Abstract
Grazing extensification and intensification are among the main problems affecting European grasslands. We analyze the impact of grazing intensity (low and moderate) and the use of veterinary medical products (VMPs) on the dung beetle community in the province of Pesaro-Urbino (Italy). Grazing intensity is a key factor in explaining the diversity of dung beetles. In the case of the alpha diversity component, sites with a low level of grazing activity—related in a previous step to the subsequent abandonment of traditional farming—is characterized by a loss of species richness (q = 0) and a reduction in alpha diversity at the levels q = 1 and q = 2. In the case of beta diversity, sites with a different grazing intensity show remarkable differences in terms of the composition of their species assemblages. The use of VMPs is another important factor in explaining changes in dung beetle diversity. In sites with a traditional use of VMPs, a significant loss of species richness and biomass is observed, as is a notable effect on beta diversity. In addition, the absence of indicator species in sites with a historical use of VMPs corroborates the hypothesis that these substances have a ubiquitous effect on dung beetles. However, the interaction between grazing activity and VMPs when it comes to explaining changes in dung beetle diversity is less significant (or is not significant) than the main effects (each factor separately) for alpha diversity, biomass and species composition. This may be explained if we consider that both factors affect the various species differently. In other words, the reduction in dung availability affects several larger species more than it does very small species, although this does not imply that the former are more susceptible to injury caused by the ingestion of dung contaminated with VMPs. Finally, in order to prevent negative consequences for dung beetle diversity, we propose the maintenance of a moderate grazing intensity and the rational use of VMPs. It is our view that organic management can prevent excessive extensification while providing an economic stimulus to the sector. Simultaneously, it can also prevent the abuse of VMPs.
Highlights
Land use changes play a pivotal role in the loss of biodiversity (Sala et al, 2000)
This breaks down into: 122,611 specimens belonging to 42 species for the low grazing treatment (25 Aphodiidae, 15 Scarabaeidae, 2 Geotrupidae); 26,057 individuals belonging to 54 species for the moderate grazing treatment (35 Aphodiidae, 16 Scarabaeidae, three Geotrupidae); 128,616 specimens from 53 species for the veterinary medical products (VMPs)-free treatment (35 Aphodiidae, 16 Scarabaeidae, two Geotrupidae); and 20,052 individuals belonging to 41 species for the VMP-use condition (24 Aphodiidae, 14 Scarabaeidae, three Geotrupidae) (Supplemental Information 1)
The present analysis highlighted that the moderate grazing VMP-free treatment seems to be the more appropriate management system for maintaining a higher number of dung beetle species, as well as greater diversity and biomass
Summary
Land use changes play a pivotal role in the loss of biodiversity (Sala et al, 2000). In the Mediterranean Basin, starting about 10,000 years ago, the human population modified the landscape for agriculture and livestock grazing purposes (Blondel, 2006). Semi-natural grasslands are one of the keystone habitats of this landscape. They were developed and managed by man (Blondel et al, 2010) using extensive livestock grazing that prevented the homogenization of the landscape (Perevolotsky & Seligman, 1998; Diacon-Bolli et al, 2012). This grazing provides an energy input to the system through the cattle dung that was previously produced by wild herbivores
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