Marine ecosystem restoration and biodiversity offset

Abstract The mitigation hierarchy is increasingly used in environmental policy as a way of reconciling economic development and biodiversity conservation. The principle of the mitigation hierarchy is to avoid, reduce and offset the environmental impacts arising from development projects by providing ecological gains through conservation or restoration measures. Most of the research on its implementation to date has focused on terrestrial ecosystems. In this study, we investigated the relevance of marine ecosystem restoration in meeting offset requirements. Stemming from a brief literature review on existing restoration techniques for marine ecosystems (e.g. coral reefs, seagrass meadows, macroalgae beds, ‘green’ marine construction, and marine sediment remediation) and our experience on Environmental Impact Assessments undertaken in mainland France and in its oversea territories, we discuss the main criteria ensuring a suitable use of ‘restoration’ practice regarding offset requirements. We then clarify the different levels of equivalence that should be met when designing offsets relying on ‘restoration’ techniques. This study aims to clarify to what extent the environmental impacts of economic activity on marine biodiversity can be offset through marine ecosystem restoration.