Ecosystem invaders: How do invasive species affect humans?

Ellen Cameron
17 July 2018

Above: A forest damaged by pine beetles, an invasive species - Image © sassy1902,

Aliens are among us!

Scientists refer to organisms in their originated zones as native species. These include plants, insects and animals that have a specific role in their ecosystem. Native species live in specific areas because they need certain environmental conditions, resources and interactions with other species.

For example, we don’t expect to see elephants in the wild in Canada. But why? Elephants do not like to live in the cold, winter conditions found in Canada. Elephants are also very big and eat up to 300 pounds of food a day! While Canada has lots of tasty food for Canadian animals, it doesn’t contain the food that elephants need. Elephants also play an important role in their native ecosystems. They clear out vegetation on plains and create new land for new plants to grow. Would an elephant be happy in Canada playing in the snow, far from its favorite foods? Probably not!

But what happens when a species ends up in an area that it’s not native to? Aliens!

Alien organisms are organisms in areas outside of their natural range. They can be introduced into the new area through humans or by a change in the environment.

Let’s look at the relationship between humans and alien species. How can human activities cause alien species, and how can alien species affect human activities?

Can humans bring in alien species?

Humans often introduce alien organisms on purpose or by accident. For example, some people may plant decorative plants in their gardens. This is an example of alien species that humans introduced intentionally. Meanwhile, some animals catch a free ride on various forms of transportation, such as boats. These are examples of alien species that humans introduced accidentally.

Did you know? Scientists believe zebra mussels arrived in Canada as stowaways on commercial boats!

Climate change and alien species

Alien species are also able to extend outside their natural range because of climate change. Human activities (such as driving cars) are contributing to climate change, and temperatures are increasing at a faster rate. This lets alien species spread to new areas.

Places that were once too cold for some species are now warm enough for them to live in. For example, the mountain pine beetle originally lived only in western North America. But due to climate change, winters are milder and summers are warmer. The mountain pine beetle has now extended north in British Columbia and is extending eastward through the Boreal forest in Alberta. This beetle is also able to fly, so it’s able to reach new regions very easily.

As you can see, invasive species don’t necessarily have to come from another country!

How do invasive species affect humans?

Alien species become a concern when they become invasive. Invasive alien species threaten an ecosystem because they can destroy resources and hurt native species. For example, invasive species threaten native species by acting as predators, parasites or competitors. Alien species don’t always directly affect humans. However, they disrupt and damage the environment. This can cause problems for human health and economy.

Did you know? Zebra mussels make it harder for native species to find the resources they need to survive and thrive.

The mountain pine beetle poses a threat to forest communities. Trees are damaged when female pine beetles make holes to lay their eggs inside the tree. When the eggs hatch, the larvae spend time feeding underneath the tree bark. Eventually, this leads to the death of the tree.

During the 1990s and early 2000s, mountain pine beetles damaged over 18 million hectares of forests in roughly ten years. That’s roughly 18 million football fields!

How to stop ecosystem invaders

The Canadian government has developed ways to help protect Canadian ecosystems from current and new invasive alien species. For example, technicians and border agents now inspect containers on ships and planes to make sure no alien species are hiding.

Did you know? Damage caused by invasive alien species is predicted to cost just under 30 billion dollars a year! $20 billion of those costs are for impacts on the forestry sector.

When alien species do get in, it’s important to detect them early on and remove them before they severely damage an ecosystem. For example, to help prevent the spread of the mountain pine beetle, provinces are burning trees that are infested with this species.

Native species often are not equipped to survive against alien species. That means it’s up to us humans to help protect our ecosystems from invaders!

Listen to Diana Six, Professor of Forest Entomology/Pathology, discuss why mountain pine beetles are so devastating:

Let's talk about it

Learn More!

Unwelcome Guests: The High Cost of Invasive Species (2015)
CurioCity by Let’s Talk Science

Invasive Species (2017)
Government of Canada

The Threat of Invasive Species (2016)


Alien Species in a Warmer World: Risks and Opportunities
Walther, G-R. et al.,Trends in Ecology and Evolution (2009)

An Invasive Alien Species Strategy for Canada (2004)
Environment Canada

Canadian Biodiversity: Ecosystem Status and Trends (2010)
Federal, Provincial and Territorial Governments of Canada

Invasive Species (2017)
Canadian Food Inspection Agency

Mountain Pine Beetle (2016)
Natural Resources Canada

Mountain Pine Beetle (2015)
Natural Resources Canada

Mountain Pine BEetle (Fact Sheet) (2017)
Natural Resources Canada

The Introduction and Spread of Zebra Mussels in North America (1994)
O’Neille, C.R., Proceedings of The Fourth International Zebra Mussel Conference

African Elephants: Strong, Smart but Vulnerable (2018)
World Wildlife Foundation

Elephant (2018)
African Wildlife Foundation

Ellen Cameron

I grew up next to Lake Ontario and have always been interested in water because of this. During my BSc I gravitated towards ecology and botany courses. Now, pursuing my PhD at the University of Waterloo, I get to combine my love for water, ecology and botany by working in the field of phycology (the study of algae). I spend all my free time exploring trails with my Newfoundland dog, Freddie.

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