Vulnerability of Canadian forests to invasive insects under climate change

Invasive insects threaten the resilience and sustainability of Canadian forests, but we lack a comprehensive national perspective on the extent of this vulnerability. We assessed Canadian forest exposure to invasive pests by quantifying host biomass intersecting with recent (1981-2010) and near-future (2021-2040) climate niches of 14 invasive insects. Of the 37 most abundant tree species in Canada, 24 were affected by at least one of the 14 focal pests. We combined spatial assessments of exposure and outbreak severity to create an integrated spatial portrait of vulnerability. Under current conditions, 3.2 billion tonnes of tree biomass could be exposed to at least one of these pests; this is projected to increase to 13.6 billion tonnes of biomass within two decades. Two vulnerability hotspots were identified: north-central British Columbia near the BC–Alberta border and the St. Lawrence Seaway near the U.S. border. To highlight the importance of surveillance and early eradication programmes, we show that a re-invasion of the Asian longhorned beetle (Anoplophora glabripennis) into Canadian forests would put six additional tree species and 3.1 billion tonnes of tree biomass at risk. This nation-wide view aims to support risk assessments, guide the prioritization of monitoring efforts, and inform adaptive forest management.