Biodiversity Net Gain: What’s the latest?

Biodiversity Net Gain (BNG) is now mandatory for major developments in England. We outline the terminology, tools, metrics and guidance developers should be aware of.

Katie Smith
Written by:

Katie Smith

January 17, 2024
Senior Ecologist

at Ecus

Updated 19/01/2024

Biodiversity net gain (BNG) will become mandatory from 12 Feb 2024 for major developments (residential projects with 10 or more dwellings or sites larger than 0.5 hectares)

For smaller developments, BNG requirements will start from 2 April 2024. This includes residential developments with 1-9 dwellings or sites under 0.5 hectares, and commercial projects with less than 1,000 square meters of floor space or sites under 1 hectare.

As we reach mid-January, we’re on the verge of Biodiversity Net Gain (BNG) becoming mandatory for major developments in England. Back in November 2023 the long-awaited secondary legislation was published in draft format as six statutory instruments – referred to as regulations. The secondary legislation will support the primary legislation (The Environment Act 2021) by setting out specific measures on how BNG will be delivered, including more detail on information such as the biodiversity gain site register, exemptions, and irreplaceable habitats.

The secondary legislation is one of the last main puzzle pieces that will enable BNG to become mandatory. At the time of writing the first two statutory instruments have been laid before parliament and are awaiting approval. Once approved, the remaining four statutory instruments will be laid before parliament for approval. All statutory instruments must be approved ahead of BNG being mandatory which has now been confirmed as 12th February 2024 for major development (unless otherwise exempt).

Alongside the draft secondary legislation, in November 2023, Defra also published a variety of updated tools, resources and guidance which further our understanding of how the application of BNG will look once mandatory. Below, we have summarised some of these updates and have included some key points to be aware of during the BNG process based on our current knowledge and understanding.

Statutory Biodiversity Metric

To date, we are familiar with numerous versions of the metric. The updates in November 2023 included publication of the statutory biodiversity metric and associated tools, including a user guide (currently published in draft format) and habitat condition assessment sheets. The draft user guide sets out the rules and principles of the metric and guidance on how to complete the metric calculations. It is expected this will be the only accepted version of the metric for Planning in England once BNG becomes mandatory, and more guidance is due to be released for how to use data from previous metric versions in the statutory metric. As an ecologist and regular user of the metric it will be interesting to see how we will be advised on how to convert data from previous metric versions into the statutory metric.

Biodiversity Gain Hierarchy

This is new terminology to set out the approach to achieving a 10% overall gain. The Biodiversity Gain Hierarchy requires that following consideration of avoiding and/or mitigating impacts to on-site habitats, biodiversity gains are firstly considered through on-site habitat enhancement, followed by on-site habitat creation, then registered off-site gains, and as a last resort, statutory credits may be purchased. This is a key consideration from early in the design stages and adherence to this is to be demonstrated in the Biodiversity Gain Plan.

The Biodiversity Gain Hierarchy differs to the mitigation hierarchy, which is set out in the National Planning Policy Framework (2023) and which should also be followed (and evidenced) during the process of identifying how a net gain will be achieved.

The Biodiversity Gain Plan and planning requirements

A Biodiversity Gain Plan is a document in which a developer will demonstrate exactly how a proposed development will achieve the biodiversity gain objective of at least 10%. The plan must include details such as pre-development and post-development habitat information, the completed metric calculation tool, details of habitat maintenance and monitoring and how this will legally be secured (e.g. planning condition, planning obligation, conservation covenant), and whether statutory credits have been purchased. This will be a pre-commencement planning condition and must be submitted to the local planning authority after planning permission has been granted. The local planning authority will have eight weeks to approve the plan.

Whilst the Biodiversity Gain Plan will be a post-permission requirement, it is important to remember that BNG should be considered early in the development process and at all stages to maximise the possible gains the development can deliver.

For development where BNG is required, planning applications must include details of the pre-development biodiversity value as a minimum, including the completed metric calculation tool and a plan of on-site habitats to enable the application to be validated. Local Planning Authorities are likely to require further information to assist in considering BNG for a development and local requirements should be referred to in addition.

Significant/non-significant on-Site enhancements

Defra have now shared definitions of ‘significant’ and ‘non-significant’ enhancements when it comes to enhancing or creating habitats to contribute towards on-site net gain. Significant enhancements, as defined by Defra, will require habitat maintenance to be secured legally through either a planning condition, planning obligation or conservation covenant for a minimum of 30 years, similar to off-site gains. Habitat Management and Monitoring Plans will be required to demonstrate what practical actions will be taken to ensure successful delivery of significant on-site enhancements (and off-site gains). Non-significant enhancements will not require maintenance to be secured for at least 30 years, unless required for other reasons within local planning policy.

Takeaway thoughts

Whilst we are awaiting parliamentary approval of the statutory instruments, we do have many of the tools, resources and knowledge to be as prepared as possible for the implementation of mandatory BNG. Many Local Planning Authorities already require a degree of net gain demonstrated through the use of a metric tool so we are well prepared to continue this once BNG is mandatory.

As ecologists we are continuously working with developers and landowners to assist with BNG and provide support throughout the process of identifying how a measurable net gain will be delivered. From our experiences so far it is clear that early ecological involvement and stakeholder engagement during a project are vital in securing the best outcomes for biodiversity and meeting the biodiversity gain objective in accordance with good practice principles. Early engagement also allows developers to be aware of potential constraints at an early stage and implement solutions during the design process – where more flexible solutions can be considered and there is increased opportunity to avoid adverse impacts.

More detailed information published by Defra can be found at the links below. If this raises any questions or you would like our support with any BNG projects, feel free to get in touch with us.

Information you need for biodiversity net gain (BNG).

Defra – Land use: policies and framework blog