Widespread tree-cover gains across Europe over two decades were strongest in regions of agricultural retreat

Abstract Changes in canopy cover and spatial arrangement of trees can strongly influence ecosystem functioning and biodiversity. Yet, long-term, continent-wide assessments have largely focused on tree cover alone. Here, we develop an integrated framework quantifying tree cover, connectivity, and tree-cover heterogeneity, and assess their dynamics across Europe from 2001 to 2021. We further examine how trends in these metrics are associated with forest management regimes, agricultural retreat, natural disturbances, climate and human activities. The most widespread combination of structural trends, covering 23% of the analyzed area, combined increasing tree cover and connectivity with declining heterogeneity. At the landscape scale, 0.25° grid cells with larger fractions of former cropland tended to exhibit more positive trends in tree cover and connectivity and more negative trends in heterogeneity. These contrasting trajectories show that tree-cover gains do not necessarily coincide with increasing tree-cover heterogeneity, with potential benefits for carbon accumulation and forest-associated species but possible costs for species dependent on open or structurally heterogeneous habitats.