CIVITY NGE Blog

Ecological assessments undertaken by qualified ecologists form the foundation of any biodiversity net gain (BNG) project. For landowners and land managers seeking to generate income through the sale of biodiversity units, understanding the ecological baseline of a site is the critical first step. Before habitat creation or biodiversity enhancements can be designed, the ecological value of a site must be assessed through a structured process of surveys, data analysis and reporting. This ensures that biodiversity net gain can be measured accurately and that any future gains are credible, compliant and deliverable. The Role of Ecological Assessments in Biodiversity Net Gain Under the Environment Act 2021, biodiversity net gain is now a mandatory requirement for most development. Developers must demonstrate measurable improvements in biodiversity using the DEFRA Biodiversity Metric. For landowners looking to create and sell biodiversity units, ecological assessments establish the baseline biodiversity value against which gains will be calculated. Without a robust ecological assessment, it is not possible to determine how many biodiversity units a site can generate. This process is also essential for identifying ecological constraints, potential impacts and opportunities for habitat enhancement. What Is a Preliminary Ecological Appraisal? The first stage of ecological assessment is typically a Preliminary Ecological Appraisal (PEA). This combines a desktop study with an initial site walkover survey to identify habitats present, potential ecological constraints and the likely presence of protected and priority species. The desktop study gathers data from sources such as local environmental records centres and the National Biodiversity Network Atlas. The site survey then assesses habitat types, ecological condition and any signs of notable species. The outcome is a PEA report that: Identifies ecological constraints Highlights potential impacts Recommends whether further surveys are required When Is an Ecological Impact Assessment Required? For sites with greater ecological complexity or those associated with development proposals, a more detailed Ecological Impact Assessment (EcIA) may be required. The EcIA evaluates the potential effects of a development on habitats, species and designated sites. It considers: Direct and indirect habitat loss Disturbance and fragmentation Mitigation and enhancement opportunities The process follows guidance set by the Chartered Institute of Ecology and Environmental Management (CIEEM), ensuring consistency and professional standards. The Importance of Ecological Surveys Ecological surveys provide the evidence base for both baseline assessment and biodiversity metric calculations. These may include: Habitat condition assessments Botanical surveys Species-specific surveys (e.g. birds, bats, great crested newts) Survey work is often seasonally constrained, meaning that timing can affect both programme and viability. Accurate survey data is essential to ensure that biodiversity metric calculations reflect the true ecological value of a site and that any biodiversity units generated are defensible within the planning system. Identifying Ecological Constraints and Opportunities Ecological assessments do more than identify constraints. They also highlight opportunities for habitat creation and enhancement. Sites with lower baseline biodiversity, such as underperforming arable or improved grassland, may offer significant potential for habitat restoration and biodiversity uplift. Conversely, sites with higher ecological value may be more constrained but still capable of delivering targeted enhancements. Understanding these factors allows landowners to design habitat strategies that balance ecological value with long-term land use objectives. From Assessment to Biodiversity Units Once ecological surveys are complete, the data is used within the DEFRA Biodiversity Metric to calculate baseline biodiversity units and model post-enhancement scenarios. This process determines how many biodiversity units can be generated through habitat creation or enhancement. It also considers: Habitat distinctiveness Condition Strategic significance Long-term management requirements The number and type of units generated will directly influence the commercial viability of a site within the BNG market. Legal and Registration Considerations Ecological assessments underpin the legal and regulatory framework required to deliver off-site biodiversity units. To bring a site forward, land must be: Supported by a Habitat Management and Monitoring Plan (HMMP) Secured through a legal agreement (Section 106 agreement or Conservation Covenant) Registered on Natural England’s Biodiversity Gain Site Register The quality and robustness of ecological data is critical to securing approval and ensuring that biodiversity units can be lawfully allocated to development projects. Supporting Nature Recovery and Long-Term Land Management Ecological assessments play a central role in ensuring that biodiversity net gain delivers meaningful environmental outcomes. By identifying appropriate habitats and realistic management strategies, they support: Long-term habitat creation and enhancement Improved ecological resilience Alignment with Local Nature Recovery Strategies (LNRS) This ensures that biodiversity net gain functions as more than a compliance requirement, contributing to wider nature recovery objectives. At Civity At Civity, we work with landowners to bring forward biodiversity gain sites. Using ecological survey data and biodiversity metric outputs prepared by qualified ecologists, we: Assess the commercial viability of a site Identify suitable habitat creation options Prepare the Habitat Management and Monitoring Plans (HMMPs) Structure legal agreements and oversee site registration Facilitate the sale of biodiversity units to developers through our landbank Summary Ecological assessments are the starting point for any biodiversity net gain project, providing the baseline data required to measure, design and deliver biodiversity improvements. For landowners, they are a critical step in understanding both the ecological potential and commercial viability of a site. For developers, they underpin the credibility and compliance of biodiversity gain calculations. As the BNG market continues to develop, robust ecological data, clear legal structuring and long-term management planning will remain essential to delivering biodiversity units that are both policy-compliant and ecologically meaningful. Disclaimer This article is intended for general informational purposes and reflects current ecological assessment practices and biodiversity net gain requirements in England. It does not constitute ecological, legal or planning advice. Landowners and developers should seek professional advice tailored to their specific site and refer to up-to-date guidance from Natural England and relevant regulatory bodies.

Biodiversity net gain (BNG) is now a central requirement within the English planning system, requiring most development projects to deliver at least a 10% increase in biodiversity value. While the principle is consistent, the delivery of biodiversity net gain can take two distinct forms: on-site biodiversity net gain within the development site or off-site biodiversity units secured elsewhere. Understanding the difference between BNG off-site credits and on-site biodiversity net gain is essential for developers, land managers and planning professionals seeking to meet biodiversity net gain requirements efficiently and compliantly. The Policy Context and Legal Framework Mandatory biodiversity net gain is established under the Environment Act 2021 and supported by detailed policy and technical guidance.    All biodiversity gains must be calculated using the statutory biodiversity metric, developed by Natural England and available through the statutory biodiversity metric tool and guidance. Local planning authorities are responsible for ensuring that development proposals meet the biodiversity gain objective, typically through the submission and approval of a biodiversity gain plan. What Is On-Site Biodiversity Net Gain? On-site biodiversity net gain refers to habitat creation, habitat enhancement and biodiversity improvements delivered within the red line boundary of the development site. This approach focuses on enhancing on-site habitats as part of the development design. Examples include green infrastructure, tree planting, restoring natural habitats or improving existing habitat conditions to increase biodiversity units. The biodiversity metric tool is used to calculate baseline biodiversity value and model post-development biodiversity value. Developers must demonstrate that on-site gains contribute meaningfully to achieving biodiversity net gain to include them within their calculations; this usually involves securing their ongoing management and maintenance via a Section 106 agreement for at least 30 years. On-site delivery aligns closely with the mitigation hierarchy, which prioritises avoiding and minimising biodiversity loss before considering compensation. As a result, local planning authorities expect significant on-site gains wherever feasible. What Are BNG Off-Site Credits? BNG off-site credits, more accurately described as off-site biodiversity units, are biodiversity gains delivered outside the development site. These units are generated through habitat creation or restoration on separate land, often referred to as habitat banks or gain sites. Off-site biodiversity gains must be legally secured for at least 30 years and registered on the statutory register maintained by Natural England. The operation of this system is explained within the biodiversity gain site register guidance. Developers may purchase biodiversity units from these sites to compensate for any shortfall in on-site biodiversity net gain. The units are then allocated to the development and recorded as part of the biodiversity gain plan. The Role of the Biodiversity Gain Hierarchy The biodiversity gain hierarchy governs how biodiversity net gain should be delivered. It requires developers to prioritise on-site habitat enhancement before relying on off-site solutions. This hierarchy reflects the broader mitigation hierarchy within planning policy, ensuring that biodiversity loss is first avoided as the preferred approach, then minimised within the development site before, finally, compensation is considered. Local planning authorities will scrutinise biodiversity gain plans to ensure that off-site gains are not used prematurely or in place of achievable on-site improvements. When Are Off-Site Units Used? Off-site biodiversity units are typically required where the development site has limited capacity to deliver sufficient biodiversity gains. This may occur in high-density urban developments, constrained sites or schemes involving significant habitat loss. In these cases, off-site solutions allow developers to achieve biodiversity net gain by investing in habitat creation elsewhere. Off-site habitats may deliver greater ecological value where they are strategically located, larger in scale, or aligned with Local Nature Recovery Strategy priorities. The statutory biodiversity metric applies spatial multipliers, meaning that units located within the same local planning authority area or in proximity to the development site are more valuable. Statutory Biodiversity Credits as a Last Resort Where neither on-site gains nor off-site biodiversity units are available, developers may buy statutory biodiversity credits from the government. These credits are intentionally priced higher than market-based off-site units to encourage private habitat creation and restoration. Their use is restricted to situations where other options have been exhausted, as outlined in the statutory biodiversity credits framework. Comparing On-Site and Off-Site Approaches On-site biodiversity net gain offers clear advantages in terms of integrating biodiversity into development design, supporting local ecosystems and aligning with planning policy expectations. It also reduces reliance on external agreements and simplifies long-term governance, where appropriately managed. However, on-site delivery is often constrained by site viability, land availability and competing development priorities. Off-site biodiversity net gain provides flexibility, allowing developers to secure biodiversity units from dedicated habitat banks designed specifically to deliver ecological value. These sites can deliver biodiversity improvements at scale and contribute to wider environmental objectives. The most effective biodiversity net gain delivery strategies often involve a combination of on-site gains and off-site gains, ensuring compliance with the biodiversity gain hierarchy while achieving the required net gain efficiently. Legal and Long-Term Considerations Both on-site and off-site biodiversity gains must be secured through legal agreements and supported by a monitoring plan lasting at least 30 years. Off-site units are typically secured through conservation covenants or section 106 planning obligations. Government guidance on conservation covenants is available through the conservation covenant framework. Local authorities and responsible bodies oversee compliance, ensuring that habitat enhancement works are delivered and maintained over time. Strategic Decision-Making for Developers Choosing between on-site and off-site biodiversity net gain requires a detailed understanding of the development site, baseline biodiversity value and planning constraints. Early engagement with ecologists and planning professionals is essential to identify the most effective approach. Developers should model different scenarios using the biodiversity metric to determine the optimal balance between on-site habitat enhancements and off-site solutions. Consideration should also be given to programme timelines, cost, land ownership constraints and the availability of suitable off-site units within the relevant local planning authority area. Expert Support for BNG Delivery Delivering biodiversity net gain in compliance with current regulations requires technical expertise in biodiversity metric calculations, legal structuring and habitat management. At Civity, we facilitate the delivery of compliant biodiversity net gain by providing access to pre-registered off-site biodiversity units from our land bank. We work with landowners to bring forward biodiversity gain sites and secure them through the appropriate legal agreements and registration processes. For developers, we review submitted biodiversity metrics, identify unit requirements, and allocate suitable off-site units in line with statutory trading rules. We can also support the completion of relevant sections of the Biodiversity Gain Plan, working alongside the project ecologist where required. Disclaimer This article is intended for general informational purposes and reflects the biodiversity net gain framework in England at the time of writing. It does not constitute legal, ecological or planning advice. Developers and landowners should seek professional advice tailored to their specific circumstances and refer to current government and Natural England guidance to ensure compliance with evolving biodiversity net gain regulations.

Biodiversity Net Gain (BNG) is now a mandatory requirement for most development projects in England. Introduced under the Environment Act 2021 and embedded within Schedule 7A of the Town and Country Planning Act, it requires developers to deliver at least a 10% increase in biodiversity value compared to the baseline condition of a development site. While the principle is straightforward, delivery in practice involves a structured process of ecological assessment, metric calculation, planning compliance, legal agreement, and long-term habitat management. This article explains how BNG operates in practice, from initial baseline measurement through to delivery and monitoring. The Legal Framework Behind Biodiversity Net Gain Mandatory BNG is secured through the planning system. A biodiversity gain condition is attached to planning permission, requiring the submission and approval of a Biodiversity Gain Plan before development can lawfully commence. This framework is supported by: Schedule 7A of the Town and Country Planning Act DEFRA guidance and the statutory Biodiversity Metric The mitigation hierarchy, which prioritises avoidance, on-site delivery, and then off-site compensation Local Planning Authorities (LPAs) are responsible for reviewing Biodiversity Gain Plans and ensuring that proposals meet statutory requirements. Increasingly, LPAs are scrutinising both the quality of metric inputs and the realism of proposed habitat delivery. Step 1: Measuring Baseline Biodiversity Value The first stage in delivering BNG is establishing the baseline biodiversity value of the development site. This is undertaken by a qualified ecologist, who surveys existing habitats within the red line boundary and classifies them using the UK Habitat Classification system. These habitats are then assessed using the DEFRA Biodiversity Metric. The metric calculates biodiversity units based on: Habitat type and distinctiveness Condition Area Strategic significance and location This baseline provides the benchmark against which post-development biodiversity value is measured. For smaller development sites, a simplified small sites metric may be used, although most major developments require full metric calculations. Step 2: Designing On-Site Biodiversity Net Gain Developers must first seek to achieve BNG on-site, in line with the mitigation hierarchy. This involves enhancing or creating habitats within the development boundary. Examples include: Creating species-rich grassland Planting trees and native scrub Incorporating green roofs or sustainable drainage systems (SuDS) Improving the condition of retained habitats LPAs expect developers to demonstrate that on-site opportunities have been reasonably maximised before relying on off-site solutions. The Biodiversity Metric is used to model proposed habitat changes and calculate how many biodiversity units will be delivered on-site. Step 3: Addressing Shortfalls Through Off-Site Biodiversity Units Where sufficient gains cannot be achieved on-site, developers must secure off-site biodiversity units. These units are generated from land that is managed specifically for habitat creation or enhancement, commonly referred to as biodiversity gain sites. To be valid, these sites must: Be secured through a legal agreement (Section 106 agreement or Conservation Covenant) Be registered on Natural England’s Biodiversity Gain Site Register Commit to habitat creation and management for a minimum of 30 years Off-site units must be allocated to a specific development and recorded within the Biodiversity Gain Plan. The DEFRA Biodiversity Metric applies spatial risk multipliers, meaning that units located closer to the development site, or within the same local planning authority area, are generally more valuable in meeting requirements. Step 4: Using Statutory Biodiversity Credits as a Last Resort If developers cannot deliver sufficient on-site or off-site biodiversity gains, they may purchase statutory biodiversity credits from the government. These credits are deliberately priced at a premium and are intended to act as a last resort. Their use must be justified within the Biodiversity Gain Plan and is typically discouraged where market-based solutions are available. Step 5: Submitting and Securing Approval of the Biodiversity Gain Plan Once planning permission is achieved, the pre-commencement requirement to achieve biodiversity net gain is satisfied by detailing the approach taken (see steps 1-4 above) with a biodiversity gain plan, submitted to the relevant local planning authority. The Biodiversity Gain Plan is a statutory requirement and a central component of BNG compliance. It must set out: Baseline biodiversity value Proposed on-site habitat enhancements Any off-site biodiversity units secured Use of statutory credits (if applicable) The plan must demonstrate how the development will achieve at least a 10% net gain in accordance with the DEFRA Biodiversity Metric and the mitigation hierarchy. Development cannot lawfully begin until the Biodiversity Gain Plan has been approved by the Local Planning Authority. Step 6: Legal Agreements and Long-Term Management All off-site biodiversity gains, and some on-site enhancements, must be secured through legally binding agreements. These typically take the form of: Section 106 agreements with the Local Planning Authority, or Conservation Covenants with a Responsible Body A Habitat Management and Monitoring Plan (HMMP) is required to set out how habitats will be created, managed, and monitored over time. These agreements ensure that biodiversity gains are delivered and maintained for a minimum of 30 years, with clear responsibilities for monitoring and reporting. Practical Considerations in Delivering BNG In practice, the delivery of BNG is often influenced by legal, commercial, and programme constraints. Key considerations include: Registration and legal agreements can be a critical path, particularly for off-site units Developers increasingly require pre-registered, policy-compliant units to avoid delays The availability of suitable off-site units can vary significantly by location LPAs are placing greater emphasis on deliverability and long-term management certainty As the market matures, there is a growing distinction between: Registered and legally secured biodiversity units, which are readily usable Early-stage or speculative sites, which may not meet planning requirements Special Considerations for Infrastructure and Irreplaceable Habitats Nationally Significant Infrastructure Projects (NSIPs) follow a separate consenting regime, although similar principles apply. Irreplaceable habitats, such as ancient woodland, are treated differently within the Biodiversity Metric. In these cases, compensation is not considered adequate, and avoidance remains the primary objective. Delivering Biodiversity Net Gain in Practice In practice, BNG is a structured and measurable process that integrates ecological assessment, planning, legal compliance, and long-term land management. Successful delivery requires coordination between developers, ecologists, landowners, and local authorities to ensure that biodiversity gains are realistic, measurable, and secured for the long term. As the BNG market continues to develop, off-site biodiversity units and formally registered gain sites are becoming an increasingly important part of how developments achieve compliance. At Civity At Civity, we facilitate compliant biodiversity net gain by connecting developers with pre-registered off-site biodiversity units from our landbank. We work with landowners to bring forward biodiversity gain sites, including structuring legal agreements, supporting site registration, and ensuring alignment with DEFRA metric requirements. For developers, we: Review submitted biodiversity metrics Identify the number and type of units required Allocate suitable off-site units in line with statutory trading rules Support completion of relevant sections of the Biodiversity Gain Plan, working alongside the project ecologist where required Summary Biodiversity Net Gain is now an embedded part of the planning system in England, requiring developers to demonstrate measurable and lasting improvements to biodiversity. Its delivery relies on a combination of accurate ecological assessment, robust metric application, legally secured habitat creation, and long-term management. As implementation progresses, the focus is increasingly on certainty, compliance, and deliverability ensuring that biodiversity gains are not only calculated, but successfully realised over a 30-year timeframe. Disclaimer: This article is provided for general informational purposes and reflects the biodiversity net gain framework in England at the time of writing. It does not constitute legal, ecological or planning advice. Developers and landowners should seek professional advice tailored to their specific circumstances and refer to current government and Natural England guidance to ensure compliance.

The introduction of mandatory biodiversity net gain (BNG) under the Environment Act 2021 has reshaped the economics of land management in England. Developers must now deliver at least a 10% net gain in biodiversity for most new developments, creating a regulated BNG market for off-site biodiversity units. For farmers and landowners, this presents a significant opportunity. By creating BNG units through habitat creation and ecological restoration, landowners can generate additional income while contributing to environmental sustainability and nature recovery. This article explains how landowners’ BNG opportunities work in practice, the legal framework involved, and how to leverage BNG credits to generate new income streams responsibly and profitably. The Legal Basis for Biodiversity Net Gain Biodiversity net gain is a statutory planning requirement introduced by the Environment Act 2021. Official policy and operational guidance are published through the government’s biodiversity net gain guidance. Under BNG requirements, developers must demonstrate measurable biodiversity improvements using the statutory biodiversity metric developed by Natural England. The metric tool and methodology are available through the statutory biodiversity metric guidance. Where development projects cannot achieve BNG entirely on site, they must secure off-site BNG units or, as a last resort, purchase statutory biodiversity credits from the government. This requirement underpins the emerging BNG market. Understanding Biodiversity Units and Ecological Value Biodiversity units measure ecological value based on habitat type, condition, distinctiveness and habitat size. A baseline assessment calculates the existing biodiversity value of the land. Proposed habitat creation or habitat restoration is then modelled through the biodiversity metric to determine how many biodiversity units can be generated. Factors such as difficulty, time to maturity and spatial location influence how many biodiversity units a site can realistically deliver. The number of BNG units available for sale depends on habitat enhancement design, ecological importance and long-term management commitments. Sites capable of delivering high-quality habitat enhancements such as wetland creation, wildflower meadows or woodland restoration may generate stronger market demand due to their contribution to nature recovery and wider ecosystem services, including carbon sequestration. How Landowners Generate Income from BNG Credits To leverage BNG credits, landowners must legally secure land for biodiversity management for a minimum of 30 years. This is achieved through legally binding agreements, typically either a section 106 agreement with a local planning authority or conservation covenants entered into with a responsible body. Government guidance on conservation covenants is available through the conservation covenant framework. Once legally secured, the land must be registered as a biodiversity gain site on the statutory register operated by Natural England. The process is outlined in the Biodiversity Gain Site Register Guidance. Only after registration can land managers allocate BNG units to development sites requiring off-site biodiversity units to meet planning permission conditions. Income is generated through the sale of biodiversity credits or off-site BNG units to developers seeking to achieve BNG obligations linked to property development, infrastructure schemes or nationally significant infrastructure projects. Strategic Land Management and Market Positioning Landowners seeking to generate income through BNG should undertake early engagement with ecologists, land agents and legal advisers. Strategic positioning within a local planning authority area can significantly influence demand. Developers are incentivised through spatial risk multipliers within the biodiversity metric to source units locally. Enhancing habitats in proximity to development sites can therefore increase commercial attractiveness. Aligning habitat creation with local nature recovery strategies may also strengthen ecological value and marketability. BNG credits may also complement other nature markets such as nutrient credits linked to nutrient neutrality requirements or emerging carbon credits markets focused on carbon sequestration. Integrated land management strategies can create diversified income streams grounded in environmental sustainability. Financial Considerations and Long-Term Obligations While BNG units can generate additional income, landowners must understand the long-term nature of the commitment. Habitat created under BNG must be maintained for at least 30 years. Ongoing management, monitoring plans and reporting obligations are enforceable under legal agreements. Tax implications, inheritance considerations and potential impact on agricultural direct payments should be reviewed carefully. Professional advice is essential before committing land to off-site BNG. It is also important to recognise that statutory biodiversity credits sold by the government function as a pricing backstop. These are designed to encourage private market participation rather than replace it. Risk Management and Environmental Integrity Successful landowners’ BNG schemes require ecological integrity. Poorly designed habitat restoration projects may fail to deliver projected biodiversity improvements, creating reputational and legal risks. Robust biodiversity management planning, clear governance structures and collaboration with conservation organisations or conservation groups can strengthen delivery and enhance credibility within the BNG market. The goal is not simply to create habitats for commercial purposes, but to deliver measurable biodiversity impacts that contribute to long-term nature recovery. Integrating BNG into Sustainable Land Management BNG aligns closely with sustainable land management principles. Habitat restoration, green spaces, ecological restoration and enhancing biodiversity all contribute to wider ecosystem services. For farmers and landowners facing volatile commodity markets, leveraging BNG credits offers a mechanism to generate income linked directly to environmental outcomes. This shift reflects broader private investment trends within nature markets and growing regulatory emphasis on environmental sustainability. Expert Guidance for Landowners The regulatory framework governing biodiversity net gain is technical and evolving. Success depends on accurate metric modelling, robust legal structuring and strategic engagement with developers and local authorities. As a specialist provider in biodiversity net gain and habitat banking, Civity NGE supports landowners in assessing land suitability, creating BNG units, securing conservation covenants and positioning sites effectively within the BNG market. Disclaimer This article provides general information on biodiversity net gain in England and reflects current legislation and guidance at the time of writing. It does not constitute legal, financial or ecological advice. Landowners should obtain independent professional advice tailored to their circumstances before entering into legally binding agreements or committing land to biodiversity net gain schemes. Regulations, guidance and market conditions may change.

Since February 2024, most developments in England have been subject to mandatory Biodiversity Net Gain (BNG) under the Environment Act 2021. For developers navigating planning permission, one of the most common questions is: What is the process for purchasing BNG units to meet planning requirements? Where a scheme cannot fully deliver biodiversity net gain on site, developers must secure legally compliant off-site biodiversity units before their Biodiversity Gain Plan can be approved by the local planning authority (LPA). This article explains the regulatory framework, the practical steps involved in purchasing BNG units, and how to ensure compliance with BNG regulations. Understanding Biodiversity Net Gain Requirements Under the current biodiversity net gain requirements, developers must demonstrate a minimum 10% uplift in biodiversity value. The process begins with a baseline assessment of the development site using the statutory biodiversity metric. This establishes: The pre-development biodiversity value The predicted post-development biodiversity value The resulting gain or loss in biodiversity units   The metric calculation quantifies habitat type, ecological quality, condition and strategic significance. It ensures that biodiversity improvements are measurable and transparent. BNG prioritises enhancing biodiversity through a structured framework known as the mitigation hierarchy: Avoid harm Minimise impacts Restore on site Compensate via off-site gains (only when necessary)   Only after exhausting opportunities for on-site enhancements should developers consider purchasing offsite BNG units. Step 1: Maximise On-Site Gains The first obligation is to deliver as much uplift as possible within the red line boundary of the development site. Common BNG measures include: Retaining and enhancing existing on-site habitat Creating new habitats such as woodland, wetland or species-rich grassland Upgrading habitats such as modified grassland Integrating sustainable drainage features   For major developments and many smaller schemes, achieving significant on-site gains reduces exposure to off-site costs and aligns with sustainable development principles. If, after applying the metric tool, there remains a shortfall in net gain units, off-site BNG must be secured. Step 2: Identify the Required Off-Site Units The metric output will specify: Number of biodiversity units required Habitat type (e.g. grassland, woodland, wetland) Whether any units are subject to trading rules Strategic significance requirements   Importantly, BNG regulations incorporate a biodiversity gain hierarchy and a spatial element known as the BNG proximity principle. The BNG Proximity Principle and Spatial Multiplier Under the BNG spatial multiplier, units located further from the development site attract a higher unit requirement. In simple terms: Units within the same local planning authority area are most favourable Units in an adjacent LPA may be acceptable Units further afield require more biodiversity units to compensate   This reflects the policy objective of maintaining ecological integrity within local habitats and protecting the natural environment at a landscape scale. The proximity principle means developers should prioritise: Onsite BNG Off-site units within the same LPA/NCA Units in an adjacent LPA/NCA Government statutory biodiversity credits (as a last resort) Step 3: Source Suitable Units from Registered Habitat Banks Offsite BNG units must come from land that is: Legally secured via a Conservation Covenant or Section 106 agreement Registered on the Biodiversity Gain Site Register Supported by a long-term monitoring plan Overseen by a designated responsible body or local authority Compliant with Natural England requirements   These sites are often referred to as habitat banks or local habitat banks. Before purchasing BNG units, developers should verify: The site is formally listed on the Biodiversity Gain Site Register The units are available and unallocated The habitat type matches the trading rules The units meet proximity and spatial multiplier requirements The off-site habitat is secured for at least 30 years   Failure to confirm registration risks delays in local planning approval. Step 4: Enter into a Legal Allocation Agreement When developers buy BNG units, they are securing: A quantified number of biodiversity units From a specific biodiversity gain site Legally secured for long-term habitat creation and management   The agreement will typically: Allocate a defined number of net gain units Reference the gain site register entry Confirm compliance with statutory biodiversity rules Provide documentation for submission with the Biodiversity Gain Plan   At this stage, units are formally linked to the development project. Step 5: Submit the Biodiversity Gain Plan Before development can commence, the developer must submit a compliant Biodiversity Gain Plan to the local planning authority. The plan must demonstrate: Pre-development biodiversity baseline Post-development biodiversity calculation On-site gains achieved Off-site gains secured Evidence of legal security Monitoring and reporting arrangements   The LPA will assess whether the plan satisfies statutory biodiversity net requirements before discharging the condition. What If Off-Site Units Are Not Available? If suitable off-site biodiversity units cannot be sourced locally, developers may purchase statutory biodiversity credits from the government via Natural England. However: Statutory credits are intentionally priced higher than market units They are designed as a last resort The biodiversity gain hierarchy must be demonstrated first   For nationally significant infrastructure projects, separate but aligned statutory biodiversity requirements apply, though the core principles remain consistent. Key Compliance Risks to Avoid When purchasing BNG units, developers should ensure: The biodiversity metric calculation is accurate and signed off Units are sourced from a legally secured gain site Spatial multiplier implications are accounted for The biodiversity gain hierarchy is clearly evidenced The monitoring plan aligns with statutory expectations Allocation agreements are robust and auditable   Local authorities are scrutinising biodiversity gain plans carefully, and incomplete documentation may delay planning permission. At Civity At Civity, we support developers through the structured process of purchasing BNG units to meet planning requirements. We: Review statutory biodiversity metric outputs Confirm unit shortfalls and trading rule implications Identify suitable units within the relevant local planning authority area as first priority Allocate offsite BNG units from registered habitat banks Provide all necessary documentation to support Biodiversity Gain Plan submission Liaise with your project ecologist where required   We do not carry out on-site ecological surveys or calculate the biodiversity metric for development land. Our role is to facilitate compliant, transparent allocation of legally secured off site units from third-party land managers. Delivering Biodiversity Net Gain with Certainty Purchasing BNG units is not simply a financial transaction. It is a regulatory step embedded within the planning system to ensure measurable biodiversity improvements. To summarise, the process involves: Completing a statutory biodiversity baseline assessment Maximising onsite BNG Identifying any shortfall in biodiversity units Applying the BNG proximity principle Securing suitable units from the Biodiversity Gain Site Register Submitting a compliant Biodiversity Gain Plan   When structured correctly, off site BNG supports sustainable development while maintaining ecological integrity across local habitats. As biodiversity net gain becomes a permanent feature of planning and development plans, early engagement and careful coordination are essential to avoid delays and ensure full compliance with BNG regulations. Disclaimer This article is intended for general guidance only and does not constitute legal, ecological, financial, or planning advice. Biodiversity Net Gain requirements are governed by the Environment Act 2021, associated regulations, and guidance issued by DEFRA and Natural England, which may be updated over time. Developers should seek independent professional advice specific to their development site, biodiversity metric calculations, and local planning authority requirements before purchasing BNG units or statutory biodiversity credits.