Biodiversity net gain

In England, BNG is mandatory under Schedule 7A of the Town and Country Planning Act 1990 (as inserted by Schedule 14 of the Environment Act 2021).

Developers must deliver a BNG of a minimum of 10%.

This means a development will result in more or better quality natural habitat than there was before development.

More information on how to deliver a BNG

• Step by step guidance for developers
• Step by step guidance for land managers

The diagram shows the difference between net loss, no net loss and net gain of biodiversity.

• BNG became mandatory for new major development applications submitted on or after Monday 12 February 2024
• BNG became mandatory for small sites applications submitted on or after Tuesday 2 April 2024

Some developments are exempt from BNG regulations and will not need to deliver BNG. Some examples of development which is exempt are:

• householder applications
• Prior Approval applications
• self-build and custom build applications
• development ‘below the threshold’ – where the on-site habitat is less than 25 square metres  of non-priority area habitat (for example grassland) and/or less than 5m of non-linear habitats (for example hedgerows or watercourses)

Find out more about what types of development are exempt

A statement will be needed that says whether the planning permission is subject to the BNG condition or not, and if not, what exemption is being applied. You may need to submit extra evidence to show that the exemption applies in order for your application to be validated (e.g. photographs).

If the property being applied for meets the definition of self or custom build that is set out in the Self-build and Custom Housebuilding Act 2015, the council has a pro forma to fill in and submit with your application.

Read the Self-build and Custom Housebuilding Act 2015

•    Self-build pro forma (Word, 34KB)

These applications will be subject to a planning condition that ensures any homes permitted are occupied as self or custom build homes. More information can be found at ‘Build your own home’

If the development is not exempt, the following information is required at validation stage for every application

• completed and dated Statutory Biodiversity Metric – please use the macro disabled version or Small Sites metric. This must be submitted as an Excel document (not as a PDF). You can only use the Small sites metric if your development meets the criteria to do so.
• the pre-development biodiversity value of the on-site habitat at the date of application (the metric will calculate this)
• if an earlier date than the application date is used, please provide reasons for using that earlier date
• a statement confirming whether the biodiversity value of onsite habitat is lower on the application date due to any activity that has led to the degradation of habitats since 30 January 2020, with supporting evidence of that activity and degradation (if this is the case, the value will be taken as ‘pre-degradation)
• description of any irreplaceable habitat (set out in column 1 of the Schedule of the Biodiversity Gain requirements (Irreplaceable Habitat) Regulations [2024]) on the application site that exists on the application date (or earlier where justified)
• scale plan (with North arrow) showing all existing onsite habitat within the red line boundary of the application site on the application date (or earlier where justified) including any irreplaceable habitat

Our local validation list will tell you what else you need to submit, depending on the size proposals and the size of the development.

• view our local validation list

This information may include:

• information to show that the site is suitable for the habitats that are proposed, such as additional ecological information
• a draft habitat management and monitoring plan (HMMP)
• other plans showing post-development habitat enhancement and creation (such as a Landscape Environmental Management plan)
• legal agreements to secure monitoring of on-site significant enhancements or off-site gain sites

Please note

• without all this information, we must refuse to validate the application
• applicants can submit more BNG information than the minimum requirements if they would like to
  
• it is important to note that you will still need to submit specific tree and/or ecology information and reports in addition to the BNG documentation
• applicants are encouraged to use our pre-application service if they have specific questions about BNG

Sometimes we will ask for more information before a decision is made to show that it is possible for the proposed BNG to be delivered on the site. This could include

• confirmation that the BNG units to be purchased from habitat banks are likely to be available (for high/very high distinctiveness habitats)
• information on ‘bespoke compensation’

Planning officers will inform you if other information is needed from you.

Unless degradation has occurred on the site, you should use the date of the application (not the date of the metric).

We will automatically use the date of application as the ‘relevant date’ for the purposes of validation unless degradation of habitats has occurred on the site.

More information can be found on GOV.UK

• GOV.UK: Biodiversity net gain
  

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

• size
• quality of habitats
• location
• type of habitats

To measure the biodiversity value of a site you must use the Statutory Biodiversity Metric, or the Small Sites Metric, whichever is applicable, which calculates:

• how many units a habitat contains before development
• how many units are needed to replace the units of habitat lost or changed by the development to achieve a minimum of 10% BNG

The Statutory Biodiversity Metric User Guide and Small Sites Metric User Guide explains how to complete the metric correctly.

The Statutory Biodiversity Metric needs to be completed by a qualified ecologist.

The Small Sites Metric (SSM) can only be used for sites under 1 hectare where there are no European protected species, designated sites or priority habitat on the site. The SSM must be filled in by a ‘competent person’, but not necessarily an ecologist. A competent person is someone who is able to identify all the different habitats on the specific site they are assessing.

If a site contains habitats that are not listed in the SSM, the developer should ask a qualified ecologist to complete the metric.

Degradation in the context of BNG is the carrying out of activities that reduce the biodiversity value of the site, prior to the date of application. Activities may include felling trees, removing other vegetation such as scrub and hedgerows and scraping sites to bare ground.

The BNG regulations discourage deliberate degradation.

If degradation has taken place since 30 January 2020, the value of the habitat immediately before degradation took place will need to be calculated as the pre-development value in the submitted metric.

If activities to implement or in connection with a planning permission have been carried out on the site since 25 August 2023 that have resulted in degradation, the value of the habitat immediately before degradation took place will need to be calculated as the pre-development value in the submitted metric.

More information about degradation from GOV.UK

There are different ways to achieve the minimum 10% BNG

1. On-site by either enhancing or creating habitat within the red line boundary of the application site
2. Off-site by enhancing or creating habitats on the applicants own land, outside of the application site
3. Buy off-site biodiversity units (e.g. from a habitat bank)
4. Buy statutory biodiversity credits from the government (this should be used as a last resort)

• More information about statutory biodiversity credits from GOV.UK

A combination of ways can be used but BNG delivery must follow the biodiversity gain hierarchy

'On-site’ includes all land within the red line boundary of a project.

Developers should include on-site biodiversity enhancements within their development. These can be ‘non-significant' onsite gains or ‘significant’ onsite gains.

These include gains such as increasing vegetated areas in private gardens, planting a few trees or creating small areas of wildflower meadow.

Non-significant gains are usually secured by a condition on the planning permission that asks for planting and landscaping details.

Significant onsite gains are areas of habitat creation and enhancement which contribute significantly to a development’s BNG relative to the biodiversity value before development. This is because of the type and size of habitats that are being created or enhanced. Government guidance can be found on this

• GOV.UK: Significant on-site enhancements 

Significant on-site gains need additional monitoring by the landowner and local planning authority to ensure they are delivered successfully. Maintenance and monitoring of significant on-site gains for 30 years needs to be secured through a Section 106 agreement if:

 A) The total number of biodiversity units (BU) created or enhanced across all modules in the metric (area habitats, hedgerows and watercourse added together) is equal to or greater than 0.5BU (excluding gains within private gardens / private green roofs).

and/or 

B) The total area of habitats created or enhanced (excluding gains within private gardens / private green roofs) is equal to or greater than 500m2, or the total length of linear habitats to be created or enhanced is equal to or greater than 50m.

In line with Government guidance, existing habitats that are retained post-development (i.e. no change in biodiversity value) will not be included when calculating significant on-site biodiversity gains. However, the LPA recommends that ongoing management measures for retained habitats are still included within any Habitat Management Monitoring Plan (HMMP).

Please note, each planning application will be considered on its own merit. Therefore, there may be instances where exceptions to this rationale will apply.

This definition of ‘significant on-site gains’ was set by the LPA on 12 August 2025 and therefore applies to all non-exempt planning applications decided on or after that date.

‘Off-site’ is all land outside of the development site’s boundary (red line), regardless of ownership.

Applicants can use other land they own to deliver BNG for a development, for example, land within the blue line on their application site plan.

Other land can also be used to provide off-site BNG units, which can be sold to developers so they can achieve BNG on their developments.

Sites that have been set up in advance of selling off-site units on the market are known as habitat banks.

All off-site BNG sites (blue line land and habitat banks) need to be secured via a legal agreement between the landowner and the local planning authority. The site then needs to be registered on the national biodiversity gain sites register and allocated to the development.

• search the biodiversity gain sites register
  
• record allocation of off-site biodiversity gains to a development
  

Off-site biodiversity credits can be found by looking at the national biodiversity gain sites register.

Sites on the Isle of Wight currently on the national biodiversity gain sites register

• Kings Manor Farm (BGS - 100624001) Contact: environmental@kingsmanorfarm.com

Please note that the sites are not owned or managed by the Isle of Wight Council.

All questions should be directed to the site owners / managers using the contact information provided.

The Isle of Wight Council has no control over the price of BNG units from private sites and the purchase of such credits is a commercial transaction between the buyer and seller.

If developers are unable to deliver BNG units on-site or off-site, as a last resort they can purchase statutory credits from the government. The funds from these will be used to create habitat across England. Developers will need permission from the local planning authority if they want to buy statutory credits.

Statutory biodiversity credits - GOV.UK

A Biodiversity Gain Plan is a document that shows how you will achieve BNG.

The local planning authority will secure the submission of a Biodiversity Gain Plan before development commences by adding BNG conditions to planning decision notices.

Local planning authorities are then required to monitor the implementation of Biodiversity Gain Plans.

• BNG PPG Paragraph: 002 Reference ID: 74-002-20240214

Depending on the scale and type of BNG being proposed within the Biodiversity Gain Plan there may be a need to prepare a Habitat Management and Monitoring Plan (HMMP) and submit monitoring reports, and a monitoring fee may be payable.

As the local planning authority needs to review the HMMP and sign-off those monitoring reports, it is allowed to charge a monitoring fee, that is secured through a planning obligation, to cover the cost of this over the 30 years that BNG is required to be in place.

The local planning authority is required to monitor the following for 30 years:

• any off-site BNG (unless you are buying off-site BNG units from a habitat bank);
• ‘significant on-site gains’

We will therefore require monitoring reports and a monitoring fee if the proposed on-site BNG is considered 'significant on-site gains' by the Council.

The Isle of Wight Council has three levels of BNG monitoring fee and these are set out in the table below. The level of fee paid will depend on the size and type of habitats created and the amount of ecology expertise required within the local planning authority to monitor them.

The local planning authority will advise during the determination of an application what level of fee is required.

These fees will be secured by planning obligation and be payable in full prior to the commencement of development.

There may be occasions when a bespoke fee is payable if a complicated BNG package is put forward and this will be considered by the local planning authority on a site by site basis.

These fees will be reviewed on an annual basis and may be adjusted in line with inflation on 1 April each year

Note these monitoring fees relate to BNG that is provided as part of a planning application. They do not apply to BNG habitat banks. For any enquiries about setting up a BNG habitat bank and the monitoring fees that may apply contact planning.policy@iow.gov.uk

Section 106 Agreement is a legal agreement between an LPA and a landowner that secures measures that a developer must take to mitigate the impacts of their development. It can be used to secure BNG.

The Planning Advisory Service (PAS) has produced templates for legal agreements that can be used to secure significant on-site gains or offsite BNG. Applicants should get their own legal advice if they need to submit a legal agreement as part of their application.

Local planning authorities need to monitor significant on-site gains and off-site BNG to make sure that the habitats are kept and maintained for 30 years after the development is completed.

• PAS Biodiversity Net Gain (BNG) Legal Agreement and Planning Condition Templates
  

All off-site biodiversity gains and ‘significant’ on-site biodiversity gains must be secured for a minimum of 30 years, although habitats with a ‘time to target condition’ longer than 30 years may need to be secured for longer.

The Biodiversity Gain Plan is a document which sets out how a development will deliver biodiversity net gain and allows the planning authority to check whether the proposals meet the biodiversity gain objective. It contains information about the on-site and / or off-site BNG that will be delivered by the developer and any off-site units and statutory biodiversity credits purchased.

Once planning permission has been given, and before they start development, the developer needs to submit their final plans for how the development will deliver BNG in a biodiversity gain plan, with a final completed metric and any other BNG information required by condition.

• Biodiversity gain plan information from GOV.UK
  

Your decision notice will say that you are required to submit final information to us about how you will deliver BNG before you start development. This information needs to be submitted in a completed Biodiversity Gain Plan and a final completed metric.

You may also have other conditions on your decision notice that require you to submit final landscaping details via a plan.

If you have signed a section 106 agreement you will need to send monitoring reports to the local authority at agreed intervals for the next 30 years after completing your development. We will write to you to remind you when these are due.

• Biodiversity gain plan templates from GOV.UK
  

More information for developers and applicants

• Where can I find more information about guidance on what BNG is and how it affects applicants, landowners and developers
• Planning Advisory Service frequently asked questions on BNG
  
• Future Homes Hub Launches New Guide to Simplify Biodiversity Net Gain On-Site
  

A private garden is a garden within the curtilage of a privately owned or tenanted dwelling house.

Private gardens can contain important features for biodiversity, including mature trees and hedgerows. When recording habitats at baseline within a private garden you may need to assess any important features as individual habitat parcels to avoid under-recording biodiversity.

This may include:

• recording individual trees
• recording hedgerows
• recording other habitats, such as ponds

Gardens can contribute to on-site BNG, however, these gains should not be classed as "significant" (as the habitats have low distinctiveness values) and would therefore not be secured for 30 years via s106.

No - the condition cannot be varied or removed – it is set in legislation and deemed to apply.