27 Nov How should habitats below solar panels be classified within the Statutory Biodiversity Metric?
This technical note discusses the classification of habitats below solar panels in the Statutory Biodiversity Metric (SBM). It considers industry guidance, evidence, and details some recent clarification from Natural England, which is likely to be of interest to all those involved in solar farm developments.
Confusion over how UK Hab should be applied to solar arrays has led some solar farm projects being asked to record grassland habitat below solar panels as ‘Developed land; sealed-surface’ in the metric. Apart from being inaccurate, doing so would make biodiversity gain harder to achieve and lead to significant additional costs for solar farm developers. This note sets out an evidence-based position and explains how it is supported by industry guidance.
Is grassland developed land with a sealed impervious surface?
BSG Ecology has worked on numerous solar development schemes throughout England involving biodiversity gain, including several recent projects that have obtained planning consent using the SBM. In all these projects, including a Nationally Significant Infrastructure Project (NSIP) and projects that have been scrutinised and achieved consent at appeal, habitat below the solar arrays was classified as grassland (e.g. modified grassland). We are also aware of various similar consented projects which include grassland below panels that we have had no direct involvement in.
We have noted that some solar farm developers have been asked by a planning authority to classify habitat below solar panels as ‘Developed land; sealed surface’ when calculating biodiversity gain. This is confusing as there is plenty of evidence that vegetation will grow beneath solar panels, including supporting industry guidance[1]. We also note that a soon-to-be-published study[2] has undertaken research on (vegetated) habitat types that can be established below solar arrays. This has led us to challenge this approach based on accuracy and in the interests of our clients.
The origin of the request derives from a narrow interpretation of part of the UK Hab Classification (a system designed for classifying habitats, which is separate from the metric). This is heavily reliant on the wording of secondary code ‘83 Solar Panel Array’. This states “record the strips of panels as u1b6 [i.e. other developed land] and the strips of vegetation in between the rows separately” and has been used to justify the request for solar developers to assign post-development habitats below the panels as u1b in the SBM (i.e. Developed land; sealed surface, which is the closest equivalent to u1b6 in the SBM). While this makes sense for the panels, it does not work for the vegetation underneath, particularly when a grassland primary code can also be applied.
In summary, this requested approach is based on an oversimplification of UK Hab’s classification system and a misunderstanding of how it should be applied to the metric (as discussed in more detail below); this leads to a number of problems:
- It is not accurate or evidence-based – the habitat below the panels is generally not developed land with a sealed impervious surface;
- If it is vegetated (e.g. modified grassland), it is of some ecological value, and since the SBM needs to be underpinned by accurate data, the habitat and condition used within the metric should accurately reflect what will be created;
- For a solar developer, classifying the habitat below the panels as ‘Developed land; sealed surface’ would undervalue this post-intervention habitat. This could make a significant difference to the post-intervention metric calculation, and therefore the ability to achieve biodiversity gain and the cost of providing offsite habitat.
Natural England’s position
We requested clarification from Natural England’s metric team who advised the following (by email, 21 November 2025):
“UKHab solar panel habitat type does not apply to the metric, instead users should record the habitat found beneath the solar panels (e.g. modified grassland in poor condition) within the metric.“
This helpfully provides a very clear position moving forwards.
This advice is consistent with a statement in the Solar Energy UK (SEUK) Natural Capital Best Practice Guidance[3] which states that “research (awaiting publication) shows that in most cases, habitats within solar farms can be classified as other neutral grassland of moderate condition within the metric (where the site is formerly arable or pasture). The habitat directly under the panels is more variable, but in most cases, a similar habitat can be achieved. Natural England has advised SEUK that in the absence of empirical evidence, ecologists should categorise it as one area or sub-categorise it into multiple areas based on their experience of the habitats under panel areas.”
Statutory Biodiversity Metric User Guide – considering key principles
The SBM User Guide[4], which describes how to use the metric, sets out several principles to follow when using the metric. These reinforce the need for professional judgement, objectivity and accuracy.
- Principle 3 states that the “biodiversity Metric should be used in accordance with established good practice guidance and professional codes” (such as the CIEEM Code of Professional Conduct, the industry code for professional ecologists, which refers to the need for objectivity, accuracy, and to have regard to relevant scientific literature, published evidence…).
- Principle 4 states that the “biodiversity metric is not a complex or comprehensive ecological model and is not a substitute for expert ecological advice”;
- Principle 6 states that the “biodiversity metric is designed to inform decisions in conjunction with locally relevant evidence, expert input or guidance”.
Each of these principles support the use of an evidence-based approach to identifying habitat below solar arrays – i.e. accuracy is important and required by the SBM User Guide.
Applying UK Hab to solar farms
UK Hab was designed independently from Biodiversity Gain; and since habitat categories do not always match precisely professional judgement is needed when translating from UK Hab to the SBM.
On first glance, UK Hab can appear inconsistent regarding the treatment of solar farms. For example, Secondary Code 83 “Solar Panel Array” suggests that “the panels should be recorded as u1b6, and that strips of vegetation between panels should be recorded separately”, however, the system also allows for the use of primary habitat codes, including grassland (g~).
UK Hab is intended to record habitats as if viewed from above (i.e. in a two-dimensional landscape). Where more complex habitats are present, such as multi-layered land or vegetation, these can be captured using both primary and secondary codes. In other words, if using the full breadth of UK Hab’s system, it is possible to accurately describe a solar array, including both the solar panels and the habitat below the panels. The onus is on the assessor to apply both parts of the UK Hab, and to use professional judgement while doing so. Although, given Natural England’s advice above, this level of detail is not likely to be necessary when completing the post-intervention habitat data within the SBM.
In conclusion, when describing post-intervention habitats in the SBM, the habitat assigned below solar panel arrays should accurately reflect what will be there (e.g. grassland) taking account of any potential limitations with respect to the grassland type and condition achievable.
BSG Ecology has a wealth of experience of providing ecological support on solar farms of varying size and complexity. You can read about some of our solar project experience here: Energy Capability
For further information please contact us: info@bsg-ecology.com
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[1] https://solarenergyuk.org/wp-content/uploads/2022/05/Natural-Capital-Best-Practice-Guidance.pdf
[2] Although the research (by Natural England and consultants Clarkson Woods) is awaiting publication, a 2024 presentation on the work (solar farms and biodiversity) is published on the Planning Advisory Service (part of the Local Government Association) which discusses under-panel habitats, and the contribution these habitats make to BNG. https://www.local.gov.uk/pas/environment/biodiversity-net-gain-bng-local-planning-authorities/bng-library/pas-bng-event and https://youtu.be/S9JuthfUnYs
[3] This SEUK guidance, which includes a specific section on BNG within and under solar panels, was produced with input from Natural England’s BNG team and contains a forward written by Tony Juniper (Natural England Chair).
[4] The Statutory Biodiversity Metric User Guide