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Biodiversity Net Gain Planning Condition

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Biodiversity net gain (BNG) is now a compulsory element of all future development projects in England, as it is now part of UK legislation. This process involves taking into account the impact of a project on the environment, specifically with regards to biodiversity. The goal is to ensure that the overall biodiversity is improved as a result of the project. This is done by avoiding loss of biodiversity, preserving different types of habitats, and protecting significant ecological assets.

Local planning authorities require evidence of BNG to inform planning applications. This is done with the aim of demonstrating how the proposed development will contribute to measurable improvements in biodiversity. BNG is now a policy requirement for planning consent and can also act as a planning condition. This means it can significantly influence the final decision of planning authorities when they are considering whether to grant or refuse a planning application.

Utility providers, transport companies, and other organisations are also introducing BNG into their internal policies. Some companies are even setting targets for a greater percentage gain than the mandatory minimum. This means that those in charge of planning projects will need to ensure that mandatory BNG is factored in and recognise the importance of preserving biodiversity in development.

Biodiversity net gain planning condition

Under the Environment Act 2021 and through the application of the national planning policy framework (nppf), anyone looking to obtain planning permission through a planning application (with a few exceptions) must deliver at least 10% biodiversity net gain. This net gain will be measured using Defra’s biodiversity metric 4.0 and habitats must be maintained for at least 30 years. Alongside these requirements, further implementations were induced including:

  • A strengthened legal duty for public bodies to conserve and enhance biodiversity
  • New BNG reporting requirements for local planning authorities
  • Mandatory special strategies for nature described as “Local Nature Recovery Strategies (LNRS).

Further planning conditions may require a survey of the site’s existing biodiversity, including habitat types and species present. An assessment of the impact that the proposed project will have on surrounding biodiversity and monitoring of the site’s biodiversity over time may also be needed.

When will biodiversity net gain become mandatory?

BNG will become mandatory in England for most new projects through changes to the planning system in the Environment Act, which has made its way through the UK Parliament. The legislation is expected to come into force in late 2023, subject to the government’s approval.

Once the legislation is in force, all new projects in England that require planning permission will be required to deliver a 10% net gain in biodiversity. This will be measured using a biodiversity metric set out in the legislation. The net gain requirement will apply to projects that impact on habitats such as woodlands, wetlands, and grasslands, as well as to built environments.

The requirement for BNG will apply to all new projects, except for those that are considered to be exempt from planning permission or are covered by certain other exemptions.

The implementation of BNG is a significant step forward in the protection and enhancement of biodiversity in the UK. It is expected to help ensure that new projects contribute to the overall goal of stopping the decline in biodiversity. This will make BNG a key objective of the UK government’s 25 Year Environment Plan.

Biodiversity net gain principles

According to the Chartered Institute of Ecology and Environmental Management (CIEEM), there are ten crucial good practice principles of biodiversity net gain. These should help to achieve BNG if they are followed accordingly. The mandatory BNG principles include the following:

  • Utilise the mitigation hierarchy to minimise the impact on biodiversity
  • Eliminate any negative impacts on biodiversity
  • Communicate each BNG outcome with complete transparency
  • Cover all areas of sustainability, including societal and economic factors
  • Involve any pre-development and post-development stakeholders in creating mandatory net gain solutions
  • Focus on producing long-term environmental benefits from BNG
  • Understand the variable factors and potential risks in order to achieve biodiversity and deliver net gain
  • Offer nature conservation that exceeds the stated biodiversity net gain required
  • Determine a suitable method in order to secure measurable biodiversity net gains
  • Ensure the best possible results from BNG

For case studies and a practical guide on BNG principles, visit the CIEEM website.

Our team has strong experience completing BNG and will provide guidance throughout the planning system process. This applies from the initial land purchase agreements to monitoring assessments.

Implementing BNG

If you are unsure of how mandatory BNG may affect your planning application, you should contact your local planning authority immediately. They will be able to discuss your plans in detail and whether they align with BNG. If they indicate that your project could be impacted, we recommend that you contact an experienced ecologist as soon as possible.

Our ecologists can discuss whether your development plans meet the required standards. They can also determine any measures you may need to take in order to meet the biodiversity standards.

Our team has strong experience completing BNG and will provide guidance throughout the planning process. We can ensure that one of our experienced ecologists visit your development site to create and develop any necessary biodiversity net gain plans and any required BNG reports.

Our ecologists will complete a habitat classification assessment. The data from this assessment is then entered into a metric to measure changes to the natural environment, pre and post development. This metric is currently Defra Metric 4.0. Landscape planting plans and management plans are used to inform post development biodiversity measures.

Calculating Biodiversity Net Gain

Metrics assign every habitat on a designated site a ‘biodiversity unit value’ according to its relative importance for biodiversity. This enables comparison between the existing value of a site and what will be delivered through development or management and post development. This may include an increase in natural habitats through retention and enhancement and/or creation, which goes over and above the environmental habitat originally on site.

BNG can be calculated through the DEFRA biodiversity metric 4.0, which requires a limited number of factors. These factors include:

 The type of habitat (both on and off site)

  • Any locations (if they are local environment priorities)
  • The size of habitat parcels in kilometres or hectares
  • The condition of any habitat parcels

The government website also provides a biodiversity metric 4.0 calculation tool which can help to determine your biodiversity unit score that translates into the standards of your local planning authority.

Why is BNG required by local planning authorities?

BNG is significant for a variety of reasons and can help to positively affect the surrounding environment and wildlife. Some of the main benefits that BNG provides include:

  • It supplies oxygen and water to the surrounding environment
  • Enhances the visual appearance of the environment
  • Facilitates a scientific understanding of the environment
  • Provides jobs for agricultural occupations
  • Helps to protect special scientific interest sites and irreplaceable habitats

The concept of mandatory biodiversity net gain planning condition is a structured method of ensuring that all of the factors listed above are encouraged and supported in the years ahead. As BNG applies to all planning projects, it causes a universal approach from governing bodies and local authorities. Therefore, due to the fact that BNG is a government policy, it prevents any potential issues with key stakeholders.

Biodiversity net gain plans

In order to obtain planning permission for a project from a local planning authority, developers must be able to prove that they are taking the correct measures to increase BNG. One of the first steps in this process is to book an experienced ecologist to create a biodiversity net gain plan.

Depending on the ecologist’s findings within a biodiversity net gain assessment, the BNG plan will help to determine natural elements that could potentially be at risk as a result of the development project. The plan will also detail any mitigation methods, such as conservation covenants or habitat recreation, to be taken in order to prevent these outcomes from occurring.

The aim is to get clients to think about biodiversity during the initial planning and design stages and avoid retro-fitting once designs have been produced. Retrofitting will often lead to delays, unpredicted financial costs and difficulties with planning application determinations.

How can we assist?

Our team of ecologists and landscape architects have assisted numerous clients over the years, including biodiversity net gain condition plans. BNG is something that we are experienced and qualified in, and we can offer advice on your project. We are determined to offer you the support you need in order to reach the required mandatory biodiversity bracket.

Please get in touch if you would like consultation on biodiversity net gain planning condition or BNG plans. We also offer free CPD sessions on the BNG principles and how we can help your project to achieve them.

Our Ecology Director, Olivia Collington, holds a Natural England. If you would like to find out more about the services we provide, feel free to contact us using the form below.

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23 Bark Street East, 1st Floor, Bolton



01204 939 608


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