Perspectives: Cessation of traditional pruning threatens communal dehesas of deciduous oaks in the Western Mediterranean

Open woodlands ( dehesas ) conformed traditional agrosilvopastoral systems in the Western Mediterranean. Communal deciduous oak dehesas were essential to rural economies for centuries. They were managed through tree pruning and grazing, enabling the coexistence of pasture and tree cover. The singular nature of this ecosystem fosters the persistence of ancient trees and species associated with old growth forest, even within intensively managed ecosystems. However, unlike large private evergreen oak dehesas , smaller communal deciduous dehesas remain largely unprotected, despite being the major reservoir for old growth forest species: fungi, mosses, lichens, saproxylic invertebrates, and cavity-dwelling vertebrates. The abandonment of traditional management and pruning cessation has triggered scrub encroachment, biodiversity loss, and the structural decline of old trees. These woodland ecosystems could aid the recolonization of mature forests taxa in the expanding young forest surface. However, they are vanishing unnoticed due to their small size, isolation, and lack of formal recognition. Their preservation is urgent, yet hindered by insufficient data, lack of protection frameworks, and disappearing traditional knowledge. Communal deciduous oak dehesas exemplify how cultural landscapes can support old-growth biodiversity, aligning with EU restoration goals. • Deciduous oak communal dehesas harbor ancient trees with high biodiversity. • Pollarding favored tree preservation and the creation of old-growth characteristics. • A majority of old growth forests fauna and flora is preserved in these dehesas. • Traditional management cessation is leading to tree mortality and biodiversity loss. • Preservation of these ecosystems requires active measures.