Rabbits buffer dung beetle declines following the abandonment of traditional agropastoral practices in a semi-arid...

Although difficult to carry out, long-term studies are essential for understanding the trajectories of biological systems and organisms in response to environmental change. Despite becoming more common, studies providing interannual data on insect populations remain rare, although they have confirmed widespread insect declines. In the case of dung beetles-a key group among decomposers-no existing studies provide continuous annual data over a period exceeding 20 years. This study describes changes in species richness, abundance, biomass and assemblage composition of dung beetle assemblages across 16 sites in a semi-arid region of central Spain, sampled on 9 occasions over 26 years. The results reveal a marked regional decline in these metrics, evident in two-thirds of the sites, three-quarters of the recorded species and the main functional groups. This decline coincided with the disappearance of traditional sheep grazing in the region and involved a 50% reduction in species richness and a 65% decrease in both abundance and biomass. Despite interannual fluctuations, a slight rebound in the populations of some species was observed approximately 17 years after the decline in trophic resources. The presence of rabbit dung and the distance from urban centres emerged as key factors that may help to mitigate biodiversity loss in these assemblages following the abandonment of traditional livestock grazing. It is suggested that, after rural depopulation, wild mammals-particularly rabbits-may act as a reservoir, facilitating the recovery of dung beetle populations and preventing local extinction.