Tools for assessing the risk of biological invasion under climate change

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Context Climate being one of the principal filters limiting biological invasions, the proliferation of species harmful to ecosystems, biodiversity, or society is likely to intensify with climate change. It is important to assess the risk posed by biological invasions in order to better manage their consequences. To this end, this project brought together expertise on invasive species, vascular flora biogeography, metadata management, climatic and ecological modeling, the study of phenology, functional traits and species genetics, and ecological risk analysis. Although the research focused on plant species from a perspective of natural environment protection and enhancement, many of the approaches developed, and likely many of the findings, are applicable to other taxa, including species harmful to agriculture, forestry, or infrastructure. Objectives Develop tools and knowledge to assess the risks of invasion by plant species in Québec and eastern North America as a function of climate change. Approach Selection of 228 harmful plant species, of which 40 were deemed priority species. Acquisition of georeferenced data on their occurrences and construction of a dynamic database on the distribution of harmful plants. Modeling of the current distribution of 40 species as a function of climate and projection of their potential distribution under climate change scenarios; development of detailed fact sheets outlining the invasion risk for each species. Monitoring along a climatic gradient of the phenology of two late-flowering species, common reed (Phragmites australis) and Japanese knotweed (Fallopia japonica). Results The risk of biological invasion will increase with climate change. This increased risk results from the fact that, over time, a larger portion of Québec's territory will present favorable climatic conditions for 90% of the harmful species analyzed (more territories invaded), that climatic conditions will allow the survival in Québec of at least seven new harmful species (more invasive species), and that the climatic thresholds enabling certain species to increase their fecundity in a given region will be reached (more propagules). Detailed fact sheets describing the response of each species were produced (Figure 1). They are unique in their kind in that they describe the biological and biogeographic characteristics of each species, classify them according to their harmful character, present maps of their current and future potential distribution, and analyze the invasion risk at the scale of Québec and North America as a function of climate change. The increase in propagule numbers is attributable to the fact that both species observed in the field, common reed and Japanese knotweed, show a climatic limit to the production of viable seeds in the study area. The Eurasian common reed, despite its relatively recent introduction to the continent, can adapt its phenology to the length of the growing season, which could allow it to respond rapidly to warming. Similarly, the northern limit of viable seed production for Japanese knotweed is now located in the Québec City region, approximately 500 km further north than the previously known limit on the continent (Boston, Massachusetts). Greater plant fecundity points to an increased risk of biological invasions. Implications for adaptation The knowledge and tools generated by this project can be integrated into biodiversity management and natural area monitoring plans, into the development of prevention, early detection, and control practices, into Québec policies aimed at protecting the environment and natural heritage, as well as into scientific programs on understanding the mechanisms underlying invasion phenomena.

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