A Guide to Building a Compliant BNG Strategy for Your Development
Why Every Project Now Requires a BNG Strategy
Biodiversity Net Gain (BNG) is now mandatory for most developments in England that require planning permission. Developers must deliver at least 10% biodiversity net gain, measured using the official statutory biodiversity metric.
The first step in any BNG strategy is a BNG Assessment, which establishes the site’s baseline biodiversity units before development. This baseline determines how many units must be replaced and what uplift is required to reach the mandatory 10%.
Where on-site uplift is not achievable, BioGains provides registered off-site biodiversity units from its UK habitat banks. These units are created, managed, and monitored in line with DEFRA and Natural England requirements, giving developers a compliant route to meet their BNG obligations.
Integrating Biodiversity Net Gain Early in Planning
BNG should be considered from the earliest planning stages. Early ecological surveys and baseline assessments allow developers to:
Understand existing habitats and constraints
Identify realistic opportunities for on-site habitat creation or enhancement
Establish whether off-site biodiversity units are likely to be required
Avoid last-minute redesigns and planning delays
BioGains supports developers whose sites cannot fully meet BNG on-site by supplying off-site units that can be factored into the BNG strategy early.
How to Calculate Biodiversity Units Using the DEFRA Metric
All BNG strategies must use the Statutory Biodiversity Metric, which measures the ecological value of habitats based on:
Habitat type
Condition
Area
Distinctiveness
Strategic significance
Your BNG Assessment calculates the pre-development baseline. The same metric is then used to show how the development, plus any on-site or off-site gains, delivers the required 10% uplift.
BioGains habitat banks are designed and managed in accordance with the DEFRA biodiversity metric and are registered on the national Biodiversity Gain Site Register. This ensures the units they generate can be included in Biodiversity Gain Plans submitted to LPAs.
On-Site vs Off-Site Gains and When Each Applies
Under BNG rules, developers must follow the mitigation hierarchy:
Avoid habitat loss
Minimise and mitigate impacts
Deliver on-site habitat creation or enhancement
Use off-site biodiversity units, where on-site gains are not enough
As a last resort, purchase statutory credits.
Many developments cannot create enough on-site habitat to meet the required 10% uplift. In these cases, BioGains offers:
Off-site habitat, hedgerow and watercourse units
Units already registered on the national scheme
Professionally managed habitat banks located across the UK
These off-site units help developers satisfy the mandatory uplift where on-site options are limited.
Writing a Biodiversity Gain Plan That Satisfies Your LPA
Before development begins, developers must submit a Biodiversity Gain Plan (BGP) for approval by their Local Planning Authority.
A compliant BGP includes:
Results of the pre-development BNG Assessment
Biodiversity unit calculations using the statutory metric
Details of all on-site habitat creation or enhancement
Proof of any off-site biodiversity units purchased
Habitat management and monitoring arrangements (minimum 30 years)
Legal agreements securing any off-site gains
BioGains provides developers with the documentation required for the off-site section of the BGP. This helps ensure LPAs have the information they need to review and approve the plan.
Common Compliance Challenges and How to Avoid Them
Underestimating baseline habitats: Always carry out a full BNG Assessment before any site clearance begins.
Leaving BNG decisions too late: Early integration avoids design changes and helps determine whether off-site units will be required.
Insufficient on-site space: Compact or high-density developments often cannot meet the mandatory uplift without off-site support.
Incorrect metric use: Always use the statutory DEFRA Biodiversity Metric, not older versions.
Weak Biodiversity Gain Plans: Missing evidence, unclear management details, or unsecured off-site units can delay approval.
BioGains reduces these risks by supplying registered, DEFRA-approved, long-term managed biodiversity units, along with the documentation developers need to demonstrate compliance.
Discover more about how BioGains works with landowners
Learn how BioGains partners with landowners to create high-quality habitat banks that supply biodiversity units to developers