Impact of urban managements on soil biodiversity

Urbanization is one of the main changes in land use worldwide. In mainland France, artificially-landscaped areas represent around 10% of the territory, as a result of both metropolization and urban sprawl. Since 2007, more than half of the world's population has lived in cities, and this figure is set to rise to 70% by 2050. Although representing a relatively small surface area, urbanization has a major impact on the biosphere as a whole, particularly as a driver of climate change and the biodiversity crisis, since a city requires a surface area 1,000 times larger to meet the needs of its inhabitants. On a finer scale, negative environmental externalities (pollution of various kinds, heat islands, loss of biodiversity and outbreaks of bio-aggressors, flooding, etc.) threaten the quality of life of city-dwellers. In order to reduce the negative impacts of urbanization, but also to prepare for the consequences of the climate crisis, a transition towards more sustainable and resilient cities is necessary and has already begun. This transition relies in part on taking into account the services rendered by the biodiversity of urban ecosystems (i.e. urban biodiversity) to city dwellers, referred to as "ecosystem services" or, more recently, "nature-based solutions" (NBS). Against this backdrop, many city dwellers, practitioners and scientists are working to develop nature in the city, an approach fuelled by urban ecology.

Urban ecology refers both to the study of the city through the life sciences and the humanities, and to the improvement of the living environment for city dwellers based on environmental protection. Originating in Chicago in the 1930s, it has been amplified in France by the Grenelle laws (2009 and 2010), which recognize the importance of protecting, developing and enhancing nature in the city. This approach involves taking into account the natural spaces of cities to encourage their integration into local, regional and national "networks": urban green grids. This political will is based on national (e.g., the Ecorurb program) and European (Globenet) scientific momentum. While certain components of urban nature, such as birds and plants, have been relatively well studied, little is known about the biodiversity of urban soils. Urban spaces are not "above ground", however, and rely on a range of substrates that we will refer to as "urban soils". As in non-urban systems, soil, a biomaterial unique to our planet, plays a central role in the functioning of urban ecosystems and is home to a wealth of biodiversity. Although little is yet known about this biodiversity, it is clear from the available knowledge that the biodiversity of urban soils, and therefore also the services associated with them, depends in particular on the way in which they are developed and managed.