19th-century afforestation policies have predisposed mountain slopes to forest expansion under recent climate warming in the southern French Alps

Abstract

This interdisciplinary study investigates the long-term interplay between forests, human societies, and climate in Abriès-Ristolas (Queyras massif, southern French Alps) over the past 200 years. Drawing on archival records, dendrochronology, satellite-derived vegetation indices, and climate data, we trace the historical legacies that have shaped contemporary land cover and forest dynamics. Our findings show that recent forest expansion and land greening – often attributed solely to climate change – are also the outcome of 19th-century socio-economic shifts and environmental policies. Specifically, we find that spatial variability in greening trends aligns with the historical structure of cadastral parcels, highlighting persistent land-use effects. The 1860 Mountain Reforestation Law, locally implemented by an 1864 decree, combined with rural depopulation and a decline in pastoral activities, significantly reduced anthropogenic pressure, facilitating natural forest regeneration in this area. These historical transformations have predisposed the landscape to continued forest expansion, with recent climate warming further amplifying this trajectory over the past four decades. This case study underscores the importance of incorporating land-use legacies into interdisciplinary approaches for understanding present-day ecological change.