Ecosystem services coming from landscape infrastructures in agroecosystems : example of surface drainage ditches
Résumé
Agroecosystems are expected to provide food for 9.7 billion people by 2050, with limited harmful effects of agriculture on the environment. One of the pillars of sustainable agriculture are landscape infrastructures. Many landscape infrastructures in agroecosystems are man-made and primarily installed by farmers for one particular function : subsurface or surface water drainage for ditches, soil conservation and water infiltration for bench terraces, etc. They require frequent maintenance practices to maintain their primary function. Landscape infrastructures are non-cropped areas, and therefore often host semi-natural or natural ecosystems. A number of studies underline the multiplicity of positive ecosystem functions these landscape infrastructures can provide due to the ecosystems they host. Overviewing these different ecosystem functions, an actual challenge is thus to identify the adverse effects, the synergies and trade-offs between infrastructure functions forced by a diversity of maintenance strategies, in space and time, and at the local or the landscape scale. To illustrate this challenge, more than 15 years of research in soil science, agronomy, hydrology and ecology focusing on surface drainage ditches in the South of France are presented, as well as the remaining open questions on processes and impacts. We demonstrated that the ecosystem in these ditch networks that were traditionally built to prevent soil erosion, can play a significant role in various functions : water quality regulation, water resources provision but also in ecosystem self-maintaining functions. As a consequence, new spatio-temporal designs of the maintenance of infrastructure ecosystems by farmers appear as a way to ensure and reach more sustainable agroecosystems.