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Biodiversity Net Gain (BNG)

Biodiversity Net Gain (BNG) is an approach to development that aims to leave the natural environment in a measurably better state than before the development took place. Use this page to understand the ideas behind BNG policy, who it affects, how we are involved as your Local Planning Authority, and how you can meet the requirements when submitting your planning application.

Understanding BNG policy

New BNG requirements mean that we will use the Planning system to ensure we can deliver improved biodiversity with new development. Select a topic below to read more about how the policy has evolved.

What BNG means

BNG policy lays down a new process designed for the Planning system to make sure new development can deliver a net positive impact (called a 'biodiversity net gain') on the natural environment. It requires new developments to be designed and planned in ways that minimise any loss or damage to existing habitats, and then to compensate and off-set any damage caused. This approach will result in the extension and improvement of natural habitats, as part of a development or project, and enables new development to contribute to nature’s recovery.

The policy relies on a number of ideas or practices:

  • Measuring biodiversity damage or gains
  • Managing and monitoring biodiversity impacts from development over a long period
  • Using a mitigation hierarchy to avoid and minimise harm to biodiversity, restore any lost habitat and, as a last resort, compensate to at least equivalent ecological value.
  • Balancing on-site and off-site, off-set measures to repair or improve biodiversity

See the section on how to deliver the BNG requirement, below, for more detailed information on how these ideas are applied in legislation and guidance.

National policy

The National Planning Policy Framework (2019) sets out that planning policies and decisions ‘should contribute to and enhance the natural and local environment, by minimising impact on and providing net gains for biodiversity…’  BNG is the achievement of measurable gains for biodiversity through new development, and occurs when a development leaves biodiversity in a better state than before development.

The Environment Act (2021) contains a new BNG condition for planning permissions. The delivery of BNG is set to become a mandatory requirement of the planning system from November 2023. It directly affects people who need to secure planning permission for new projects above a certain size. It will be unlawful to issue a planning approval for any qualifying project that does not secure 10% BNG, with 30-year management and monitoring.

The Government will be providing secondary legislation, guidance, and tools to support its implementation of this policy.

B&NES policy

In July 2020, we declared an Ecological Emergency, recognising the severity of the degradation of the natural environment and loss of wildlife, and the urgent need to act to restore nature. Acting on this declaration, we agreed a set of priorities for climate and ecological action to tackle this.

Read more about how we are responding to the Climate and Ecological Emergency

We committed to bringing forward the requirement for BNG, ahead of the national mandatory requirements. We have added direct measures to help address nature conservation and biodiversity loss, through new policy NE3a in our Partial Update to our Local Plan (LPPU). The approach reflects the emerging government requirements, and uses the same ways of measuring BNG (or BNG metrics) which the government has developed. It will be formally adopted in the spring of 2023, but influences planning applications from 1 November 2022. 

View our BNG policy in the LPPU

Our role

As your local council, we have a dual role in relation to BNG:

  • As your local Planning Authority, we are responsible for processing planning applications, and must make sure they are compliant with BNG requirements. We have produced interim guidance to support you to meet the requirements when submitting your planning application, and will update this as this new practice emerges.
  • As a local landowner, we are also exploring ways that off-site habitat gains can be successfully achieved and delivered, including the role Council land could play. See below for more information about off-site biodiversity unit provision.

Implementing BNG

Select a topic below to find out more about tools and guidance you will need, to assess and deliver the BNG requirements for a development. 

How to deliver the BNG requirement

To create Biodiversity Net Gains, it's necessary to provide habitats where plants and wildlife can prosper. There are several ways of doing this, as part of a process of development:

  • The restoration of degraded habitats
  • The enhancement of existing habitats
  • The creation of new habitats

To put this policy into practice effectively, you will need standardised tools and guidance. For example:

  • Metrics for identifying markers and measuring biodiversity
  • Tools for using the metrics consistently
  • Guidance on how, when, where and how long to monitor ongoing biodiversity impacts, once developments are complete

For the latest tools and most detailed support on how to deliver BNG requirements for your development, see our list of policy and guidance resources

On-site BNG provision

Biodiversity gains can often be achieved within a development site, and can be linked to the provision of green spaces (such as community orchards and landscaped areas). These gains are usually referred to as on-site gains, and will often be the preferred solution. These can help to achieve good placemaking, providing better places to live and work, and ensuring communities have good access to nature-rich sites.

Council off-site biodiversity unit provision

Sometimes, the Biodiversity Net Gains required by a development may not be effectively achieved on-site within the development. This may be because space is very limited, or where the long-term use of the development is not compatible with the long-term maintenance of nature-rich habitats.

In these cases, the BNG can be delivered off-site, through the provision of off-set BNG habitat. This will be measured in standard BNG units, representing the habitat value to local biodiversity. 

As a local landowner, we are exploring ways that off-site habitat gains can be successfully achieved and delivered, including the role Council land could play.

For more information about our BNG off-site provision projects, please email us at

All planning projects subject to BNG requirements should consider BNG from the very outset, prior to site design, and ideally at site selection stage to help minimise the need for providing replacement habitats. 

The Mitigation Hierarchy

The mitigation hierarchy is a concept designed to help minimise the impacts of development.

The concept requires site planning and design to consider biodiversity from the outset. Harm to biodiversity must always first be avoided, and then, if this is not possible, minimised. Where avoidance of harm is not possible, mitigation approaches should be used, and as a last resort, compensation must be provided (to at least equivalent ecological value, using standard national measures). This is a critical element of the BNG process and can be used to help minimise the habitat off-setting and gains required.

What BNG means for your planning application

From 1 November 2022, most Major and Minor applications need to submit Biodiversity Information with planning applications.

Qualifying developments will have to demonstrate, and then deliver, measurable net gains for biodiversity which must be secured, managed, and monitored. The exact requirements, and methods of measurements, are different for different categories of application. 

Select a topic below, to understand in more detail which types of planning application are exempt, and what this may mean for your application.

Major applications

Major planning applications will be expected to deliver a minimum of 10% biodiversity gains, with habitat management and monitoring secured for at least 30 years. The gains must be calculated using the main government metric (currently Biodiversity Metric 3.1).

Minor applications

For minor planning applications the policy requires that no-net loss of biodiversity is secured with an appropriate biodiversity gain. The no net loss and appropriate gain must be calculated using the approved government metric for small sites.


Householder applications, changes of use, and permitted development are all exempt from the full BNG requirements of policy NE3a. However, we will still expect you to show that you have considered biodiversity, and to deliver habitat and species enhancements, as part of your planning application. These could include simple additions, such as the provision of integrated bird and bat boxes, or the use of native and nectar-rich species within landscaping schemes, for example.

View BNG tools and resources