Coastal Invasive Species Committee


Invasive Plant Impacts

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Environment Forestry & Agriculture Aquatic & Riparian Health & Safety


  • In natural ecosystems, invasive plants displace or destroy native plant populations.
  • Many rare and endangered native plants are also at risk from extinction from non-native plant invasion.
  • By removing the natural wildlife, invasive plants also reduce wildlife habitat.

Aquatic & Riparian

  • Shallow root systems can increase erosion, causing higher surface runoff, which increases stream sediment and reduces water quality.
  • Riparian invasive plants often grow in dense monocultures, resulting in negative impacts to nesting, cover and breeding habitat for fish and wildlife.
  • Infestations can change wetland structure by trapping sediments, creating higher, drier land that favours tree and shrub species rather than wetland species.


  • Invasive plants outcompete with existing forage and are often unpalatable to livestock, reducing overall levels of grazing.
  • They also compete with agricultural crops and reduce overall crop yield and quality.
  • Invasive plants require costly, long-term strategies to control and manage their spread.


  • Dense infestations of weeds increase the risk of wildfire because they are a source of fuel as they mature.
  • Noxious weed infestations compete with new tree seedlings for soil nutrients, light and moisture. This results in increased costs for silviculture.


  • Invasive plants degrade the natural beauty biodiversity of the landscapes.
  • Invasive plants can limit access for recreationalists (i.e. gorse and Himalayan blackberry).

Health & Safety

  • Some invasive plants are toxic, can cause skin and respiratory irritations (i.e. giant hogweed and daphne).
  • Some invasive plants cause seasonal allergies and hay fever (i.e. Scotch broom).
  • Some invasive plants can be toxic to horses and livestock (i.e. tansy ragwort).