The impact of pastoral activities on animal biodiversity in Europe: A systematic review and meta-analysis

Land-use changes, both in terms of land abandonment and intensification, have led to fragmentation and loss of traditional agricultural habitats. Extensive grazing is among the forms of land use that have undergone the greatest changes. This represents one of the main threats to biodiversity; consequently, a comprehensive overview about the impacts on the biodiversity of changes that are happening in pastoral activities is needed. Moreover, a clear picture of the most widely studied geographical areas, habitats, and taxonomic groups needs to be developed in order to understand the situation. In this framework, we carried out a systematic review and a meta-analysis of the publications related to the impacts of pastoral activities on animal biodiversity in Europe. We analysed 223 articles by searching the ISI Web of Science platform and combining keywords related to pastoral activities and biodiversity indicators, applying a vote count approach, i.e. simply dividing articles into categories depending on their results (non-significant ones, significant positive results, significant negative ones). Moreover, we conducted a meta-analysis on 33 articles, selecting those focusing on Arthropods (the most studied taxa). To understand the main gaps in this scientific topic, we focused on: i) the identification of the geographical, environmental, and temporal structure of the studies; ii) the description of the main target groups used as bio-indicators; iii) the comparison of different management practices (overgrazing, traditional, agri-environment schemes - AESs), plus land abandonment, to determine which is the best for biodiversity conservation and to evaluate the effectiveness of AESs. There was a bias towards lowlands in comparison to uplands, as well as a lack of long-term studies. Plants were more sensitive than animals to grazing changes. Arthropods' orders are the taxa used most frequently as indicators, in comparison with vertebrates, especially birds. We identified a generalised negative impact of overgrazing in all the habitats and geographical areas, apparently except in mountainous shrubland. Conversely, land abandonment resulted in a negative influence on biodiversity only in the mountainous areas of southern Europe (underlining the important role of traditional activities), whereas short term abandonment had a beneficial role in central Europe, where overgrazing was more widespread. The meta-analysis suggested that arthropod richness was higher in short to mid-term abandoned pastures than under either extensive or intensive grazing systems. Finally, the effectiveness of AESs for conservation purposes was not confirmed by the vote count approach, whilst meta-analysis detected a positive effect for Arthropods of these same management practices when compared to overgrazing. We highlight a lack of data on AESs, especially when compared with traditional extensive grazing or abandonment. Our findings suggest that AES seems to effectively mimic traditional pastures, contrasting overgrazing, which is one of its main goal. Since AES have a strong potential in influencing sustainable management and promoting biodiversity conservation, the European Union should focus on the most effective and well targeted AES based on research, and further studies will be necessary to continuously assess their effect.