Specifying for biodiversity net gain

With BNG now firmly embedded in planning policy and practice, most specifiers – particularly architects and landscape architects – are familiar with its requirements. Since becoming mandatory for major developments in February 2024, and for small sites from April 2025, BNG has shifted from being ‘nice to have’ to becoming a core design principle. The current construction industry focus for biodiversity is on delivery – translating policy into measurable ecological outcomes.

However, as well as establishing technical requirements, BNG also introduces complexities. The challenge lies in meeting biodiversity targets while ensuring that buildings and landscapes remain functional, aesthetically engaging, and meaningful. This balance between ecological ambition and practical design principles is a common challenge. However, specification plays a role in enabling professionals to define clear biodiversity requirements by selecting appropriate systems and products that align with BNG targets. The principles behind effective specification remain essential in driving measurable biodiversity improvements. 

BNG is underpinned by legal obligations introduced through the Environment Act 2021 and Schedule 7A of the Town and Country Planning Act 1990, requiring the majority of developments in England to achieve at least a 10% net gain in biodiversity.

Beyond compliance with legislation, stakeholders (including local authorities, clients and communities) are increasingly seeking demonstrable environmental benefits from projects. This has driven advancements in habitat creation, ecological restoration, and conservation planning. However, discussions within the landscape profession suggest that the emphasis on metrics – such as percentage gains, habitat units, and data analysis – can sometimes shift focus away from broader landscape and user-experience considerations.

Where traditional approaches fall short

While BNG presents opportunities for environmental-driven design, successful delivery requires structured coordination. When biodiversity is handled in isolation – managed through separate reports and datasets – it can lead to poor communication, lost design intent, and fragmented execution. Conservation and enhancement goals may fail to materialize on site without clear integration into project planning, which can result in non-compliance or missed ecological opportunities.

Industry experience indicates that biodiversity strategies must account for site-specific challenges. Considerations such as species selection, maintenance costs, and long-term viability must be assessed alongside ecological targets. For example, while thorny or mature species may carry more credits, they might pose practical challenges for user accessibility, maintenance, and cost issues. Similarly, smaller trees – although easier to establish – may face greater vulnerability to vandalism. Addressing these ‘trade-offs' requires flexible, site-responsive strategies that encompass both ecological and practical considerations.

How specification bridges the gap

Specification plays a critical role in translating aspirations into actionable design and execution. Rather than treating biodiversity as an additional consideration, structured specification enables integration across the design, planning, procurement and construction stages, and beyond. 

Key functions of specification in BNG delivery include:

• Ensuring consistency and clarity – embedding biodiversity requirements throughout project phases.
• Facilitating collaboration – establishing a shared reference point for ecologists, landscape architects, architects and contractors to streamline biodiversity integration. 
• Embedding the ‘golden thread’ – maintaining a continuous record of biodiversity commitments from planning to implementation and long-term management.
• Referencing digital tools – aligning with BNG calculators and biodiversity-tracking systems for measurable, auditable outcomes. 
• Supporting long-term stewardship – defining post-construction management strategies to ensure that habitats thrive over time.

Specifying BNG using NBS Chorus

By using NBS Chorus, specifiers can seamlessly integrate BNG requirements into project specifications, ensuring clarity, traceability and compliance across the full life cycle of a project. 

Some of the relevant clauses, under both CAWS and Uniclass classifications, are listed below. They provide a structured foundation for embedding ecological improvements within specification requirements.

Relevant CAWS sections

CAWS provides an industry-recognized structure for specifying biodiversity-related elements within a project. Depending on specific requirements, any of the following sections may be applicable, although this list is not exhaustive:

B ‘Complete buildings/ structures/ units’:

• B03 ‘Whole project sustainability’:
  • 125 ‘Biodiversity/ ecology strategy and parameters’.

C ‘Demolition/ alteration/ renovation’:

• C10 ‘Site surveys’:
  • 145 ‘Ecological surveys’.
  • 155 ‘Arboricultural surveys’.
  • 165 ‘Invasive species surveys’.

Q ‘Paving/ planting/ fencing/ site furniture’:

• Q30 ‘Seeding/ turfing’.
• Q31 ‘External planting’.
• Q35 ‘Landscape maintenance’.
• Q37 ‘Blue/ green/ biosolar roofs’.
• Q38 ‘Green walls’.

Relevant Uniclass codes

Uniclass offers a more detailed framework for structuring biodiversity requirements within a project. Depending on specific requirements, any of the following content may be applicable, although this list is not exhaustive:

Activities:

• Ac_15_20 ‘Ecological and environmental surveying’:
  • Ac_15_20_27/125 ‘Ecological site surveying’.

Elements/ Functions:

• EF_45 ‘Flora and fauna elements’.

Project Management:

• PM_30 ‘Site, ground and environmental information’:
  • PM_30_30_25 ‘Ecological survey report’.
• PM_35 ‘Project performance requirements’:
  • PM_35_40_08/10 ‘Biodiversity performance requirements’.
• PM_80 ‘Asset management information’:
  • PM_80_10_44 ‘Landscape and habitat management plan’.
  • PM_80_25_08 ‘Biodiversity net gain assessments’.

Systems:

• Ss_45_30 ‘Aquatic flora systems’:
  • Ss_45_30_05 ‘Aquatic and wetland planting systems’.
  • Ss_45_30_40 ‘Hydroponic planting systems’.
• Ss_45_35 ‘Ground-based flora systems’:
  • Ss_45_35_05 ‘Amenity and ornamental planting systems’.
  • Ss_45_35_08 ‘Biodiversity and environmental conservation systems’.
  • Ss_45_35_30 ‘Forestry, biomass, hedging and roadside planting systems’.
  • Ss_45_35_45 ‘Lawn and meadow planting systems’.
• Ss_45_40 ‘Artificially supported flora systems’:
  • Ss_45_40_28 ‘External container planting systems’.
  • Ss_45_40_47 ‘Living roof systems’.
  • Ss_45_40_95 ‘Vertical planting systems’.

Products:

• Pr_45_30 ‘Flora products’:
  • Pr_45_30_10 ‘Bulbs, corms, tubers and dormant roots’.
  • Pr_45_30_36 ‘Herbaceous and aquatic plants’.
  • Pr_45_30_76 ‘Seeds’.
  • Pr_45_35_80 ‘Shrubs and woody climbers’.
  • Pr_45_35_90 ‘Trees’.
• Pr_45_57 ‘Non-rigid sheet, mat and strip flora and fauna products’:
  • Pr_45_57_91 ‘Turf and pre-planted substrates’.

Key benefits and outcomes

The following key benefits and outcomes highlight how the early integration of biodiversity considerations can strengthen project delivery and long-term ecological success:

• Legal and planning alignment – supporting compliance with the Environment Act 2021, reducing risks of setbacks. 
• Enhanced collaboration – creating clear biodiversity benchmarks, improving coordination among project teams.
• Transparent, auditable delivery – ensuring that biodiversity measures remain trackable and verifiable.
• Long-term stewardship – embedded maintenance strategies to sustain ecological enhancements over time.
• Confidence in BNG targets – reducing late-stage project revisions by integrating biodiversity early in the design.

Conclusion: specification as a driver for BNG

BNG is more than a planning requirement: it presents an opportunity to deliver development projects that fully consider ecological and social value. Specification plays a crucial role in bridging the gap between biodiversity ambition and its practical delivery, ensuring that requirements are effectively embedded, traceable, and able to be maintained. By integrating biodiversity into the fabric of a project – from the initial concept through to long-term maintenance – BNG can support both ecological integrity and meaningful placemaking. This impact can be further strengthened by balancing metric-driven approaches with holistic, site-responsive design strategies.

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