Integrating environmental archives into conservation: using historical data to evaluate species suitability for reintroduction

Evidence-based conservation planning is typically informed by recent data, but anthropogenic activities have shaped biodiversity throughout history and recent prehistory, and long-term environmental archives can provide unique information on past ecological states and change. Environmental archives can be particularly important for informing conservation actions that address disrupted or lost biodiversity, such as species reintroductions, where species selection often fails to consider the full information-content or quality of past data. Here, we explore the potential to incorporate past evidence into reintroduction planning in a more systematic and comparative manner, by developing a framework of biological and ecological criteria for evaluating different aspects of the former status of lost species. These criteria help to define whether a species can be interpreted as native under modern environmental conditions, and whether its former population status, ecology or extinction is adequately understood. This framework clarifies evidence, assumptions and uncertainty around past species status, providing insights unavailable from a modern ecological perspective, and should be considered at the outset of planning to assess whether some species represent better contenders for reintroduction than others.