Revegetating high‑altitude reservoirs to mitigate their impact on biodiversity

Abstract

High-altitude reservoirs now constitute a significant portion of the network of mountain water bodies, but their construction often leads to the destruction of wetlands and functional habitats. Biological surveys conducted in these areas reveal significantly depleted communities and a near-total absence of aquatic vegetation, transforming some reservoirs into “ecological traps.” To test solutions for better environmental integration, an ecological restoration project—including an experimental component—was carried out on the Adret des Tuffes reservoir (Les Arcs 2000). Fascines of helophytes and hydrophytes were planted on the banks and on a floating raft. The helophytes thrived on the banks and the raft, while the hydrophytes survived on the raft but very few on the banks, due to spring flooding. Faunal monitoring is currently underway to assess the carrying capacity of these structures, as the reservoir initially has a low abundance of amphibians and limited diversity of invertebrates. Based on this, recommendations are proposed to enhance the ecological quality of existing reservoirs, such as improving substrate characteristics and bank slopes, planting with local species, and adjusting filling cycles to breeding periods. These measures aim to best reconcile human uses with biodiversity conservation in mountain areas.