High‐density populations of large ungulates are now widespread. However, the perception of overabundance only appears when it produces a problem for humans, such as a loss of plant diversity, damage to agricultural crops and forestry, ungulate‐vehicle collisions, a nuisance to humans, disease transmission to livestock or changes in habitat for other species. The admissible level of density depends on the ecological and socio‐economic context in which the population is located, and defining this level is important, in order to determine management strategies and actions.
We describe the main contexts in which ungulate overabundance occurs in Europe, record the causes of overabundance and evaluate which set of indicators of ecological change is the most appropriate for monitoring and diagnosing overabundance in each scenario.
Our review of 318 published papers revealed six contexts of wild ungulate overabundance in Europe (protected areas, hunting areas, forestry, arable farming, livestock farming and [peri]urban areas). In addition to population abundance, four sets of indicators of environmental change could be used to monitor overabundance within these contexts (impacts on habitats, impact on animal performance, increments in diseases and parasite loads, and increments in nuisance to humans).
Nine species of ungulate were found to be overabundant. Red deer Cervus elaphus was the species most likely to be overabundant in the contexts of protected areas (detailed in 27% of papers on that context) and hunting areas (38%); roe deer Capreolus capreolus in forestry (28%); wild boar Sus scrofa in arable farming (60%), livestock farming (29%) and (peri)urban areas (38%). Our evidence shows that the diagnosis and monitoring of ungulate population overabundance via indicators of ecological change, and the management actions required to control these undesirable situations, are strongly context‐dependent.
1 Agricultural intensification has greatly affected biodiversity in recent decades. One common and recent transformation that has taken place in Mediterranean countries is olive grove intensification, although its effects on biodiversity have rarely been studied. 2 In the present study, we investigated the effect of soil management practices, with versus without soil cover crops, on the arthropod abundance, richness, diversity and species composition in Andalusia olive groves, South Spain. 3 The results obtained show that these soil cover crops positively affect the diversity of arthropods, along with other variables such as the diversity of the plant community and Shannon index of the landscape. By contrast, the number of arthropods was higher in olive groves with bare ground as a result of the abundance of two families (Entomobryidae and Aeolothripidae), which comprised more than 50% of all the individuals collected. 4 Rank abundance diagrams and multivariate analyses showed differences between the two types of soil management systems with respect to the composition of families. 5 In conclusion, soil cover crops strongly improve the diversity of arthropods in olive orchards, which helps to maintain biodiversity in these intensive agroecosystems at the same time as improving other ecosystems services, such as soil fertility and the prevention of soil erosion.
The landscape in southern Iberia has, over the last four decades, altered as a result of the land abandonment, while the abundance of wild boar Sus scrofa and red deer Cervus elaphus has simultaneously increased, and some key prey species such as the European rabbit Oryctolagus cuniculus have declined. In this work we explore: 1) the relationships between big game species (red deer and wild boar) and rabbit abundance, and 2) whether these relationships could have effects on food quality (total nitrogen available in the pasture and percentage of leguminosae) and food availability of (herbaceous cover). We therefore selected nine big game estates with a range of abundance as regards ungulates and similar Mediterranean habitat. Wild boar abundance was statistically negative in relation to rabbit abundance, while no significant statistical relationships between rabbit abundance and habitat structure and forage quality were evidenced. However, wild boar abundance, but not that of red deer, was negatively associated with leguminosae cover, and the percentage of surface rooted by wild boar was negatively associated with the percentage of herbaceous cover. Overall, our results suggest that the abundance of wild boar is negatively related to that of rabbits, and could have a negative effects on rabbit abundances by food competition as a result of: 1) a decrease in herbaceous coverage and leguminosae in the pasture and 2) an increase in the total percentage of soil disturbed as a result of rooting.
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