Information on Biodiversity Units

Biodiversity Net Gain (BNG) is a strategy put forward by the government that aims to safeguard and improve the well-being of natural ecosystems in the UK. It’s a new approach to development that mandates a 10% increase in the overall biodiversity value of the development site, mitigating the biodiversity loss typically caused by clearing natural habitats during development.

• The Recovery of Nature
  BNG contributes towards nature recovery by promoting the creation of new habitats and the enhancement of existing ones. It also improves habitat connectivity which is vital for maintaining healthy wildlife populations and promoting biological diversity.
• Combatting Climate Change
  BNG can help tackle climate change through the restoration of ecosystem services. For example, diverse ecosystems, such as forests and wetlands, play an important role in carbon sequestration, which removes greenhouse gases from the atmosphere by storing it in vegetation and soils.
• Public Health and Well-Being
  BNG can improve our health and well-being by enhancing or creating new green spaces for public use. For example, these green spaces could be in recreational or housing areas, or places of work.
• Economic Opportunities
  BNG can create long-term income opportunities through investment in habitat management. It can also act as a green finance mechanism, delivering wider economic benefits and increasing financial and natural capital asset values.

In England, from 12th February 2024, it is mandatory for developers to deliver a BNG of at least 10% under Schedule 7A of the Town and Country Planning Act 1990 (as inserted by Schedule 14 of the Environment Act 2021). This applies to developers of small sites and major developments, developers of nationally significant infrastructure projects (from late November 2025), land managers wanting to sell in the BNG market, and local planning authorities. However, some developments are exempt from the BNG requirements.
Exemptions:
– The planning application for the development was made before 12th February 2024.
– The proposed development does not impact a priority habitat and impacts less than 25 m² of on-site habitat.
– The proposed development does not impact a priority habitat and impacts less than 5 m of linear habitats on-site, such as hedgerows.
– The planning application is made by a householder and involves a small project such as a home extension, conservatory, or loft conversion.
– The proposed development consists exclusively of self-built dwellings or custom housebuilding.
– The proposed development will be undertaken mainly for the purpose of delivering off-site BNG units for another development.
– The proposed development forms a part of the high-speed railway transport network.
– The proposed development is an urgent crown development.
– The proposed development has been granted planning permission by a development order.

1. The mitigation hierarchy
Firstly, developers should try to minimize negative impacts on biodiversity through careful site selection and thoughtful development plans. Considerations should include avoiding high-value habitats (and utilising degraded or low-value sites instead), and retaining existing significant features, such as mature trees and hedgerow. Secondly, developers should try to restore existing on-site habitat by improving their condition (habitat enhancement). Thirdly, to offset/compensate for any unavoidable habitat loss, habitat of a similar type should be created where it did not previously occur.

2. The biodiversity gain hierarchy
When enhancing and creating habitat to increase biodiversity value, the three steps that make up the biodiversity gain hierarchy must be followed in order (however, the steps can also be combined):

• On-Site units – On-site units are gained through habitat enhancement and creation within the red-line boundary of the development site.
• Off-Site units – If on-site units cannot be gained, developers can enhance or create habitat on land that lies outside of the development site’s red-line boundary. Developers can own this land themselves, or they can purchase biodiversity units on the market from other landowners.
• Statutory biodiversity credits – If it isn’t possible to obtain on-site or off-site units, developers must buy statutory biodiversity credits from the UK government. This option is a last resort. The government will use the revenue generated from selling statutory biodiversity credits to invest in habitat creation in England.

All habitat must be maintained for a minimum of 30 years.
Biodiversity net gains cannot be made in post-development private gardens as the net gains cannot be legally secured. Accordingly, habitat enhancement and creation for the purpose of BNG needs to be done outside of private gardens.

• The trading rules
  The trading rules set minimum habitat enhancement and creation requirements to compensate for the loss of specific habitats. They apply up to the point of no net habitat loss, and are based on the type and distinctiveness of the lost habitat.

It is possible to achieve a 10% gain in biodiversity units and not satisfy the trading rules, however, this would not be accepted as a BNG. The trading rules must be followed for a development to claim BNG.

When BNG cannot be achieved within the red-line boundary of a development site, biodiversity units should be sought off-site (in accordance with the biodiversity gain hierarchy. These can be gained on land that is owned by the developer or bought from other landowners, land managers, or habitat banks.

Browse the biodiversity units available for purchase through BACNET here. Identify what units you require for your project from your post-development BNG report, and then use the relevant filters to sort through the listings.
Please note that the ‘Units available’ displayed for each listing are subject to a spatial risk multiplier that considers the distance between the location of the development site and the location of the site offering biodiversity units. Depending on the distance between the sites, a spatial risk multiplier of 1.0, 0.75, or 0.5 is implemented.
Upon purchasing units off-site, a legal agreement between the developer and the landowner selling the units may be required (see below).

When purchasing off-site biodiversity units, the developer and the landowner selling the units must enter a legal agreement which must last for at least 30 years from the date all habitat enhancement and creation is completed. However, if the off-site gain is secured with a legal agreement by the landowner, the developer does not need to enter a legal agreement.
We recommend you get legal advice before entering any legal agreements regarding BNG. Please consult the government website for more detailed information.