Biodiversity Net Gain: Key Challenges for Development Projects

Biodiversity Net Gain (BNG) has become a major consideration for planning and development in recent years. Under current regulations in England, most new developments are required to deliver a minimum 10% increase in biodiversity compared to the site’s pre-development condition. This shift marks an important step towards more sustainable, ecologically responsible development — but it also introduces new complexities for architects, developers, and landowners.
 

In practice, achieving BNG can be challenging. It requires careful coordination between design teams, ecologists, planners, and contractors, as well as an understanding of how the site’s natural environment interacts with the proposed scheme.
 

Below, we explore the most common challenges associated with BNG and how early design input can help overcome them.
 

1. Understanding the Baseline Condition of the Site

BNG begins with a baseline assessment, usually carried out by an ecologist, to determine the existing value of habitats on site. This can be more challenging than expected, because:
 

• Surveys must be completed at certain times of the year to be valid

• Complex or degraded sites may require multiple habitat classifications

• Some land, even if visually unremarkable, can have unexpectedly high ecological value

• Late commissioning of ecological surveys can delay planning submissions
   

For architects, this means early engagement with specialists is essential. Baseline results influence not only the site strategy but also feasibility, layout, and the overall development potential.
 

2. Designing to Achieve the Required 10% Net Gain

Achieving the mandatory 10% gain can be surprisingly demanding, particularly on constrained sites. The challenges include:
 

• Limited land available to create or enhance habitats

• Compensating for the loss of existing high-value habitats

• Balancing development footprints with ecological uplift

• Integrating habitats without compromising access, drainage, or building performance
   

This is where design teams must think creatively. Solutions might include green roofs, biodiverse landscapes, sustainable drainage features, native planting, or habitat-rich boundary conditions. However, these must be both deliverable and maintainable, not just visually appealing.
 

3. Long-Term Management Requirements

BNG isn’t simply about delivering habitats at completion — it requires a minimum 30-year management and monitoring plan.
 

This can create challenges for:

• Private homeowners unfamiliar with long-term ecological commitments

• Developers concerned about management costs and liability

• Community or commercial schemes requiring clear stewardship arrangements
   

Management plans must specify who is responsible for maintenance, how monitoring will be undertaken, and how performance will be measured. These obligations can influence site layout, public access, planting choices, and construction detailing.
 

4. Off-Site and Mitigation Challenges

When 10% BNG cannot be achieved on-site, developers must either:
 

1. Provide off-site enhancements on nearby land; or

2. Purchase biodiversity units through an approved market.
    

Both routes introduce complications:

• Securing suitable off-site land is not always feasible

• Market-supplied units can be costly and subject to availability

• Local authorities prefer on-site solutions wherever possible

• Off-site options still require long-term management commitments
   

This makes it even more important to maximise on-site biodiversity value through clever design interventions.
 

5. Navigating Local Authority Expectations

While BNG has national standards, local authorities may apply them differently. Some require:
 

• Habitat connectivity strategies

• Greater than 10% net gain

• Specific planting palettes or ecological typologies

• Seasonal survey evidence before validation

• Integration with wider green infrastructure policies
   

Understanding these expectations early avoids re-designs, delays, and planning queries later in the process.
 

6. Coordinating BNG With Other Technical Constraints

Many design elements influence biodiversity outcomes, including:
 

• Drainage and SuDS requirements

• Plot ratio and building massing

• Access points and visibility splays

• Utilities, easements and root protection zones

• Lighting design and ecological sensitivity
   

Balancing these constraints with BNG targets often requires iterative coordination between architects, engineers, landscape architects and ecologists. A change in one area (for example, drainage strategy) can have significant knock-on effects for habitat design.
 

7. Client Expectations and Cost Implications

Finally, BNG can introduce unexpected upfront and long-term costs:
 

• Ecological surveys and assessments

• Habitat creation or enhancement works

• Planting, soft landscaping and specialist features

• Long-term management and monitoring

• Potential purchase of off-site biodiversity units
   

Helping clients understand these implications early — and designing efficiently around them — is crucial for project viability.
 

The Architect’s Role in Delivering Successful BNG

Although BNG is often seen as an ecological or planning issue, architects play a central role in shaping the site strategy. Key contributions include:
 

• Identifying opportunities for habitat creation during concept design

• Coordinating ecological input from the outset

• Designing layouts that balance development needs with ecological uplift

• Integrating green infrastructure into buildings and external spaces

• Ensuring BNG is deliverable within buildability and budget constraints
   

BNG is most effective when treated not as an obligation, but as an opportunity to enhance the quality, sustainability, and long-term resilience of the built environment.

Conclusion

Biodiversity Net Gain represents a positive shift in the way we plan and build, encouraging more sustainable relationships between development and the natural environment. However, meeting BNG requirements can bring real challenges — from baseline assessments to long-term management.
 

With early strategy, thoughtful layout design, and close coordination between the project team, architects can help ensure BNG becomes not a barrier, but a meaningful design driver that improves both ecological value and overall project quality.
 

If your project involves BNG requirements or you’re unsure how the rules apply, our team can help guide you from feasibility through to planning and construction.