Mining the rare earth elements (REEs), critical minerals important in technological applications, introduces concerns regarding the release of airborne REEs and associated radionuclides (U, Th) to surface environments. Despite expanding REE mining development, atmospheric REE sources and depositional pathways remain poorly characterized, particularly in northern regions lacking pre-disturbance baseline data. To establish a biomonitoring framework in the Canadian subarctic (Nunavik, Quebec), we analyzed 50 elements in two dominant fruticose taxa (Cladonia stellaris, Stereocaulon paschale) and soil substrate over six sampling years prior to REE mining. Mixed-effects models revealed significant spatial variability in elemental concentrations (∼40–90%), with species effects predominantly emerging among essential nutrients (Cu, K, Mn, Rb, S, Zn). Lichen-soil relationships indicated REE bioaccumulation was independent of underlying soil geochemistry and instead co-varied with radionuclides (U, Th) and lithogenic elements (Al, Fe, Ti, V, Co), characteristic of regional to long-range geogenic atmospheric transport, likely facilitated by wind erosion across the subarctic landscape. Near localized pollution sources, C. stellaris exhibited distance-based gradients in Ba and REEs within 1 km and captured As, Pb, Cd, and Cr enrichments 10-times background levels, indicating limited anthropogenic inputs consistent with transport emissions, waste incineration, and road dust resuspension. Washed samples retained the majority of REEs, suggesting accumulated REEs are strongly surface-bound or partially internalized, rather than loosely adsorbed. These results establish dominant subarctic lichens as effective atmospheric biomonitors, providing a pre-disturbance geogenic baseline and demonstrating their application to evaluating the potential mobilization of airborne contaminants, including REEs, U, and Th, surrounding future mining activities. Keywords: REE; Uranium; Thorium; Northern ecosystems; Bioaccumulation; Radionuclide; Lanthanide.