Will Biodiversity Net Gain Stand in the Way of 1.5 million New Homes?
iB Architects November 2024
In a recent roundtable hosted by iB Architects, experts explored the complex relationship between Biodiversity Net Gain (BNG) policies and the UK's ambitious housing targets. With Angela Rayner setting a goal of 1.5 million new homes, the discussion addressed whether BNG requirements might impede this aim. Participants shared insights on a range of factors impacting development, from Local Planning Authorities (LPAs) and their varied approaches to the constraints imposed by BNG itself. The debate highlighted key challenges and opportunities, touching on land availability, policy inconsistencies, and the financial implications of BNG credits.
Ultimately, the conversation painted a complex picture of BNG’s role within the planning system and its potential impact on reaching—or approaching—the housing target.
BNG is a policy requiring developers to ensure biodiversity levels on or around their project sites are increased or at least maintained. This is usually achieved by applying a quantitative "net gain" metric to demonstrate the positive or neutral impact on local ecosystems. For developers, BNG often means buying credits or providing compensatory measures to offset habitat disruption. Ideally, this initiative encourages ecologically sound practices in development projects, yet its real-world application has sparked considerable debate.
A central issue raised was the inconsistent interpretation of BNG requirements across LPAs, as each authority applies national statutory guidelines differently. This inconsistency makes it difficult for developers to predict requirements, adding complexity and cost to projects. Some local authorities, for instance, work closely with local wildlife trusts, while others rely on consultants due to limited ecological expertise. This patchwork approach often leads to consent via planning appeal, which further slows down the planning process and increases costs for developers.
Several of the experts participating in the debate expressed concerns that BNG is overly quantitative, with a simplistic "tick-box" approach that fails to account for the unique ecological characteristics of different habitats. Some habitats are given high value within the metric, but these do not necessarily reflect on-the-ground biodiversity challenges, such as geological factors. Additionally, the lack of clear industry standards on conducting BNG surveys can lead to discrepancies, as interpretations of what constitutes a "biodiversity net gain" vary widely.
BNG requirements complicate the planning process by necessitating careful and costly mitigation strategies, particularly on sites constrained by land availability or competing land-use priorities. With some LPAs setting higher BNG targets than others, developers face unpredictability, adding to delays and financial strain. Furthermore, there is a challenge in proving to local communities that mitigation is occurring in their area, as mitigation projects may happen in different locations, creating tension, planning refusal, and sometimes leading to appeals.
There is a risk that BNG credits could become a speculative market, with costs driven up by landowners who hold the credits. Predictions suggest that these costs may rise over time, complicating budgets for developers and potentially leading to inflated housing prices, which would be required to cover the additional cost of development. Additionally, questions were raised about the sustainability of BNG sites, as some of these credits come with 30-year contracts. This period raises questions about what happens when the contracts end and whether there are adequate financial provisions to sustain biodiversity in perpetuity, particularly considering inflation and ecological changes over decades.
The availability of suitable allocated development land within local plans is another significant constraint, limiting options for mitigating biodiversity loss on-site while maintaining deliverable housing numbers. With limited developable land and high BNG requirements, developers face an uphill struggle to find suitable areas to meet both housing and biodiversity goals. Many of the interested land-owning entities that are able to accommodate off-site contributions, such as the National Trust, are often in possession of land that already has a better than average biodiversity content, making it difficult to provide the required 10% uplift.
With much negativity surrounding the understanding, implementation, and impact of Biodiversity Net Gain it was suggested that some of the positives ought to be looked at, which include
Environmental stewardship: BNG incentivises developers to consider environmental impacts, making planning more ecologically sustainable.
Opportunities for rewilding: Major landowners and charitable organisations can use BNG to restore land, enhancing local ecosystems.
Long-term environmental benefits: When implemented effectively, BNG can contribute to addressing climate and biodiversity challenges, aligning with national climate goals.
However, the negatives clearly need further thought
Increased complexity and cost: For developers, the additional requirements add layers of complexity, delay, and financial burden, especially due to inconsistency across LPAs.
Potential for market manipulation: The speculative nature of BNG credits could make housing projects more costly, affecting affordability.
Disparities in local vs. remote mitigation: Mitigating biodiversity impacts in remote areas may not satisfy local communities, leading to potential opposition.
The consensus at the roundtable was that achieving 1.5 million new homes within the next five years is an unrealistic goal under current conditions. While BNG requirements add complexity and cost, the real barrier lies in the broader planning system, which suffers from under-resourced LPAs, inconsistent application of regulations, and local political resistance. However, participants agreed that the higher the target set by the government, the more likely housing numbers will increase overall—even if the ultimate goal remains out of reach. Setting ambitious targets can function as a catalyst, encouraging higher housing output and motivating more streamlined planning efforts.
To make meaningful progress, regional planning is essential. A regional approach would help dilute the influence of local politics, providing a more unified strategy that aligns housing growth with both national environmental goals and local needs. With greater coordination between government bodies, developers, and LPAs, it may be possible to pursue significant housing development that respects biodiversity goals and meets evolving demands. Although challenging, the integration of BNG within housing targets can be a step toward sustainable growth rather than an outright barrier.
Around the Table with iB Architects were:
Helen Evriviades Stantec
James Iles Pro Vision
Louisa Jones Pro Vision
Derek Ching Boyes Turner
Cara Groves Boyes Turner
Giles Perry Openview Developments
Aaron Smith Master Land & Planning
Marcus Clarke Satao Group
Luke Challenger Black Box Planning
Fergus Hodge Simmons & Sons
Stuart Walter Backhouse
Nikita Lad iB Architects
Penny Dixon iB Architects
Ian Blake iB Architects