Impact of rural depopulation on the community of vertebrate scavengers in mountain areas

    The natural revegetation derived from the abandonment of the rural environment and its traditional agro-pastoral practices reduces the efficiency of carrion consumption by the guild of scavenger vertebrates and increases the persistence of carrion and the potential health risks derived from it.


    The rural environment in Europe has been shaped by traditional land uses, fundamentally linked to agricultural, livestock and forestry use, giving rise to cultural landscapes that offer a multitude of ecosystem services and that have a high value for the conservation of biodiversity. Unfortunately, these cultural landscapes and their ecosystem services have been slowly disappearing since the mid-XNUMXth century due to socioeconomic changes, the modernization and intensification of traditional agro-livestock systems and the widespread depopulation of the countryside.

    Specifically, the processes of plant succession –first through scrub and then through forests– without human intervention (“passive rewilding”) derived from the abandonment of rural areas are associated with a cascade of socioeconomic, landscape and biological consequences whose ecological repercussions are still unknown.

     

    Especially in mountain areas, such as the Pyrenees, traditional agricultural and livestock practices have favored biodiversity by promoting the spatial heterogeneity of the landscape in mountain agro-ecosystems (Photo: Antoni Margalida).

    Scientists from the Research Group in Game Resources and Wildlife Management of the Instituto de Investigación en Recursos Cinegéticos (IREC – CSIC, UCLM, JCCM), the University of Lleida, the University of Alicante and the Pyrenean Institute of Ecology (IPE – CSIC) have analyzed the ecological consequences of the abandonment of rural areas on the structure and function of the guild of scavenging vertebrates, taking as study area the Pyrenees.

    Thus, scientists have evaluated the richness and abundance of scavenger species and the efficiency of carrion consumption in a Pyrenean agro-ecosystem subjected to processes of rewilding or landscape closure due to widespread expansion of woody vegetation (“woody encroachment”) after the abandonment of traditional lands and grazing practices, through the monitoring of 178 carrion in three types of landscapes: open, scrub and forest.

    The results obtained suggest that the type of landscape was the main determinant of the dynamics of carrion consumption. Total and average scavenger richness was similar in open and scrubland landscapes, while forests contained the lowest number of scavengers, mainly mammals. Unlike mammals, detection and consumption of carrion by avian species decreased as vegetation cover increased, especially for obligate scavengers, ie vultures.

     

    These are some of the most frequently recorded scavenger species in the three mountain landscapes studied in the Pyrenees: Open landscape (AD), scrubland landscape (EG) and wooded landscape (HJ). A: Griffon Vulture; B: Black Vulture, Egyptian Vulture and Griffon Vulture; C: bearded vulture; D: Red Kite; E: Egyptian vulture; F: Golden eagle; G: Black Vulture and Griffon Vulture; H: wild boar; I: Raven; J: Fox.

    Open landscapes favored faster detection and exploitation of carrion due to efficient consumption by vultures and attracted greater numbers of scavengers.. Carrion size did not influence detection and consumption times, although it did affect richness, abundance, and consumption rates. Consumption rates were higher in open landscapes and were strongly associated with the presence of the Griffon vulture (Gyps fulvus).

    The scientists found that griffon vultures influenced scavenging dynamics through facilitation processes, especially for other threatened scavenger bird species. However, woody encroachment and consequent landscape closure could reduce the scavenging role of this species, while favoring facultative scavenging species, particularly mammals. Finally, the results of this research work highlight the important regulatory service of griffon vultures, mediated by landscape characteristics, in reducing the persistence of carrion in natural spaces.

     

    Percentage of carrion consumed by the main species of obligate and facultative scavengers recorded in open, scrubland and wooded landscapes in the Pyrenees. For each species, the significant differences between types of landscape are shown (values ​​of p) as well as the preference for larger carrion (circles).

    This study highlights that The changes in the composition and structure of the landscape associated with the abandonment of the rural environment and its traditional agro-pastoral practices can alter the scavenger functionality of the scavenger community in mountain areas., reducing the efficiency of the guild and increasing the persistence of carrion in the field and the derived health risks. The authors recommend the need to preserve open areas by promoting traditional agricultural and livestock practices to mitigate the impact of rural depopulation on the functionality of the guild of scavengers.

    The scientific publication of this research is available at: