We’re here to answer all your top questions! In this blog post, we’ll dive into 5 commonly googled questions about invasive species.
1. Do Invasive Species Occur Naturally?
The short answer? No, they don’t typically occur naturally. Invasive species are species that are introduced to an area, and they can cause all sorts of problems. The main way that invasive species are introduced to a new place is by us, humans.
Some plants have been intentionally planted in gardens or sold (even internationally!) as pretty ornamentals, but people often don’t realize these plants are invasive until after they’ve already established.
Some human-caused introductions are accidental. A good example is invasive insects, such as the emerald ash borer or the spongy moth. These pests can unknowingly be spread by people moving firewood that carries the eggs or larvae of these unwanted insects.
A spongy moth caterpillar on a tree trunk. Photo credit: Karla Salp, Washington State Department of Agriculture, Bugwood.org
Whether intentional or accidental, most introductions are ultimately caused by humans and are not natural. If it weren’t for the influence of humans, it is unlikely that invasive species would be nearly as widespread as they are now.
If you want to dive more in-depth into what it means for a species to occur naturally, check out our blog post: How do we define native species?
2. How do invasive species spread?
Invasive species spread through a variety of manners. Like all organisms, they reproduce — plants spread through seeds or vegetative reproduction, while animals reproduce sexually.
There are a few environmental factors that help invasive species spread:
- Wild animals can eat seeds or pick up burs and bring them to new locations.
- Wind dispersal can blow some seeds to new areas.
- Water transport can spread invasive plant parts or aquatic animals to new areas. Rivers can transport invasive species over long distances downstream, and flooding can also increase the risk of spread by allowing water to reach more areas inland.
Rivers can bring invasive seeds or plant parts downstream to establish in new locations.
Humans can exacerbate the distance and rate of spread by introducing more vectors of spread. Humans can transport invasive plant and animal material much further than they would typically be able to travel; for example:
- Vehicles and boats can carry invasive species over long distances when mud, plant fragments, or small animals hitch a ride on tires, trailers, or hulls.
- Soil transport can bring contaminated soil from one location to another, allowing infestations to take root in completely new areas.
- Gardening may allow invasive species to establish if gardeners plant invasive species without knowing.
- Wood transport can increase the risk of bringing invasive insects from one area to another if their eggs or larvae are hidden in the wood bundles.
Check out all the different vectors of spread here.
3. Why are invasive species a problem?
Invasive species are a problem because they have negative impacts on the areas where they are introduced. Their negative impacts can be broken down into three general categories:
Economic Impacts
- Invasive species can cause huge economic costs for landowners, businesses and governments.
- Some invasive species, such as Japanese knotweed, can grow through concrete and cause structural damage, resulting in significant repair costs.
- If invasive species establish on farmland, they can form monocultures that greatly reduce crop yields. The estimated cost of crop losses for the B.C. agriculture industry is over $50 million annually.
- It is also costly to manage, control, and remove invasive species, which incurs labour and equipment costs.
Environmental Impacts
- Invasive species are the second biggest threat to biodiversity, after habitat loss.
- They don’t have any control mechanisms (like disease or predators), and this allows them to spread rapidly, outcompete native species, and often form monocultures.
- In some cases, extreme weather events can exacerbate the spread of invasive species, and invasive species can also exacerbate the occurrence of extreme weather events.
Orange hawkweed forms dense monocultures that outcompete native species.
Societal Impacts
- Some invasive species are toxic and can harm human health. For example, touching the sap of giant hogweed can lead to severe burns, and the berries of spurge laurel are extremely poisonous.
- Invasive species can also block sightlines and obstruct access to recreational sites.
Read more about the impact of invasive species here.
4. Where do invasive species come from?
Invasive species come from all over the world! Any species that is invasive to B.C. is native to somewhere else in the world. Here are a few examples:
- Orange hawkweed is native to Europe.
- Scotch broom is native to Scotland.
- Himalayan balsam is native to the Western Himalayas.
- English holly is native to the British Isles, as well as Southern and Central Europe
- Tree of Heaven is native to China and Taiwan
As suggested in its name, Scotch broom hails from Scotland.
5. What are the worst invasive species in the Sea to Sky region?
It depends on what we mean by “the worst invasive species”! Moreover, the Sea to Sky region’s landscapes and ecosystems are so diverse that we can’t just give one answer.
Below, we present some species that we consider high-priority due to the damage they cause to the environment or human health.
In Squamish, the worst invasive species is knotweed.
- Knotweed forms dense monocultures, grows through concrete, and increases flood risk due to increased soil erosion.
- Check out Squamish’s Most Wanted to learn more about the worst species impacting Squamish.
In Whistler, the worst invasive species are Scotch broom and yellow flag iris.
- Scotch broom is highly flammable, and its seeds can remain dormant for more than 50 years, which makes it extremely difficult to eradicate.
- Yellow flag iris damages fish habitats and easily spreads downstream from waterbodies.
- Thankfully, SSISC has worked hard to reduce the populations of both these species within Whistler, so they’re not very common nowadays.
In Pemberton, the worst invasive species is wild parsnip.
- Wild parsnip is toxic to humans and animals, and there is a large population present in the Mt. Currie area.
Yellow flag iris is a provincially noxious weed and a high priority species in the Sea to Sky region.
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