Monitoring protocols for the evaluation of the impact of wild boar (Sus scrofa) rooting on plants and animals in forest ecosystems

The management of wild boar (Sus scrofa) is an issue of increasing global conservation concern. Statistically robust monitoring protocols, allowing the detection of biologically relevant changes in biodiversity indices due to wild boar activities, are crucial tools for the management of wild boar populations. The goal of our study was to present a robust procedure targeted towards elaborating monitoring protocols for the evaluation of the impact of wild boar rooting on forest plants and animals. We compared two pairs of macro-areas characterized by contrasting levels of rooting activity. We then evaluated the effect of rooting on several parameters of four forest communities: understorey vascular plants, ground invertebrates, Carabid beetles and small mammals. We found that the evenness of the Carabid community was significantly higher in high-rooting macro-areas. Moreover, the diversity and evenness indices of understorey vascular plants were higher in high-rooting macroareas, while the abundance of the Etruscan shrew (Suncus etruscus) was higher in the low-rooting macro-areas, although these differences were only marginally significant. The results of the remaining tests were all non-significant. However, confidence intervals of measured effect sizes always included biologically relevant effects; therefore, these results should be considered inconclusive. The magnitude of the effect we detected on several biodiversity indices was considerably small (probably due to a certain degree of rooting affecting currently and in the past all the macro-areas), therefore high sampling effort should be required to detect such subtle differences. Researchers and practitioners should carefully consider the complexity of monitoring the impact of wild boar and the choice of the parameters to investigate since our study clearly shows that monitoring some biodiversity indices requires a substantial investment of sampling effort and a well-structured a priori-planning phase. Failing to do so will inevitably lead to a waste of resources and /or wrong management decisions.