Bachelor Thesis

Landscape level effects of settlement area shares on the richness and compositional similarity of protected species inventories in the European Union

Verena Herrmann (02/2023-08/2023)

Support: Carl Beierkuhnlein, Samuel Hoffmann

Several studies have shown that there is a positive correlation between species richness and human activity indicators, like population density, on large spatial scales. In sites of intermedi-ate urbanisation intensity (i.e. suburban intensity), species richness of plants and birds is fre-quently higher than in the adjacent agricultural landscape. Conservation efforts in settlements are frequently complicated by conflicts of interests. This study investigates the effect of settlement area on the richness and compositional similarity of protected species pools in the European Union at a landscape scale. It utilises species distri-bution data within a grid of 10 km x 10 km cells reported under the European Birds and Habitats Directives. A unimodal relationship of species richness with settlement area share (SAS) was expected, based on the assumption that pools of protected species in settlements and in their surroundings differed enough for small SAS to constitute an enrichment of the local species assemblage but that high SAS would lead to a loss in n2k-species and an increase in similarity of species pools with increasing SAS. Settlements are also generally assumed to have a homog-enising effect on the local biota since environmental conditions are modified to fit the needs of the citizens and they are connected by anthropogenic dispersal vectors. I hyothesised therefore, that species pool similarity of cells will increase with increasing SAS. An increase of mean species richness (SR) for low SAS (< 20%) occurs for the dataset as a whole, within the data subsets for all major biogeographic regions, most of the species groups and several of the member states. Lower mean SR values for high SAS cells only occur for cells with SAS > 60%, which exist in only a few member states. There is no consistent monotonic decrease of mean SR values for high SAS apparent. Similarity of species pools is higher for high SAS cells. Patterns for both biodiversity metrics. are likely considerably contributed to by correlations of settlement placement with environmental factors and sampling artefacts. The results highlight that substantial species richness persists even in highly urbanised regions which constitutes both, opportunities and challenges for species conservation.