BNG Mitigation Hierarchy Explained: Avoid, Minimise, Restore & Offset

Quick Answer: What is the BNG Mitigation Hierarchy?

The BNG mitigation hierarchy is a 4-step framework that developers must follow for biodiversity net gain compliance: Avoid → Minimise → Restore → Offset. This systematic approach prioritises preventing biodiversity loss before compensating for it through offsets or biodiversity units.

Why the Hierarchy Order Matters

The sequence is legally binding under BNG regulations - you cannot skip straight to offsetting without demonstrating you’ve properly considered avoidance, minimisation and restoration first.

Developers are expected to follow the mitigation hierarchy step by step, prioritising avoidance and minimisation before using biodiversity units.

The 4 Steps of BNG Mitigation Hierarchy

• Step 1: Avoidance

  The foundation of the hierarchy lies in avoiding impacts on biodiversity wherever possible. This means careful site selection and project design to sidestep areas of high ecological value or vulnerability.

  Practical examples:

  • Choosing development sites with lower biodiversity value

  • Redesigning layouts to avoid ancient woodlands or priority habitats

  • Timing construction to avoid sensitive breeding seasons

  • Creating buffer zones around valuable habitats

• Step 2: Minimisation

  If avoidance is not entirely feasible, the next step involves minimising adverse impacts. This may entail adjusting project layouts or incorporating green infrastructure to reduce ecological footprints.

  Practical examples:

  • Reducing the development footprint

  • Using sustainable drainage systems (SuDS)

  • Installing wildlife-friendly lighting

  • Creating wildlife corridors through the site

  • Phased construction to minimise disturbance

• Step 3: Restoration

  Should unavoidable impacts occur, the hierarchy encourages restoration efforts. This involves rehabilitating or enhancing ecosystems that have been disturbed, aiming to return them to a state of ecological health and functionality.

  Practical examples:

  • Restoring degraded habitats on-site

  • Enhancing existing low-value habitats to higher distinctiveness

  • Reconnecting fragmented habitats

  • Removing invasive species and replanting native vegetation

• Step 4: Offsetting

  As a final measure, after all other avenues have been exhausted, the hierarchy permits offsetting. This involves compensating for residual biodiversity loss by investing in conservation measures elsewhere.

  Offsetting options:

  • On-site biodiversity unit creation

  • Off-site biodiversity units

  • Statutory biodiversity credits (as a last resort)

BNG Hierarchy: On-Site vs Off-Site Applications

On-Site BNG Delivery

Developers undertaking BNG commitments must diligently apply each step to ensure a comprehensive and effective approach. The hierarchy is particularly crucial for on-site BNG delivery. Developers must rigorously adhere to avoidance and minimisation strategies, integrating biodiversity into the development fabric.

On-site considerations:

• Site-specific habitat surveys

• Integration with landscape design

• Long-term management planning

• Monitoring requirements

Off-Site BNG Initiatives

For off-site initiatives, the hierarchy remains a consistent guide. Here, the spatial risk multiplier comes into play, a nuanced tool within the mitigation hierarchy that recognises the spatial context of biodiversity and acknowledging that not all habitats are interchangeable.

Off-site considerations:

• Location relative to impact site

• Habitat type matching

• Local nature recovery strategies

• Community benefits

Common BNG Hierarchy Mistakes to Avoid

• Jumping straight to offsetting:

  Many developers try to skip the first three steps and go straight to buying biodiversity units. This approach can fail planning scrutiny and cost more in the long run.

• Inadequate Avoidance Assessment

  Not properly surveying sites or considering alternative locations can lead to unnecessary biodiversity loss and higher BNG requirements.

• Poor Documentation

  Failing to document how each step of the hierarchy has been considered can cause planning delays and regulatory challenges.

Frequently Asked Questions

• What is the BNG mitigation hierarchy?

  The BNG mitigation hierarchy is a legal framework requiring developers to avoid, minimise, restore, and offset biodiversity impacts in that specific order.

• Can I skip steps in the mitigation hierarchy?

  No - you must demonstrate consideration of each step before moving to the next. You cannot skip straight to offsetting without showing avoidance and minimisation efforts.

• What's the difference between biodiversity hierarchy and mitigation hierarchy?

  These terms refer to the same concept - the 4-step framework for BNG compliance. “Mitigation hierarchy” is the technical term, while “biodiversity hierarchy” is commonly used shorthand.

• When is offsetting acceptable in the BNG hierarchy?

  Offsetting is only acceptable after you’ve demonstrated that avoidance, minimisation, and restoration options have been exhausted or are not feasible.

• How does the spatial risk multiplier relate to the mitigation hierarchy?

  The spatial risk multiplier applies to the offsetting step, ensuring that off-site biodiversity units are appropriately valued based on their distance and relevance to the impact site.

Expert BNG Hierarchy Support

By embracing the mitigation hierarchy, developers can work on their journey towards sustainable development, in a way that respects and enhances biodiversity. Whether applied on-site or as part of off-site BNG initiatives, this hierarchical framework ensures that every effort is made to minimise and offset the ecological footprint of development projects.

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Need help applying the BNG mitigation hierarchy to your development project? Our BNG experts can guide you through each step, from initial avoidance strategies to final offsetting solutions. Contact ILM today for specialist BNG consultancy.