Effects of urbanisation, habitat characteristics, and management on garden pond biodiversity: Findings from a large-scale citizen science survey

The rapid expansion of urban areas often leads to degradation, fragmentation, and loss of natural habitats, threatening biodiversity. While urban ponds might contribute substantially to the biodiversity of urban blue-green infrastructure, the role of garden ponds is still largely unknown. We lack a comprehensive understanding of how local habitat features, different forms of management, and urbanisation might impact the biodiversity of these habitats. This study aimed to reveal the importance of garden ponds via a country-wide online citizen science survey in Hungary, Central Europe. Data from over 800 pond owners revealed the occurrence and local frequency of various native animal taxa (amphibians, odonates, and birds), and introduced animals (e.g., fish). We collected data about pond features and management practices. We tested the effects of pond features, pond management, and landscape-level drivers (urbanisation, surrounding wetland coverage) on the presence of conspicuous animal taxa (adult amphibians and tadpoles, birds, odonates) to identify the potential drivers of the biodiversity of garden ponds. Key pond features including pond age, area, aquatic and shoreline vegetation were the most important factors, while algaecide addition was the most influential management practice negatively affecting amphibian presence. Urbanisation negatively affected the presence of adult amphibians and their tadpoles, but it was not associated negatively with the presence of odonates and birds. Our results indicate the high potential to utilise garden ponds as urban habitats surveyed with the help of the public. Developing effective urban biodiversity monitoring and conservation strategies are necessary for a better functioning blue-green infrastructure. The high level of engagement of pond owners, as in our survey, can create valuable data for achieving these aims.