Biodiversity Net Gain

UK Planning Requirement for 10% Biodiversity Net Gain

Check BNG RequirementsBNG Calculation Guide

BNG Implementation Timeline

12 February 2024

All TCPA 1990 planning applications (major and minor)

2 April 2024

Small-sites temporary exemption lapses

2 November 2026

NSIPs — DCO applications (machinery in force from 7 May 2026)

What is Biodiversity Net Gain?

Biodiversity Net Gain (BNG) is a mandatory planning requirement where developers must ensure development projects deliver at least 10% net gain in biodiversity value compared to the pre-development baseline. The duty commenced for all Town and Country Planning Act applications — major and minor — on 12 February 2024 (small sites had a temporary exemption that lapsed for applications made on or after 2 April 2024).

It's measured using the Defra Biodiversity Metric, and the resulting figures increasingly surface in corporate sustainability reporting as well as in planning submissions.

10% Minimum

Mandatory 10% biodiversity net gain for most developments

Metric-Based

Calculated using the current statutory biodiversity metric (metric 4.0 and earlier are no longer accepted)

30-Year Minimum

BNG habitat management secured for at least 30 years

BNG Requirements & Scope

Developments Requiring BNG

  • Most planning applications requiring planning permission
  • Small sites (1-9 homes or under 1 hectare) — in scope once the temporary exemption lapsed on 2 April 2024
  • Permitted development rights with prior approval
  • Nationally Significant Infrastructure Projects (DCO applications made on or after 2 November 2026)
  • Marine developments affecting intertidal habitats

Exemptions

  • De minimis development — less than 25m² of onsite habitat with biodiversity value greater than zero, and less than 5 metres of onsite linear habitat
  • Householder applications (extensions, outbuildings)
  • Self-build and custom housebuilding — this exemption was omitted from 6 August 2026 and now applies only to applications made before that date
  • Brownfield sites in certain circumstances
  • Development with alternative environmental assessment (e.g., EIA)

BNG Calculation Process

1

Baseline Assessment

Survey and map existing habitats on site using UK Habitat Classification system

  • Comprehensive ecological survey by qualified ecologist
  • Map all habitat types and their condition
  • Calculate baseline biodiversity units using the current statutory biodiversity metric
  • Consider habitat distinctiveness, condition, and strategic significance
2

Post-Development Assessment

Calculate biodiversity value after development using the same methodology

  • Map proposed habitat creation, retention, and enhancement
  • Apply condition scores for new and retained habitats
  • Include time-to-target multipliers for habitat establishment
  • Account for spatial risk factors and difficulty of creation
3

Net Gain Calculation

Compare post-development to baseline to determine net gain percentage

  • Calculate: ((Post-development units - Baseline units) / Baseline units) × 100
  • Must achieve minimum 10% net gain
  • Habitat trading rules apply (like-for-like or higher value)
  • Rivers and linear features calculated separately
4

Mitigation Hierarchy

Apply avoid, mitigate, compensate hierarchy before considering offsite units

  • Avoid: Minimize impact on highest value habitats
  • Mitigate: Reduce impacts through design modifications
  • Compensate: On-site habitat creation and enhancement
  • Offset: Purchase off-site biodiversity credits if needed

BNG Delivery Options

On-site Provision

Create, restore, or enhance habitats within the development site boundary

  • • Preferred option in mitigation hierarchy
  • • Integrated landscape design
  • • Green infrastructure creation
  • • Habitat corridors and connectivity

Best for: Sites with space and suitable conditions

Off-site Provision

Deliver BNG on land outside the development site but within the local area

  • • Local planning authority area preferred
  • • Neighbouring authority if justified
  • • Must be additional to existing commitments
  • • 30-year management requirement

Best for: Constrained sites with local land available

Biodiversity Credits

Purchase statutory biodiversity credits from government as last resort

  • • Available when on/off-site not possible
  • • Significantly more expensive option
  • • Credits fund habitat creation elsewhere
  • • Immediate payment required

Note: a “spatial risk multiplier” doubles the number of statutory credits needed relative to the shortfall being compensated for

BNG Planning Application Process

Pre-Application

  • Commission baseline habitat survey
  • Complete Biodiversity Metric calculation
  • Design development to minimize biodiversity loss
  • Identify on-site and off-site BNG opportunities
  • Consult with Local Planning Authority

With Application

  • Biodiversity Net Gain Statement
  • Statutory biodiversity metric calculation
  • Habitat Management and Monitoring Plan
  • Legal agreements for off-site provision
  • Financial security arrangements

Common BNG Challenges & Solutions

Challenges

  • Limited off-site land availability

    Suitable land for habitat creation is scarce near development sites

  • High cost of statutory credits

    Prices are tiered by habitat, and a spatial risk multiplier doubles the units required, making credits the most expensive route

  • Complex metric calculations

    The statutory biodiversity metric requires specialist ecological expertise

  • 30-year management commitment

    Long-term habitat management and monitoring obligations

Solutions

  • Early engagement with habitat banks

    Partner with habitat banking providers for guaranteed off-site units

  • Maximize on-site provision

    Integrate green infrastructure and biodiversity into design

  • Specialist ecological consultancy

    Engage qualified ecologists early in design process

  • Conservation covenants

    Use legal mechanisms to secure long-term habitat management

Habitat Banking Market

Market Development

A growing market of habitat banks and environmental consultancies is emerging to provide off-site biodiversity units, offering an alternative to expensive government credits.

  • • Habitat banking operators create and manage sites
  • • Advance habitat creation before selling units
  • • Competitive pricing vs government credits
  • • Focus on high-value habitat creation

Market Context

Habitat banking is an emerging market shaped by mandatory BNG demand rather than discretionary purchasing.

This is general market information, not investment or financial advice.

  • • Habitat bank unit prices vary by habitat type, condition and location
  • • Government (statutory) credit prices are published by Defra and reviewed every six months

BNG Integration with Other Requirements

Environmental Impact Assessment

BNG requirements apply alongside EIA for major developments

  • • Coordinate biodiversity assessments
  • • Align mitigation measures
  • • Integrate monitoring requirements

Protected Species Licensing

BNG delivery can support mitigation for protected species

  • • Great crested newt district licencing
  • • Bat mitigation and compensation
  • • Habitat creation for multiple species

Corporate Biodiversity Reporting

BNG delivery supports biodiversity reporting commitments

  • • Demonstrate nature positive impact
  • • TNFD disclosure alignment
  • • Support biodiversity duty compliance

Biodiversity Net Gain FAQs

What happens if I can't achieve 10% net gain on-site?
You must follow the mitigation hierarchy: first avoid and minimize impacts, then compensate through off-site habitat provision or as a last resort purchase statutory biodiversity credits. Government credit prices are tiered by habitat and a spatial risk multiplier doubles the units required, so off-site provision through habitat banks is often more cost-effective.
How long do BNG obligations last?
BNG habitat creation and enhancement must be secured for at least 30 years through legal agreements, conservation covenants, or planning obligations. This includes ongoing management, monitoring, and replacement of failed habitat creation. Financial security is required to guarantee delivery.
Can BNG be delivered on the same site as carbon offsets?
Yes, many habitat types deliver both biodiversity and carbon benefits. Woodland creation, peatland restoration, and grassland enhancement can contribute to both BNG requirements and carbon offsetting. However, you cannot "double count" the same area for both purposes.
What about developments on brownfield sites?
Most brownfield developments still require 10% BNG unless the baseline biodiversity value is below 2 units per hectare. However, local planning policies may provide flexibility for brownfield redevelopment. Early ecological survey is essential to understand baseline conditions.
How does BNG relate to other biodiversity requirements?
BNG is additional to existing protected species licensing and nature conservation requirements. It complements biodiversity duty reporting for public bodies and supports corporate biodiversity reporting. BNG delivery can be integrated with other environmental mitigation measures.

Want to Talk It Through?

BNG sits alongside a planning application, not a sustainability report — but if it would help to talk through how it connects to your wider reporting, we offer a free, no-obligation call.

Book a Free Call

Related Biodiversity Resources

Biodiversity Reporting

Corporate nature disclosure and TNFD reporting

Biodiversity Duty

Public sector biodiversity reporting requirements (Section 40 NERC Act) — not yet covered on this site

Environmental Reporting

Navigate UK environmental compliance requirements