Need a Biodiversity Net Gain Report?

Biodiversity Net Gain background

Biodiversity net gain (BNG) is a key component of environmental planning, having been introduced in England’s Environment Act 2021. BNG was introduced following a two-year transition period, and it ensures that development projects leave the natural environment in a measurably better state than before.

BNG places a priority on the material consideration of valuable habitats, and satisfying BNG requirements is now a requirement of planning applications. Using the statutory biodiversity metric, a pre-development biodiversity value record must be taken of the current development site, along with a post-development biodiversity value prediction, based on scrutiny of the development plans. The gap between the readings must be eliminated, the level of biodiversity value must be retained and increased by a 10% minimum and be maintained for at least 30 years.

BNG can be achieved by various methods including new habitat creation and habitat enhancement. If these options are not viable and on-site provision of net gain is not possible, the last resort option is outsourcing off-site habitat.

A planning application must contain information about how BNG requirements will be met. A BNG Plan will provide additional information about the proposed approach for achieving mandatory BNG. Failure to meet BNG standards can result in delays or refusals of planning applications.

How BNG Requirements Can Be Met

Developers can meet BNG requirements in several ways, including:

On-site enhancements

Achieving a minimum 10% uplift in biodiversity on-site is the preferred approach, and might involve improving biodiversity within the development site, such as creating green roofs, planting native vegetation, or restoring habitats. However, if, according to the biodiversity gain hierarchy, it is not possible to improve or create habitat to the required threshold, sourcing off-site biodiversity gains is a last resort option.

Off-site provision of BNG and Biodiversity Gain Sites

If on-site biodiversity improvements are unfeasible, developers can invest in off-site biodiversity projects or purchase conservation credits through a trading market.

Off-site contributions

Developers can purchase credits or fund habitat enhancement or creation on other designated land areas.

Biodiversity Gain Sites

These are designated areas created across the country where off-site net gain projects are implemented, registered with Natural England, and managed for long-term biodiversity enhancement. These sites often involve collaboration with local planning authorities or conservation groups to enhance larger biodiversity gain sites. The biodiversity gain site register will hold details of available land, allowing for a suitable parcel to be identified to fulfil requirements.

Statutory biodiversity credits that equal the units needed within the red-line boundary of the development site would be purchased as off-site biodiversity units from the habitat bank managers or landowners.

Biodiversity Net Gain (BNG) Exemptions – England

Existing Exemptions (in force since 2024)

The Biodiversity Gain Requirements (Exemptions) Regulations 2024 set out the categories of development exempt from the mandatory BNG condition. These include:

De minimis developments: those that don’t impact a priority habitat, or that impact less than 25 square metres of habitat or 4 metres of on-site linear habitats such as hedgerows

Pre-February 2024 applications: planning permissions relating to applications made before 12 February 2024.

• High-speed railway transport networks (HS2)
• Self-build and custom-build applications (though this is changing: see below)
• Biodiversity gain sites themselves – land being used to provide BNG for other developments
• Urgent Crown development – typically for national security or emergency response

Householder applications are also exempt from biodiversity net gain requirements.

New Exemptions Coming 31 July 2026

Defra confirmed these changes on 15 April 2026 following a 2025 consultation on how exemptions, thresholds and metrics could be refined after reports of planning delays, high costs and a stalled off-site market.

1. New 0.2 hectare area-based exemption. A new exemption will apply for developments where the site area is 0.2 hectares or below. These sites will still be subject to environmental protections via the NPPF and wider regulatory requirements but will no longer need to demonstrate a 10% net gain on or off site. Planning applications will still be refused where significant harm to biodiversity cannot be avoided, mitigated or compensated against, even on an exempt site.

2. Removal of the self and custom build exemption. From 31 July 2026, it will no longer be possible to claim BNG exemption for self or custom build dwellings. It is anticipated that the new 0.2-hectare exemption will capture many of these developments.

3. New exemption for temporary planning permissions. New regulations will exempt temporary development that is for five years or less, recognising that delivery of BNG on these sites is limited due to their temporary nature.

NSIPs (Nationally Significant Infrastructure Projects). BNG for NSIP projects will become mandatory on 2 November 2026, with a new ‘BNG boundary’ definition and flexibility on where aggregated biodiversity gain is sited – with the exception of water impacts, which must remain in the catchment.

BNG Guidance

The aim of BNG is to facilitate sustainable development while balancing economic growth and environmental stewardship. Exemptions are in place to ensure proportionality, focusing resources on projects with significant environmental impact.

If you have a development impacting habitat, it’s important to familiarise yourself with the biodiversity net gain regulations early in the development process. An ecology consultancy can provide further guidance on the best way to approach BNG on a development project.