This Practice Note looks at the practical construction consequences of biodiversity net gain (BNG) and related habitat mitigation conditions, looking at the practical impact from a construction law aspect rather than the planning law test for whether such a condition is validly imposed. Construction lawyers do not generally advise on planning procedure; what matters to their clients is the effect that a habitat condition has on programme, cost, specialist procurement, risk allocation under the building contract, and the consequences of getting it wrong. This note covers those practical impacts for developers, funders, contractors, consultants and suppliers, with worked examples including the Lower Thames Crossing and the Connah’s Quay saltmarsh proposals. Carbon capture and greenhouse gas removal (GGR) issues are addressed separately in the companion Practice Note. Why BNG affects construction delivery In England, subject to exemptions and commencement and transitional provisions, grants of planning permission under the Town and Country Planning Act 1990 are deemed to be subject to the statutory biodiversity gain (BNG) condition introduced by the Environment Act 2021. In brief,

Planning analysis: This article examines the proposed implementation of biodiversity net gain (BNG) requirements for nationally significant infrastructure projects (NSIPs) under the Environment Act 2021 (EA 2021). BNG, which mandates that developments deliver a minimum 10% net gain in biodiversity and maintain it for 30 years, and has already been introduced for Town and Country Planning Act 1990 (TCPA 1990) applications. The government has now launched a consultation on extending BNG to NSIPs, with implementation delayed from November 2025 to May 2026. The article outlines key elements of the proposal, highlights differences from the TCPA 1990 regime-particularly the requirement for earlier submission of biodiversity gain plans—and explores how BNG will apply in practice to NSIPs. It also identifies unresolved issues and areas on which views are being sought, including how to treat unused or temporarily used land. Written by Angus Walker, partner at Broadfield Law UK LLP.

This Practice Note is based on the enabling provisions in the Planning Act 2008 (PA 2008) for the biodiversity net gain (BNG) regime for nationally significant infrastructure projects (NSIPs) in England, and the 10 biodiversity gain statements (BGSs) published in June 2026. It will be updated when further regulations and procedural guidance on how the BNG regime is to operate are published. This Practice Note was last updated in June 2026. What is biodiversity net gain? BNG is a principle which aims to leave the natural environment in a measurably better state after development than beforehand. The Environment Act 2021 (EA 2021) introduced a mandatory BNG requirement in England for new developments under the Town and Country Planning Act 1990 (TCPA 1990) in 2024, meaning they must deliver 10% BNG, see Practice Note: Biodiversity net gain in England. EA 2021 also provides for a mandatory BNG requirement for NSIPs under PA 2008 in England from 2 November 2026, as explained further in this Practice Note. Mandatory planning requirement for biodiversity

STOP PRESS: A revised version of the National Planning Policy Framework was published on 17 August 2026. This content is being reviewed in light of the revised version. What is biodiversity net gain? Biodiversity net gain (BNG) is a principle which aims to leave the natural environment in a measurably better state after development than beforehand. The mandatory legislative requirements for development to provide net gain apply to planning permission granted from 12 February 2024 for development under the Town and Country Planning Act 1990 (TCPA 1990), unless exempt. Aside from the mandatory statutory requirement, biodiversity gain is encouraged by policy in the National Planning Policy Framework (NPPF), and may be a requirement of local planning policy. Some local planning authorities (LPAs) may have included BNG policies in their local plan, so it is important to check whether this is the case before submitting a planning application as both statutory and policy-based BNG may apply. The BNG Planning Practice Guidance (PPG) was finalised on 14 February 2024. It applies to statutory-based BNG (rather than policy-based). See

From 12 February 2024, all planning permissions (subject to exceptions) granted in England pursuant to planning applications submitted under the Town and Country Planning Act 1990 on or after this date are subject to a condition requiring that the biodiversity value attributable to the development exceeds the pre-development value of the onsite habitat by at least 10%.

The Environment Act 2021 (Commencement No. 8 and Transitional Provisions) Regulations 2024, SI 2024/44 were made on 17 January 2024, bringing into force parts of the Environment Act 2021 dealing with biodiversity net gain (BNG) from 12 February 2024. Consequently, all planning permissions (subject to exceptions) granted in England pursuant to planning applications submitted under the Town and Country Planning Act 1990 on or after 12 February 2024 will be subject to a condition requiring that the biodiversity value attributable to the development exceeds the pre-development value of the onsite habitat by at least 10%. The BNG requirement was initially supposed to come into force in November 2023, was subsequently delayed to January 2024, and is now confirmed as coming into force on 12 February 2024.

Purpose of Practice Note This Practice Note covers the concept of biodiversity net gain (BNG). It provides further detail from a specialist consultancy about how the mandatory BNG process is currently working in practice. It does not set out the details of the legislative framework for BNG, which is available within Practice Note: Biodiversity net gain in England, which should be read in conjunction with this Note. How does biodiversity net gain work in practice? This Practice Note aims to answer the following questions: • How are biodiversity units (BU) calculated? • What are the good practice principles for BNG? • What is typically involved in the BNG process? • What are the common challenges of delivering BNG in practice? How are biodiversity units calculated? Calculating baseline biodiversity units BNG uses habitat type and condition as a proxy for overall biodiversity value, measured in BU which are calculated using the Statutory Biodiversity Metric (SBM). BU are separated into area-based habitat units (HU), linear-based

STOP PRESS: A revised version of the National Planning Policy Framework was published on 17 August 2026. This content is being reviewed in light of this revised edition. This Practice Note explains the current position on biodiversity offsetting and mandatory and voluntary nature markets. It explains what biodiversity offsetting is, the defining characteristics of nature markets, drivers for market participants, market rules, the ‘stacking’ of multiple nature benefits and the expected future direction of biodiversity offsets and nature markets. Overview What is biodiversity offsetting? Biodiversity offsetting is the process through which organisations deliver or fund environmentally restorative projects to compensate for the harm they cause, directly or indirectly, to biodiversity through their organisational activities and value chains. Biodiversity offsetting under planning laws Protecting, enhancing, and ‘offsetting’ biodiversity impacts has been bound up within the English planning system since before 2006, when former Planning Policy Statement 9 (now subsumed into the National Planning Policy Framework) encouraged planning authorities to consider ways of ‘maintaining, restoring or adding to networks of natural habitats and other

[means the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems. OR means the wide-ranging variety of life forms that inhabit a particular habitat or ecosystem.]

Biodiversity legal and policy frameworks is a rapidly developing and often complicated area of law. In response to severe biodiversity decline in the post-war period, a body of law has emerged which seeks to tackle this issue. The success of these frameworks has been variable; however, biodiversity law and policy has now become an integral part of government policy as well as the jurisprudence of domestic and international legal systems. This is very likely to continue, not least as links are increasingly being drawn between recovering biodiversity and adapting to the effects of climate change. This Practice Note is designed to provide practitioners with the background to and key concepts behind biodiversity law. It looks at: • the background to the legislative and policy frameworks supporting biodiversity, and • the key concepts in biodiversity law It forms part of a suite of content on biodiversity which includes the following Practice Notes: • Biodiversity—policy and legislative framework • Biodiversity—international law • Biodiversity—litigation The evolution of domestic biodiversity protection While the field of environmental

This Practice Note is part of a suite of content on biodiversity including the following: • Biodiversity—evolution, background and key concepts • Biodiversity—UK policy and legislative framework • Biodiversity—caselaw and the role of the courts This Practice Note will look at the following: • Overview of UK’s obligations under international biodiversity laws • The Bern Convention and the concept of favourable conservation status • United Nations Convention on Biological Diversity (CBD) • Sustainable Development Goals 14 and 15 • The Aarhus Convention and public participation in environmental decision-making, access to environmental information, and access to justice • Biodiversity Beyond National Jurisdiction Act (‘High Seas Treaty’) Overview of UK’s obligations under international biodiversity laws Many of the UK’s obligations in relation to biodiversity and protected sites are drawn from international law, either directly or being transposed through European Union (EU) law in the form of Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora (as variously amended) (the Habitats Directive) and Directive 2009/147/EC on the conservation of wild birds (as variously amended) (the

Background The biodiversity law and policy framework is complex. In response to significant biodiversity decline in the post-war period, a body of law has emerged which seeks to tackle this issue, although its success is uncertain. The Introduction to Biodiversity Litigation (OUP, 2023) suggests that until recently the focus in litigation has been on either ‘climate change before the courts, or the environment, as a whole, before the courts. …Yet, biodiversity has unique characteristics that warrant a more specific investigation as a topic of legal scholarship.’ Biodiversity law and policy has unquestionably become an integral part of government policy and rhetoric as well as the jurisprudence of domestic and international legal systems. This is likely to continue, not least as links are being drawn between recovering biodiversity and adapting to the effects of climate change. This Practice Note aims to provide practitioners with the context and conceptual tools they will need when dealing with biodiversity law. It focusses on the role of the courts in the development of biodiversity law and the standards applied by the courts. It provides