Unsealing of urban soils: scientific knowledge is essential for optimizing practices

Soil sealing (i.e., covering the soil with impermeable material) is one of the main causes of soildegradation in Europe. Although the strongly negative consequences of sealing on the biophysicochemical properties and the functioning of soils are known, very little work has so far been devoted to the evaluation of the potential for soil renaturation after unsealing. The DESSERT project then simultaneously integrates objectives (i) of acquiring knowledge on the quality, functioning and capacity of unsealed urban soils to provide ecosystem services, (ii) proposing a typology of unsealing processes, (iii) evaluation of the effectiveness of unsealing in terms of renaturation of cities, (iv) implementation of laboratory experiments for the optimization of unsealing processes, (v) implementation and monitoring over time of in-situ pilot sites and (vi) contribution to decision support via the development and wide dissemination of a multi-attribute tool to assist in the design of urban soils unsealing projects. The DESSERT project proposes a common reference system of indicators of physico-chemical fertility and toxicity of sealed urban soils. These indicators are obtained from selected sites, to shed light on the opportunities in terms of ecosystem services provided by unsealed urban soils. The feasibility of returning sealed soils to a multi-functional state, depending on the intended uses, is studied. In terms of valorization, the project's achievements will lead to the proposal of a technical guide and a multi-attribute tool for design assistance for planners and city managers, for an increased consideration of Soil as a resource in urban planning. The challenge is then to rely on a reinforced ecology of urban landscapes taking into consideration the development of ecological corridors, in particular the recreation of soil continuities, which can participate in the regulation of many environmental (e.g., regulation of floods, biodiversity, water quality) and socio-economic issues (e.g., quality of life of inhabitants). The innovative nature of the project lies in the close collaboration between three research actors (in pedology-agronomy, ecology and urbanism), three operators of urban planning (civil engineering, urban planning, landscape architect) and a technical center acting at the interface of the different actors