The Combined Impact of Climate Change & Invasive Species

Climate change makes environments more vulnerable to invasions, while invasive species can worsen the impacts of climate change. These two stressors create complex social, economic, and environmental challenges.

Invasive Species Worsening Climate Change

field of wheat

ECOSYSTEM RESILIENCE

Invasive species make ecosystems more vulnerable to climate change. For example, invasive plants in warming and drying habitats can increase fuel for wildfires, leading to more frequent and severe fires.

CARBON SEQUESTRATION

Biodiverse ecosystems are better at storing carbon in the soil, which helps mitigate climate change. However, invasive species contribute to biodiversity loss, reducing carbon storage. In fact, some invasive species thrive in environments with more carbon dioxide, creating a cycle that favors their spread and lowers the land’s ability to store carbon.

Example: Crested Wheatgrass

Crested wheatgrass, introduced to North America in the mid-20th century, now dominates prairie ecosystems in Canada and the U.S. Unfortunately, soil under this invasive plant has 25% less carbon than soil under native species, contributing to significant carbon loss.

Climate Change Amplifying Invasive Species

Ship beside an iceberg

INVASION PATHWAYS AND VECTORS

Climate change opens new pathways for invasive species. As Arctic ice melts, shipping routes are expanding, allowing invasive species to hitchhike on hulls or in ballast water to new regions. Extreme weather events, such as hurricanes, can also transport invasive species over long distances.

Example: The Northwest Passage
Historically, thick ice prevented shipping through the Arctic Ocean. However, due to climate change, the Northwest Passage has opened, creating new opportunities for species to travel between regions, both naturally and via shipping vessels.

Fish underwater with rocky bottom

ESTABLISHMENT AND SPREAD

Many invasive species in temperate regions like Canada originally come from warmer climates. As temperatures rise, these regions begin to resemble the invasive species’ native habitats, increasing their chances of survival and spread. At the same time, native species are being pushed out of their traditional ranges, making them less resistant to invaders.

Example: Brook Trout vs. Bull Trout
In the Rocky Mountains, native bull trout once had a competitive advantage in colder waters. As streams warm, invasive brook trout are now outcompeting bull trout, potentially pushing the native species to higher elevations.

Managing the Dual Threats

Invasive species that once died back during cold winters in regions like Canada may now survive year-round due to milder temperatures. This means traditional control methods, such as relying on winter dieback or herbicides, may become less effective. Additionally, some invasive species are developing increased tolerance to herbicides as carbon dioxide levels rise, and biocontrol agents may become less effective as climate changes disrupt their natural interactions.

Climate Change’s Impact on Native Species

Climate change is also forcing native species to move to new habitats in search of suitable conditions. While these shifts can create challenges, such as new interactions with other species, they are part of natural resilience and should not be confused with invasive species, which cause more harm to ecosystems.

Example: Moose and White-tailed Deer
As temperatures rise, white-tailed deer are moving northward into moose habitats, bringing parasites that are causing significant moose population declines. Meanwhile, moose are also moving north, potentially displacing caribou populations.

Deer standing in the middle of the road.

What Needs to Be Done?

3 Key Principles

To address the dual threats of climate change and invasive species, three key principles should guide research, policy, and management strategies:

Reduce

Reduce the risk of climate change mitigation exacerbating the threat posed by invasive species.

Integrate

Integrate climate projections into invasive species management.

Align

Align climate adaptation strategies with invasive species management goals.

Reduce

Reduce the risk of climate change mitigation exacerbating the threat posed by invasive species.

Integrate

Integrate climate projections into invasive species management.

Align

Align climate adaptation strategies with invasive species management goals.

2023 Wildfire Season and Future Outlook

The Impact of Climate Change and Invasive Species on Canada’s Fire Regime

Wildfires are natural disturbances that play a crucial role in forest health and renewal. However, human-induced factors such as climate change, drought, land-use changes, and the spread of non-native species have led to more intense, frequent, and widespread fires.

Wildfires near a road

The 2023 Canadian wildfire season was unprecedented

In 2023 fires burned over an area six times larger than the historical average in Canada. Experts warn that the conditions driving these extreme fire events—such as rising temperatures and drier landscapes—are likely to worsen in the coming years. As a result, Canada’s fire regime is expected to shift further, leading to more frequent, intense, and widespread wildfires in the future.

Climate Change and Wildfires

Human-driven climate change is creating conditions that fuel large-scale, intense wildfires. These include:

  • Less frequent but more sporadic summer rainfall
  • Hotter summer temperatures
  • Earlier and longer-lasting fire seasons
  • Shifts in wind patterns
  • More frequent lightning strikes
  • Drier fuels

Invasive Species and Wildfires

INVASIVE SPECIES CAN EXACERBATE WILDFIRES

Non-native plants can act as additional fuel for wildfires, making fires spread faster and burn more intensely.

Invasive forest pests like emerald ash borer, hemlock woolly adelgid, Dutch elm disease and mountain pine beetle, can cause wide-spread tree mortality. This dead wood acts as an ideal fuel for wildfires.

WILDFIRES CAN SPREAD INVASIVE SPECIES

After wildfires, disturbed ecosystems are more vulnerable to invasive species. These species can quickly colonize burned areas, outcompeting native plants and further altering the ecosystem.

Human responses to wildfires, such as staging areas (temporary locations for fire crews, equipment, and resources), fire breaks (a strip of cleared land that acts as a barrier to wildfire spread), aerial water dumping, etc. are often the largest threat for spreading invasive species associated with wildfires.

Going Forward

Understanding the impacts that climate change and invasive species have on wildfire behaviour is important for informing management decisions. Shifts in Canada’s fire regime due to climate change, as well as invasive species management strategies need to be considered when assessing and managing wildfire risk. New and traditional practices are being adopted to mitigate the impacts invasive species have on future wildfires and post wildfire environments. These practices include prescribed/cultural burns, use of biocontrol, targeted grazing, and restoration post wildfire.

Did you miss the 2024 Wildfires, Climate Change, and Invasive Species Conference?

2024 Wildfires, Climate Change, Invasive Species conference

Identifying actions to mitigate the destructive interactions between wildfires, climate change and invasive species. Hosted by the Invasive Canada.

Following record-breaking wildfire seasons across Canada and the United States, the Wildfires, Climate Change and Invasive Species conference brought together leading experts, innovators and professionals for a day of unparalleled engagement and knowledge-sharing. Over 20 speakers from across Canada and the US shared their research and expertise to an audience of over 300. Attendees represented government, practitioners, non-profits, academia, Indigenous leaders and others. Through engaging discussions, knowledge-sharing, and communication across borders, this event tackled some of the most urgent environmental challenges facing our forests and communities.