What is Biodiversity Net Gain and how might it affect your development?

April 19, 2023
Biodiversity Net Gain (BNG) was first introduced by the Environment Act 2021. Its overarching aim is to ensure habitats for wildlife are left in a measurably better state than they were in before the development was undertaken.

It is a term used to describe the process of increasing the biodiversity value of a site and is calculated by using the Biodiversity Metric.

You will need to understand the requirements of BNG if you’re a land manager, developer or LPA, as all planning permissions granted in England (with a few exemptions) will have to deliver at least 10% biodiversity net gain.

Although the mandatory requirements of BNG will not come into force until November 2023, many local planning authorities (LPAs) are already setting their own BNG targets within their local planning policy.

With this in mind, it is important to understand how it is calculated and how you can achieve the necessary BNG for your development, as Henry Bourne and Oliver Galliford, Planners at Vail Williams, explain.

Why is it being introduced?

Although certain sites are protected, there are limited mechanisms to value, maintain, enhance, or create wider habits.

As a result, habitats continue to be lost to development, thus reducing nature’s ability to connect and thrive.

What are the key components?

The National Planning Policy Framework (NPPF) includes provisions to enhance the natural and local environment and improving biodiversity in and around developments.

This additional legislation provides further clarity on how this can be successfully achieved.

The key components of mandatory biodiversity gain are:

  • Amendments to Town & Country Planning Act (TCPA)
  • Minimum 10% biodiversity net gain required. This is to be calculated using the Biodiversity Metric and included an approved biodiversity gain plan
  • Habitat secured for at least 30 years via planning obligations or conservation covenants
  • A new statutory biodiversity credits scheme
  • National register for net gain delivery sites

How is BNG calculated?

Natural England’s Biodiversity Metric is used to calculate the biodiversity of both development and biodiversity uplift sites.

The metric is an accounting tool which assigns a measurable number of biodiversity units based on the type, extent and condition of habitats present or proposed on site.

It also takes into account how difficult the habitat is to create, the time taken to reach target condition and proximity to the development site.

This tool can be used by ecologists, developers, planners and other interested parties to assess the variations in biodiversity value (losses or gains) brought about by development or changes in land management.

An updated version (Biodiversity Metric 4.0) is expected to be launched later in 2023 and is expected to be the version in force when mandatory BNG launches this coming winter.

How can BNG be achieved?

The government has proposed a three-tier approach to addressing BNG requirements:

  • The developer can demonstrate that they have produced a 10% BNG on the site itself
  • The developer can deliver an offsite benefit of 10% BNG
  • The developer can purchase statutory biodiversity credits through a section 106 agreement

Developers and land promoters will be required to provide a biodiversity gain plan which sets out how they will achieve the BNG requirements. This will include information on:

  • The potential impacts of development on local habitats and how they have been minimised
  • The site’s pre and post-development biodiversity value
  • The biodiversity value of any offsite habitats provided in relation to the development proposed
  • Any statutory biodiversity credits purchased

The question is then whether developers and land promoters should be preparing for a 10% biodiversity net gain or 20%, and what the potential implications of this change will be on viability and land availability.

Henry Bourne, Planner, Vail Williams.

When does this come into force?

The mandatory requirement for a minimum 10% BNG is expected to come into place in November 2023.

However, in anticipation of this change in policy, local planning authorities (LPA) have been setting BNG targets within their local planning policy.

For example, in Surrey, this includes Guildford, Mole Valley and Surrey Heath. Get in touch for a full breakdown of the biodiversity requirements for the Local Authorities in this area, and elsewhere.

It should be noted that local policies are seeking a minimum 20% BNG which is double the threshold that has been set nationally.

Furthermore, Guildford’s Development Management Policies were recently adopted (March 2023) which means that this approach has been accepted by the planning inspector and is now a prescribed requirement for development within Guildford under Policy P7: Biodiversity in New Developments.

Will a minimum 20% BNG become the new norm?

It is looking increasing likely that the nationally prescribed 10% will be superseded by Local Policy which will have significantly stricter requirements and higher thresholds.

Three LPAs within Surrey, for example, already have drafted policies seeking 20% and when you look elsewhere in the country the same approach is being adopted with Greater Cambridgeshire, East Devon, Maidstone and Richmond on Thames all setting out requirements for a 20% BNG for new development.

The question is then whether developers and land promoters should be preparing for a 10% biodiversity net gain or 20%, and what the potential implications of this change will be on viability and land availability.

This is particularly important when you consider the difficulty with achieving a simple BNG on sites with other constraints.

This will raise several issues for developers who are already struggling to meet the ever-growing demands from Local Authorities and Central Government including: infrastructure, social housing, education, healthcare, heritage and landscaping. Ultimately, this is just another constraint on development which land promoters will now have to overcome.

A balance needs to be achieved between the needs of the community and environment. There is a common acceptance that space and land are required to meet the needs of the population and deliver much needed homes.

However, we shouldn’t overlook the benefits of open space and wildlife habitats. Instead, we should constantly be seeking to achieve proposals which can deliver good quality areas with social, environmental, and economic benefits.

For the biodiversity policy to be effective, it should be guiding good quality environmental development and not solely being used as a method for either rejecting development or removing a potential opportunity due to the lack of viability.

Discover more

In February 2023, Defra announced updates to its BNG policy position following a 12-week consultation process launched in January 2022.

Together with a summary of consultation responses, Defra has updated general guidance on BNG, including how to sell biodiversity units to developers as well as clarification on the stacking of BNG and environmental payments on land. This update provided much needed clarity ahead of the November 2023 start date for BNG.

If you would like help and support in relation to biodiversity net gain – whether you are a developer or LPA – get in touch with our planning team for more information.