Predicting Invasive Plant Response to Climate Change: Prioritization and Mapping of New Potential Threats to Alberta’s Biodiversity

Shauna-Lee Chai
Amy Nixon
Scott Nielsen
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Climate change will result in more hospitable conditions in Alberta for new invasive species. We assessed 16 potentially new invasive plant species not yet present in Alberta for their invasiveness and climate change-related risk, demonstrating one approach to considering potential consequences of climate change for new non-native plant invasions in the province.
Invasiveness was evaluated based on four attributes: ecological impact, biological
characteristics, dispersal ability and feasibility of control. Climate matching and habitat suitability modeling were used to predict potential invasion risk due to climate change in Alberta. Both approaches predicted an increase in potentially suitable climate space (climate matching) or habitat (habitat suitability modeling) in Alberta for 15 of 16 species between the historic/current climate (1961-1990) and projected future climate (2041-2070; the 2050s).
The top three new potential terrestrial invasive plant threats to Alberta’s biodiversity are giant knotweed (Fallopia sachalinensis), tamarisk (Tamarix chinensis) and alkali swainsonpea (Sphaerophysa salsula). These species received the highest invasiveness score and showed the greatest increase in suitable high risk habitat in Alberta between current and future projected climate.
Ten of the 16 species we assessed are already listed (or have been proposed for listing) on the Alberta Weed Control Act as prohibited noxious species. Two of the species we assessed have ‘not yet been assessed’ by Alberta’s Weed Regulatory Advisory Committee, globe thistle (Echinops sphaerocephalus) and European cotoneaster (Cotoneaster integerrimus), while a further four species assessed are not currently being considered by Alberta’s Weed Regulatory Advisory Committee. They
are: Syrian bean-caper (Zygophyllum fabago), gorse (Ulex europaeus), Scotch thistle (Onopordum acanthium), and Scotch broom (Cytisus scoparius). We provide suggestions for how climate change may be included in the consideration of these four, as yet unassessed, species under the Weed Control Act. The climate change risk assessment indicated a high risk of invasion in the Grasslands Natural Region. Predictive models for the 2050s suggest that the Municipal Districts of Pincher Creek, Cardston and County of Forty Mile will be the top three municipalities/counties with suitable high risk habitat for the greatest number of new invasive species. Back country areas that are of conservation importance including Wilmore Wilderness Park, Jasper National Park and Banff National Park are also at high risk of invasion by more than one new invasive species.
From a regional perspective, more southerly parts of North America, regions within France and northern Spain may represent areas from which new non-native plant threats to Alberta’s will emerge. Additionally, some regions around the world are predicted to have a higher climate match to Alberta by the 2050s than they do presently, including Newfoundland and Labrador, Turkey, Asia and Russia, which
may facilitate new invasions from these regions.
Managing new non-native species that arrive as a result of climate change can range from eradication to tolerance to acceptance, and deciding on a management response should be done on a case by case basis. Management strategies will require increased coordination across jurisdictions, and should be formulated across wider geographic areas (regional perspectives) and over longer time frames.