22.04.2025

What is Biodiversity Net Gain?

First of all lets understand what biodiversity is. Biodiversity is the variety of life found in one place on earth.

Biodiversity Net Gain is a concept and approach to environmental conservation aimed at improving the overall health and diversity of ecosystems. It involves developing land whilst also improving the biodiversity of the local area.

The idea is to ensure that after land has been developed, the biodiversity in the area is left in a better state than before the project began.  The goal is to halt/reverse the decline of Biodiversity across the United Kingdom. Developers are required to improve the biodiversity by at least 10%. This can be done by either improving the biodiversity of the development site or buying credits from a BNG Supplier within the local area.

There are three types of habitats covered within BNG:

• Area Habitats such as grassland or a Coniferous Woodland
• Linear Habitants: Hedgerows
• Linear Habitats: Watercourses

These are three separate Habitats, meaning for example, if your survey determines you have a small stream running through your development and a wildflower meadow you will be required to show an improvement to the biodiversity of both habitats separately and you cannot remove one and just improve the other as these are different types of habitats.

How is BNG Calculated?

BNG is calculated using the Statutory Biodiversity Metric (currently Metric 3.1 at the time of writing), this was produced by Natural England and measures the biodiversity value, in turn creating a numerical value for BNG. This metric helps developers design, plan and make land management decisions that better support the biodiversity.

There are four factors that determine the BNG, these are:

• Location
• Distinctiveness
• Habitat size
• Condition

How to Deliver a Net Gain?

There are two main ways a developer can deliver a net gain:

• Remove existing habitats and replace them with a new habitat of higher value, for example removing low quality grassland and planting a high-quality flower meadow.
• Retain existing habitats and improve their biodiversity value by enhancing their quality/condition.

As development often provides very low valued habitats such as concrete a net gain may not always be deliverable on-site in all cases. The same measures can therefore be applied to off-site habitats to deliver an overall net gain for a project.

There are three methods enabling a developer to achieve this:

• Registered off-site Biodiversity Net Gain – Developers can create or enhance habitat they already own (The further away from the development the less BNG credits you receive). The land is secured with a Section 106 Agreement, is registered with the Biodiversity Net Gains register and is specifically allocated to the development. The legal agreement states this land must be maintained for 30 years.
•  Commercial Units – Developers can buy credits from an off-site provider who will undertake the habitat creation or enhancement work themselves, the same thing applies with the Section 106 Agreement which means the land must be maintained for 30 years.
• Statutory Credits –Developers can purchase credits from the Government who will then fund third parties to undertake the work. The same applies with their 30 year maintenance along with a S106 Agreement but this is deemed to be a last resort and all other options must be exhausted before attempting this option as it is intended to be a last resort and is priced as such.

What is a Section 106 Agreement?

A Section 106 Agreement is a legal agreement between usually a developer of land and Local Planning Authorities that require developers to contribute towards a range of things to help improve the local authority/surrounding area of the development. In this case as a BNG Credit Supplier you may not be a developer but will still be required to enter into a Section 106 Agreement, please contact us for any further information regarding this, as we are happy to help.

How to Become a Supplier of BNG Credits?

First of all, you must familiarise yourself with the requirements and legislation you will need to comply with. The Environment Act 2021 made Biodiversity Net Gain a mandatory part of the planning process in the United Kingdom. Your project(s) must meet a minimum standard of biodiversity improvement of at least 10% and comply with the department for Environment, Food and Rural Affairs guidelines on BNG.

Secondly, you will need to identify land you own that you could enhance the biodiversity of, this can include habitat restoration, improving existing natural environments or creating wildlife corridors.

Once you have identified the piece(s) of land, you will need an Ecologist to assess the current biodiversity within the land using the BNG metric. This will outline the current biodiversity within the land and help you determine what can be done to improve said land.

Once the land has been assessed, you will need to engage in meaningful biodiversity improvements such as creating wetlands or planting native trees, to increase the biodiversity of the area. This is a long-term project and therefore needs to be demonstrated over a 30-year period, which is part of the planning requirements to become a BNG Credits Supplier. The local authority will monitor this land for 30 years to confirm the increase in biodiversity over the long term, you may be required to make improvements if the biodiversity drops below the 10% threshold of Net Gain but the use of this land cannot change once the Section 106 is entered into.

From here you want to get the land assessed by an Ecologist or a Qualified Environmental Consultant to conduct an environmental assessment to determine the level of biodiversity improvement achieved through the project.

Once an improvement of 10% has been achieved, you can then enter into a Section 106 Agreement with the Local Authority, this will be continually monitored for 30 years to confirm the obligations of the Section 106 Agreement are met. This will then be added to the Local Land Charges register.

Before you can list your land for BNG Credits you must have produced a ‘Habitat Management and Monitoring Plan’, this may form part of your Section 106 Agreement, but you cannot sell credits without it. You will also require the written sign off (mentioned above) from an Ecologist or Qualified Environmental Consultant.

Now you will be in a position to list your BNG Credits for sale, this is doable on the Natural England Biodiversity Net Gain Register or other third-party platforms. This is where Developers are looking to offset their BNG with your credits. Prices of the BNG Credits are determined by the type and quality of the habitat created/improved.

Once implemented and sold, a credit supplier must ensure the habitat remains in good condition and that any necessary corrective measures are taken if biodiversity declines.

In Summary

Following the Environment Act 2021 Biodiversity Net Gain is required by all developments that exceed 25m squared or 5m of linear habitat. This means virtually all development applications approved after 12^th February 2024 require at least a 10% Net improvement of Biodiversity.

Becoming a BNG credit supplier involves identifying land appropriate for biodiversity enhancement, apply the Biodiversity Net Gain Metric to calculate the improvements made and ensuring long-term management and compliance with the regulatory requirements. You will also need to instruct a Solicitor to agree the Section 106 Agreement with the Local Authority.

Let’s have a Conversation

If becoming a supplier is something you are interested in or you just want to learn more about how BNG works, please get in touch as we would be more than happy to help.

If you want to learn more about the Section 106 and how this would potentially affect your land as a BNG Credits Supplier please also get in touch.

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About the Author Matthew Jones 

Matthew is a paralegal within our Residential Development team and is is being guided by Director and Head of Residential Development, Matthew Roach.

T:   01922 639 080

@:  mj@walkersolicitors.com