Biodiversity Net Gain (BNG) is an approach to development which helps to ensure that habitats for wildlife are left in a measurably better state than they were before the development. 

BNG in the UK affects businesses by requiring developers to deliver a 10% increase in biodiversity value for new developments. Introduced in February 2024 the regulations mean that developers need to create or improve habitats on or off-site, and can also purchase statutory biodiversity credits as a last resort.  

This affects businesses by potentially increasing development costs, adding to planning and design complexities, and influencing housing market prices. However, it also presents opportunities for landowners to generate revenue through selling off-site biodiversity units. In England, BNG is mandatory under Schedule 7A of the Town and Country Planning Act 19901. 

Who BNG rules affect  

• developer of major developments  

• developer of small sites    

• developer of nationally significant infrastructure projects from late November 2025    

• land manager wanting to sell in the BNG market  

• local planning authority (LPA)  

Some developments are exempt from BNG requirements, particularly those that do not affect a priority habitat and impacts less than 25 square metres (5m by 5m) of on-site habitat, or 5 metres of on-site linear habitats such as hedgerows. Small projects like home extensions, conservatories or loft conversions are also outside of the BNG rules. 

BNG adds to the cost of development projects, as developers must now factor in the cost of delivering the required biodiversity gain. At the same time, developing a Biodiversity Gain Plan that meets the 10% requirement and is approved by the local planning authority adds to the planning and design process.  

BNG guidance for developers 

Unless exempt, developers in England are required to provide BNG on all habitats within the redline boundary of their development, whether or not they are impacted. They need to check if the Local Planning Authority (LPA) requires delivery of  more BNG. Separate arrangements apply to on-site irreplaceable habitat. 

Measuring biodiversity value 

The government advises that when considering biodiversity value, developers should consult an ecologist who would measure the biodiversity value of the existing habitat  and advise on suitable habitat creation or enhancement for the land. 

There is a statutory biodiversity metric that developers must use to measure how many units a habitat contains before development and how many are needed to replace the units of habitat lost and to achieve 10% BNG.  

To calculate the number of biodiversity units for existing habitat, or habitat enhancements to achieve BNG, developers need to use the statutory biodiversity metric tool, a calculator that applies the statutory biodiversity metric formula2.  

When using use off-site units, developers should record the allocation of off-site biodiversity gains on the public biodiversity gain sites register, with the land owner’s permission3. They should  estimate the cost of and buy statutory biodiversity credits if unable to use on-site or off-site units.  

For off-site gains and significant on-site gains, developers must maintain habitats created or enhanced for a minimum of 30 years, starting from completion, for example, after one year of tree planting, pond digging or seeding. 

If it is a small project, developers can either use the simpler small sites biodiversity metric tool or complete a survey and make a calculation. This could be the project manager, gardener or  landscape architect, for example.   

Planning permission and BNG 

When applying for planning permission, developers must confirm whether the project is exempt. If not, they would need to gives details on meeting  the BNG objective, including any significant on-site enhancements.   

If a legal agreement is required, the terms should set out responsibilities for creating, enhancing, monitoring and reporting.  Developers might also need a habitat management and monitoring plan (HMMP)4. 

If the LPA grants planning permission, developers must create the biodiversity gain plan that shows how BNG will be achieved, with evidence informing at least some of the BNG decisions, and a metric tool calculation. This plan would normally be approved or refused by the LPA within 8 weeks. No work should start before approval. 

Enforcement 

Developers who not meet BNG requirements might be in breach of planning conditions, planning obligations or legal agreement and the LPA could take enforcement action.    

Land managers 

BNG impacts UK land managers by offering new opportunities for income and nature recovery through habitat creation and enhancement, as well as potential for selling biodiversity units to developers. Land managers can also create and enhance habitats on their land to generate biodiversity units and nutrient credits, potentially leading to long-term income streams1.  

Within the BNG regulatory framework the term “land manager” covers:  

• landowner  

• farmer  

• estate owner  

• habitat bank operator  

• facilities, property or estate manager  

• land agent  

• land advisor   

• planning authority using land they own  

• developer using land they own  

Selling on the BNG market is a potential source of revenue and could fund nature recovery work. Land managers can sell off-site biodiversity units  to developers, who may need to buy these under mandatory BNG requirements.  

Land managers need a legal agreement with a responsible body or local authority, which will set details around creation, enhancement, maintenance and monitoring of the biodiversity of registered units in order to deliver off-site BNG, lasting a minimum of 30 years. 

When selling units, the land manager or developer, with permission, need to apply to record the allocation of off-site biodiversity gains to a development. BNG registration would be necessary1. 

Measuring biodiversity   

For the purposes of BNG, biodiversity value is measured in standardised biodiversity units. A habitat will contain a number of biodiversity units, depending on: 

• size   

• quality   

• location    

• type 

Biodiversity units can be lost through development or generated through work to create and enhance habitats.  

3 ways to achieve BNG 

1. Developers can create biodiversity on-site - within the red line boundary of a development site.  

1. If developers cannot achieve all of their BNG on-site, they can deliver through a mixture of on-site and off-site. Developers can either make off-site biodiversity gains on their own land outside the development site, or buy off-site biodiversity units on the market. 

1. If developers cannot achieve on-site or off-site BNG, they must buy statutory biodiversity credits from the government. This should be a last resort. The government will use the revenue to invest in habitat creation in England.   

Developers can combine all 3 options, but must follow the steps in order, called the “biodiversity gain hierarchy”5.  

SaveMoneyCutCarbon advises that for on-site BNG, developers could: 

• Create new habitats: Implement features like green roofs, native planting, and wildlife corridors to create new biodiversity hotspots. 

• Integrate green infrastructure: Incorporate green spaces and natural elements into the development design. 

For off-site BNG, developers could work with landowners to enhance biodiversity in nearby areas and any gains should be recorded in the public biodiversity gain sites register after the landowner has granted permission. In this way, developers could help regional biodiversity goals while meeting regulatory requirements. 

Potential BNG benefits 

SaveMoneyCutCarbon advises that sites where achieving the 10% gain is easier may become more desirable and potentially command a higher price. 

Further potential advantages: 

• BNG creates a new market for landowners to sell off-site biodiversity units to developers, potentially offering an alternative source of income. 

• Projects that incorporate BNG can create more attractive environments, potentially boosting property values and attracting buyers or tenants.  

• Demonstrating a commitment to biodiversity can improve a business's image and attract environmentally conscious customers or investors.  

• Landowners can generate income by selling off-site biodiversity units to developers who need to meet their BNG obligations. 

• BNG contributes to broader sustainability goals, such as improving air quality, reducing the urban heat island effect, and promoting biodiversity resilience. 

Bibliography 

1”Understanding biodiversity net gain” (Accessed May 2025) https://www.gov.uk/guidance/understanding-biodiversity-net-gain 

2 “Calculate biodiversity value with the statutory biodiversity metric” (Accessed May 2025) https://www.gov.uk/guidance/biodiversity-metric-calculate-the-biodiversity-net-gain-of-a-project-or-development  

3”Search the biodiversity gain sites register” (Accessed May 2025) https://www.gov.uk/guidance/search-the-biodiversity-gain-sites-register  

4”Creating a habitat management and monitoring plan for BNG” (Accessed May 2025) https://www.gov.uk/guidance/creating-a-habitat-management-and-monitoring-plan-for-biodiversity-net-gain  

5“Biodiversity net gain” (Accessed May 2025) https://www.gov.uk/guidance/biodiversity-net-gain