Introduced and Invasive Species

Introduced, Invasive and Native Species

People often mistakenly use these words interchangeably when they are in fact quite different from each other.

What's the difference?

Introduced (or exotic) species are non-native plants or animals that are introduced into a new location by human activity, either intentionally or by accident. Introduced or exotic plants and animals do not have negative environmental, economic, or social impacts.

Invasive species are non-native plants or animals that have been introduced, either intentionally or accidentally, into the environment from other areas. Without their natural predators, they are capable of moving aggressively into an area, and using resources such as light, nutrients, water, and space which other plants or animals need. Invasive plants and animals threaten natural ecosystem functions, species biodiversity, food security, human health and safety, and economic development.


The terms introduced and invasive are often used incorrectly. One way to understand their difference is to think of it in terms of dogs:

All dalmatians are dogs
not all dogs are dalmatians.

In this example, dalmatians can be replaced with invasive species, and dogs can be replaced with introduced:

All invasive species are introduced,
not all introduced species are invasive.

Invasive Plants in Nanaimo

Nanaimo has many invasive plant species, however, the City of Nanaimo has outline a few ‘priority’ invasive plants which are actively removed from parks and other public land.

Priority Invasive Plants

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Native species are plants or animals that reached their location without assistance from people. In Canada and the United States, native plants and animals are ones that already existed here at the time of European colonization.


Invasive Species

Invasive Plants in Nanaimo

Nanaimo has many invasive plant species, however, the City of Nanaimo has outline a few ‘priority’ invasive plants which are actively removed from parks and other public land.

Priority Invasive Plants

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Invasive Animal Species in Nanaimo

Nanaimo also has several invasive animal species, however, removal of these species can be more complicated than removal of invasive plant species due to social and ethical factors.

frogThe American Bullfrog eats native frogs, outcompetes them for food, and spreads infectious diseases like chytridiomycosis, driving over 100 native frog species to extinction. Several community-based eradication committees have been established across the island to rid local ponds of the American Bullfrog, however, work parties have had limited success removing them entirely from local areas.¹

RabbitEasternCottontail_003While the eradication of the American Bullfrog is met with little opposition, removal of other (often cuter) invasive animals is more difficult. The invasive Eastern Cottontail Rabbit is able to drastically change ecosystems. Rabbits damage plants, including oak seedlings and wild flowers. They kill shrubs and trees by eating the bark and exposed roots, and can overgraze an area. With an increase in rabbits, predators prosper, disrupting nature’s balance.  They can also carry parasites and diseases such as tularaemia (“Rabbit Fever”) that can infect humans.

The University of Victoria was faced with a public relations disaster when it tried to cull over a thousand rabbits that had taken over the campus. Due to public pressure, the university relocated most of their rabbits, and culled the rest to maintain a population of only about 200 animals.²

A few other invasive animal species:


Introduced Species

Introduced Plants in Nanaimo

Nanaimo is also home to several types on non-invasive introduced plants. Several of these plants are found in people’s gardens, as brightly coloured and fragnant flowers have been brought over from all over the globe.

The Japanese Water Iris is believed to have been brought over from Japan many years ago. The Japanese Water Iris’s vibrant purple leaves make it a beautiful addition to any garden, while not negatively impacting any native plant or animal species.

The Invasive Species Council of BC has developed a list of ‘alternative plants’ which are ‘expert recommended’ exotic or native plants for gardeners to choose instead of invasive plants.  See the list here.

Introduced Animal Species in Nanaimo

Non-invasive introduced animal species include most types of livestock which are grown and consumed in British Columbia, as well as many companion animals. What decides whether an animal is invasive or not is reflected in the benefits and enjoyment we receive from alien species as well as the potential economic and environmental costs when they become invasive and result in undesirable outcomes.


Black Oystercatcher eating a Varnish clam

Some animal species introduced to BC may be actually beneficial to the ecosystem. The Varnish clam is an alien species originally from Korea, China and Southern Japan that is suspected to have been introduced into the Pacific coastal waters via ballast water from ships. Recent studies suggest that the Varnish clam may be an important food source for a species of high conservation concern, then Black Oystercatcher.

Emily Tranfield, a VIU student writes in her research project:

“Black Oystercatchers appear to exploit the varnish clams and may be able to obtain a substantial part of their daily energy requirements from this invasive species. The indirect effects of this subsidy on either marine or terrestrial food webs remain unknown and could be the subject of further studies.”


How You Can Help

The Invasive Species Council of British Columbia has several programs to encourage the community to help stop the spread of invasive plants and animals:


PlantWise is a consumer and industry education program designed to cdd_logo_text_09_05_12build understanding of the problems caused by invasive species, increasing demand for non-invasive plants, and to support the horticulture industry’s transition to becoming free of invasive species.

Clean Drain Dry

Clean Drain Dry encourages you to ‘clean drain dry’ all boats and equipment to help reduce the spread of invasive plants and organisms to BC waters.

Don’t Let it Loose

Water gardeners, aquarium and terrarium owners can select from a variety of aquatic plants, invertebrates, reptiles and fish. Unfortunately, some of these Dont-let-it-loose-logo-webexotic species have the potential to become invasive. Pets that become too much for an owner to care for are sometimes let loose into nearby water or woods—Don’t Let it Loose!

Play Clean Go

PlayCleanGo is an education and outreach campaign for outdoor recreationalists that encourages outdoor recreation while protecting our valuable natural resources. The objective is to slow or stop the spread of terrestrial invasive species (those that occur on land) through changes in our behaviour. PlayCleanGo is designed to foster actions that interrupt recreational pathways of spread for invasive species.  ISCBC is a PlayCleanGo partner, a program launched with a group of interagency partners in Minnesota, including the University of Minnesota Extension, Minnesota departments of Agriculture and Transportation, and Explore Minnesota, the Minnesota Department of…learn more

Buy it Where you Burn itDontMoveFirewood_PlayCleanGo_web

BC’s forests are threatened by non-native insects that can kill large numbers of trees, and new infestations of tree-killing insects and diseases are often first found in campgrounds and parks. Two examples of introduced insects—emerald ash borer and Asian longhorned beetle (PDF poster)—are wood-infesting species that can be transported long distances in firewood. Once transported into new areas, these insects can become established and kill local trees. One of the most important things we can do to protect trees is stop moving invasive pests and diseases to new areas on firewood. …learn more


Invasive species are threatening BC’s aquatic and riparian ecosystems, such as streams, lakes, and wetlands, and the species that rely on them. They spread alarmingly fast between waterbodies and can create lasting ecological and economic damage, especially to the recreational areas that we enjoy.

Community Weed Pulls

The Communities Pulling Together program enables volunteer groups to learn about and remove local invasive plants. Participants gain hands-on experience by helping to remove an invasive plant infestation in their community.

Invasive Alien Plant Program (IAPP)

Managed by the Ministry of Forests and Range (MOFR), IAPP is a web-based database that stores information on comprehensive invasive plant data in BC.

Spotters Network

You are invited to join the growing team of “Spotters” who are part of BC’s Spotter’s Network! Volunteers around the province are actively helping to report and respond to invasive species—and you can too!

Invasive Species Training

ISCBC, in partnership with TransCanada Corporation, is pleased to announce a new training program on invasive species in BC, with a special focus on BC’s North, titled “Invasive Species in BC—You Can Help Prevent the Spread!” This one day workshop, along with one additional module, will support concerned citizens and natural resources workers across BC’s North in identifying key invasive species, understanding their huge economic and environmental impacts, and learning how they can be prevented and managed.

Together in Action Awards

In 2015, the Invasive Species Council of BC initiated an engaging and exciting ‘Together in Action’ Awards Program to celebrate the work of those preventing the introduction of invasive species, or reducing their impact. The ISCBC’s annual forum is the ideal opportunity to present awards to those groups and individuals who have made an outstanding contribution in the past year. At the 2015 Forum in January, the ISCBC announced the first 2015 award winners and celebrated all of the nominees. Congratulations to all award winners!

Hot Spots

The Hot Spots program was a highly successful two-year program (2008-2011) that jump-started business development and employment in over 30 different communities across BC in 2010.

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