Urban soil contamination and impacts on biodiversity

The world's population continues to grow (7.8 billion in 2021, projected to rise to 9.8 billion in 2050), as does the proportion of the population living in urban areas (14% of the world's population in 1920, projected to rise to 70% in 2050). As a result, the impact of human activity on the various compartments of the urban ecosystem (air, water, soil) continues to grow. However, this impact is still relatively unknown when it comes to soil, despite the fact that this epidermis covering the earth's surface is the substrate on which 95% of our food is based. The definition given by Girard et al. : "Soil is an organized (in different horizons), evolving whole, where life is present and whose material is earth. It is the place where flows of water, air, energy and life are transferred". This porous material, just a few centimetres to a few metres thick (compared to the 30 to 70 km thickness of the earth's crust), results from the weathering of rocks, and is more or less enriched at its surface by organic matter (natural deposits of leaves, addition of straw by farmers, etc.). Soil harbors a much richer and more varied biodiversity than that found above it (five times more biomass; a quarter of terrestrial biodiversity). Due to their characteristics and functioning, soils provide numerous services, including supply (water, agricultural production, genetic resources, etc.) and regulation (of climate, water flows, plant diseases, etc.). In an urban context, soils very often differ from those in rural and forested areas, in their characteristics, functions and consequently in the services they provide. The origin and composition of urban soils are highly varied, from those close to natural soils to those constructed from a variety of materials. Last but not least, urban soils are often highly heterogeneous in terms of their spatial distribution. .

The article focuses on the chemical pollution linked to human activity (industry, service activities,...