Effects of extensive livestock abandonment on the structure and composition of vertebrate scavenger assemblages

Abstract

Scavenger vertebrate communities play a crucial role in ecosystem functioning through the removal and recycling of dead animal matter (carrion). The abandonment of extensive livestock farming, often associated to rural depopulation, is driving widespread habitat transformation across large areas of Europe, particularly in mountain regions, potentially altering the ecological dynamics of these communities. In this experimental study, we evaluated the impact of extensive livestock abandonment on vertebrate scavenger communities in a mountain area of the Central System (Spain), comparing plots with and without livestock activity using small carcasses (whole feathered chickens, 0.3–1.2 kg) monitored with camera traps. We partitioned diversity across multiple spatial scales (alpha, beta, and gamma) and examined the influence of habitat type and vegetation structure on community diversity and composition.

Beta diversity (spatial variation in species composition) contributed significantly to regional diversity (gamma) of the study area, especially in grazed habitats—likely due to the spatio-temporal unpredictability of resources, which favours stochastic species assembly processes. Abandoned habitats hosted less diverse and functionally impoverished communities, driven by the loss of key functional scavenger guilds such as obligate scavengers (vultures) and apex predators (e.g., imperial eagle). These communities were also characterized by a nested structure, comprising subsets of the species found in grazed habitats, and were dominated by mesopredators and omnivorous mammals. Finally, we discuss the role of passive rewilding as a potential strategy to meet the goals of the European Nature Restoration Law, offering an alternative to traditional approaches based on active management of agricultural and forested lands