Navigating uncertainty in LCA-based approaches to biodiversity footprinting

The use of Life cycle assessment (LCA) methods is rapidly expanding as a means of estimating the biodiversity impacts of organisations across complex value chains. However, these methods have limitations and substantial uncertainties, which are rarely communicated in the results of LCAs. Drawing upon the ecological and LCA literature on uncertainty and two worked examples of biodiversity footprinting, we outline where different types of uncertainty occur across multiple stages of the LCA process, from input data to the choice of biodiversity metric. Some uncertainties are epistemic, incorporating structural (e.g., the types of pressures included in models), parametric (e.g., uncertainty around conversion factors), and measurement uncertainty, as well as natural variability, stochasticity, and information gaps. Other uncertainties are linguistic (e.g., ambiguity around definitions of biodiversity) and decision-based (e.g., choices made when matching company data to inventory categories). We provide suggestions for understanding, reducing, and navigating uncertainties when using LCAs for biodiversity footprinting. Understanding the risks posed by these uncertainties, weighing them against the costs of inappropriate action or inaction, and ensuring decisions are robust to these uncertainties, is vital for designing effective biodiversity strategies. With a full understanding of these uncertainties, opportunities exist to utilise LCAs for high-level risk screening to prioritise action and highlight areas where focused effort and more granular data are needed, to track progress towards abating impacts year-on-year and identify low risk actions. However, biodiversity strategies should not be based solely on absolute LCA impact results. Instead, LCAs should be used alongside other approaches to guide location-specific and robust action to deliver a Nature Positive future.