Introduction to Biodiversity Net Gain (BNG)
As landscape architects, we have a responsibility to design landscapes that not only enhance human environments but also support the health of ecosystems. Biodiversity Net Gain (BNG) is a concept that has gained significant traction in the UK as a key driver for sustainable development. In essence, BNG refers to the principle of leaving biodiversity in a better state than it was before development. It is no longer enough to simply mitigate harm; we must actively restore and enhance habitats to ensure a measurable improvement in biodiversity.
At Anna French Associates, we understand the importance of integrating BNG into our landscape design processes, ensuring that developments contribute positively to the environment. In this blog, we will delve into the technical aspects of BNG, its legislative framework, its implementation in practice, and how landscape architects can play a critical role in achieving successful biodiversity outcomes.
Legislative Context and Policy Drivers
The UK is at the forefront of the BNG movement, with several key legislative and policy frameworks pushing the agenda. The most notable of these is the Environment Act 2021, which mandates a minimum 10% biodiversity net gain for all new developments in England. This legislation requires developers to quantify their biodiversity impacts using the Biodiversity Metric 3.1, produced by Natural England. The metric calculates the existing biodiversity value of a site and the proposed enhancements, providing a measurable way to assess whether a development achieves a net gain.
BNG policies also intersect with National Planning Policy Framework (NPPF) guidelines, which emphasise that planning decisions should result in measurable gains for biodiversity. Local planning authorities are increasingly embedding BNG into their requirements, further cementing its role in the design and approval process for development projects.
Natural Capital and Ecosystem Services approaches, as outlined by Defra, are also intrinsic to the BNG concept, recognising the multi-functional benefits of natural systems. Beyond compliance, BNG aligns with the UK’s 25-Year Environment Plan, which aims to improve the environment for future generations.
BNG and Landscape Architecture: A Symbiotic Relationship
BNG offers landscape architects a unique opportunity to demonstrate the value of ecologically informed design. As professionals who shape outdoor spaces, we are in a prime position to integrate BNG principles into the development process from the earliest design stages. Landscape architects play a pivotal role in ensuring that biodiversity considerations are not just an afterthought, but a central feature of the project’s design and implementation.
Designing for habitat creation and connectivity: A key component of BNG is the creation or restoration of habitats that contribute to local biodiversity. This might include the establishment of wildflower meadows, woodland planting, or wetland habitats. However, it is not enough to simply create these habitats in isolation; they must be connected, providing ecological corridors that enable species movement and genetic diversity. Landscape architects, with their expertise in spatial planning, are essential in designing layouts that optimise habitat connectivity.
Soil and vegetation management: The careful selection of native species that support local wildlife is a fundamental aspect of BNG. Landscape architects must take into account soil types, hydrology, and microclimates to ensure that plantings are both sustainable and beneficial to biodiversity. Moreover, long-term management plans are critical to ensuring that these gains are not eroded over time. Regular monitoring and adaptive management practices must be integrated into the landscape design process to guarantee that the BNG objectives are met in the long term.
Urban biodiversity solutions: In urban settings, where space is often limited, landscape architects must think creatively to enhance biodiversity. Green roofs, living walls, and rain gardens can provide vital habitats for pollinators and other species, contributing to BNG in urban environments. These interventions not only improve biodiversity but also deliver ecosystem services such as stormwater management, air quality improvement, and urban cooling.
Technical Considerations and Challenges
Implementing BNG on real-world projects requires careful consideration of several technical factors. The Biodiversity Metric 3.1, developed by Natural England, is the primary tool used to quantify biodiversity losses and gains. The metric assigns biodiversity units to habitats based on their type, condition, and distinctiveness. Landscape architects must be proficient in applying this metric to their designs, ensuring that all calculations are accurate and reflect realistic ecological outcomes.
Baseline biodiversity surveys: A comprehensive understanding of the existing ecological conditions of a site is crucial for accurate BNG calculations. Ecological consultants often carry out these baseline surveys, identifying habitats, species, and ecological networks that might be impacted by development. Landscape architects must work closely with ecologists to ensure that the survey data is correctly incorporated into the design process.
Habitat condition assessments: The condition of habitats plays a significant role in determining their biodiversity value. For example, a species-poor grassland in poor condition will have a lower biodiversity unit score compared to a species-rich meadow in good condition. As landscape architects, we must understand how to influence and improve habitat condition through our designs and management plans. This might include measures such as selective planting, appropriate grazing regimes, or the creation of structural diversity within habitats.
Offsetting and the mitigation hierarchy: In some cases, it may not be possible to achieve the required biodiversity net gain on-site. In such situations, developers may need to invest in off-site biodiversity projects or purchase biodiversity credits. However, the mitigation hierarchy, which prioritises avoidance of harm, minimisation of impacts, and on-site compensation before resorting to offsetting, remains central to the BNG ethos. Landscape architects must strive to achieve as much BNG as possible within the project boundaries before considering off-site options.
Case Studies and Best Practices
Thamesmead, London
One of the largest regeneration projects in the UK, Thamesmead has integrated BNG principles throughout its design. Landscape architects played a crucial role in transforming previously neglected spaces into biodiverse habitats, including wetlands and wildflower meadows, while enhancing pedestrian and ecological connectivity. The project achieved a 20% biodiversity net gain, far exceeding the minimum requirements.
Kingsbrook, Aylesbury
Kingsbrook, a large-scale housing development in Buckinghamshire, is a prime example of how BNG can be integrated into residential design. Working in partnership with the RSPB, landscape architects created a variety of habitats, including woodlands, ponds, and grasslands, specifically designed to support local wildlife, including endangered species such as the black hairstreak butterfly.
The Role of Technology and Innovation
Emerging technologies offer new tools to support the implementation of BNG. Geographic Information Systems (GIS) and remote sensing are increasingly being used to map habitats and assess their biodiversity value. Additionally, innovations in biodiversity monitoring, such as the use of environmental DNA (eDNA) and acoustic sensors, allow for more precise tracking of species presence and habitat condition over time.
Digital twins—virtual models of real-world environments—are another exciting development that allows landscape architects to simulate and monitor the biodiversity impacts of different design scenarios before construction begins. By using these tools, landscape architects can ensure that their designs deliver the maximum biodiversity benefits.
Conclusion: The Future of BNG in Landscape Architecture
Biodiversity Net Gain is more than a regulatory requirement; it is an opportunity for landscape architects to lead the way in creating sustainable, biodiverse environments. At Anna French Associates, we are committed to incorporating BNG into all of our projects, ensuring that our designs not only meet the needs of people but also contribute positively to the natural world. By staying informed about the latest policy developments, technical tools, and ecological knowledge, landscape architects can play a pivotal role in shaping a greener, more biodiverse future.
Appendix: Key References
- Natural England – Biodiversity Metric 3.1:
https://www.gov.uk/government/publications/technical-supplement-biodiversity-metric-31 - Environment Act 2021:
https://www.legislation.gov.uk/ukpga/2021/30/enacted - National Planning Policy Framework (NPPF):
https://www.gov.uk/government/publications/national-planning-policy-framework–2 - UK 25 Year Environment Plan:
https://www.gov.uk/government/publications/25-year-environment-plan - Defra Biodiversity Offsetting Guidelines:
https://www.gov.uk/government/publications/technical-paper-the-metric-for-the-biodiversity-offsetting-pilot-in-england - Thamesmead Biodiversity Project – Peabody:
https://www.peabody.org.uk/thamesmead/nature-and-biodiversity - Kingsbrook, Aylesbury – RSPB Partnership:
https://www.rspb.org.uk/our-work/conservation/projects/kingsbrook
