Biodiversity Net Gain

Biodiversity Net Gain

What is Biodiversity Net Gain (BNG)?

Biodiversity Net Gain (BNG) is an approach to development and land management that leaves biodiversity in a measurably better state than before the development took place. A minimum 10% ‘net gain’ is required as part of development as calculated using a Biodiversity Metric Calculation Tool.

The purpose of BNG is to encourage the retention and enhancement of existing habitats, create new habitats and ensure ecological connectivity for wildlife is retained and improved. Habitats must be secured for a minimum of 30 years.

BNG is additional to existing habitat and species protections and is intended to reinforce the mitigation hierarchy (avoid - mitigate – and compensate as last resort).

BNG is implemented under Schedule 14 of the Environment Act 2021 ‘Biodiversity gain as a condition of planning permission’. Mandatory BNG became effective on 12th February 2024 for all Town and Country Planning Act development and ‘non-major developments’ on 2nd April 2024 (with certain exemptions developments).

What applications are exempt from BNG?

There are exemptions to BNG, and these include:

Householder applications.
Applications which do not impact priority habitat and less than ≤25m² of habitat / ≤5m linear habitat such hedgerows/treelines.
Self-builds listed under the Section 1(A1) of the Self-build and Custom Housebuilding Act 2015.
High speed railway and urgent crown developments.
Developments granted by a development order (such as permitted development) including Class Q conversions.
Currently Nationally Significant Infrastructure Projects (NSIPs) (estimated to require BNG from November 2025).

Additionally, if the baseline habitats on site are at 0 (this includes all concrete sites with no habitats present) legal BNG would not be applicable, however, LPAs may be imposing their own BNG policies for these exempt developments.

The BNG Process

Before the site survey, we will request:

A redline boundary for the site (1:500).
An arboricultural report and accompanying tree constraints plan (where available).
A proposed site plan in an adobe PDF file type at a minimum 1:500 scale at A1 size. A wider context plan may be issued if available.
If there are any details on landscaping within the development site / an indicative landscaping plan. This does not apply to landscaping which will be in private gardens.
A blue line boundary of additional land which could be used for new habitat creation (referred to as ‘offsite’ habitat offsetting) and where we cannot achieve a minimum 10% net gain onsite (within the red line boundary). Please be aware we will need to survey this additional land to ensure the development provides a minimum 10% net gain. Please note that the attached quotation does not cover a survey of additional land at this stage unless otherwise discussed and agreed prior.

The site survey consists of in-depth Preliminary ecological survey:

A Phase 1 Habitat survey which utilises the UKHabs system of habitat classification is undertaken by our ecologists. Biodiversity net gain also requires condition assessments to be undertaken for all habitats on site (including trees and hedgerows). These habitats will then be mapped accurately using COREO, whilst onsite.
The survey also identifies any potential ecological 'constraints' on the proposed development. For example, protected species and the presence of high quality habitats.
The ecologist will identify the requirement for further, more detailed surveys. For example, bat emergence surveys or reptile surveys.

Please do not clear your site before or after a site visit. If it is evident site clearance has taken place (using historic satellite imagery), we have to act in accordance to the statutory guidance. Within Schedule 14 of the Environment Act 2021, measures are included that allow LPAs to recognise any habitat degradation since 30th January 2020 and to take the earlier habitat state as the BNG baseline in Good condition. This can make it more difficult to obtain a minimum 10% net gain onsite. Additionally, there would be a need to account for the time between the habitat loss and compensation, which will see further penalisations applied.

All ecologists on site will have undertaken suitable training, including CIEEM certified training in the Biodiversity Metric 4.0 and UK Habs.

After the site survey:

Using the baseline habitat map we created onsite, we will layer over the proposed plans and create a post development map. This will be exported into the statutory biodiversity metric.

Metric calculation:

The statutory metric will inform us if a net gain was achieved onsite in each category; Area habitats (A), Hedgerows (H) and Watercourses (including ditches)(W). For example, if you have area habitats and hedgerows onsite at baseline, but no watercourses, you will need to get a separate 10% net gain in area habitats and hedgerows. You will not need to get a net gain in watercourses.

Habitat creation / enhancement:

If your development allows, we may be able to suggest habitat creation or enhancements which may help you achieve a net gain onsite / reduce the number of units or credits which will need to purchased. These areas of habitats which will be created or enhanced will need to be managed for the length of the development by a suitably qualified company, and subject to continuous monitoring. Once this is agreed, we can re-run the metric based on the new proposed habitats.

If a net gain cannot be achieved onsite, offsite gains will be needed. These options are not mutually exclusive, and can be used in any combination to secure a 10% net gain. Offsite gains can be achieved in three ways:

Blue line land

This is land under ownership of the applicant. To be included in the metric, it would have needed to been surveyed at the time of the baseline survey, or it will need a return site visit survey (at cost). The land used to achieve net gain onsite will need to be legally secured for a minimum of 30 years and registered as a Biodiversity Gains Site. The land used for the 10% net gain cannot be developed for a minimum of 30 years.

Biodiversity units

Biodiversity units can be purchased from a number of private suppliers. The units ideally would be within the same Local planning authority (LPA) or National character area (NCA) as the development. Due to a spatial risk multiplier (SRM), the further the purchased units are away from your site, the more units will need to be purchased to achieve net gain. The spatial risk multiplier is 1.5 x for neighbouring LPA or NCA's, 2x for any other LPA / NCA.
These units are constantly changing depending on availability, however they are often significantly cheaper than statutory credits.
Biodiversity units will need to be secured as part of the planning consent.

Statutory credits

Statutory credits can be purchased from the government as a last resort. The number of units automatically has the highest SRM applied, and therefore this option is often the most expensive and in-turn the worst case scenario for the site.

For example, in the metric above, Statutory credits for 1.11 units of area habitat (A1) is equivalent to £46,620, and 0.02 units for hedgerows (H) is equivalent to £880, therefore giving a worst case scenario for this site as £47,500. The statutory credit estimation tool can be found at the following link : https://www.gov.uk/guidance/estimate-the-cost-of-statutory-biodiversity-credits

ABR Ecology LTD

Email us for a quote: abrecology@gmail.com