Biodiversity Health Index
One Number. Four Ecological Signals.
The Biodiversity Health Index (BHI) synthesizes eDNA species richness, IUCN threat status weighting, acoustic complexity, and soundscape health into a single auditable score on a 0–100 scale. The score is the credit's quality marker and its price anchor.
Score Composition
How the BHI Score is Computed
eDNA Species Richness
Count of species detected at ≥90% sequence identity, normalized against a Pacific Northwest ecosystem-type reference database updated annually. Higher richness relative to ecosystem type = higher sub-score.
IUCN Status Weighting
Each detected species is cross-referenced with the IUCN Red List API. Threatened and near-threatened species are multiplied: VU ×1.5, EN ×2.0, CR ×3.0. Sites with endangered species score significantly higher.
Acoustic Complexity (ACI)
30-day mean Acoustic Complexity Index from the AudioMoth array, normalized against the ecosystem-type reference distribution. ACI correlates with soundscape complexity and multi-taxa presence.
Soundscape Integrity (NDSI)
Normalized Difference Soundscape Index measuring the ratio of biological to anthropogenic sound. Values near +1 indicate low human noise intrusion and valid ecological signal in the acoustic data.
Credit Tiers by BHI Score
Why BHI Matters
Scores That Reflect Actual Ecosystem Condition
Generic offset programs use land cover as a proxy for biodiversity. BHI uses organisms. The difference is observable: a riparian site can achieve full canopy cover and still show no Rana pretiosa or Oncorhynchus mykiss detections in eDNA — a restoration failure that an area-based metric records as success. BHI does not claim to be a comprehensive biodiversity index; it is a practical, auditable scoring tool calibrated for Pacific Northwest ecosystems and designed to improve on what existed before.