Pond biodiversity in European pondscapes: investigating long-term dynamics and the impacts of NBS implementation

Pondscapes (i.e., networks of ponds) host a rich biodiversity and largely contribute to human well-being by providing fundamental services (e.g., flood protection, pollution control, carbon cycling, etc.). However, ponds and other aquatic systems are under pressure: their biodiversity is declining worldwide at an alarming rate. Monitoring these freshwater communities is therefore important, notably to guide conservation measures and assess their effectiveness. Recent years have seen the rise of “Nature-based solutions” (NBS) as a concept to highlight the importance and usefulness of ecosystems in delivering services to people and contributing to our well-being. NBS are defined by the IUCN as “actions to protect, sustainably manage, and restore natural or modified ecosystems, that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits”. In the context of pondscapes, NBS implementation revolves around the creation, restoration and management of ponds. However, the benefits of these measures for biodiversity are not necessarily assessed and are likely to vary depending on the settings (e.g., rural environment, nature reserves, cities) and overarching aim (e.g., flood mitigation, human recreation, promotion of biodiversity). Investigating the impacts of NBS on biodiversity as well as the changes in pond communities, notably in the relatively long term, is valuable to encourage best practices regarding pondscape conservation. This thesis focuses on the temporal dynamics of pond and pondscape biodiversity and the potential impacts of NBS on these communities, in three main contexts: an alpine pondscape in the Swiss National Park, rural pondscapes in lowland Switzerland, and urban ponds in the Geneva area.