H latitude regions around the world are experiencing particularly rapid climate change. These regions include the 625 million ha North American boreal region, which contains 16% of the world’s forests and plays a major role in the global carbon cycle (Brandt et al. 2013). Boreal ecosystems are particularly susceptible to rapid climatedriven vegetation change initiated by standreplacing natural disturbances (notably fires), which have increased in number, extent, and frequency (Kasischke and Turetsky 2006; Hanes et al. 2018) and are expected to continue under future climate change (Boulanger et al. 2014). Such disturbances will increasingly complicate species persistence, and it will therefore be critical to identify locations of possible climatechange refugia (areas “relatively buffered from contemporary climate change”) (Morelli et al. 2016). These “slow lanes” for biodiversity will be especially important for conservation and management of boreal species and ecosystems (Morelli et al. 2020). Practically speaking, the refugia concept can translate into specific sites or regions that are expected to be more resistant to the influence of climate change than other areas (“in situ refugia”; Ashcroft 2010). Refugia may also encompass sites or regions to which species may more readily retreat as climate conditions change (“ex situ refugia”; Ashcroft 2010; Keppel et al. 2012), as well as temporary “stepping stones” (Hannah et al. 2014) linking current and future habitats. In addition to areas that are climatically buffered, fire refugia – “places that are disturbed less frequently or less severely by wildfire” (Krawchuk et al. 2016) – may also play key roles in promoting ecosystem persistence under changing conditions (Meddens et al. 2018). Previous examinations of climatechange refugia have primarily emphasized external, terrainmediated mechanisms. Factors such as topographic shading and temperature inverClimatechange refugia in boreal North America: what, where, and for how long?

Abstract Over the last decade, considerable progress has been made in developing vulnerability assessment tools and in applying these methodologies to identify and implement climate change adaptation approaches for forest ecosystems and forest management organizations in Canada and the United States. However, given that adaptation processes are in early stages, evaluation of approaches across agency, organizational, and geographic boundaries is critical. Thus, we conducted a qualitative comparison of three conceptual frameworks for climate change vulnerability assessment and adaptation efforts in the Canadian and United States forestry agency contexts. We focus our comparison on components of the conceptual frameworks, development process, intended users, similarities and differences in institutional contexts (geographic and organizational), and implementation. Finally, we present case studies to illustrate how the frameworks have been implemented on the ground and in different contexts. Despite different trajectories of development, the Canadian and US forest agencies have developed similar conceptual frameworks for vulnerability assessment and adaptation. We found that key components of the conceptual frameworks included: establishing a science-management partnership; evaluating current forest conditions and management objectives; conducting detailed science-based vulnerability assessments; developing adaptation approaches and on-the-ground tactics; implementing adaptation tactics; and monitoring outcomes and adjusting as needed. However, the contexts in which these frameworks are implemented vary considerably within and between countries, mostly because of differences in land ownership, management norms, and organizational cultures. On-the-ground applications, although slow to develop, are beginning to proliferate, providing examples that can be emulated by others. A strategy for accelerating implementation of adaptation in Canada and the United States is suggested, building on successes by federal agencies and extending to public, private, and crown lands.