Biodiversity net gain publication

Biodiversity net gain (BNG) is an approach to development, and/or land management, that aims to leave the natural environment in a measurably better state than it was beforehand.

Overview & FAQs

Picture of biodiverse grassland and tree planting with housing in background at Kidbrooke Village in southeast London

This page provides advice and guidance for planners and councillors involved in planning on biodiversity net gain. It is currently under development.

Biodiversity net gain delivers measurable improvements for biodiversity by creating or enhancing habitats in association with development. Biodiversity net gain can be achieved on-site, off-site or through a combination of on-site and off-site measures. For a simple overview, view Natural England's Introduction to Biodiversity Net Gain on YouTube. Natural England have also produced a Biodiversity Net Gain brochure. There is also a recording from our introductory BNG events below.

We have worked with Natural England and Defra to answer the questions we are most frequently asked by local authority officers and members about biodiversity net gain and those that have come up at events so far: Biodiversity Net Gain FAQs - Frequently Asked Questions.

Biodiversity net gain now

National policy sets out that planning should provide biodiversity net gains where possible. National Planning Policy Framework (NPPF) Paragraphs 170(d), 174(b) and 175(d) refer to this policy requirement and the Natural Environment Planning Practice Guidance (PPG) provides further explanation on how this should be done. Delivering net gain is also referred to in the National Infrastructure Commission's Design Principles, National Policy Statements and the National design guide.

The Government's 25 Year Environment Plan sets out the aspiration to mainstream biodiversity net gain in the planning system and move towards approaches that integrate natural capital benefits.

A updated Biodiversity Metric 3.1 was published in April 2022. This is an update to version 3.0 launched in July 2021: a summary of changes made in version 3.1 is available on the Biodiversity Metric website. The Biodiversity Metric is designed to provide ecologists, developers, planners and other interested parties with a means of assessing changes in biodiversity value (losses or gains) brought about by development or changes in land management. The metric is a habitat based approach to determining a proxy biodiversity value. A Small Sites Metric, a beta version designed to simplify the process of calculating biodiversity net gain on smaller development sites, is also available. A recording of the webinar launching these tools is available on YouTube

For more detailed information on the Biodiversity Metric, a recording of our October 2021 PAS-hosted Natural England training session for local authority planners on Biodiversity Metric 3 is available, along with slides from the event.

CIEEM, IEMA and CIRIA have set out Good Practice Principles for Development and an associated Practical Guide and Case Studies for biodiversity net gain.

There is now a British Standard on biodiversity net gain and development projects: BS 8683:2021 Process for designing and implementing Biodiversity Net Gain.  The standard specifies requirements for a process to design and implement BNG for development projects. It doesn’t cover the actual delivery of BNG, but provides a framework to demonstrate that a project has followed a process based on UK-wide good practice. Find out more from the British Standards Institute (BSI) webinar replay of 21 May 2021.

CIEEM have also published Biodiversity Net Gain Report and Audit Templates that provide a framework for writing reports for projects that are aiming to achieve BNG. The templates set out a suggested structure and content for reports specifically produced in relation to BNG assessments.

This article in LGA's first magazine for councillors highlights why councils should start thinking about and planning for biodiversity net gain now.

Mandatory BNG and the Environment Act

The Government announced it would mandate net gains for biodiversity in the Environment Bill in the 2019 Spring Statement. This followed a consultation on net gain from December 2018. Defra's response to the consultation was published in July 2019. An impact assessment on biodiversity net gain and Local Nature Recovery Strategies was published in late 2019.

The Environment Bill received Royal Assent on 9 November 2021, meaning it is now an Act of Parliament: World-leading Environment Act becomes law - GOV.UK (

Mandatory biodiversity net gain as set out in the Environment Act applies in England only by amending the Town & Country Planning Act (TCPA) and is likely to become law in 2023. The Act sets out the following key components to mandatory BNG:

  • Minimum 10% gain required calculated using Biodiversity Metric & approval of net gain plan
  • Habitat secured for at least 30 years via obligations/ conservation covenant
  • Habitat can be delivered on-site, off-site or via statutory biodiversity credits
  • There will be a national register for net gain delivery sites
  • The mitigation hierarchy still applies of avoidance, mitigation and compensation for biodiversity loss
  • Will also apply to Nationally Significant Infrastructure Projects (NSIPs)
  • Does not apply to marine development
  • Does not change existing legal environmental and wildlife protections

The Government published a consultation on Biodiversity Net Gain Regulations and Implementation on 11 January 2022. The consultation sets out proposals on the detail of implementation of mandatory BNG and closed on 5 April 2022.


The timelines for introduction of mandatory BNG are dependent on a number of factors. The below is our current understanding of the likely timetable towards mandatory BNG.
Autumn 2021:
  • 9 Nov - Environment Bill gets Royal Assent - now the Environment Act

Winter 2021/22:

Spring 2022:

Spring 2023:

  • BNG site register and statutory credits sales platform go live

Winter 2023:

  • Biodiversity net gain expected to become mandatory for all TCPA developments

PAS Events

Biodiversity Net Gain consultation

In February and March 2022, PAS ran events for local authorities on Defra’s consultation on Biodiversity Net Gain regulations and implementation.

The events were intended to help LPAs understand what the consultation covers and how best to respond. We ran overview events and deep-dive discussion sessions on key topics. Slides and recordings of the events plus a summary of what we heard are available here.

The deep-dive discussion sessions on the consultation focused on the following topics:

  • BNG offsite delivery and opportunities for LPAs
  • BNG evaluation, monitoring and enforcement
  • BNG process for TCPA development
  • BNG and additionality
  • Biodiversity gain plan

Biodiversity Metric

PAS hosted a Natural England training session for local authority planners on Biodiversity Metric 3 on Monday 18th October 2021. The recording and slides from the event are available.

Summer 2021 workshops

We ran workshops from May to July 2021 to get input from local planners and councillors. We ran three events for officers, one for councillors and one focused on London Boroughs.

You can access the slides from the workshops here for an overview of the situation with biodiversity net gain and the Environment Bill in Summer 2020 and to see what we discussed with attendees.

A summary of the outputs from the workshops is available, including what local authorities are doing now on biodiversity net gain (BNG) and what they need to enable them to be ready for mandatory BNG.

This recording from one of the officer events provides an overview of BNG and the Environment Bill.