Biodiversity Net Gain (BNG) is a policy and legal requirement within the English planning system designed to ensure that new development results in a measurable improvement in biodiversity — in other words, that nature is left in a better state than before the development occurred. Rather than just avoiding or mitigating harm to nature, BNG aims for a positive outcome for wildlife and habitat.
At its core:
- Developers must plan and deliver enhancements so that, after completion, the biodiversity value of a site is at least 10% higher than it was before development.
- Biodiversity is measured using a standardised metric tool that assigns numerical values to habitats based on their type, condition, size, and location.
Legal Framework in England
In England, BNG is now a statutory requirement under Schedule 7A of the Town and Country Planning Act 1990, as inserted by the Environment Act 2021 and subsequently brought into force from 12 February 2024 for most developments.
Key features of the legal framework:
- Mandatory 10% net gain: Most planning permissions must deliver at least a 10% increase in biodiversity value over pre-development levels.
- Post-permission condition: The BNG requirement is enforced through a pre-commencement planning condition — a Biodiversity Gain Plan must be approved by the local planning authority (LPA) before development starts.
- Exemptions & transitional arrangements: There are some exemptions (e.g., certain forms of retrospective applications) and transitional arrangements for permissions granted before implementation dates.
- Irreplaceable habitats have special treatment to ensure development doesn’t destroy habitats that cannot be recreated or restored.
BNG became mandatory for major developments from February 2024, with small sites included from April 2024, and rules for nationally significant infrastructure projects (NSIPs) due to apply from mid-2026.
How BNG Works in Practice
1. Before Development
- Baseline assessment: An ecological assessment establishes the current biodiversity value of the site using the statutory metric.
- Avoidance and minimisation: Developers should seek to avoid harm where possible by thoughtful design and site selection — this is part of the biodiversity gain hierarchy.
2. Delivering Net Gain
There are three main ways developers can achieve their biodiversity target:
- On-site gains: Creating or enhancing natural habitats within the development boundary.
- Off-site gains: If on-site measures aren’t sufficient, developers can secure additional biodiversity units on other land they own or control.
- Statutory biodiversity credits: As a last resort, developers purchase credits from government-approved schemes.
All enhancements must be maintained for a minimum period (typically 30 years) to ensure that ecological benefits are sustained.
3. Biodiversity Gain Plan
After planning permission is granted, developers must submit a Biodiversity Gain Plan for approval before starting work. This plan:
- Sets out how the net gain target will be met
- Includes metric calculations, habitat creation or enhancement proposals
- Lists any off-site units or statutory credits to be used
Local planning authorities have 8 weeks to approve the plan and cannot lawfully allow development to start without it.
Role in the Planning Process
BNG interacts with other planning controls but is a distinct statutory requirement:
- It is not typically a reason to refuse planning permission, but rather a condition that must be capable of being fulfilled through the approved Biodiversity Gain Plan.
- LPAs review metric calculations and manage legal agreements or covenants to secure long-term habitat management.
In policy terms, the National Planning Policy Framework (NPPF) also encourages planning strategies and decisions to seek measurable net gains for biodiversity and integrate ecological considerations early in plan preparation and application design.
Policy Rationale and Broader Context
The main aim of BNG is to align development activity with broader environmental objectives:
- To help reverse habitat loss and support wildlife recovery
- To create resilient landscapes that contribute to ecosystem services
- To integrate nature restoration into mainstream planning and development decisions
BNG represents a shift in planning policy from avoiding harm toward designing positive ecological outcomes, supported by standardised measurement and long-term management commitments.
Challenges and Debates
While mandatory BNG is a landmark reform, there are ongoing debates and adjustments in policy implementation:
- Some developers and environmental groups discuss how effective a minimum 10% gain is in practice for restoring nature at landscape scales.
- Recent coverage highlights tensions around potential exemptions for very small sites (e.g., under certain size thresholds) and concerns about environmental safeguards.
The Coventry Context
As an example of how BNG might impact on Coventry, there has been a recent announcement about the establishment of a nature reserve on the site of the former Brandon Golf Course. This is to be funded by the use of BNG units from developments.
Coventry policy requires any Coventry development to deliver BNG within the immediate area or close by and within the city boundary. It is being used to improve the quality of the city’s greenspaces and waterways to help create new urban nature networks and green corridors across the city for local people to enjoy. The creation of the nature reserve is outside the city boundary and will therefore mainly provide BNG for developments in Warwickshire and the West Midlands.