What England's Biodiversity Net Gain Rules Mean for Local Planning

England's planning system now asks a simple question of many developments: can you leave nature better off than you found it? Since early 2024, Biodiversity Net Gain has moved from voluntary good practice to a legal requirement for most major schemes. The rule is straightforward on paper — a 10% uplift in habitat value — but the detail is where local planning authorities, developers and communities are finding the real work. This guide explains what the requirement means in practice, from the metric used to measure habitats to the way councils scrutinise and monitor plans.

The 10% uplift, explained without the jargon

The statutory biodiversity metric calculates the baseline value of habitats on a site before development. It scores habitats by size, distinctiveness (a species-rich meadow scores higher than improved grassland), condition (poor, moderate or good), and location. A development must result in at least a 10% higher score overall. That is not 10% more trees or ponds; it is 10% more biodiversity units.

For example, a field of ryegrass might score low. Replacing it with a species-rich meadow, native hedgerows and a pond could exceed the 10% gain. But you cannot simply trade down. The metric has rules to prevent the destruction of valuable habitats being offset by creating something much poorer. Irreplaceable habitats, such as ancient woodland, receive strong protection and cannot normally be replaced by off-site gains.

What developers are now required to do

Developers must follow the mitigation hierarchy:

1. Avoid impacts: design the scheme to keep important habitats.
2. Minimise impacts: reduce the footprint where possible.
3. Restore on-site: repair or enhance what remains.
4. Offset: only then create or buy habitat elsewhere.

A biodiversity gain plan must be submitted to and approved by the local planning authority before development begins. It must show how the 10% gain will be achieved, how the habitat will be managed for at least 30 years, and how that management will be funded.

On-site gains are created within the development boundary. Off-site gains come from registered sites, often secured through conservation covenants or planning obligations. As a last resort, developers can buy biodiversity credits from a government-backed scheme. The gain plan is not a document to produce after permission is granted; it is a condition that must be met before work starts. Some applications are exempt — householder extensions and certain self-build schemes, for instance — but most residential and commercial projects are in scope.

How councils check the numbers

Local planning authorities must validate applications and scrutinise the biodiversity gain plan. They will check:

• Is the baseline survey accurate and up to date? Habitats must be classified correctly.
• Has the mitigation hierarchy been followed, with evidence of avoidance and minimisation?
• Does the metric calculation genuinely deliver a 10% gain?
• Is any off-site habitat registered and secure for the long term?
• Is the 30-year management and monitoring plan credible and funded?

Many councils employ ecologists or external consultants to review these documents. They can attach conditions to planning permission, and they can refuse schemes that fail to demonstrate the required gain. However, resources are tight. Some authorities rely heavily on the developer's own ecologists, which puts pressure on officers to ask searching questions. After development is complete, councils may monitor whether the promised habitat has been created and is being managed. Enforcement action is possible if it has not.

Where Local Nature Recovery Strategies fit

Local Nature Recovery Strategies (LNRS) are county-level maps that identify priority areas for nature recovery. They do not replace Biodiversity Net Gain, but they matter. Off-site gains should align with these strategies where possible. Developers can use the LNRS to find suitable sites for habitat creation. Councils should consider them when preparing local plans and determining applications. This helps direct investment to places where it will do the most for wildlife, rather than scattering habitats randomly.

Common sticking points and how to smooth them

• Starting too late. Ecological surveys often need to be done in specific seasons. Engage an ecologist before designs are fixed.
• Treating the metric as a tick-box. It is a tool for better design, not a target to game. Think about nature from the outset.
• Underestimating management costs. Thirty years of management is a long commitment. Budget for it realistically.
• Poor record-keeping. Keep clear evidence of baseline surveys, calculations and decisions. This will speed up validation.
• Assuming off-site is easy. Finding a suitable, registered site can take months. Start early.

What it means for local communities and councillors

Residents and parish councils can ask direct questions: Will this development deliver the 10% gain? Where exactly will the habitat be? Who will manage it, and for how long? Councillors can scrutinise the biodiversity gain plan as part of the planning process. Biodiversity Net Gain can be a lever for better green spaces, but only if the plans are specific and monitored. It is not a substitute for protecting existing wildlife sites, and it should not be used to justify damage to irreplaceable habitats.

Practical steps if you're involved in a planning application

If you are a developer, talk to the local planning authority early. Get ecological advice before you finalise the layout. Use the metric honestly, and plan for long-term management. If you are a councillor or community group, ask for the biodiversity gain plan. Check the baseline, ask about monitoring and enforcement, and make sure the promised habitat is secured. If you are a landowner, you might consider registering land as an off-site gain site. It can provide income, but it comes with long-term commitments. For any legal or financial decisions, seek professional advice.

Photo: jarmoluk / Pixabay