Big Cities, Big Impacts? A spatial analysis of 3,335 ecological offsets in France since 2012

This paper assesses the French policy of mitigation hierarchy, with the aim of no net loss of biodiversity, by studying the geographical aspects of the application of the concept of ecological offsets in equivalence between losses and gains using spatialized data. We seek to know whether the dynamics of urban and interurban development (notably built-up and transport infrastructures) lead to a spatially integrated implementation of biodiversity offsets taking into account local characteristics and areas under pressure from land artificialization. Our main finding reveals that the majority of ecological offsets are generated by projects related to transport infrastructures (38%) and urban planning and construction projects (23%). However, if there are fewer, the ecological offsets of projects such as waste storage or energy development are mostly located in natural preserved areas, revealing a potential risk of non additionnality of offset measures and a risk that the private sector (through ecological offsets) will gradually replace the state in the protection of biodiversity. Our analysis also points out that despite the diversity of projects, habitats and protected species across France, there is a typical spatial layout profile of ecological offsets, pleading for a “one size fits all” offsetting in the French policy context of tenuous regulators’ availability in time and competence level due to weakness of refresh training and downsizing of public services in the environment. This last result argues for a stronger control from environmental agencies between two tremendously tricky concepts of offsetting, the equivalence valuation methods and the adjustments coefficients (time delay and ecological risk), to drive ecological offsetting future decisions at local but above all regional- and national-level planning documents. •There is a typical layout profile of ecological offsets despite the diversity of habitats and protected species.•Most of ecological offsets are small and fragmented, which implead a major brake for ecological restoration to offset.•Ecological offsets managed at project scale without a territorial framework reduces their effectiveness.•Urban and inter-urban development projects lead to the majority (61%) of ecological offsets.•Land scarcity causes a spatial mismatch between the impact zone and the offset zone.