As we enter 2025, the full implementation of the Environment Act 2021 marks a turning point for Biodiversity Net Gain (BNG) in the UK. With a legal requirement for most development projects to deliver a measurable 10% net gain in biodiversity, this year presents both challenges and opportunities for ecologists, developers, local planning authorities (LPAs), and landowners. 

BNG isn’t just about compliance—it’s a transformative approach to balancing development with ecological restoration. Tools like the Statutory Biodiversity Metric and the BNG Small Sites Metric are now essential for delivering projects that leave habitats in a better state than before. Developers must act quickly to meet deadlines, ecologists are in high demand to guide compliance, and landowners have new opportunities to generate income through habitat enhancement. 

This guide offers a roadmap to succeed with Biodiversity Net Gain in 2025, tailored to each stakeholder group – ecologists, developers, local planning authorities (LPAs), and landowners. Let’s explore how we can work together to align development with sustainability goals in the year ahead. 

What is Biodiversity Net Gain?

Biodiversity Net Gain (BNG) is an approach to development and land management that aims to leave biodiversity in a better state than before the intervention. The principle is simple: a project must enhance biodiversity by delivering measurable improvements to habitats. 

Under the Environment Act 2021, most developments in England will be required to achieve at least a 10% net gain in biodiversity, as calculated using DEFRA’s Statutory Biodiversity Metric. Developers must ensure that habitats lost due to development are compensated through habitat creation, restoration, or enhancement, either on-site or off-site.

Watch a webinar on BNG for developers here.

Key Components of Biodiversity Net Gain (BNG)

Achieving Biodiversity Net Gain (BNG) involves more than just ecological assessments or habitat restoration—it’s a structured process designed to ensure measurable and sustainable improvements to biodiversity as part of development projects. To comply, stakeholders must navigate a series of interconnected steps and principles, using tools like the Statutory Biodiversity Metric and the BNG Small Sites Metric to quantify and deliver net gain. Below are the key components of BNG that ecologists, developers, LPAs, and landowners need to understand: 

1. Baseline habitat assessment 

The foundation of any BNG project is a baseline habitat assessment, which establishes the existing ecological value of a site before development begins. This assessment determines the “starting point” for biodiversity and helps calculate the impact of the project.

What it involves: 

• Habitat identification: Mapping and classifying habitats using the UK Habitat Classification (UKHab) system or another approved method.  
• Condition assessments: Evaluating the ecological condition of habitats, including vegetation structure, species diversity, and connectivity.
• Defining the biodiversity units: Calculating the current biodiversity value of the site in terms of baseline biodiversity units using the Statutory Biodiversity Metric or the Small Sites Metric.

2. Avoidance and minimisation of impact – Mitigation Hierarchy 

Before compensating for biodiversity losses, developers are required to follow the mitigation hierarchy, which prioritises:  

1. Avoidance: Minimising harm to existing biodiversity by altering project design (e.g., rerouting infrastructure to avoid sensitive habitats).  
2. Minimisation: Reducing the impact of unavoidable habitat loss through careful management practices during construction. 

3. Biodiversity metric calculation 

Central to BNG is the use of the Statutory Biodiversity Metric, developed by DEFRA, which standardises how biodiversity losses and gains are measured.  

What it involves: 

• Quantifying biodiversity units: The metric assigns biodiversity units based on habitat size, condition, distinctiveness, and connectivity.  
• Calculating losses and gains: The metric determines how many biodiversity units are lost due to development and how many must be created or restored to achieve the required 10% net gain.  
• Use of the Small Sites Metric: For smaller projects, the BNG Small Sites Metric simplifies these calculations while ensuring compliance. 

4. Delivery of Biodiversity Net Gain (on-site or off-site)  

Once biodiversity impacts are quantified, developers must deliver net gain by creating, restoring, or enhancing habitats. This can be achieved either on-site (within the development area) or off-site (through external partnerships or biodiversity credits).

On-site delivery: 

• Includes habitat creation or enhancement within the project’s boundaries (e.g., green roofs, wildflower meadows, or tree planting).
• Allows developers to integrate biodiversity improvements into their projects, providing visible benefits for local communities. 

Off-site delivery:

• Developers may use external land (owned by landowners or conservation organisations) to deliver habitat enhancements.
• When on-site delivery is not feasible, developers can purchase biodiversity credits through marketplaces or partnerships to fund off-site habitat restoration projects.

5. Securing long-term commitments (30-year management plans) 

BNG is not just about short-term habitat creation—it’s about ensuring long-term biodiversity improvements. All net gain commitments must include a 30-year management and monitoring plan to guarantee that habitats are successfully maintained and continue to provide ecological value.

What it involves: 

• Management plans: Clear documentation of how habitats will be maintained, including grazing, mowing, or species monitoring.  
• Monitoring programs: Regular monitoring to evaluate habitat success, detect issues, and implement corrective measures.  
• Legal agreements: Use of Section 106 agreements or conservation covenants to legally secure the land for biodiversity purposes.Read a case study on how Langley Abbey Environment Project completed its First BNG Section 106 Agreement with LPA here.

6. Use of Biodiversity Net Gain tools 

To implement BNG effectively, stakeholders rely on specific tools and methodologies:  

• Statutory Biodiversity Metric: Quantifies biodiversity losses and gains using consistent and transparent calculations. 
• BNG Small Sites Metric: A simplified version of the biodiversity metric designed for small residential or non-residential developments, making compliance easier for smaller projects. 
• GIS and remote sensing: Tools like GIS mapping, remote sensing technology combined with AI enable ecologists to assess habitats at scale and with high accuracy. 
• Monitoring software: Platforms to track long-term biodiversity commitments and generate reports for regulators and stakeholders.

7. Collaboration across stakeholders 

Delivering BNG requires effective collaboration among developers, ecologists, local planning authorities, and landowners. Stakeholders must work together to balance development goals with biodiversity objectives.  

The key components of Biodiversity Net Gain form a structured and measurable approach to integrating biodiversity conservation into development projects. By focusing on baseline assessments, adherence to the Statutory Biodiversity Metric, habitat delivery, and long-term management, stakeholders can ensure that BNG commitments are both compliant and impactful.  

Understanding and implementing these components is essential for ecologists, developers, local planning authorities, and landowners to successfully navigate the demands of BNG while contributing to a sustainable future for biodiversity.

Why Biodiversity Net Gain Matters

BNG is not just about meeting legal obligations; it is a transformative approach to balancing development with environmental sustainability. By embedding biodiversity into planning and construction, BNG creates a win-win scenario: 

• For nature: Enhanced habitats lead to improved biodiversity, ecosystem services, and climate resilience. 
• For communities: Green spaces and restored habitats improve quality of life and support local wildlife. 
• For developers: BNG fosters sustainable development practices, enhancing reputation and securing planning approval.  

Biodiversity Net Gain for Different Stakeholders

1. Biodiversity Net Gain for Ecologists

Challenges for Ecologists
BNG places ecologists at the heart of compliance. From conducting baseline surveys to calculating biodiversity metrics, ecologists face several challenges, including: 

• Conducting habitat surveys and ensuring accurate condition assessments. 
• Using DEFRA’s Statutory Biodiversity Metric for complex biodiversity unit calculations. 
• Meeting tight project deadlines while ensuring compliance with BNG requirements. 
• Navigating the Small Sites Metric for smaller-scale projects.

How ecologists can succeed in BNG  

• Use technology: Adopt tools like remote sensing, GIS and automated metric calculators to streamline workflows. 
• Stay updated: Attend trainings, engage with ecologist communities via in-person meetings or online groups, and if feasible, partner with new players in the industry offering technology-driven solutions. 
• Collaborate: Partner with developers, local planning authorities, and landowners to achieve balanced, achievable BNG plans. 
• Monitor and report: Implement robust monitoring strategies to ensure long-term success of biodiversity interventions.

Opportunities for ecologists

• Increased demand for skilled professionals to conduct BNG assessments. 
• Opportunities to lead habitat restoration and biodiversity offsetting projects. 
• Developing expertise in emerging tools like the BNG Small Sites Metric.

2. Biodiversity Net Gain for Developers

For developers, achieving BNG is no longer optional—it’s a requirement to secure planning approval under the Environment Act. Key benefits of complying with BNG include: 

• Faster planning approvals from LPAs. 
• Enhanced project sustainability and reputation. 
• Access to biodiversity credits for off-site compensation.

Key considerations for developers

• Early engagement with ecologists: Involve ecological consultants at the start of the project to avoid delays. 
• Understand the metrics: Familiarise yourself with the Statutory Biodiversity Metric to quantify biodiversity losses and gains. 
• Explore on-site vs. off-site options: Decide whether BNG will be delivered on-site or through partnerships with landowners or conservation organizations. 
• 30-year commitment: Plan for the long-term management and monitoring of biodiversity interventions. 

BNG Small Sites Metric for developers 

If your project qualifies as a small site, the BNG Small Sites Metric offers a simplified route to compliance. Smaller residential and non-residential projects can use this streamlined approach, making it faster and less resource-intensive to deliver net gain.

3. Biodiversity Net Gain for Local Planning Authorities (LPAs)

Local Planning Authorities are responsible for ensuring that all planning applications meet BNG requirements. LPAs must: 

• Review BNG plans and calculations submitted by developers. 
• Ensure the use of the Statutory Biodiversity Metric or Small Sites Metric for assessments. 
• Monitor long-term compliance with BNG commitments, including 30-year habitat management plans. 

Challenges for LPAs 

• Limited in-house ecological expertise to review complex biodiversity assessments. 
• Balancing the pressures of housing and infrastructure targets with environmental obligations. 
• Ensuring developers maintain their BNG commitments over the long term.

How LPAs can support BNG delivery

• Invest in training for planning officers on DEFRA metrics and habitat condition assessments.
• Use planning conditions and legal agreements (e.g., Section 106 agreements) to enforce long-term biodiversity commitments. 
• Collaborate with developers and ecologists to ensure realistic, deliverable BNG plans.

4. Biodiversity Net Gain for Landowners

Landowners have a unique opportunity to play a central role in delivering off-site biodiversity net gain. By offering land for habitat creation or enhancement, landowners can: 

• Generate income through biodiversity credits.
• Support biodiversity conservation and sustainable land management.
• Increase the ecological and financial value of their land. 

How landowners can get involved 

• Partner with developers: Offer land as a location for off-site BNG interventions, such as tree planting, wetland creation, or wildflower meadows. 
• Join biodiversity credit schemes: Register your land as part of biodiversity credit marketplaces to attract projects. 
• Engage with conservation groups: Collaborate with conservation organisations to ensure effective habitat design and management. 

BNG opportunities for landowners

BNG offers a long-term income stream for landowners willing to commit to 30 years of biodiversity management. By working with developers and ecologists, landowners can align their goals with national biodiversity priorities. 

Delivering Biodiversity Net Gain Together

BNG represents a paradigm shift in how the UK balances development and biodiversity conservation. Whether you’re an ecologist, developer, LPA, or landowner, understanding your role in delivering net gain is critical to ensuring the success of this ambitious initiative. 

By leveraging tools like the Statutory Biodiversity Metric and the BNG Small Sites Metric, collaborating with stakeholders, and committing to long-term habitat management, we can create a future where development and biodiversity thrive together. 

Explore your role in delivering Biodiversity Net Gain today. Let’s build a better future for nature and communities alike. 

Need help with BNG?

Check back regularly for the latest insights and news. Learn how AiDash Biodiversity Net Gain Management System™ (BNGAI™) can help with 10% BNG planning for urban projects. Start your first BNG project now!

Read how BNGAI™ by AiDASH set a new benchmark for natural capital management for Affinity Water here.