problems they cause are not. Yellow flag iris is admired for its big blooms; Periwinkle is a pretty ground cover and English holly is a Christmas favourite. But each wreaks havoc in our parks and other natural areas by displacing native plant species needed by wildlife and/or by altering water flow, stealing nutrients and sunlight.

Invasive plants can be easy to grow and can grow quickly, but that’s also what makes them invasive. Sometimes, homeowners looking for a quick solution to a bare spot will choose a plant lauded as a “fast spreader” or a “vigorous self-seeder.” Unfortunately, invasive plants tend to spread or seed themselves right out of your garden and into the parks and natural spaces nearby.

Invasive plants can be readily available, but so are more appropriate alternatives. Many garden centres, supermarkets and corner stores continue to sell invasive species such as English ivy, English holly and lamium. But just because something is being sold doesn’t mean it’s a wise choice. Discriminating consumers who choose non-invasive alternatives can help to change company purchasing habits. Read about how SSISC is helping to reduce invasive plant sales through the PlantWise program.

ffffHow do I remove or control an invasive in my yard?
Invasive species are typically fast growing and fast spreading. Because of this, a variety of control methods are typically used in combination to limit their growth or eradicate them. For species specific advice on how to control an invasive, see our species Factsheets found here.
ffffWhat can I do?

  • Learn to identify local invasive species in your area.
  • Report Invasive Species.
  • Remove and control invasive species on your property.
  • Attend local activities like weed-pulling days.
  • Do not purchase invasive weed seeds from suppliers or catalogues; ask what’s in the wildflower mixes.
  • Contain creeping plants by growing them in containers, or not growing them at all.
  • Don’t let invasive plants go to seed, or remove them from your property.
  • Grow alternative plant species by substituting less aggressive plants for non-native invaders.
  • Keep aggressive plants from escaping your garden or landscaped area.
  • Do not use roadside or “wild” plants in flower arrangements if you cannot identify them.
  • Clean equipment, tools, vehicles and footwear before leaving an area that is infested with invasive plants. See Clean-Drain-Dry for the prevention of aquatic invasive species spread.
  • Organize a “weed-free” space, like a local schoolyard or roadway.

On a global basis the two great destroyers of biodiversity are habitat destruction and invasion by exotic species

Dr. Edward O. Wilson Harvard biologist

Invasive alien species are a major driver of biodiversity loss… and are the most common threat associated with extinctions of amphibians, reptiles and mammals.

The International Union for Conservation of Nature (IUCN)

When a native species is displaced by an aggressive invasive species, ecosystem functions are disrupted and ecosystem services are threatened.

Invasive Species Council of British Columbia