Risks to the long-term effectiveness of the biodiversity net gain scheme
[edit] Scope of the National Audit Office (NAO) report in brief.
The report examines the progress Defra and Natural England have made in implementing statutory BNG, and whether they have done so in a way that maximises benefits and effectively manages risks. We have produced it in response to a request from the Environmental Audit Committee to contribute to its inquiry into the role of natural capital in the green economy. It covers:
- Government’s approach to implementing statutory BNG, and how it expects the policy to contribute to its biodiversity objectives
- How the government designed and launched statutory BNG
- Key risks the government will need to manage as it seeks to maximise the value statutory BNG can provide
- Recommendations aimed at supporting Defra and Natural England to maximise value and manage risks to statutory BNG as policy implementation becomes business as usual
[edit] Managing the risks of BNG implementation
The Department for Environment, Food and Rural Affairs (Defra) launched a novel and complex biodiversity scheme without having all elements in place to ensure its long-term success.
Defra needs to manage a range of risks including whether a new biodiversity market emerges, and whether compliance and enforcement by local authorities will be effective. Defra is still developing a way to spend money it receives from developers on biodiversity; and also how to judge whether its policy is working.
There are risks to the long-term effectiveness of a new policy, launched by the government in February, to make sure developers in England protect or improve biodiversity on land they are developing, according to the new National Audit Office (NAO) report.
The independent public spending watchdog’s latest report assessed whether Defra and Natural England have made good and effective progress implementing statutory biodiversity net gain.
[edit] A unique national legal requirement
Statutory biodiversity net gain (BNG) was legislated for as part of Defra’s 2021 Environment Act. The new rules – which are unique to England – require development to have a measurably positive impact (‘net gain’) on biodiversity compared to what was there before.1 This is the first time a government has introduced statutory BNG as a national legal requirement.
Developers must improve the habitats they harm by a net 10%, ideally on-site. When on-site gains are not enough to meet the 10% requirement, off-site gains can be created by the developer elsewhere or purchased through a new private market for biodiversity units.
BNG is being implemented in three stages, with major developments in scope from February 2024; small developments from April 2024; and nationally significant developments from November 20253.
Stakeholders support the scheme, but had concerns about its implementation prior to launch. These concerns included uncertainty about the launch and preparation costs.
[edit] Preparation and governance
The government provided either £26,807 or £43,4674 to each local authority to help them prepare in each of the two years proceeding launch. Local authorities had discretion to spend the money: for instance, on recruiting and training new ecologists, procuring new software, and processing legal work. However, Defra acknowledged mixed readiness among local authorities at launch.
There are risks to local authorities carrying out effective compliance and enforcement for statutory BNG. Local authorities have discretion in how they enforce planning regulations. Defra did not give local authorities additional money specifically to monitor or enforce on-site gains4. However, government expects that local authorities can also generate income from BNG legal agreements, which can fund monitoring and enforcement work.
Defra is still developing its governance arrangements for BNG and intends to make Natural England responsible for important elements of the policy. But in developing these new arrangements, Defra does not intend to provide central monitoring of how well on-and off-site biodiversity gains are being enforced by local authorities.
[edit] Evaluation and assessment
Natural England and Defra also lack all the relevant information they need to effectively evaluate the regime and determine whether it’s a success. For instance, they currently do not have a comprehensive source of information of habitat enhancement taking place on site. Defra is exploring what information might be available from local authority reporting against the statutory biodiversity duty, although this will only be available at five-yearly intervals.
Defra is relying on a private sector market for biodiversity units emerging but does not know how rapidly it can scale up or satisfy demand. Where private markets fail to provide enough off-site credits, Defra will step in as a provider of last resort, with the money raised ring-fenced for government mandated improvements to UK biodiversity. Presently, Defra does not have a legally compliant mechanism to spend income from statutory credit sales to enhance biodiversity.
Overall, the government expects BNG to provide a small contribution to separate, national biodiversity targets. Defra’s 2019 impact assessment suggested that BNG, as designed, could be expected to deliver genuine net gain, or at least no net loss.
The NAO recommends that government establishes a mechanism for spending income from the sales of statutory biodiversity credits. It also says that local authorities should have sufficient and timely funding certainty to allow for longer-term planning regarding their role in locally agreeing and enforcing the scheme.
[edit] Comment from NAO
Gareth Davies, head of NAO said:
“The statutory biodiversity net gain scheme is the first national scheme of its kind to build requirements for enhancing biodiversity into planning approval. However, it was launched with risks to the long-term effectiveness of the policy.
“These include uncertainty about whether the fledgling market for biodiversity units scales up to satisfy developers’ demand, risks to enforcement and gaps in its information.
“Defra must address these issues, including by plugging gaps in its information so that it can effectively evaluate the scheme’s success.”
[edit] Conclusions of the National Audit Office (NAO) report in brief
In November 2021 Defra publicly committed to launch statutory BNG within two years. It worked quickly, developing a novel policy through an existing and complex planning system, and statutory BNG was launched in February 2024. However, in prioritising launching the policy it accepted some significant risks to effectiveness which it must now manage as the policy moves from implementation to business as usual.
Defra launched its policy before having all the elements in place that it needs to ensure statutory BNG is a success in the long term. Although it considered that the arrangements it had in place at launch were sufficient, it has a long way to go before it can be confident that damage to biodiversity through development will not be understated and that the benefits of biodiversity enhancements will actually be delivered. For its market-led approach to work, Defra needs the market to scale up to meet demand, and for statutory biodiversity credits to deliver biodiversity when the market fails to do so.
Local authorities manage many aspects of statutory BNG through the planning process, including ensuring compliance and enforcement. For now, there is doubt about whether local authorities will be able to discharge these duties effectively. In addition, it is not clear whether Defra will have sufficiently granular monitoring data to assess policy performance. Without these, Defra will not have assurance that its statutory BNG policy is delivering biodiversity outcomes and value for money for taxpayers.
[edit] Download links and about the NAO
- Report - Implementing statutory biodiversity net gain (.pdf — 390 KB)
- Summary - Implementing statutory biodiversity net gain (.pdf — 130 KB)
- ePub - Implementing statutory biodiversity net gain (.epub — 1 MB)
Publication details: ISBN: 978-1-78604-550-8 [Buy a hard copy of this report]. HC: 729, 2023-24
The National Audit Office (NAO) scrutinises public spending for Parliament and is independent of government and the civil service. It helps Parliament hold government to account and it uses its insights to help people who manage and govern public bodies improve public services.
The Comptroller and Auditor General (C&AG), Gareth Davies, is an Officer of the House of Commons and leads the NAO. The NAO audits the financial accounts of departments and other public bodies. It also examines and reports on the value for money of how public money has been spent.
In 2022, the NAO's work led to a positive financial impact through reduced costs, improved service delivery, or other benefits to citizens, of £572 million.
This article is based on the Press Release 'Risks to the long-term effectiveness of new biodiversity net gain scheme' dated May 17, 2024, and the updates from Implementing statutory biodiversity net gain webpage as of May 20, 2024.
[edit] Related articles on Designing Buildings
- Biodiversity.
- Biodiversity and the built environment digital series
- Biodiversity gain.
- Biodiversity in the urban environment.
- Biodiversity net gain (BNG) regulations and implementation; Government response.
- Biodiversity offsetting.
- Biophilia.
- BREEAM Enhancing site ecology.
- BREEAM Long term impact on biodiversity.
- Ecological network.
- Ecological impact assessment.
- Ecology.
- Ecology compensation.
- Ecology connectivity.
- Environmental impact assessment.
- Environmental net gain.
- Green infrastructure.
- Green roofs.
- Guidance on tree specification, BNG and more.
- Nature improvement area.
- Natural environment white paper.
- Private finance initiative.
- Sustainable development toolkit.
- The future of green infrastructure.
Featured articles and news
Key points for construction at a glance with industry reactions.
Functionality, visibility and sustainability
The simpler approach to specification.
Architects, architecture, buildings, and inspiration in film
The close ties between makers and the movies, with our long list of suggested viewing.
SELECT three-point plan for action issued to MSPs
Call for Scottish regulation, green skills and recognition of electrotechnical industry as part of a manifesto for Scottish Parliamentary elections.
UCEM becomes the University of the Built Environment
Major milestone in its 106-year history, follows recent merger with London School of Architecture (LSE).
Professional practical experience for Architects in training
The long process to transform the nature of education and professional practical experience in the Architecture profession following recent reports.
A people-first approach to retrofit
Moving away from the destructive paradigm of fabric-first.
International Electrician Day, 10 June 2025
Celebrating the role of electrical engineers from André-Marie Amperè, today and for the future.
New guide for clients launched at Houses of Parliament
'There has never been a more important time for clients to step up and ...ask the right questions'
The impact of recycled slate tiles
Innovation across the decades.
EPC changes for existing buildings
Changes and their context as the new RdSAP methodology comes into use from 15 June.
Skills England publishes Sector skills needs assessments
Priority areas relating to the built environment highlighted and described in brief.
BSRIA HVAC Market Watch - May 2025 Edition
Heat Pump Market Outlook: Policy, Performance & Refrigerant Trends for 2025–2028.
Committing to EDI in construction with CIOB
Built Environment professional bodies deepen commitment to EDI with two new signatories: CIAT and CICES.
Government Grenfell progress report at a glance
Line by line recomendation overview, with links to more details.
An engaging and lively review of his professional life.
Sustainable heating for listed buildings
A problem that needs to be approached intelligently.
50th Golden anniversary ECA Edmundson apprentice award
Deadline for entries has been extended to Friday 27 June, so don't miss out!
CIAT at the London Festival of Architecture
Designing for Everyone: Breaking Barriers in Inclusive Architecture.
Mixed reactions to apprenticeship and skills reform 2025
A 'welcome shift' for some and a 'backwards step' for others.