Biodiversity Net Gain (BNG)
Biodiversity Net Gain is an approach to development that leaves biodiversity in a measurably better state after development than before, after first avoiding and minimising harm.
From 12 February 2024 all major developments in England have to deliver 10% BNG and from 2 April 2024 all developments (except for some exceptions, such as householder applications) will have to deliver 10% BNG. This requirement does not replace, but is in addition to, the existing policy and legal requirements related to biodiversity and development.
To measure BNG and assess the impacts of planning applications Defra’s Biodiversity Metric (or for smaller sites the small sites metric) should be used. Local guidance on the biodiversity metric is provided below. The local authorities across Gloucestershire and the Gloucestershire Local Nature Partnership worked together to prepare guidance in 2023. This useful guidance was adapted for use in West Oxfordshire. The guidance will be regularly updated to reflect changes in national and local guidance and initiatives:
Biodiversity Net Gain: Good practice principles for development (published by CIEEM) should be followed when designing developments and preparing planning applications. Further advice can be obtained from the council via our pre-application advice service.
Planning applicants will need to provide information on the biodiversity value of their application site and how they plan to deliver 10% BNG as part of their application. Details can be found on our validation webpages.
In most cases, BNG should be provided on the development site, i.e. within the red line boundary, but in some cases, and in agreement with the council, it may be necessary to provide the net gain off-site. This could be on land within the planning applicant’s control (e.g. land within the blue line boundary via legal agreement) or through the purchase of the required biodiversity units (quantity and type) from a habitat bank. Details of local habitat banks can be found on the Oxfordshire Local Nature Partnership website: https://www.olnp.org.uk/biodiversity-net-gain-bng-sites-in-oxfordshire Those listed here have been certified with the Oxfordshire NatureMark by demonstrating a commitment to delivering genuine, high quality outcomes for biodiversity.
Government guidance on the BNG process is available at: Developer guidance.
Strategic Significance
For the strategic significance multiplier in the biodiversity metric, we are currently using the draft publication of the Oxfordshire Local Nature Recovery Strategy (LNRS) map and the existing Conservation Target Areas in the district until the LNRS is published by Oxfordshire County Council shortly after 12th November 2025.
On-Site Significant Enhancement
To identify onsite significant enhancements, we are using the Verna Mycelia software in combination with the national guidance published by Defra which can be found here: https://www.gov.uk/guidance/make-on-site-biodiversity-gains-as-a-developer#significant-on-site-enhancements
This states:
“What counts as a significant enhancement will vary depending on the scale of development and existing habitat, but these would normally be:
- habitats of medium or higher distinctiveness in the biodiversity metric
- habitats of low distinctiveness which create a large number of biodiversity units relative to the biodiversity value of the site before development
- habitat creation or enhancement where distinctiveness is increased relative to the distinctiveness of the habitat before development
- areas of habitat creation or enhancement which are significant in area relative to the size of the development
- enhancements to habitat condition, for example from poor or moderate to good
Non-significant enhancements are habitat enhancements whose loss will not significantly decrease the development’s biodiversity value. They should still be included in your metric calculations. Examples could include private gardens which have a low distinctiveness value, or container planting. These enhancements do not normally require maintenance provisions, so for non-significant enhancements, you do not need to have an HMMP, legal agreement or commitment to maintain them for 30 years.”
Private gardens, ornamental planting, and small areas of amenity grassland are unlikely to be considered ‘significant’. Local planning authorities are not obliged to secure the long-term management of these features for the purpose of mandatory BNG, but these areas (excluding private gardens) will likely still have long-term management secured through other mechanisms.
Monitoring the delivery of BNG
Where the proposed onsite gains are not significant, management and monitoring do not need to be secured for the statutory 30-year period. The delivery of these habitats would be secured via conditions relating to the implementation of the details, the landscaping scheme and a Landscape and Ecology Management Plan (LEMP) that would cover the period up to when the habitats are expected to reach their target condition with a final audit report to confirm successful implementation.
Where the proposed onsite gains are significant enhancements, the council will still include relevant planning conditions for the submission of landscaping details and a Habitat Management and Monitoring Plan (HMMP) for approval. However, the council may decide to secure the 30-years of management and monitoring by S106 agreement. This decision would depend on the type of development, the habitat type and distinctiveness, the difficulty rating of creating or enhancing the habitats, and who has responsibility for implementing the approved HMMP. A S106 agreement is considered to be important for residential developments where responsibility would pass from the developer to another management body.
Section 106 agreements can also used to secure the delivery of off-site BNG on land owned by the developer and on habitat banks.
The council can also recoup the costs associated with monitoring the delivery of BNG for the 30-year period via the S106 agreement. Planning Practice Guidance (PPG) states: “Local planning authorities can charge a monitoring fee though section 106 planning obligations, to cover the cost of monitoring and reporting on delivery of that section 106 agreement for both off-site and on-site BNG.”
Habitat Management and Monitoring Plan (HMMP)
The HMMP sets out the monitoring regime for each BNG site for the 30-year period in terms of how the habitats will be checked by the developer’s or the habitat bank owner’s ecological consultant(s), what remedial measures may need to be implemented and when monitoring reports will be submitted to the council.
A standard timeline is becoming widely used and monitoring events are generally expected to take place in years 1, 3, 5, 10, 15, 20, 25 and 30 following the completion of development (or completion of the habitat creation/enhancement works for habitat banks). WODC is also conditioning a final audit report that may be submitted in year 31 to confirm the success of the BNG delivery for the full statutory period. The actual timing of monitoring may differ depending on the development type, habitat types and any specific site constraints or considerations, e.g. soil type, flood risk, etc, and is usually confirmed as part of the HMMP.
Council Monitoring Responsibilities
When the monitoring reports are submitted to the council, it may be necessary for them to carry out their own monitoring to ensure that the BNG is being delivered effectively. This could include:
- Setting up an internal monitoring system;
- Ensuring that monitoring reports are received at the agreed times;
- Reviewing the reports for adequacy and quality;
- Reviewing the results of the report to ensure that the BNG outcomes are being delivered;
- Ground-truthing the reports from time to time through site visits;
- Communicating the council’s findings to the applicant, landowner or habitat bank operator, or other interested third parties;
- Taking enforcement action where reports are not received, are of insufficient quality, or show that the required BNG is not being delivered;
- Agreeing remedial actions that need to be taken and ensuring that these are carried out; and
- Reviewing and agreeing updated Habitat Management and Monitoring Plans.
Verna BNG Monitoring Fee Calculator
The Verna BNG Monitoring Fee Calculator was developed to assist local planning authorities (LPA) and is publicly available to download on their website https://verna.earth/news-item/free-tool-how-to-calculate-biodiversity-net-gain-monitoring-charges/
The calculator takes account of the cost to the LPA in both reporting and non-reporting years and translates costs in future years into the value of today’s money. The calculator assumes that the monitoring fee is received in a single upfront payment. Using this free resource ensures that the monitoring fee calculations are replicable and consistent, and can therefore be effectively reviewed by the council, e.g. on an annual basis, to take account of increasing costs.
In the calculators used by WODC, categorisation of the types of BNG monitoring are based on the size of the site [small (0 to 5ha), medium (5.1 to 20ha), large (20.1 to 40ha) and a bespoke approach to sites larger than 40 hectares (ha)] and the complexity of creating or enhancing habitats based on the highest technical difficulty rating in the Statutory Biodiversity Metric [low, moderate or high].
The monitoring frequency is set as a standard for all sites at years 1, 3, 5, 10, 15, 20, 25 and 30. This equates to at least 8 no. monitoring events within the 30-year period. This could be updated on a bespoke basis for individual developments depending on the specifics of the case.
Monitoring fees
Monitoring fees will be calculated on a bespoke basis for BNG sites of over 40ha or where phased delivery of BNG is likely to take place (there is a separate process in Planning Practice Guidance for phased developments https://www.gov.uk/guidance/biodiversity-net-gain#determination-of-the-planning-application – paragraphs 053 to 063). The bespoke approach would consider the size and complexity of the BNG proposal and other relevant factors. The Verna BNG monitoring fees calculator would be used to produce a bespoke figure on a case by case basis.
Monitoring fees would normally be paid as a one-off sum within 10 working days of the commencement of development or shortly after habitat banks or other offsite BNG sites have been formally added to the National Biodiversity Gain Site Register. The payment terms would be set as part of the associated S106 agreement.
There may be requests to spread payments over 18 – 24 months and these will be considered on a case-by-case basis.
The Trust for Oxfordshire’s Environment (TOE) advocates reasonable and equitable costs for all types of developer and landowner regarding both development sites and habitat banks, and WODC has therefore taken this into account when preparing the fee schedule below.
The fees will be reviewed annually as part of the Council’s overall review of fees. This review would include an analysis of salary, inflation rate and other known costs, and reference to other LPAs’ monitoring fees at that time to ensure that the fees generated by the Verna Calculator are comparable.
WODC’s BNG monitoring fees are provided in the table below.
| West Oxfordshire District Council's BNG Monitoring Fees 2025 - 26 | ||
|---|---|---|
| Size of site | Complexity | Associated Fee |
| Small (0-5 ha) | Low | £3,000 |
| Moderate | £4,000 | |
| High | £5,000 | |
| Medium (5+ to 20 ha) | Low | £6,250 |
| Moderate | £7,500 | |
| High | £8,500 | |
| Large (20+ to 40 ha) | Low | £10,250 |
| Moderate | £12,500 | |
| High | £14,500 | |
| 40+ ha | Bespoke approach will be needed | |
District Licence and Biodiversity Net Gain (BNG)
Users of the District Licence scheme can also benefit from the integrated Biodiversity Net Gain package managed by NatureSpace and the Newt Conservation Partnership. More information on this can be found on the NatureSpace website.