Bending the curve of biodiversity loss requires the business and financial sectors to disclose and reduce their biodiversity impacts and help fund nature recovery. This has sparked interest in developing generalizable, standardized measurements of biodiversity—essentially a ‘unit of nature’. We examine how such units are defined in the rapidly growing voluntary biodiversity credits market and present a framework exploring how biodiversity is quantified, how delivery of positive outcomes is detected and attributed to the investment and how the number of credits issued is adjusted to account for uncertainties….