View of a soil pit. © BRGM
Outstanding result / Ecological reconstruction of degraded soils to improve ecosystem services
Ecosystem services are the services provided by ecosystems that benefit humans. Soil-dependent services are based on the good condition of the ecological functions that tend to be taken into account in the management of degraded soils. In a cross-cutting approach BRGM experts from different disciplines contribute their expertise in different areas including contaminated sites and soils and microbiology. The researchers are working on emerging scientific concepts: new methods for measuring and ecologically remediating soils, but also integrating these measurements into the choices of how to manage degraded sites. The purpose is to rehabilitate and promote well-functioning soils.
Soil: a fragile resource
Soils are a fragile, non-renewable resource that can provide many ecosystem services. However, due to soil sealing and urban or industrial contamination, they are no longer always able to constitute an ecosystem that is conducive to biodiversity and human life.
The last few years have marked a turning point in the management of degraded surfaces and waste-type materials (quarry sludge, excavated soil, sediments, etc.) and in the way the ecological functions of soils are taken into account, with biodiversity becoming a central factor. This intention is embodied in regulatory texts (Zero Net Artificialisation, Biodiversity Act, etc.), but this is a broad topic considered on a general, not specialised level.
In this context, the soil engineering developed at BRGM comes into its own: from bio-indicators to soil reconstruction, life cycle analysis and decision-making support tools. Tools that meet the challenges of restoring life to the soil and incorporating the circular economy in spatial planning.
New measures and soil “reconstruction”: AGREGE
The AGREGE project, in which BRGM is involved, is a new branch of soil construction based on innovative materials for urban development.
Three demonstration sites are currently in operation. In terms of methods and technologies, BRGM’s idea is to integrate fine-textured soils (of no geotechnical interest) into a soil manufacturing process consisting of topsoil (for plant regrowth) and more mineral-rich, technical subsoil layers that can retain or, inversely, evacuate water, for example. On one of the demonstration sites, soils from the 10 compost and/or clay trials were analysed for their functional capacities. The results showed that the addition of clustered amorphous organic matter tends to increase the microbial activity of soils (observable by measuring CO2), but that adding clay reduced this activity by trapping the organic matter.
Sampling to quantify the biomass produced in built-up soils. © BRGM – P. Bataillard
Integration of measurements into management choices: RECORD
Moreover, since de-industrialisation, there are many brownfield sites in urban and suburban areas. The tendency is to favour the construction of “cities on top of cities”, to reduce the artificialisation of the ground. But there are very few operational tools, methods or indicators to guide the design of such redevelopment projects.
The RECORD study involves three partners: Soltis environnement, BRGM and VertigoLab. It puts forward a conceptual and methodological approach to guide a redevelopment project that promotes ecological remediation through the implementation of nature-based solutions.
Using an Excel-based tool and a user’s guide, a manager or an industrial company can have access to a list of nature-based solutions that can replace high-impact conventional solutions: functional monitoring indicators, ecosystem services, etc. The project also provides a review of the main known indicators for measuring key ecosystem functions. In general, this work opens up interesting prospects for assessing the restoration of degraded sites.
Diagram of the soil reconstruction process. © BRGM