Preliminary Assessment of the Knowledge Gaps to Reduce Soil Sealing and Increase the Reuse of Urban Soil

To achieve the ambitious goal of 100% healthy soils in 2050, in the last few years the European Union has set up a complex policy framework for soil protection. The framework includes the Soil Strategy, the Directive on Soil Monitoring and Resilience (Soil Monitoring Law, European Commission 2023), the European Soil Observatory, and the Mission “A soil deal for Europe” (European Commission, Directorate-General for Research and Innovation 2022), as well as relevant sectoral policies (e.g., carbon policies). The EU Soil Strategy for 2030 (European Commission 2021b), approved in November 2021, is a key deliverable of the EU Biodiversity Strategy (European Commission, Directorate-General for Environment 2021) and aims to ensure that, by 2050, all EU soil ecosystems are healthy and more resilient and can therefore continue to provide their crucial services; there is no net land take and soil pollution is reduced to levels that are no longer harmful to people’s health or ecosystems; and protecting soils, managing them sustainably and restoring degraded soils is a common standard. The Mission “A Soil Deal for Europe”, or EU Soil Mission (European Commission, Directorate-General for Research and Innovation 2022), supports the implementation of the strategy by finding solutions to protect and restore soil health. The mission defines eight specific objectives that future research and innovation activities should address. The third specific objective is to achieve no net soil sealing and increase the reuse of urban soil. Soil sealing is the main process that causes land degradation in urban areas (EEA European Environment Agency et al. 2022). When soil is sealed, an impermeable layer interrupts the connection between the soil and the atmosphere, which leads to a loss of soil resources, biodiversity, and ecosystem services. The process of soil sealing is strictly linked to that of land take (see definitions in the next Section). The reuse of urban soil instead refers to the use of excavated soil from construction sites for other purposes, instead of considering it as waste (Reicosky and Wilts 2005). Beside the Soil Mission, another key action of the Soil Strategy is the proposal of a Soil Monitoring Law drafted in 2023, aiming to specify the conditions for healthy soils and lay out rules conducive to sustainable soil use and restoration. The proposal includes a mandatory monitoring of land take and soil sealing by Member States, to be conducted according to a common framework defining indicators and minimum methodological criteria (European Commission 2023). The indicators defined by the Soil Monitoring Law are: total artificial land; land take, including reverse land take (i.e., the renaturalization of previously developed land) and net land take (i.e., total minus reverse land take); and soil sealing. Member States may also measure optional indicators such as land fragmentation, land taken for specific uses, and impact on ecosystem services. According to the proposal, the values of soil sealing and land take indicators should be updated at least every year. The third specific objective of the Soil Mission (no net soil sealing and increase the reuse of urban soils) is linked to several other strategies, goals, and targets of the EU, including those expressed in the Roadmap to a Resource Efficient Europe (European Commission 2011) (especially the target of “no net land take” by 2050), the EU Biodiversity Strategy to 2030 (European Commission, Directorate-General for Environment 2021), the proposal of a Nature Restoration Law (European Commission, Directorate-General for Environment 2022), and the EU Action Plan “Towards Zero Pollution for Air, Water and Soil” (European Commission 2021a). Achieving no net soil sealing and increasing the reuse of urban soils would also contribute to other EU Missions and related policy areas, such as Oceans, Seas and Waters (management of water quality and quantity in urban areas), Adaptation to Climate Change (flood mitigation), and Climate Neutral and Smart Cities (climate mitigation and resource efficiency). In addition, the specific objective is directly linked to several targets of SDG 11 - Make cities and human settlements inclusive, safe, resilient and sustainable. The aim of this document is to provide an initial overview of the topics addressed by the mission objective of no net soil sealing and increase the reuse of urban soils and a preliminary list of associated knowledge gaps. The contents have been progressively integrated and refined during two online and one in-person meetings where the members of the dedicated Think Tank set up by the project SOLO shared their views and opinions. In an effort to gather different perspectives, the fourteen contributors to this first version come from eleven countries and include academics and researchers, consultants, and representatives of public agencies and institutes of different Member States.