Knowledge influences perceptions and values of nature-based solutions: The example of soil and water bioengineering techniques applied to urban rivers

Soil and water bioengineering (SWBE) is a nature-based solution (NBS) that can be used to stabilize riverbanks with living vegetation. Aside to protecting property and people, SWBE provides benefits for human well-being and biodiversity. Its use remains modest in cities, where the presumed benefits are important in a context of biodiversity crisis and warming. Negative public perceptions have been identified as one barrier to the dissemination of NBS. This article studies how environmental expertise influences perceptions and values associated with SWBE, and how the possible differences in perceptions and values induced by knowledge contribute to hindering or promoting the dissemination of these solutions. We carried out an original interdisciplinary study based on a sociological survey and ecological field measurements to characterize: (1) the perceived value that actors associate with several riverbanks equipped with different protection structures (green, hybrid, or gray) according to their level of expertise in the aquatic environment; (2) the interactions between these perceived values and the ecological values measured by restoration ecologists; and (3) the perceived benefits and drawbacks of SBWE techniques. Our results show that the ecological and social benefits provided by NBS are recognized by all, whatever their level of knowledge. Despite this consensus, we observed different hierarchies of value associated with bank protection structures among the surveyed actors, depending on their level of environmental expertise (some prioritising ecological values, others relational values), and these could hinder the dissemination of NBS. The most tangible obstacle to the dissemination of NBS in urban areas relates to the risk perceptions of lay people, who experience a higher sense of vulnerability than they do with traditional gray solutions.