Impacts of dogs on urban grassland ecosystems

Dog walking is a highly popular leisure activity in cities around the globe. It is also a controversial issue for urban conservation and green space management due to presumed ecological impacts of dogs. Yet regulations allowing or prohibiting the presence of dogs in areas of conservation concern are rarely based on demonstrated effects of dogs on urban nature. To unravel the relationships between the presence of dogs at a site and soil features and plant and animal diversity, we selected dry grassland as our study system since this type of ecosystem is of conservation concern in many cities and is frequently used for dog walking. We combined data on the number and movement patterns of dogs and their owners in 52 dry grassland patches in Berlin, Germany, to create a novel index of dog presence and activity. We then analysed the relationship between the index and soil features, species richness of plants and seven invertebrate taxa, and abundances of sand lizards, a species of particular conservation interest. Generalised linear models revealed significant relationships between the dog index and one soil parameter and some biodiversity measures. The dog index was positively related to phosphorus and nonnative plant richness but negatively to spider diversity. While dogs may facilitate biological invasions, likely through a combination of eutrophication and disturbance, overall relationships with general species richness or richness of endangered plant or animal species were weak. These results indicate opportunities for reconciling urban nature conservation with moderate dog walking in urban grassland areas. Still, urban policies should consider remaining dog-related risks in other ecosystem types - a promising direction for further urban research.