What are Alien Species?Alien species are plants, animals and microorganisms from one part of the world that are transported beyond their natural range and become established in a new area. They are sometimes also called "exotic," "introduced," "non-native," "non-indigenous" or "invasive" species.
Species that are considered aliens in this province may come from outside British Columbia or be native to some parts of British Columbia, but are counted as aliens in regions of the province where they have been introduced.
Not all species that arrive in new places are able to make themselves at home and start reproducing and spreading. However, alien species can get established if given advantages such as:
an agreeable climate;
no or few natural predators, parasites or diseases;
an abundance of food plants or prey that lack protection against the newcomer; and
an ability to out-compete native species and corner the best resources.
Why Should We Be Concerned?
Most non-native species that make their way to British Columbia are either beneficial or relatively harmless, and only a small percentage of these species will be able to survive independently - fewer still will be detrimental. However, all alien species must be treated with caution, because it is difficult to predict which ones will cause problems over time. Even those that have been harmless in the past could become troublesome if conditions change to conditions that are more hospitable and encourage reproduction and expansion (e.g., because of global climate change).
There is cause for concern because the rate of alien species introduction is accelerating rapidly as global commerce and travel increase. In San Francisco Bay, for example, roughly half of the alien species now living there arrived in the past 35 years.
Between 1851 and 1960, a new species became established in the bay and estuary every 55 weeks.
Between 1961 and 1995, the rate of establishment was one new species every 14 weeks.
Even though harmful aliens are a minority of all non-native species, the damage they do can be severe and wide ranging.
What are the Ecological Consequences?
Alien species are the second greatest threat to biodiversity, after habitat loss and degradation. When alien species move in, native species' populations often decrease in parts of their natural range or, in the worst-case scenario, the native species become extinct. The number of plant and animal species may remain the same in an area as common or widespread species replace unique, local species, but the integrity and vitality of natural ecosystems is damaged.
Alien species affect native species through:
competition for limited resources (including space, light, moisture, food, breeding sites and pollinators);
predation, grazing and browsing pressure;
introduction of diseases and parasites; and
hybridization.
Species at Risk
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) estimates that 25% of endangered species; 31% of threatened species; and 16% of Special Concern species are negatively affected by alien species.
What is Being Done?
When it comes to alien species, an ounce of prevention is definitely worth a pound of cure. It is far less expensive to keep unwanted aliens from crossing borders than to try to eradicate or contain them once they have arrived.
NEW! Invasive Alien Species Framework for BC: Identifying and Addressing Threats to Biodiversity
The document "Invasive Alien Species Framework for BC: Identifying and Addressing Threats to Biodiversity" (PDF 1.77MB) is a background document on invasive alien species issues that affect biodiversity in British Columbia. It sets out a framework for the use of science, and coordinated involvement of partners, to address the threats to BC’s environment and economy posed by invasive alien species.