A tractor tending to a wildflower meadow, one example of a habitat for BNG

On-site or off-site BNG: which is right for your development?

Exploring the benefits and limitations of on-site vs off-site biodiversity net gain (BNG)

In order to reach the required 10% biodiversity net gain (BNG), developers must choose between on-site and off-site units.

While on-site options must be considered first under the ‘biodiversity gain hierarchy’, practical constraints such as long-term risk, space limitations and planning challenges often make off-site biodiversity net gain a more viable option. With off-site units now available through providers such as BNG Units Ltd, achieving BNG compliance is easier than ever.

In this article, we will explore the advantages and disadvantages of both options, including biodiversity, planning and cost considerations.

The Advantages and Disadvantages of On-site Biodiversity Net Gain

Advantages of on-site BNG:

Many property developers opt for on-site biodiversity solutions, citing benefits such as:

Planning preference: On-site delivery is prioritised by Local Planning Authorities (LPAs) under the biodiversity gain hierarchy.
Direct mitigation: On-site habitats directly compensate for any ecological losses caused by development.
Value enhancement: Well-designed habitats can enhance and beautify development sites, increasing property value and potentially attracting eco-conscious buyers.
Cost advantages: On-site delivery can sometimes reduce costs and logistical complexities by avoiding third-party agreements.

Disadvantages of on-site BNG:

Despite these benefits, on-site solutions come with some notable limitations:

Space constraints: Many developments lack sufficient land to deliver meaningful biodiversity uplift.
Low-quality habitats: On-site BNG often results in small, fragmented patches of habitat that are disconnected from surrounding landscapes, limiting ecological value.
Human impact: Proximity to residents can lead to high levels of habitat disturbance.
Risk of failure: Evidence suggests that small, isolated habitats have a low likelihood of maturing into valuable ecosystems.
30-year liability: Sites with significant on-site habitat enhancements require the developer to enter into a Section 106 agreement with their LPA and remain responsible for the habitat management for 30 years. In practice, this responsibility is often transferred to residents’ associations or management companies, which may lack the necessary ecological expertise or refuse the responsibility altogether, creating a heightened risk of non-compliance and subsequent penalties.
Reduced development potential: Allocating land for on-site BNG reduces the amount of land available for development, potentially lowering site density and profitability.

Wildflowers growing along a lakeside — Well-planned off-site biodiversity net gain can deliver more resilient habitats, including species-rich lakeside environments

Advantages of Off-site Biodiversity Net Gain

There are several compelling benefits to opting for off-site BNG solutions, including:

Increased developable land: By delivering BNG off-site, developers can retain a greater proportion of their land for housing and commercial use. This will improve site efficiency and overall profitability.
Stronger ecological outcomes: Off-site projects deliver larger, higher-quality habitats that are connected to wider landscapes. This makes them more resilient and less vulnerable to human impact.
Long-term security: The 30-year management and legal compliance obligations are transferred to specialist providers with ecological expertise.
Greater flexibility: Opting for off-site BNG units will allow developers to focus on their projects and avoid the logistical challenges of creating habitats on a construction site
Cost efficiency: While off-site BNG involves upfront costs, it is often more cost-effective over the long term than designing, implementing and maintaining complex on-site habitats.
Higher habitat potential: Off-site land for BNG is selected for its ecological advantages. This offers greater potential for flourishing eco-systems than simple, on-site ‘green spaces’

When to opt for off-site BNG

While on-site biodiversity net gain (BNG) options present some advantages, the delivery of on-site units is often constrained by space, cost and long-term risk. Off-site BNG options offer significant ecological and logistical advantages. Off-site biodiversity net gain should be considered when:

Space constraints would result in small, fragmented habitats;
Site conditions aren’t suitable for the required habitats;
Development plans include high-density layouts or complex construction programmes;
Developers wish to relinquish the burden of long-term habitat management;
Developers are seeking certainty and reduced liability.

Should developers in the East of England opt for off-site BNG, BNG Units Ltd provides a wide range of high-quality off-site BNG units, helping developers achieve full compliance with government requirements efficiently and with confidence.