What is Biodiversity Net Gain?
Biodiversity Net Gain, often shortened to BNG, is a planning requirement designed to make sure development leaves the natural environment in a measurably better condition than before.
For developers, this usually means showing how a project will deliver at least a 10% improvement in biodiversity value. This can be achieved through habitat improvements on the development site, off-site habitat creation, or a combination of both.
Where the required uplift cannot be delivered on site, developers may need to purchase off-site BNG units from a suitable habitat bank.
If you already know you need off-site units, you can view our BNG units for sale in Kent for pricing, availability and allocation guidance.
What are BNG units?
BNG units are a way of measuring biodiversity value. They are calculated using Natural England’s Biodiversity Metric, which considers factors such as habitat type, size, condition, distinctiveness and location.
A development will usually have an existing biodiversity value before work begins. The proposed development then needs to show how it will protect, replace or improve habitats so the final result provides a net gain.
In simple terms, BNG units help turn biodiversity impact into something measurable. They allow developers, ecologists and planning authorities to understand whether a scheme meets the required uplift.
When are off-site BNG units needed?
Off-site BNG units may be needed when a development cannot deliver the required biodiversity uplift within the site boundary.
This can happen when:
- the site is too small to create enough habitat
- the development layout leaves limited space for meaningful biodiversity improvements
- on-site habitat creation would be difficult to manage long term
- the required habitat type is better delivered elsewhere
- a planning authority requires a clearer or more secure biodiversity solution
In these cases, developers can use off-site units from a managed habitat bank to help meet their Biodiversity Net Gain requirements.
How spatial risk multipliers work
Location matters when buying off-site BNG units.
The Biodiversity Metric applies a spatial risk multiplier, which reflects how close the off-site habitat is to the development. The further away the habitat is from the development area, the more units may be needed.
As a general guide:
- Off-site units within the same Local Planning Authority or National Character Area may count at a stronger rate.
- Units from a neighbouring Local Planning Authority or National Character Area may require a higher number of units.
- Units from further away may carry a greater spatial risk adjustment.
This is why choosing the right habitat bank matters. A well-located off-site BNG solution can make the process clearer, more efficient and easier to justify through planning.
Why LPAs and NCAs matter
Local Planning Authorities and National Character Areas are important because they help determine the relationship between the development site and the off-site habitat.
A Local Planning Authority is the council or planning body responsible for deciding planning applications in a particular area.
A National Character Area is a wider landscape classification used to describe areas with similar natural features, landform, habitats and environmental character.
When off-site BNG units are located close to the development, they may be more relevant to the local landscape and ecological network. This can support the planning case and reduce the risk of needing additional units because of distance.
BNG units from Chalksole Farm in Kent
Biodiversity & Habitat Solutions provides off-site BNG units from Chalksole Farm, a managed habitat bank in the Kent Downs.
The site supports a range of habitat creation and enhancement work, including grassland restoration, scrub, hedgerows, ponds and woodland features. It is managed with long-term biodiversity value in mind, helping developers meet planning requirements while supporting meaningful ecological improvement.
Chalksole Farm is positioned to support developments across Kent and neighbouring planning authorities, with pricing and current availability available through our brochure.
View available BNG units
Need off-site BNG units?
If your development cannot deliver the required biodiversity uplift on site, off-site BNG units may provide a clear and practical route forward.
Our team can help you understand current unit availability, habitat types, pricing and the next steps for allocation.
Download brochure and pricing