In October, the Sea to Sky region was hit by an atmospheric river, where the region saw more than 100 mm of rainfall in less than 48 hours.
This extreme weather event is just one example of the growing impact of climate change. Scientists predict that extreme weather events will become more frequent in the years ahead, raising an important question: Can invasive species make a bad weather event worse? How?
Extreme weather events increase the spread of invasive species
According to the Invasive Species Centre, extreme weather events – such as the atmospheric river we experienced last month, or the widespread flooding in 2021 – can stress native species and create opportunities for invasive species to establish in new areas. Because invasive species are often more adaptable to a wide range of conditions and often thrive in disturbed areas, they may be better equipped to survive extreme weather than native plants and animals.
Flooding, in particular, can help spread invasive species, as many plant seeds are carried by water. For example, the seedpods of yellow flag iris can remain afloat for up to seven months, allowing them to travel long distances along watercourses and establish in new locations.
Yellow flag iris grows along waterways, and high-water events can help its seed spread downstream.
Invasive species exacerbate the impacts of extreme weather events
Invasive species can intensify the impacts of extreme rainfall events by increasing flood risk. Some invasive plants, such as smallflower touch-me-not or Himalayan balsam, can cause erosion, as their roots are too shallow to hold onto the soil properly. Other plants, like Japanese knotweed, also cause erosion as their roots lack well-developed hairs required to stabilize water-logged soil. This erosion leads to sediment buildup downstream and makes the remaining soil less able to retain water, further increasing the risk of flooding.
Himalayan balsam has shallow roots that can increase erosion.
Invasive species can also increase flood risk by clogging rivers and stream channels with their plant matter. For example, yellow flag iris forms dense mats that trap sediment, obstructing water flow.
So… now what?
Not only can extreme weather events increase the spread of invasive species, but invasive species increase the impact of extreme weather events. These phenomena form a feedback loop: more invasive species might lead to more flooding, more flooding might lead to more invasive species, and so on.
One thing we can all do is help prevent the spread of invasive species.
How can we stop this feedback loop?
- Play Clean Go: clean your gear for plant parts and seeds between adventures.
- Be Plantwise: make informed choices about common invasives to avoid and alternative plants to use in your garden.
- Report invasive species: if you see any invasive species, please report them to us so we can manage their spread.
- Familiarise yourself with invasive species: learn more about invasive species, how they spread, and their impact.
Learn more:
References:
- Canadian Council on Invasive Species, National Invasive Species and Climate Change Network
- Government of Canada, The science of climate change
- Invasive Species Centre, Climate change
- Northeast Regional Invasive Species and Climate Change Network, “Double Trouble: Understanding risks from invasive species + climate change”
- Northwest Regional Invasive Species and Climate Change Network, Webinar: “Itadori knotweed (Reynoutria japonica) [Japanese knotweed] and climate resiliency”
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