The issue of ecological equivalence in designing and sizing appropriate offsets for impacts on biodiversity and natural habitats

Abstract

Changes in the regulatory context have reinforced the obligation to compensate "in kind" for impacts on biodiversity that could not be avoided or reduced. In this context, assessing the equivalence between the losses caused by these impacts and the biodiversity gains expected from compensation actions raises scientific and technical questions about the concepts and knowledge to be mobilised and the assessment methods to be developed and implemented. In particular, it involves identifying the biodiversity elements to be considered, developing appropriate indicators to compare losses and gains, selecting a reference state for calculating losses and gains and taking into account ecological dynamics and uncertainties in assessing the fate of offset sites. Through these issues, ecological equivalence provides an explicit reasoning framework for the design and dimensioning of compensation that can be appropriated by each of the stakeholders concerned.