Biodiversity Net Gain - FAQs

Biodiversity Net Gain (BNG) in principle is about developments leaving biodiversity in a better state than it was before by creating and enhancing natural habitats.  In England, BNG became mandatory on 12th February 2024 under Schedule 7A of the Town and Country Planning Act 1990 (as inserted by Schedule 14 of the Environment Act 2021), meaning planning applications must deliver a minimum of a measurable 10% net gain in biodiversity, in order to validate their application. 

With this new and revolutionary legislation, there are a lot of changes to the ecological process and a lot of new terminology to understand.  Below are some frequently asked questions that we have answered to help create a better understanding of BNG and tackle through the jargon. 

• What is the biodiversity metric tool?

The biodiversity metric tool is used to calculate biodiversity value for the purposes of biodiversity net gain.  The biodiversity metric tool can calculate different types of ‘biodiversity units’. The biodiversity metric tool can be used throughout all stages of a project, from site selection to detailed design and delivery.

• What are biodiversity units?

‘Biodiversity units’ are used to describe relative biodiversity value. There are three types of biodiversity units: area habitat units, hedgerow units, and watercourse units. Each of these are calculated in separate ‘modules’ of the biodiversity metric.

• What is an area habitat?

Habitats recorded in the biodiversity metric tool in area (hectares). This includes woodlands, grassland, ponds, scrub etc.

• What is a linear habitat?

Habitats recorded in the biodiversity metric according to length (kilometres) instead of area (hectares). This includes habitats in the hedgerow and watercourse modules. It’s taken as a centre line measurement along the length of the feature.

• What is a watercourse habitat?

Similar to a linear habitat, these are aquatic habitats recorded in the biodiversity metric according to length (kilometres). 

• What does baseline habitat mean?

The baseline habitat represents all the habitats that currently exist on site.  The baseline habitats are defined by their habitat type, distinctiveness, condition, and strategic significance. 

• What does post-development habitats mean?

The post-development habitats comprise all the habitats present once the development is complete.  This includes the baseline habitats that have been retained, new habitats that have been created, and the baseline habitats that have been enhanced.  Similar to baseline habitats, the post-development habitats are defined by their habitat type, distinctiveness, condition, and strategic significance. 

• What does distinctiveness mean?

A measure based on the type of habitat and its distinguishing features. This includes:

1. Consideration of species richness and rarity.

2. The extent to which the habitat is protected by designations.

3. The degree to which a habitat supports species rarely found in other habitats.

• What does condition mean?

A measure of the habitat against its ecological optimum state. Condition is a way of measuring variation in the quality of patches of the same habitat type.

• What is a habitat condition assessment?

The process of assigning habitat condition, to be undertaken by a competent person such as an ecologist. 

• What does strategic significance mean?

Describes the local significance of the habitat based on its location and the habitat type. 

• What is the difference between onsite and offsite?

On-site means all land within a red line boundary of a development.  Off-site for the purposes of the metric calculation tool means land outside of the on-site boundary, which is dedicated to habitat interventions (habitat enhancement or creation), regardless of proximity or ownership. 

• Should I clear the site before the BNG Assessment?

No.  It is strongly advised that clients and landowner do not clear the site before the BNG Assessment has been completed.  To complete a BNG assessment, a suitably qualified ecologist needs to complete a habitat condition assessment of the baseline habitats on site, to assess the quality of the baseline habitats.  Under the principals of BNG, if the habitats on site have been degraded or destroyed before a habitat condition assessment has been completed, then the ecologist must take a precautionary approach to assess the habitats prior to when they were cleared, which could mean the habitats are assessed to be in ‘good’ condition.  This will mean in the biodiversity metric calculation tool, the ‘good’ condition habitat will be marked as ‘lost’.  This makes it harder to achieve net gain because there will be a greater biodiversity unit deficit to recover before achieving a net gain in biodiversity units. 

• What are the trading rules?

The trading rules set minimum habitat creation and enhancement requirements to compensate for specific habitat losses, up to the point of no net loss. They are based on the habitat type and distinctiveness of the lost habitat.  The trading rules do not apply beyond no net loss. 

• Do I need to achieve a total of a 10% net gain on-site or 10% net gain in each habitat type?

You must achieve a minimum of a 10% net gain in each habitat type that is present in your baseline: Area habitats, Hedgerow habitats, and Watercourses habitats including on-site and off-site. 

• What do I do if I can’t get a 10% net gain on-site?

There are two options at your disposal.  Firstly, there is offsite habitat creation/enhancement, where new habitats are created or existing habitats are made better on land outside of the red line boundary of the development, which can be used to make up the deficit in biodiversity units on-site.  This is the preferred option for Local Planning Authorities.  If this is not possible, the final option is purchasing biodiversity credits, which is the last resort.  Buying statutory credits means that as well as, or instead of, creating and enhancing biodiversity on or offsite, developers can make a financial contribution, which counts towards their mandatory 10% BNG.  This contribution will be used to fund biodiversity enhancements across England. 

• Do I need to manage the habitats, if so, how long for?

The landowner will be legally responsible for creating/enhancing habitats, and managing these habitats for at least 30 years to achieve the target condition. This applies to on-site and offsite habitats.

• What is an offsite provider?

An off-site provider can create or enhance habitats to generate biodiversity units for developments and allow them to meet their BNG requirement. An offsite provider could be a land manager, a landowner, or an organisation acting as a habitat bank.

• What is a Section 106 Agreement and do I need one?

A Section 106 Agreement is a legal agreement between the local planning authority and the landowner, outlining the landowner's obligations as part of the planning process.

If you are creating/enhancing habitats on- or offsite, a Section 106 Agreement will be required because you will be legally reposonsible for delivering the post-development biodiveristy units; however, if you are purchasing biodiversity units from an offsite provider, the offsite provider will need to obtain a Section 106 Agreement with the local planning authority because the offsite provider will be legally responsible for delivering he post-development biodiveristy units.

• What is a biodiversity credit?

A biodiversity credit is a financial mechanism that represents an asset created through investments in the restoration, conservation, and development of biodiversity in a specific landscape.  

If you need a BNG Assessment carried out for your project or you have any questions regarding BNG, please contact us here.  More information about BNG can be found on our blog here.