Afforestation on Nordic grasslands: Trade-offs and synergies for climate mitigation, biodiversity, and ecosystem services

Afforestation of abandoned grasslands has been proposed as a global climate mitigation strategy, but the climate benefits of tree planting on grasslands remain contentious. Studies worldwide indicate that grassland soils have large potential for carbon storage, while semi-natural grasslands often support high biodiversity and provide multiple ecosystem services, including grazing resources, pollinator habitats, and aesthetic landscape values. In boreal and alpine regions of the Nordic countries, grasslands sustain extensive low intensity farming, contributing to milk and meat production and enhancing food self-sufficiency. Evaluating the impact of afforestation on climate mitigation requires a comprehensive assessment that, in addition to the carbon balance, considers both geophysical forcing (such as albedo and evapotranspiration) and the broader landscape-level effects on biodiversity in displaced ecosystems. The article postulates for policy to be inclusive of both biodiversity preservation and climate change mitigation. Such an approach should be grounded in evidence-based assessments of the ecological and climate-related impacts of afforestation on the biodiversity of semi-natural grasslands.