A methodological framework for assessing the equivalence between biodiversity losses and gains induced by development projects and their offsets

Abstract

In France, the mitigation hierarchy aims to achieve the "no net loss" (NNL) of biodiversity at the development projects scale. One of the key issues to achieve this goal is to demonstrate the ecological equivalence between the gains associated with offsets due to compensatory measures (CM) and the losses caused by the impacts. Despite regulatory improvements, the French law does not include a method to follow for determining equivalence, and none is unanimously recognized. This leads to heterogeneous practices and difficulty in reaching the NNL. In this context, we have developed a methodological framework for assessing equivalence adapted to the French regulatory and ecological context and combining three challenges: operationality, scientific basis and comprehensiveness. This methodological framework makes it possible 1 / to evaluate the biodiversity found on impacted and compensating sites by taking into account ordinary biodiversity ordinary and high-stake biodiversity with a focus on functionalities, 2 / to estimate the value of the indicators after impact and MC in the short and long term, taking into account associated uncertainties, and 3 / calculating losses and gains leading to a quantitative and transparent equivalence assessment. The use of the methodological framework favors dialogue between actors and also allows monitoring of offsets over time.