Weighty matters for Biodiversity Net Gain

Ned Helme looks at a High Court judge’s recent guidance to decision-makers on weighing biodiversity net gain improvements.

As readers will know, statutory (mandatory) biodiversity net gain (“BNG”) for Town and Country Planning Act 1990 (“TCPA”) development went live on 12^th February 2024^[1] (with transitional provisions^[2] and a temporary exemption for non-major development until 2^nd April 2024^[3]). However, there was a long run-up to this following the enactment of the Environment Act 2021 on 9^th November 2021; and in the non-mandatory period, developers increasingly offered (and Councils increasingly expected) BNG to be secured. Yet decision makers have sometimes struggled in knowing how to weigh BNG in the planning balance, as the decisions in NRS Saredon Aggregates Ltd v Secretary of State for Levelling Up, Housing and Communities [2023] EWHC 2795 (Admin) and R (Weston Homes Plc) v Secretary of State for Levelling Up, Housing and Communities [2024] EWHC 2089 (Admin) make clear; and there is a risk of this continuing for applications and appeals subject to mandatory BNG.

Holgate J’s guidance to decision-makers on weighing BNG improvements in Vistry Homes Ltd v Secretary of State for Levelling Up, Housing and Communities; Fairfax Acquisitions Ltd v Secretary of State for Levelling Up, Housing and Communities [2024] EWHC 2088 (Admin) (at [148]-[163]) is therefore welcome. The case involved two s.288 TCPA claims concerning decisions by Inspectors on planning appeals relating to residential schemes involving “inappropriate development” in the Green Belt, one in St Albans, the other in Hertsmere. Both claims sought to challenge the way in which the Inspector had dealt with BNG benefits (among other matters) for applications to which mandatory BNG did not apply, but the guidance provided by Holgate J addresses the issues for both non-mandatory and mandatory BNG. The following points are of particular interest, both in the BNG context and more widely.

First, there is no legal principle that where a development makes provision for something which is required by a policy or by legislation, that cannot be regarded as a benefit at all. If a measure is required for a project to consume its own smoke (i.e. the benefit offsets an equal harm), it would not be a benefit. But a genuine benefit remains a benefit whether or not it is required by policy or legislation. For schemes subject to mandatory (as well as those offering non-mandatory) BNG, the provision of BNG will therefore be a benefit to be weighed in the balance. Whether a measure should be treated as a benefit, depends upon, among other things, its nature and purpose, including whether it would help to meet a need which is, or is not, related to the development proposed. And although weight is always a matter for the decision maker (absent Wednesbury error),^[4] in the light of the underlying justification for the requirement to reverse a national decline in biodiversity over many years, Holgate J found it difficult to see how logically a decision-maker (in a case to which mandatory BNG applied) could give no weight at all to provision of 10% BNG because that equated to no more than the requirement in Schedule 7A to the TCPA. It also follows that, where a development would provide BNG of more than 10%, a decision-maker is not entitled to say that only that part of the BNG which exceeds 10% can qualify as a benefit in deciding whether to grant planning permission.

Second, if a decision-maker were to reduce the weight which he would otherwise give to a benefit on the basis that it was no more than required by legislation or policy, that would also be objectionable, certainly in the absence of any logical explanation. Rather, in assessing weight, the decision maker should be assessing how the benefit stands in relation to the justification for the level required by statute or policy. For mandatory BNG, a blanket 10% figure is imposed for a broad range of development to alleviate a national problem, and Holgate J therefore considered it to be a benefit of a generalised nature, contrasting it with the benefit of providing affordable housing which is related to: (a) the highly specific needs identified by a local planning authority for its area; and (b) ensuring that the release of housing land meets the need for affordable housing as well as general housing. Holgate J suggested that such considerations may affect the weight to be given to benefits, but highlighted that this is a matter for the decision-maker in the particular case.

Third, little help can be gained from looking at the decisions of Inspectors on other planning appeals since usually there is insufficient information to help determine true comparability. Decision letters often do not explain why a particular weighting was adopted. Moreover, it can be meaningless simply to compare percentages of BNG without also being told the absolute size of the increase in biodiversity units.

Fourth, notwithstanding the above points, the statutory requirement for BNG of 10% can properly be used as a simple benchmark for comparing the BNG to be provided for a proposed development, so long as the decision maker understands the limitations of using percentages and does not commit any other errors.

Fifth, where substantially more than the mandatory minimum 10% BNG is offered, it may be necessary for a decision-maker to consider Regulation 122 of the Community Infrastructure Levy Regulations 2010 and the principles in, for example, R (Wright) v Energy Severndale Limited [2019] 1 WLR 6562. However, Holgate J emphasised that he did not receive submissions on that particular point, and it should be approached with circumspection. Plan-makers are entitled to seek a higher percentage than the 10% minimum where such a policy is justified and evidenced^[5]. And even where there is no such development plan requirement, there is clearly scope for argument (in general terms and particular cases) on the Regulation 122 and Wright issues.

Sixth, and finally, where the application predates the statutory requirement, that requirement should not be treated as having been applicable, nor should that be the effect of the decision-maker's reasoning. The 10% BNG provision in Schedule 7A to the TCPA 1990 may be used in such cases, but only as a benchmark, in assessing the weight to be given to a BNG contribution. It must not be used to reduce the weight that the decision-maker would otherwise have given to the provision of BNG in a particular case.

These are salutary principles, though they reveal the complexity of the decision-maker’s task in identifying and weighing benefits in the planning balance. It is to be hoped they assist decision makers in avoiding the errors into which the Inspectors fell in the Saredon and Weston Homes cases. But BNG is a highly complex and evolving new area, and the body of case law on it is only beginning to develop.  

Ned Helme is a barrister at 39 Essex Chambers.

^[1] Regulation 2 of the Environment Act 2021 (Commencement No. 8 and Transitional Provisions) Regulations 2024.

^[2] ibid Regulations 3 and 4.

^[3] Regulation 3 of the Biodiversity Gain Requirements (Exemptions) Regulations 2024. There are also various permanent exemptions and exceptions, helpfully set out in the Planning Practice Guidance section on BNG at Paragraph: 003 Reference ID: 74-003-20240214.

^[4] See Lord Hoffmann’s famous passage in Tesco Stores Ltd v Secretary of State for the Environment [1995] 1 WLR 759 at p.780 F-H.

^[5] See the Planning Practice Guidance section on BNG at Paragraph: 006 Reference ID: 74-006-20240214.