Biodiversity Net Gain (BNG)
What is BNG
Biodiversity Net Gain is a planning policy mechanism that requires development to leave biodiversity in a measurably better state than before development began. In England, BNG is mandatory under the Environment Act 2021 at a minimum of 10% net gain.
BNG is mentioned across 8+ wiki pages because it is the primary intersection between planning (housing and infrastructure) and nature recovery.
How it works
- Baseline assessment: Developer or local authority assesses the biodiversity value of the development site before work begins (using the Biodiversity Metric)
- 10% uplift requirement: Planning permission requires the scheme to deliver at least 10% more biodiversity value than the baseline
- Delivery options:
- On-site: BNG delivered within the development (wildflower areas, hedgerows, green roofs, habitat management)
- Off-site: Developer purchases biodiversity units from a habitat bank or off-site BNG provider
- Statutory credits: Developer pays into government BNG credit system (last resort; highest cost)
- Nature Restoration Fund (NRF): Developer contributes to NRF (pooled strategic investment — enabled by PIA 2025)
Timeline
| Date | Milestone |
|---|---|
| February 2024 | Mandatory BNG for most planning permissions (Town and Country Planning Act) |
| April 2024 | Mandatory BNG for small sites |
| May 2026 | Mandatory BNG for Nationally Significant Infrastructure Projects (NSIPs) |
Biodiversity Metric
Natural England’s Biodiversity Metric (version 4.0) quantifies biodiversity value in “biodiversity units” based on:
- Habitat type (heathland has higher value than amenity grassland)
- Habitat condition (good condition = higher value)
- Habitat distinctiveness (irreplaceable habitats cannot be offset)
- Location factors
Key issues
Irreplaceable habitats
Ancient woodland, lowland fen, and other irreplaceable habitats cannot be offset — development on these sites must be refused or the impact avoided entirely.
BNG for NSIPs (from May 2026)
NSIPs — including offshore wind, grid infrastructure, and large housing schemes — require BNG from May 2026. The Nature Restoration Fund (NRF) was specifically created to handle NSIP BNG at scale, avoiding the complexity of individual scheme BNG assessments for nationally significant projects.
Natural England capacity
Natural England administers BNG nationally — processing applications, approving off-site habitat banks, and overseeing the NRF Environmental Delivery Plans (EDPs). Institutional capacity to process all of this simultaneously (alongside SSSI assessments, OWEIP work, and ELM scheme processing) has not been publicly assessed.
Relationship to housing-biodiversity tension
BNG is the core policy mechanism attempting to resolve the housing-biodiversity tension: mandatory BNG means housing development cannot simply destroy habitat without offsetting. However:
- On-site BNG in housing schemes often produces low-quality habitat (amenity grassland, ornamental planting)
- Off-site BNG creates habitat markets that may not be spatially coordinated with nature recovery priorities
- The NRF is designed to address this by pooling contributions for strategic landscape-scale delivery
Connection to ELM
Off-site BNG habitat banks are often established by farmers entering long-term (30+ year) habitat management agreements. This overlaps with ELM Landscape Recovery and Countryside Stewardship — farmers can receive BNG income alongside ELM payments, but the schemes must be compatible.