Why go offsite for BNG?

Off-site biodiversity net gain (BNG) units can unlock more space for nature, expediate planning outcomes, maximise revenue, and provide better long-term ecological results than trying to squeeze all habitat creation into constrained development plots. For many schemes, going off-site is often the only realistic way to meet the mandatory 10% biodiversity net gain requirement while still delivering a financially viable project.

Understanding biodiversity net gain

Biodiversity net gain is a planning policy requirement that asks developments to leave habitats in a measurably better state than before. In England, this typically means achieving at least a 10% uplift in biodiversity value, calculated using a standardised metric that scores different habitat types, sizes and conditions. Developers can meet this uplift on-site, off-site, or through a combination of both, as long as the gains are secured and maintained for at least 30 years.

Limits of onsite-only delivery

In principle, delivering all BNG onsite sounds attractive because it keeps everything in one place. In practice, however, many sites simply do not have the land take, layout flexibility, or ecological potential to deliver high-quality, connected habitats once buildings, roads, drainage and open space requirements are accommodated. The outcome can be a scattering of small green pockets and ornamental landscaping that may score poorly in the biodiversity metric and struggle to support meaningful wildlife populations over time.

The ecological case for going off-site

Off-site BNG units allow habitat creation and enhancement to take place on land specifically selected for its ecological value and strategic location in the wider landscape. Instead of being constrained by development footprints, these sites can deliver larger, more continuous habitat blocks that support species movement and contribute to local nature recovery strategies and ecological networks. This landscape scale approach tends to provide more robust gains, because bigger and better-connected habitats are more resilient to climate change and other pressures.

Invest in offsite BNG habitat banks to create the maximum impactful space for all species.

Securing durable, long-term outcomes

Another key advantage of off-site biodiversity net gain units is the way they are secured and managed. Off-site gains are underpinned by section 106 agreements or conservation covenants, with detailed management plans, defined monitoring regimes and reporting obligations extending over a minimum 30-year period. Dedicated land managers or habitat providers are responsible for delivering the agreed outcomes, giving local planning authorities and investors greater confidence that the promised biodiversity uplift will actually materialise and be maintained. Once the units are purchased the developer retains no responsibility for the maintenance of the units over the 30 year period.

Hand over every aspect of running a BNG program for 30 years to the experts.

Practical and financial benefits for developers

From a developer’s perspective, purchasing off-site units can often be more practical and cost-effective than attempting to retrofit high-quality habitat into a constrained layout late in the design process. Off site biodiversity net gain solutions can free up more of the development site for its primary use, reduce design complexity, and provide a clear, auditable route to compliance with BNG policy. This can de-risk planning, accelerate decision-making and help maintain project viability, while delivering credible environmental gains that benefit local communities and the wider landscape.

Using off-site BNG units is typically cheaper overall than delivering the same biodiversity uplift fully on-site, mainly because you avoid sacrificing developable land and can tap into specialist habitat banks. However, actual costs vary widely by location, habitat type and the ecological condition of the land that is being developed.

True cost of on-site delivery

On-site BNG can look cheaper on paper if you only count planting and management, but becomes much more expensive once you factor in the value of the land you are giving up and the homes or floorspace you can no longer build. One detailed study estimated that a fully costed on-site unit could reach around £896,000 per unit once lost development value and foregone profit are included, and even under more conservative assumptions the on-site cost was still around £112,000 per unit versus about £27,000 off-site. At scheme level, this translated into on-site BNG adding around £12,000–£15,000 per house, compared with roughly £3,000 per house when the requirement was met entirely off-site.​ Getting a BNG specialist team onto your site early will help with planning the design, keeping ecologically valuable assets and either creating bespoke habitat banks to minimise your costs or advising on locally available BNG units to purchase.

Why off-site often works out cheaper

Off-site providers can create multiple units per hectare on lower-value land, spreading the cost of design, establishment and 30-year management across a larger and more suitable site. Developers can then use their prime plots, and can cut the cost of compliance from on-site delivery. Responsibility for the ongoing 30 years of management lies with the seller of the off site BNG units, the developers duty ends as soon as the units are purchased and allocated for their development.

Where to buy BNG units for Sussex & Hampshire

Buy from the local experts. Eco-logical Landscapes have ready to go BNG units for sale and can also offer a bespoke service for complex development projects. Our expertise applied to your project will cut costs for ecological compliance and deliver the best outcomes for local communities. It's as simple as that.