Why are developers moving away from on-site BNG
Biodiversity Net Gain as a planning requirement is an ecological imperative, representing a response to the loss of half of the UK’s biodiversity since the 1970s. But it is also proving to be a significant challenge for developers navigating compliance in the space.
Since it became mandatory for most developments in England in February 2024, developers have faced an important decision: deliver biodiversity gains on-site, or secure off-site biodiversity units through a specialist provider.
While on-site BNG may initially appear to offer greater control, many developers are now recognising the practical, financial and long-term challenged involved. As a result, off-site BNG solutions are becoming an increasingly popular route for projects of all sizes.
At BNG Units Ltd, we are seeing a clear shift towards strategically managed off-site habitat creation. Developers in particular are seeking certainty, efficiency and reduced long-term risk.
What challenges are developers facing with on-site BNG
Delivering biodiversity improvements within a development boundary can work well in certain circumstances. However, for many developments, achieving meaningful biodiversity gains on-site is far more complicated than expected.
Developers must balance:
- land value,
- planning requirements,
- public access,
- maintenance responsibilities,
- and ecological performance.
This often results in fragmented or constrained habitat areas that are difficult to manage effectively over the required 30-year period.
For smaller and medium-sized developments especially, allocating valuable development land to ecological mitigation can significantly impact scheme viability.
The financial cost of on-site BNG
Many developers have opted for on-site BNG under the assumption it would be the cheaper option. However, evidence suggests on-site BNG can prove more costly for developers then seeking off-site options.
A 2025 report by Environment Bank found that costs are approximately four times higher than if all BNG were delivered off-site. This takes into consideration the land value and lost development potential.
The same study also noted that on-site BNG could add £12,000 to £15,000 per house to development costs, compared to just £3,000 per house when delivered off-site.
The hidden cost of long-term management
One of the main reasons developers are moving away from on-site BNG is the long-term management commitment. Under current legislation, biodiversity gains must be maintained for at least 30 years. This leaves developers responsible for ongoing habitat management, monitoring, reporting, and HMMP compliance. Over time, these obligations can become costly and time-consuming – particularly as managing ecological habitats often requires specialist expertise to meet Biodiversity Metric targets.
Why off-site BNG is becoming the preferred option
Off-site biodiversity units provide developers with a more streamlined and lower-risk solution. Instead of attempting to create and maintain habitats within a constrained site boundary, developers can secure biodiversity gains through dedicated habitats managed by experienced landowners.
Despite government expectations that over 50% of BNG would be delivered off-site, current data suggests that only around 10% or less is being delivered this way. This gap represents both a missed opportunity for nature recovery and a signal that current policy incentives are not yet aligning developer behaviour with the best ecological outcomes.
Greater development efficiency
Using off-site BNG allows developers to maximise the developable area of a site without compromising biodiversity obligations. Rather than allocating developable land to habitat creation, developments can be designed more efficiently while biodiversity enhancements are delivered at larger, strategically managed locations elsewhere.
Better ecological outcomes
Large-scale habitat creation delivers significantly greater biodiversity value than isolated on-site habitat pockets. This distinction is particularly important considering before BNG was introduced, the UK sat at the bottom of the Biodiversity Intactness Index for all G7 nations.
Reduced long-term risk
Off-site providers take responsibility for the ongoing habitat management and monitoring requirements associated with biodiversity units. For developers, this can substantially reduce future liabilities. Working with an established BNG provider also helps ensure that habitats are managed by teams with the appropriate ecological expertise and long-term stewardship capabilities.
The importance of choosing the right BNG partner
As demand for biodiversity units continues to grow, developers are becoming increasingly selective about who they work with. Not all BNG providers operate in the same way. Some act purely as brokers, while others are directly involved in land management and habitat creation projects.
This distinction matters. Developers need confidence that habitats will be delivered, monitored, and maintained successfully for decades to come. Working with experienced landowners and established habitat projects can provide greater transparency, accountability, and long-term security.
If you’re assessing your BNG obligations on an upcoming project, get in touch with our team and let us find the right solution for you.