Understanding forest soil degradation in Canada: threats, indicators and knowledge gaps

Canadian forests, encompassing approximately 367 million hectares, play an important role in global biodiversity conservation, carbon sequestration, hydrological regulation, and timber production. Nevertheless, these ecosystems are subjected to degradation pressures arising from anthropogenic activities such as forestry operations and their interaction with natural disturbances, which may compromise their ecological integrity and productivity. Forest soil degradation is characterized by reduced soil quality and diminished ability to support essential ecosystem functions and services. This review identifies how the major global threats to soils, including soil erosion, organic carbon loss, biodiversity loss, nutrient mismanagement, salt accumulation, pollution, sealing and physical degradation, affect Canadian forests. Emphasis was placed on the indicators of degradation documented in scientific literature and their applicability within the context of Canadian temperate and boreal forests. We highlight challenges and critical gaps in the scientific literature surrounding both threat effects and appropriate indicators. A key challenge is the disconnect between monitoring timescales and the decadal persistence of threats. Additionally, critical spatial data gaps persist in northern regions regarding boreal soil degradation and threat impacts. Bridging these gaps requires a framework that integrates indicators and remote sensing. We conclude that shifting to a dynamic, threat-responsive monitoring system is essential for sustainable management.