Peri-Urban Lakes, Society, and Environment – PULSE

Peri-urban areas are transition zones, where urban and agricultural activities are juxtaposed in a complex landscape constituted by a mosaic of rural, industrial, urban, forested and aquatic areas. We have constructed a project at the scale of the Île-de-France, the most populated region of France, in order to study the impacts of global changes and other anthropogenic pressures on these peri-urban aquatic ecosystems, and propose adaptation and mitigation strategies to reduce the impacts of these planetary changes on lake quality and services. Lakes situated in such landscapes are highly vulnerable ecosystems, generally impacted by a large variety of environmental stressors, which act both at the local (land use changes, agricultural and industrial pollutants, eutrophication, human perturbations, invasive species) and the global scales (CO2 and temperature increases, atmospheric pollution), with complex and mostly unknown interaction effects. Moreover, they present a complex set of environments in the same geographic area. Thus, they constitute particularly well-suited systems for studying the impacts of multiple pressures on biodiversity, ecosystem functioning, and services provided by aquatic ecosystems. Due to their peri-urban situation, they are also particularly relevant for studying the human and social dimensions of ecosystem vulnerability, and the adaptability of societies to planetary environmental changes.
To tackle these issues our project combines (1) comparative analyses on a set of 50 lakes representing the diversity of the regional landscape, (2) seasonal analyses on a pilot lake (Lake Créteil), (3) microcosm experiments in the laboratory and in the field, (4) in situ and ex situ mesocosm long-term experiments on the main environmental stressors and on their interactions. These descriptive, comparative, and experimental approaches will be coupled with theoretical modelling, and scenario building to evaluate the evolution of lake quality during the next century. These approaches will be also associated to comparative analyses on the perceptions of lake quality and management priorities by scientists from different academic origins (geography, social sciences, ecology, limnology, physics, chemistry), and the main categories of stakeholders concerned by these ecosystems. Finally, decision trees will be proposed in order to offer adaptation and mitigation strategies for reducing impacts of planetary changes on lake quality and services.