Rewilding project from above

Complete guide to purchasing Biodiversity Net Gain

Biodiversity Net Gain is the biggest change to planning permission requirements in decades. It’s designed to put biodiversity at the heart of planning by making sure that the nature and habitats on a site are left in a measurably better state than they were before the development. 

In England, BNG is mandatory, so developers must demonstrate how they will meet habitat trading requirements and achieve a BNG increase of at least 10% to gain planning permission. If BNG is well implemented, new developments will need to provide a measurable increase in quality habitat than existed prior to development. If you’re new to Biodiversity Net Gain, this can feel complicated.  To help you understand what to consider when purchasing BNG units, we created this Complete Guide to Purchasing Biodiversity Net Gain. 



Your first task as a developer is to assess your site to establish its nature value. This is your ecological baseline. An ecologist will assess the ecological baseline of your site, and then they will overlay the impact your proposed development will have on the value of that ecological baseline value. They then calculate the amount and type of units that you will need to offset that loss, plus another 10%. 

Based on this, you will need to provide a Biodiversity Net Gain (BNG) Plan showing how you will meet the requirements. The Local Planning Authority (LPA) will then need to sign off your BNG Plan for planning to be granted. You then sign a legal agreement with the authority detailing how this plan will be delivered. 
The mitigation hierarchy details the four steps to achieving BNG requirements in the order they should be approached: 

  • 1. Avoid or minimise any loss of existing biodiverse habitats on a development site. 
  • 2. Add to or improve the biodiverse habitats on the development site. 
  • 3. Enter an agreement with an off-site habitat gain provider to boost biodiversity elsewhere, creating a net gain of 10% across the two (or more) sites. 
  • 4. Purchase government statutory BNG credits (this is intended as an option of last resort, with the credits priced at a level to discourage this approach as much as possible) 

The Government has provided a statutory biodiversity metric tool which must be used to assess the biodiversity of a site before and after a development in order to demonstrate the required 10% improvement has been achieved. 

Bee on flower


The implementation of Biodiversity Net Gain (BNG) has sparked a debate surrounding the effectiveness of onsite versus offsite delivery approaches. Let’s explore some key differences: 

Two key benefits of implementing onsite Biodiversity Net Gain include: 

  • Gains are created where they have been lost, typically in usable green spaces within development sites. 
  • Often less ambitious but easier to achieve, however, you may face viability challenges and risk of degradation over time if not properly managed. 

Two key benefits of implementing offsite Biodiversity Net Gain: 

  • Higher ecological ambition with multi-layered, complex habitat creation on a larger scale. 
  • Greater resilience to damage and disturbance, reducing risks and providing more secure long-term investments. 

There are, of course, more differences between onsite versus offsite BNG delivery. 
Every implementation of Biodiversity Net Gain is unique. In many cases, the limitations of the site mean BNG can’t be provided. Where there is a choice, it’s worth remembering both onsite and offsite approaches have their merits. It’s crucial to consider what will best meet the needs of the project, nature, and the community. Ultimately, a comprehensive understanding of each option is essential for successful biodiversity conservation efforts. 

FACTORS To consider before purchasing bNG units

Feasibility reports for Biodiversity Net Gain are now crucial for development projects. They must outline strategies that not only mitigate ecological impact but also enhance habitats to benefit wildlife. Early planning of these reports is essential. 

A BNG objective report should: 

  • Assess whether the project can achieve BNG considering all project aspects. 
  • Provide clear guidance on maximising BNG potential, considering factors like location, design, construction methods, and schedule. 
  • Explore options for delivering BNG, including on-site or off-site measures such as purchasing biodiversity units. 
Woodland trees


The trading rules set minimum habitat creation and enhancement requirements. These are designed to compensate for specific habitat losses, up to the point of no net loss. There are 15 broad habitat types, including woodlands, hedges, cropland, grassland, urban, heathland, wetland, ponds, rivers and a few rarer options such as “sparsely vegetated land” and “intertidal hard structures”. These different habitats are then split up by distinctiveness. 

For reference, here are the 12 habitat unit types available at Belmont’s Watercress Farm site


The Government suggests using a habitat management and monitoring plan (HMMP) to capture management and monitoring information. Natural England have published a HMMP template and accompanying tools and released a video explaining the HMMP template


Biodiversity Net Gain may be delivered anywhere in England, but you should consider the following when deciding where to source your offsite BNG units: 

1. Calculate your biodiversity metric 

Before development, calculate your biodiversity metric to identify how much BNG you can deliver onsite. The Government provides tools to help you calculate your biodiversity metric.

2. Explore the offsite bng marketplace

Focus on sites that: 

  • will create and enhance habitat to meet the needs of your specific BNG requirements. 
  • has already started creating and enhancing habitat that meets your BNG needs. 

3. the proximity of bng units to your site

The ‘spatial risk multiplier’ is designed to encourage local nature recovery. For local planning authority or national character areas (NCAs), units are worth a standard 1x unit value, meanwhile units in the adjoining local planning authority or national character area are worth 0.75 a standard unit, and units in other parts of England are 0.5 a standard unit. That means, depending on the units’ proximity to your site, you may need to provide 1x, 1.33x or 2x the unit. For reference, Belmont is adjacent to 4 other LPAs and 4 other NCAs

4. Agreement of purchase

It is up to you and the unit provider how you arrange the sale, including any contract of sale you choose to enter into. You may want to seek legal advice on the sale. A contract of sale, should include: 

  • the number and type of units to be registered and allocated to your development. 
  • a commitment from the land manager to record the allocation of units once you have paid. 
  • a commitment to a transaction schedule, including deposit and final payment. 

5. Submit yout biodiversity net gain plan

If you can meet your BNG requirement with offsite gains and have recorded the allocation of any offsite biodiversity gains you’re using, you’re ready to complete your BNG plan and submit it to the LPA. 

6. Understanding the bng

As a developer, you or your lawyer should review and understand the BNG plan before submitting the planning application. 

7. Secure your offsite gains

You’ll need to do this by entering into a legal agreement such as a section 106 agreement or a conservation covenant before you get planning permission. 

8. Get planning permission

You cannot start your development before the approval of your BNG plan. 

9. record the allocation of offsite gains to yout development

Once you have found a provider of biodiversity net gain and agreed a contract with them, either the land manager or you (with the land manager’s permission) must apply to record the allocation of the biodiversity units to your development on the biodiversity net gain sites register. 

10. Receive your biodiversity credit certificate

If the planning application is successful, you will be issued a Biodiversity credit certificate from the provider. This discharges your BNG obligations and liability is passed to the provider for the 30-year term.


Delivering and maintaining biodiversity net gain over 30 years via ecosystem restoration at a nature-friendly scale demands passionate habitat restoration experts. Nature restoration is our mission. BNG units are a consequence of our work, not the primary goal. That’s why we say we’re not ‘BNG providers’ but proud providers of BNG
While BNG isn’t flawless, it’s a vital initial step toward nature recovery. Partnering with experienced nature restoration experts means robust ecological outcomes, meeting stringent planning requirements. At Belmont, our commitment extends beyond compliance, embracing responsibility and recovery. 

Moth surveying


Once you’ve decided on a provider, you should schedule a meeting as quickly as possible to help them understand the scope of the project and to review the ecology report. Once an intent to proceed has been agreed and the ecology report approved, you should be issued with an offer confirming: 1) the unit pricing and 2) the process.  
With terms agreed, you then pay a deposit to secure the BNG units. Then a developer can submit their planning application. To support the application, you should be issued with: 

  • a purchase agreement 
  • a copy of a 30-year management plan (HMMP) 
  • a letter of support for the application 

After planning has been granted and payment for the BNG units received, the developer will be issued a biodiversity credit certificate. This discharges the developer’s BNG obligations, and liability is passed to the delivery partner. Overseen by an appointed responsible body, a diligent delivery partner will undertake accredited third-party monitoring and reporting, ensuring complete peace of mind for the full 30-year term.


One challenge is the dependence on third parties, like local authorities, who lack commercial incentives and adequate resources. To make the system self-sustaining, there’s a need for a clear legal framework and properly funded stakeholders. While there may be initial hurdles, addressing them over time should reduce delays. 

Pricing comparisons are also a challenge in emerging markets like BNG. As the market is in its infancy, we arguably haven’t yet reached a fully competitive stage on pricing. This will come with time as more applications for development are made and the mandatory requirements apply.  

Similarly, there’s a range of supply and demand dynamics for BNG across the UK. The current delays could cause an imbalance of supply and demand which may, as with any market, impact prices. However, as BNG policy matures, supply will become more even across the country. 

Moth surveying


Biodiversity Net Gain represents a pivotal shift towards sustainable development, placing nature conservation at the forefront of planning processes. By mandating a measurable improvement in biodiversity following development, the UK Government has established a framework that prioritises environmental stewardship alongside economic growth. 

Whether through onsite enhancements or offsite investments, it’s vital that you adopt a holistic approach that goes beyond compliance – one that balances ecological ambition with practical feasibility. By partnering with experienced restoration professionals, adhering to regulatory requirements, and committing to long-term monitoring and management, developers can ensure that BNG initiatives not only meet statutory obligations but also contribute meaningfully to nature recovery efforts. 

Of course, at Belmont, we have a team of experienced restoration experts with many years of experience overseeing habitat restoration at scale. Led by Director of Estates Gil Martin and assessed by a chartered ecologist, we restore wetlands, regenerate natural woodland, and cultivate wildflower meadows across seven habitat types, offering 13 different BNG unit types provided through natural regeneration. We’re also happy to take on all management responsibility and liability for the 30-year term. This is a key benefit of working with a partner that looks beyond compliance, to responsibility and recovery.

We are passionate about rewilding, rewetting, peatland and woodland restoration because it benefits our climate and our communities. When you choose Belmont as your BNG provider, you’re investing in a better future for nature. Support our work and start your BNG journey by booking a call with our team.