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Invasive species

Purple loosestrife (Lythrum salicaria) was imported as an ornamental.
Photo: Jardin botanique de Montréal (Michel Tremblay)
Lythrum salicaria.
  • Lythrum salicaria.
  • Lythrum salicaria.

The introduction of exotic species into a new environment, whether intended, as exotic garden plants or pets, or unintended, as “stowaways” in a traveller’s clothing or in packing and transport materials, is recognized as an important cause of biodiversity loss. Most such introductions do not become established but in a few cases, the introduced species, having “fortuitously” left behind its predators, competitors, parasites, diseases and other factors that naturally kept its population under control in its original habitat, finds itself in new and favourable conditions and thrives. Only a small percentage becomes truly invasive but these have significant economic impacts, will importantly affect natural habitats and may push native species into extinction. With the increased international transfers of goods and people that come with globalization, a greater number of exotic species are reaching faraway destinations.

Recent examples include the zebra mussel, that came with the ballast water of ships and now clogs waterways and ducts in the Great Lakes region; the Asian long-horned beetle that arrived in wooden pallets and now inflicts serious damage to the forests; and purple loosestrife that was imported as an ornamental and has taken over large tracts of natural ecosystems.

Identifying these invasive species, understanding the ecological equilibria that naturally control them in their original habitats, measuring their impacts and developing control strategies that will not themselves cause greater imbalances are all critically dependent on our understanding of the biodiversity and ecology of the ecosystems and species involved.

International regulations, border inspections and a generally greater awareness and compliance of the public are key aspects in preventing the introduction of exotic species. Government regulations, scientific research and public participation are also essential aspects of the fight against established invasive species.

These texts have been provided by the Université de Montréal Biodiversity Centre.

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