Biodiversity Intactness Index
This layer estimates how much of an area's original biodiversity remains intact despite human impacts.
Source: Biodiversity Intactness Index (Natural History Museum) Year: 2016 Category: Transition risks · Sensitive areas · High integrity areas Coverage: Global Format: Raster grid Used in risk analysis: Yes — gates Sensitive areas
What it shows
This layer estimates how much of an area's original biodiversity remains intact despite human impacts. It expresses, as a percentage, how many of the species originally present still occur and how abundant they remain. Areas with high intactness retain near-natural ecological communities, while low values indicate communities heavily altered by human pressure. This helps identify where activities may affect still-intact nature.
How it is built
The source is the Biodiversity Intactness Index from the Natural History Museum. The measure estimates the proportion of the original number of species, and their abundance, that persist in a given area after accounting for human impacts such as land use. Values can be averaged across areas — a site, region, country or the globe — to summarise the remaining biodiversity across that extent.
How to read it
Values are expressed as a percentage of the original biodiversity remaining. Higher values mean more intact biodiversity (closer to natural conditions); lower values mean more degraded communities with fewer of the original species and lower abundance. Higher-intactness areas warrant particular care.
Class thresholds
The underlying quantity is an index, not a physical flux: the Biodiversity Intactness Index (BII) — the estimated proportion (0–1, read here as 0–100%) of the original number of species and their abundance that persist after human impacts. Because higher intactness means lower nature-related risk, the risk scale is inverted: the five risk classes map to BII as follows:
| Class | Intactness (BII) |
|---|---|
| Very High Risk | < 60% |
| High Risk | 60 – 70% |
| Moderate Risk | 70 – 80% |
| Low Risk | 80 – 90% |
| Very Low Risk | ≥ 90% |
(The map legend itself bins the index more finely — into ten colour bands at 60/70/75/80/85/90/95/97.5/100% — for visualisation.) For the proximity gate, a site is flagged on the Sensitive areas dimension when the layer value is above 95% (BII ≥ 0.95) — i.e. very-high-intactness, sensitive habitat — provided the entity's matching ENCORE "Sensitive area disturbance" pressure is also material.
How these thresholds were set. This is a Darwin in-house classification of the Natural History Museum BII surface: the five risk classes are fixed round-number cut-offs (60/70/80/90%) applied to the index and inverted (low intactness = high risk), held in Darwin's country-risk-profile configuration. They are not derived from a published BII threshold standard. The separate 0.95 proximity flag is a further Darwin choice marking very-high-intactness habitat.
Source
Natural History Museum — Biodiversity Intactness Index.
Comparison with the WWF Risk Filter Suite
This layer relates to WWF Biodiversity Risk Filter indicators S2_4 and S14_5 Ecosystem Condition (intactness of biodiversity). It is a complementary intactness measure to WWF's ecosystem-condition composite, which is built around the Ecosystem Integrity Index rather than the Biodiversity Intactness Index.
Risk analysis
A site is flagged on a dimension by combining a proximity trigger (this layer) with an activity trigger (the entity's ENCORE pressure/service). Proximity only → Potentially material; proximity and the matching ENCORE pressure/service is material → Very material; neither → Not material.
| Dimension | ENCORE service / pressure | Proximity trigger (this layer) | Activity trigger (entity) |
|---|---|---|---|
| Sensitive areas | Sensitive area disturbance | Layer value above 95 | impact ratio ≥ 10%; “Disturbances (e.g noise, light)” pressure ≥ 4; “Introduction of invasive species” pressure ≥ 4; “Area of freshwater use” pressure ≥ 4; “Area of seabed use” pressure ≥ 4; “Area of land use” pressure ≥ 4; “Other biotic resource extraction (e.g. fish, timber)” pressure ≥ 4; “Volume of water use” pressure ≥ 4; “Emissions of non-GHG air pollutants” pressure ≥ 4; “Generation and release of solid waste” pressure ≥ 4; “Emissions of toxic soil and water pollutants” pressure ≥ 4; “Emissions of nutrient soil and water pollutants” pressure ≥ 4 |
Legend
Symbolised field: Intactness index
| Value (Intactness index) | Label | Colour |
|---|---|---|
| 0 | ≤ 60 | #a50026 |
| 0.6 | ≤ 70 | #d73027 |
| 0.7 | ≤ 75 | #f46d43 |
| 0.75 | ≤ 80 | #fdae61 |
| 0.8 | ≤ 85 | #fee08b |
| 0.85 | ≤ 90 | #d9ef8b |
| 0.9 | ≤ 95 | #a6d96a |
| 0.95 | ≤ 97.5 | #66bd63 |
| 0.975 | ≤ 100 | #1a9850 |
| 1 | > 100 | #006837 |
Generated from darwin/layers/layer-biodiversity-intactness-index.toml and risk_indicator_pairs.toml (develop).