The effect of settlements on the occurrence of protected species in Europe

Several studies have shown that there is a positive correlation between species richness and human activity indicators like population density on large scales. In sites of intermediate urbanisation intensity (i.e. suburban intensity), species richness of plants and birds is frequently higher than in the adjacent agricultural landscape. Conservation efforts in settlements, however, are complicated by conflicts of interest. This study investigated the relationship between settlement area and the occurrence of protected species in the European Union. For this, presence / absence records of the species listed in the annexes of the Birds (2009/147/EC) and Habitats (92/43/EEC) Directives with a resolution of 10 km x 10 km were used. The relationship of species richness to the share of settlement area in each cell was analysed. The influence of biogeographic region, member state reporting quality and the taxonomic group was considered. There is a strong overall positive correlation between reported species numbers and settlement area share for settlement area shares < 20% and a slight decrease in species numbers for settlement area shares > 50%. A relatively clear increase in species richness for low to medium settlement area shares is also specifically present in many of the individual member states and in the major biogeographic regions, i.e. the alpine, atlantic, boreal, continental and mediterranean regions. The overwhelming majority of species records (close to 80%) belong to bird species. The reported species numbers per cell for the other taxonomic groups are comparatively small. Yet, similar patterns can be observed for other taxonomic groups as well. They are especially pronounced not only for birds, but also for mammals and amphibians. It is possible that these patterns occur due to sampling biases in the data.