Incomplete coverage of the state of nature across biodiversity credit methodologies: an assessment using the State of Nature metrics framework

Kota Kato 

Biodiversity credits are growing rapidly, yet the proliferation of methodologies has raised concerns about their quality and integrity. Because biodiversity cannot be reduced to a single common unit, methodologies differ in their choice of indicators; previous comparative studies, however, have examined only aggregation levels or taxonomic focus, leaving unaddressed how comprehensively methodologies measure the state of nature. The recently developed State of Nature (SoN) metrics framework is emerging as a globally aligned framework for measuring the state of nature. Using its four core indicators, ecosystem extent, ecosystem condition, species extinction risk, and species populations, this study analyzed 13 biodiversity credit methodologies by organizing 51 extracted metrics into 21 indicators. These indicators were mapped onto the core indicators, and their cumulative publication counts for 1980–2025 were compared with the number of methodologies in which they were adopted. Coverage was uneven: 16 indicators corresponded to ecosystem condition and only 2 indicators to species-related core indicators, and 11 of 13 methodologies lacked at least one core indicator. For several abiotic indicators, adoption remained limited despite substantial research accumulation. Most methodologies therefore fail to assess at least one aspect of the state of nature, and broader coverage, particularly of species-related indicators, is needed.