10 min read | May 26, 2023

How irreplaceable habitat works in BNG

In this blog, we explore the concept of irreplaceable habitats, their importance in maintaining ecosystems, and how they are safeguarded in BNG and in other government plans and policies.

Irreplaceable habitats hold immense biodiversity value and are incredibly difficult, if not impossible, to restore, recreate, or replace once destroyed. These rare sites are vital parts of our national environmental heritage, and they cannot be compensated. Examples include ancient woodland, ancient and veteran trees, blanket bog, limestone pavement, sand dunes, salt marsh and lowland fen.

The unique characteristics of irreplaceable habitats necessitate special attention and protections - which they are afforded under the Biodiversity Net Gain (BNG) framework. In this blog, we explore the concept of irreplaceable habitats, their importance in maintaining ecosystems, and how they are safeguarded in BNG and in other government plans and policies. 

Understanding Irreplaceable Habitats 

The National Planning Policy Framework (NPPF) defines irreplaceable habitats as those that are technically very challenging or time-consuming to restore, considering factors such as age, uniqueness, species diversity, or rarity. However, the definition is not exhaustive, which has led to ongoing debates about which habitats qualify as irreplaceable. 

These debates often get heated, but one area of agreement is that these habitats often support rare or endangered species and provide critical ecosystem services, such as water purification, carbon sequestration, and flood prevention. It’s also widely agreed that their loss can result in significant, long-term, and sometimes irreversible negative impacts on local and regional ecosystems, as well as the communities that depend on them. 

Irreplaceable habitats are a prime example of why a comprehensive biodiversity assessment process should include both qualitative and quantitative evaluations. A purely quantitative approach, such as calculating the number of biodiversity units gained or lost, may fail to account for the unique characteristics and complexities of these habitats. By incorporating qualitative assessments, the BNG policy appreciates the intrinsic value of irreplaceable habitats and makes more informed decisions regarding their conservation and management. 

To be clear, quantitative assessments, which primarily focus on measuring and comparing the numerical values of biodiversity units or habitat sizes, can provide useful insights into the overall ecological health of an area. However, they may not adequately capture the unique attributes of irreplaceable habitats, such as their rarity, age, uniqueness, or the presence of specific species that are critical to maintaining ecosystem function. This can result in an underestimation of the true value and importance of these habitats and potentially lead to suboptimal conservation decisions. On the other hand, qualitative assessments consider the full ecological values of habitats, which are often difficult to quantify. 

This approach allows for a more comprehensive understanding of the factors that contribute to a habitat's irreplaceability, such as its role in supporting the life cycle of rare or threatened species, its role in maintaining ecosystem processes, or perhaps even its cultural and historical significance. By taking a qualitative approach, we can better identify the specific elements that make irreplaceable habitats so valuable and better inform conservation efforts that aim to protect and enhance these areas. 

Integrating both qualitative and quantitative assessments in the biodiversity assessment process can help to ensure that the unique characteristics of irreplaceable habitats are recognised and considered in decision-making processes. For example, a quantitative assessment may reveal a loss of biodiversity units due to a proposed development, while a qualitative assessment could provide insight into the potential impacts on rare or threatened species and the overall ecosystem function. This holistic approach allows for a more robust evaluation of potential impacts and can inform the development of targeted conservation measures that address the specific needs of irreplaceable habitats. 

Biodiversity Net Gain and Irreplaceable Habitats 

Under the Environment Act, irreplaceable habitats are excluded from the quantitative mandatory BNG objective. Instead, the government aims to protect and manage these habitats through several measures: 

  • Definition and listing of irreplaceable habitats: Secondary legislation will provide a clear definition and list of habitat types considered irreplaceable. This list will be accompanied by short supporting guidance on what constitutes irreplaceability and a set of principles to guide the implementation of bespoke compensation approaches. 
  • Compensation requirements: The planning authority must ensure that any mitigation or compensation plans for such habitats meet the requirements outlined in relevant policies and guidance, and decisions on planning applications should be made in line with the NPPF. Compensation should be informed by ecological expertise and typically exceed the requirements set through BNG. 
  • Biodiversity gain plan submission: Developments involving irreplaceable habitats will require the submission of a biodiversity gain plan, providing information about the habitats present before and after development. This plan should be accompanied by a robust summary statement of reasonable alternatives explored to avoid the loss of irreplaceable habitats and explain why they were not feasible. 
  • Prohibition of statutory biodiversity credits: Statutory biodiversity credits cannot be used to compensate for residual irreplaceable net losses resulting from development or land use change. Instead, appropriate compensation should be informed by ecological expertise and typically exceed the requirements set through BNG. 
  • Enhancements to irreplaceable habitats: Where there are no direct or indirect negative impacts on an irreplaceable habitat, appropriate enhancements could be made to it as part of a net gain plan. These enhancements would be included as part of the overall biodiversity metric calculation. 

The big development that will come here will be the publication of a clear list of ‘irreplacable habitats’. The UK Government has said that it will collaborate with Natural England and various external stakeholders to draft definitions and guidance, ensuring these precious habitats receive the protections they deserve. This collaboration will involve working with ecologists, conservationists, local authorities, and other stakeholders to identify the most effective strategies for safeguarding irreplaceable habitats. 

How irreplaceable habitats can be protected

Developers and planning authorities play a crucial role in protecting irreplaceable habitats - they should engage in early consultation and adopt a nature-first approach in decision-making, prioritising the avoidance of harm to irreplaceable habitats. This can be achieved by thoroughly assessing site suitability, exploring alternative development locations, and implementing robust mitigation measures when necessary. Developers should also engage with LPAs and make sure that local strategies are consulted to identify and protect irreplaceable habitats. 

Such documents include (as examples) Local Nature Recovery Strategies; National Character Areas Objectives; Local Ecological Networks Shoreline Management Plans; Estuary Strategies; Green Infrastructure Strategies. These local strategies help identify areas of high ecological value, including irreplaceable habitats, and guide development plans accordingly. 

The future of irreplaceable habitats

Although irreplaceable habitats are afforded special consideration and protection, challenges remain - not least the lack of a comprehensive and universally accepted list of irreplaceable habitats which can lead to inconsistencies in their identification and management. Furthermore, the complex nature of these habitats makes it difficult to measure their true ecological value and accurately assess the impacts of development. 

To overcome these challenges, it is essential to invest in research, monitoring, and data collection to improve our understanding of irreplaceable habitats and the factors that influence their resilience and recovery. Additionally, strengthening collaborations between government agencies, researchers, conservation organisations, and local communities can foster the development of innovative and effective strategies to safeguard these vital ecosystems. 

How Joe’s Blooms helps

With Joe’s Blooms tools we are able to automatically search for key information about different habitats. We will be able to incorporate information on which habitats are considered irreplaceable. We will also be able to give LPAs the chance, via a new portal service, to ensure that local priorities and needs are brought into the user journey. 


Incorporating qualitative assessments in the evaluation process isn’t just smart ecological practice - it can encourage greater stakeholder engagement and collaboration. By considering the social, cultural, and ecological values of irreplaceable habitats, we can create opportunities for local communities, conservation organisations, and researchers to share their knowledge, perspectives, and expertise. This collaborative approach can foster a deeper understanding of the complexities of irreplaceable habitats and support the development of innovative and effective conservation strategies. 

The unique and complex nature of irreplaceable habitats highlights the importance of incorporating both qualitative and quantitative assessments in the biodiversity evaluation process. By combining these approaches, we can better understand the true value of these habitats and develop more effective conservation measures that protect and enhance them. A comprehensive assessment process that takes into account the ecological, social, and cultural dimensions of irreplaceable habitats can help to ensure that these vital ecosystems are preserved for future generations and continue to provide essential services to support the health and well-being of our planet.

Irreplaceable habitats are critical to maintaining the Earth's biodiversity and providing essential ecosystem services. As we move forward, continued research and monitoring efforts, along with the development and implementation of innovative conservation strategies, will be crucial in preserving these invaluable habitats. By prioritising the protection and enhancement of irreplaceable habitats, we can contribute to a more sustainable future for our planet and all its inhabitants.

Oliver Lewis

Founder of Joe’s Blooms

Oliver Lewis is the founder of Joe’s Blooms, providing end-to-end digital solutions to help you create best-in-class Biodiversity Gain Plans. Expert in this field, he shares his knowledge on the Environment Bill which will be effective in November 2023.

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