Why the Future of Development Requires On-Site Design and Offsite BNG Units

Designing for People, Scaling for Nature: Why the Future of Development Requires On-Site Design and Offsite BNG Units

When the mandatory Biodiversity Net Gain (BNG) framework was introduced, it sparked a major debate across the development sector: Should biodiversity enhancements be delivered entirely on-site, or is securing offsite BNG units the more practical route?

The truth is, viewing this as an "either/or" choice misses the bigger picture. To successfully improve biodiversity and build thriving communities, we don't need to choose between on-site and off-site mitigation. We need a combination of both. When used together strategically, on-site design and offsite BNG units act as partners rather than rivals.

The Dual Approach: Local Lifelines vs. Biodiversity at Scale

Both delivery methods play a unique, irreplaceable role in environmental recovery and urban planning.

1. On-Site BNG: The Local Lifeline

While delivering biodiversity gains directly on a development site can be logistically challenging, on-site improvements are essential for those living in the new space.

• For People: Integrating green infrastructure provides vital areas for recreation, improving mental health and keeping urban residents connected to the natural world.

• For Micro-Wildlife: Small on-site meadow pockets, waterways and street trees are crucial for insects with short flight spans, such as solitary bees, that require immediate, local food sources and resting places.

2. Offsite BNG Units: Biodiversity at Scale

1. Ecological Scalability and Connectivity

The biggest limitation of on-site BNG is space. Urban developments naturally lead to fragmented patches of nature. In contrast, offsite habitat banks are typically large, continuous expanses of land.

• Buffering Protected Sites: Locating habitat banks directly adjacent to existing Sites of Special Scientific Interest (SSSIs) and Ramsar wetlands exponentially increases their ecological value. By expanding these existing protected areas, we provide vital buffer zones that allow rare and threatened species a genuine chance to expand their territories and migrate safely.

• Wildlife Corridors: Larger plots allow for the creation of connected wildlife corridors. This is essential for larger mammals, reptiles, and birds that require expansive territories to forage, mate, and survive.

• Complex Ecosystems: Bigger sites can support diverse, complex habitats (such as rich woodlands, wetlands, and species-rich grasslands) that simply cannot coexist on a compact housing or commercial footprint.

2. Long-Term Legal and Financial Security

Offsite BNG units provide an extra layer of permanence that can be difficult to guarantee within a bustling urban development.

• Dedicated Management: Habitat banks are backed by legally binding 30-year covenants (such as Section 106 agreements or Conservation Covenants). They are managed by professional ecologists and land managers whose sole job is to ensure the habitat thrives.

• Protection from Urban Pressures: On-site green spaces are vulnerable to domestic pets, litter, urban foot traffic, and future alterations by residents. Offsite units are protected from these everyday disturbances, allowing sensitive or threatened species a safe space to establish themselves.

3. Economies of Scale and Efficiency

From a practical and financial standpoint, offsite habitat banks deliver much higher ecological return on investment.

• Cost-Effective Restoration: Restoring multiple hectares of connected land is significantly more cost-effective per hectare than trying to implement and maintain dozens of tiny, isolated green patches across separate housing developments.

• Strategic Allocation: Habitat banks are often strategically located in areas identified by Local Nature Recovery Strategies (LNRS). Sourcing offsite BNG units ensures funding goes directly where nature recovery is most critically needed on a regional scale.

4. Risk Mitigation for Developers

For developers, offsite BNG units streamline the planning and construction process.

• Transfer of Liability: Once offsite units are purchased and allocated to a project, the long-term legal responsibility for maintaining that habitat and meeting the 30-year target shifts to the habitat bank operator or landowner.

• Design Flexibility: Relying entirely on on-site BNG can severely constrain a development's layout, reducing the number of deliverable homes or commercial spaces. Offsite units allow developers to maximise the efficiency of their primary construction site while still achieving their environmental targets.

If a project relies solely on on-site delivery, we risk creating isolated, fragile islands of greenery. If it relies entirely on offsite BNG units, local communities lose daily access to nature. True success lies in the balance.

Case Study: Balancing the Scales at East Barnwell

A prime example of this balanced strategy in action is the recent regeneration project at East Barnwell Local Centre delivered by the Cambridge Investment Partnership (CIP). By combining high-quality on-site design with strategic purchasing of offsite BNG units, the partnership successfully unlocked a total 20% BNG uplift for the development.

High-Value On-Site Wins

CIP led the ground-level design at East Barnwell, prioritising urban nature directly where incoming residents will live and work. The on-site enhancements included:

• Tree-lined streets featuring diverse, wildlife-friendly planting.

• A central, public community square alongside generous open green spaces.

• Maximised retention of the site’s existing mature trees and native hedgerows.

Tailored Offsite BNG Units from Boxworth Habitat Bank

To fulfil the remaining biodiversity deficit and reach their ambitious targets, BNG Partnership stepped in as the specialist provider.

Conveniently located just a 15-minute drive from the East Barnwell construction site, our neighbouring Boxworth Habitat Bank provided the ideal solution. We supplied 1.17 tailored offsite BNG units to the project, including specific hedgerow units that can be difficult to source.

The Bigger Picture

The East Barnwell project demonstrates exactly how the policy was intended to work. By using on-site design to create immediate, accessible green spaces for residents and pollinators, and utilising local offsite BNG units to secure large-scale nature recovery, developers can achieve both commercial and environmental success.

Rather than viewing offsite mitigation as a compromise, the industry can look to offsite BNG units as a powerful, landscape-scale partner to smart urban design.

Want to know more? Contact us below to talk to our experts.

‍