Developer FAQs

Biodiversity Net Gain (BNG) is a mandatory approach to development introduced under the Environment Act 2021. It requires projects to deliver a measurable improvement in biodiversity value, specifically a minimum 10% increase compared to pre-development levels, maintained for at least 30 years post-completion.

Net gain can be achieved through three primary measures:

• On-site interventions
• Off-site interventions (on developer land or through purchased units)
• Purchasing statutory credits (as a last resort)

BNG aims to address the decline in biodiversity caused by development. It ensures that construction projects contribute positively to nature conservation, and encourages developers to consider biodiversity from the outset of projects.

Biodiversity value is measured in standardised 'biodiversity units' using the Defra Biodiversity Metric (currently version 4.0).

This tool assesses habitat type and size, distinctiveness and condition, strategic significance, and connectivity to other habitats. A qualified ecologist typically conducts this assessment, providing a baseline for your BNG calculations.

BNG requirements apply to most developments in England with planning applications submitted after February 12, 2024. This encompasses a wide range of projects, including:

• Residential developments (both large-scale and small-scale);
• Commercial and industrial projects;
• Infrastructure projects;
• Mixed-use developments;
• Change of use applications that involve land or building alterations.

While BNG casts a wide net, there are some notable exemptions:

• Householder applications (e.g. extensions/loft conversions) are exempt.
• Self-build/custom housebuilding schemes of up to 9 units.
• Developments impacting less than 25m² of habitat or 5m of linear features.
• Permitted developments
• Urgent Crown developments.


N.B. Developments exclusively impacting previously developed land with no biodiversity value may also be exempt.

BNG is being rolled out in phases:

• January 2024: Large sites (10+ dwellings or 0.5+ hectares)
• February 12, 2024: All non-exempt developments
• April 2, 2024: Small sites
• November 2025: Nationally Significant Infrastructure Projects (NSIPs)

BNG introduces additional steps into the planning process, including early ecological surveys, integration of biodiversity enhancements into project design, and submission of BNG information with planning applications.

It requires the preparation and approval of a Biodiversity Gain Plan and long-term management commitments.

These requirements necessitate early consideration of BNG in the development process and may impact project timelines and budgets.

Failing to deliver on BNG commitments can lead to breaches of planning conditions or obligations, enforcement action, financial penalties, reputational damage, and difficulty obtaining planning permission for future projects. To mitigate these risks, it's crucial to have robust plans and contingencies in place.

BNG can impact development viability through increased land requirements for on-site habitat creation, costs for purchasing off-site biodiversity units, long-term management and monitoring expenses, potential planning process delays, and restrictions on developable area to protect existing habitats.

However, well-planned BNG can also add value through improved amenity, increased property values, and enhanced corporate social responsibility.

The Biodiversity Gain Hierarchy is an approach developers must follow when planning and implementing biodiversity improvements. It outlines a series of steps in order of priority, emphasising on-site measures before exploring off-site options.

This ensures developments make the most effective contributions to local biodiversity while achieving the mandatory 10% net gain.

• Avoid Adverse Effects: Preserve existing habitats where possible, especially areas with medium, high, or very high distinctiveness.

• Mitigate & Minimise Unavoidable Effects: Where impacts can't be entirely avoided, minimise and mitigate them as much as possible.

• Enhance Habitats On-Site: Once impacts have been minimised, enhance the quality of existing habitats within the development site.

• Create Habitats On-Site: If further action is needed to achieve a 10% net gain, explore creating new habitats within the development area.

• Secure Off-Site Biodiversity Units: If on-site measures fall short, secure off-site biodiversity units, representing habitat creation or enhancement elsewhere.

• Purchase Statutory Credits: As a last resort, if all previous options have been exhausted, purchase statutory biodiversity credits from the government.

Developers must demonstrate their adherence to this hierarchy in their Biodiversity Gain Plan (BGP).

This involves documenting decision-making at each stage, justifying progression to subsequent steps, quantifying biodiversity outcomes using the metric, and showing consideration of local ecological networks, stakeholders, and strategies.

Failure to demonstrate adherence could result in planning approval delays, increased costs, potential legal challenges, and reputational damage. It's crucial to document your approach thoroughly and justify any deviations from the hierarchy.

Effective implementation requires early ecological assessments, integration of biodiversity considerations into initial site designs, early engagement with ecologists and local authorities, comprehensive documentation of decisions, and exploration of on-site solutions before considering off-site options.

Calculating BNG requirements involves the following steps:

• Baseline Assessment: Conduct a habitat survey of the development site using UK Habitat Classification.

• Input Data: Use the statutory biodiversity metric tool to calculate pre-development biodiversity units.

• Assess Development Impact: Evaluate the post-development scenario, including any on-site habitat retention or creation.

• Calculate Net Change: Determine the difference between pre- and post-development biodiversity units.

• Achieve 10% Net Gain: Ensure the post-development value is at least 10% higher than the pre-development baseline

A qualified ecologist should conduct the assessment for most projects. Their expertise is crucial for accurately classifying habitats, assessing their condition, and using the metric tool correctly. However, for small sites (<10 dwellings), developers can use the simplified Small Sites Metric, which can be completed by someone familiar with the site, such as a project manager or landscape architect.

BNG calculations may be influenced by the following factors:

• Habitat Condition: The overall health and quality of existing habitats.

• Habitat Distinctiveness: How rare or ecologically important a habitat type is.

• Strategic Location: How well the habitat connects to other natural areas or aligns with local conservation priorities.

• Temporal Risks: The time it takes for newly created habitats to reach their 'target condition'.

• Spatial Risks: How far compensatory/offsite habitat is from the development site.

• Additionality: Ensuring BNG gains are genuinely new and wouldn't have happened anyway.

Understanding these factors helps optimize BNG strategies, potentially reducing costs. For instance, enhancing an existing poor-quality habitat may offer greater value and be more cost-effective than creating a new habitat entirely.

BNG calculations should be reviewed at key stages: during initial assessment and design, when submitting the planning application, if significant changes are made to plans, when preparing the final Biodiversity Gain Plan, and periodically during the 30-year management period.

Regular reviews ensure the strategy remains accurate and achievable throughout the development process.

Planning applications must include:

• Confirmation of BNG applicability
• Pre-development biodiversity value
• Proposed approach to achieving 10% gain
• Details of significant on-site enhancements

A draft Biodiversity Gain Plan (BGP) is often beneficial, though not mandatory at the application stage.

A comprehensive Biodiversity Gain Plan should contain:

• Pre- and post-development biodiversity values
• Detailed habitat creation/enhancement proposals
• Off-site gain details (if applicable)
• A 30+ year Habitat Management and Monitoring Plan
• Evidence of adherence to the mitigation hierarchy

This plan is crucial for demonstrating BNG compliance and must be approved before development can commence.

Submit your Biodiversity Gain Plan to your Local Planning Authority (LPA) after receiving planning permission but before starting development. The LPA then has 8 weeks to approve or refuse your plan. Early preparation and submission can help avoid delays to your project timeline.

No, you cannot start development until the LPA has approved your BGP. This approval is a pre-commencement condition of your planning permission.

To increase the likelihood of approval, ensure your plan is comprehensive, clearly demonstrates adherence to the Biodiversity Gain Hierarchy, provides robust evidence for your biodiversity calculations, and outlines a feasible long-term management strategy. Early engagement with the LPA can also help align your plan with local biodiversity priorities.

Off-site units represent biodiversity improvements made outside your development. They can be created on other land you own, purchased from third-party providers like Wellshead Natural Capital (WNC), or acquired through habitat banks.

All off-site gains must be registered on the national biodiversity gain sites register to ensure transparency and prevent double-counting.

Off-site units represent biodiversity improvements made outside your development. They can be created on other land you own, purchased from third-party providers like Wellshead Natural Capital (WNC), or acquired through habitat banks.

All off-site gains must be registered on the national biodiversity gain sites register to ensure transparency and prevent double-counting.

Trading rules ensure "no net loss" of biodiversity. Key principles include:

• Trading up or like-for-like (replacing lost habitats with similar or higher value ones)
• Recognising that very high distinctiveness habitats are considered irreplaceable
• Accounting for spatial risk (units created further from the impact site are less valuable)
• Ensuring additionality (gains must be new and not already planned or funded)

As of 2024, prices for offsite units range from £10,000 to £45,000 per unit, though outliers exist.

For example, woodland units in strategically significant locations near major cities might command up to £60,000/unit, while grassland units in less competitive areas may be available for around £15,000. Wetland and intertidal habitats often sit at the higher end of the price range due to their ecological importance and the challenges in their creation.

At Wellshead Natural Capital, we monitor these market trends closely to provide our clients with up-to-date pricing information and competitive unit options.

The market for biodiversity units is still maturing, with regional variations and fluctuations based on supply and demand. As the market evolves and more data becomes available, pricing is expected to become more standardised.

However, local factors will likely continue to play a significant role in determining unit costs. Future policy changes could also impact unit pricing and availability.

Developers can optimise their BNG unit purchases through early engagement, bulk purchasing, aligning with Local Nature Recovery Strategies, balancing on-site measures with off-site purchases, market analysis, establishing long-term partnerships, and considering phased acquisition for long-term projects.

Wellshead Natural Capital (WNC) offers tailored strategies to help developers maximise the value of their BNG investments, leveraging our market insights and established networks.

Off-site units can be sourced through local habitat banks, direct agreements with landowners, brokers, and trading platforms. The new national biodiversity gain sites register provides a central database of available units. Early engagement with potential providers is advisable to secure suitable units at competitive prices.

Wellshead Natural Capital facilitates this process by offering access to a diverse portfolio of verified, high-quality off-site units across the South West and beyond. Our team can help you navigate the options and find units that best meet your project's needs and budget.