Case study site: Grand-Lieu Lake (France)

Lake Grand-Lieu is a large lake with extensive beds of floating-leaved macrophytes. Two non-native aquatic plants (Ludwigia peploides and L. grandiflora) colonized the lake in the 1990s, developing dense mats in the lake and canals and causing problems for biodiversity conservation and for human activities such as fishing and boating. The lake is affected by eutrophication, climate change, hydromorphological alterations and the invasion of the non-native Ludwigia sp.

Since 2002, 5-10 tons of Ludwigia were removed annually. The management of these invasive species is costly and inefficient, because regrowth is regularly observed, and macrophyte removal reportedly enhanced the development of cyanobacteria in the lake, with negative consequences for fishing and on biodiversity.

The stakeholder involved in this case study is the Natural Reserve of Lake Grand-Lieu.