Passive rewilding in the Cantabrian Mountain Range: scientific basis and challenges for socio-ecological sustainability

Abstract

Passive rewilding means the spontaneous regeneration of ecosystems after the abandonment of human land use. It may represent an opportunity to recover biodiversity and ecosystem services under global environmental crisis, but may also entail declines of certain species, changes in disturbance regimes and losses of cultural values. In this review, we integrate the current knowledge on the ecological patterns and processes of passive rewilding in the Cantabrian Cordillera (NW Spain) in order to provide a primary basis of scientific evidence for developing environmental management guidelines. There is a main pattern of expansion of forest and shrubland in areas previously occupied by rangeland pastures and crop fields, which involves changes in landscape structure, richness and composition of ecological communities, carbon accumulation in biomass and soil, and the provision of different ecosystem services. Among the driving processes of rewilding are: 1) organism dispersal, which conditions ecological succession and species persistence at the regional scale; 2) trophic dynamics, whose functioning depends on the occurrence of large apex predators and the landscape structure; and 3) ecological disturbance regimes, currently dominated by the dynamics of cattle ranging and anthropogenic fire. Due to its ecological effects, passive rewilding emerges as an effective strategy to restore the structure and key functions of forest and shrubland ecosystems in the Cantabrian Cordillera. The social sustainability of this process will depend on its compatibility with current land use for cattle ranging and ecotourism, for which different environmental, agricultural and forestry policies are now available.