Night light
This layer maps the brightness of artificial light at night across the globe.
Source: VIIRS DNB (NOAA / Colorado School of Mines) Year: 2024 Category: Transition risks · Pollution · Disturbance Coverage: Global Format: Raster grid Used in risk analysis: Yes — gates Pollution
What it shows
This layer maps the brightness of artificial light at night across the globe. Night-time light is a proxy for human presence, infrastructure and disturbance, and is itself a form of pollution — light pollution disrupts nocturnal wildlife, migration and natural cycles. It helps identify where ecosystems are exposed to chronic artificial illumination and associated human activity.
How it is built
The layer is built from VIIRS night-time imagery, using composite measurements of average monthly radiance captured by the satellite's day/night sensing capability. The composites apply a parasitic-light correction that extends usable coverage closer to the poles and improves the range of brightness that can be distinguished. Cloud cover is screened out using a dedicated cloud mask, and data near the sensor's edge zones are excluded. Some gaps can remain where cloud cover or solar illumination prevent clean observations, and minor artefacts can appear in polar regions as a result of the correction procedure.
How to read it
Higher values indicate brighter artificial light at night — denser human presence, infrastructure and greater light-pollution pressure. Lower values indicate darker areas with little artificial illumination. Areas with no recorded light should not automatically be read as truly dark, since gaps can arise from cloud cover or limited observations rather than the genuine absence of light.
Class thresholds
The underlying layer models a physical flux: artificial night-time radiance (the VIIRS day/night-band "Night light index") — the average light energy emitted upward per unit area, measured in nanowatts per square centimetre per steradian (nW/cm²/sr). The symbolised values are binned into a graded brightness scale; the breaks (in nW/cm²/sr) are:
| Class break (Night light index) | Radiance (nW/cm²/sr) |
|---|---|
| Darkest | -11 (background / negative-corrected) |
| 5 | |
| 10 – 50 (in steps of 5) | |
| 60 – 100 (in steps of 10) | |
| 120 – 180 (in steps of 20) | |
| Brightest | 200 (top class, up to a 75 000 saturation cap) |
The scale is graded rather than a five-class risk ladder: brighter radiance means more light pollution and human disturbance, darker radiance means little artificial illumination.
On the Pollution dimension this layer acts as a proximity trigger for low-light (dark, light-pollution-sensitive) areas: the proximity condition ("low light pollution area") fires when the layer value is below 5 nW/cm²/sr. A site is then Potentially material on Pollution, becoming Very material if the entity's ENCORE "Disturbances (e.g. noise, light)" pressure is also material (≥ 4).
How these thresholds were set. This is a Darwin in-house classification: the brightness scale is a set of fixed round-number radiance cut-offs (5-unit steps at low radiance, widening to 10- and 20-unit steps as brightness increases) applied to the VIIRS DNB composites for visualisation, and the single risk-flag cut-off of 5 nW/cm²/sr is Darwin's own threshold for a "dark" / light-sensitive area. The breaks are not derived from WWF or any other published standard — there is no light-pollution indicator in the WWF Risk Filter Suite.
Source
VIIRS day/night band night-time radiance composites (Earth Observation Group, Colorado School of Mines).
Comparison with the WWF Risk Filter Suite
There is no light-pollution indicator in the WWF Risk Filter Suite. This is a Darwin extension: it captures a recognised form of pollution and human disturbance that the WWF methodology does not include, so it has no direct WWF equivalent and should be read as additional context alongside the WWF indicators.
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) |
|---|---|---|---|
| Pollution | Disturbances (e.g noise, light) | Layer value below 5 | “Disturbances (e.g noise, light)” pressure ≥ 4 |
Legend
Symbolised field: Night light index
| Value (Night light index) | Label | Colour |
|---|---|---|
| -11 | 0 | #4b4b4b |
| 5 | 5 | #002540 |
| 10 | 10 | #001338 |
| 15 | 15 | #002255 |
| 20 | 20 | #00407f |
| 25 | 25 | #0059ad |
| 30 | 30 | #0073c9 |
| 35 | 35 | #0094d6 |
| 40 | 40 | #00a787 |
| 45 | 45 | #00b294 |
| 50 | 50 | #006837 |
| 60 | 60 | #1a9850 |
| 70 | 70 | #66bd63 |
| 80 | 80 | #a6d96a |
| 90 | 90 | #d9ef8b |
| 100 | 100 | #fee08b |
| 120 | 120 | #fdae61 |
| 140 | 140 | #f46d43 |
| 160 | 160 | #d73027 |
| 180 | 180 | #a50026 |
| 75000 | 200 | #cb0822ee |
Generated from darwin/layers/layer-night-light.toml and risk_indicator_pairs.toml (develop).