The biodiversity duty and how councils must apply it

Every council in England carries a biodiversity duty that applies to planning decisions, and it is not the same thing as biodiversity net gain. It sits in section 40 of the Natural Environment and Rural Communities Act 2006, it was strengthened by the Environment Act 2021, and it requires public authorities to consider what they can do to further biodiversity and then to act on that consideration. For anyone writing an objection or a representation, it is one of the more useful provisions in the toolkit, because it applies to every decision rather than to a defined class of development.

It is also frequently reduced to a single sentence in an officer report. Knowing what the duty actually demands helps you tell a considered sentence from a copied one.

Where the duty comes from

Section 40 originally required public authorities to have regard to conserving biodiversity in exercising their functions. Conserving was defined to include restoring or enhancing a population or a habitat, which matters because it makes the duty active rather than protective.

The Environment Act 2021 rewrote it. The current version requires an authority to consider from time to time what action it can properly take, consistent with the proper exercise of its functions, to further the general biodiversity objective, and then to take that action. There is a separate reporting obligation on local authorities, and a duty to have regard to any relevant local nature recovery strategy.

The practical change is the shift from a passive standard to a two-stage requirement: think about it, then do something. A council that has never written down what it decided to do has not completed the first stage.

What the duty is not

It is not the biodiversity gain condition. That is a separate regime inserted into the Town and Country Planning Act 1990 by the Environment Act 2021, applying a percentage gain requirement to most planning permissions, measured with the statutory metric and secured through a biodiversity gain plan approved by the authority.

The two overlap in subject matter and diverge in almost everything else. The gain condition is a mandatory arithmetic test applied to a permission. The biodiversity duty is a continuing obligation on the authority itself, applying to plan making, to decisions, and to how it manages its own land.

Confusing them weakens a representation. An objector who argues that the duty requires a particular percentage of gain will be told, correctly, that the duty does no such thing. A biodiversity net gain assessment answers the arithmetic question and has to be prepared by a competent person under the Environment Act 2021 regime.

What furthering biodiversity means in a planning decision

Courts have consistently treated duties of this kind as duties of process rather than duties of outcome. The authority must actually consider the question and give it the weight it thinks appropriate. It does not have to reach a particular answer.

That still leaves plenty of ground. In practice the duty shows up through:

• The weight given to habitat loss that falls below the threshold for a designation.
• Whether the authority sought ecological information before deciding, rather than conditioning it afterwards.
• Whether conditions requiring habitat creation are drafted so they can actually be enforced.
• Whether the decision took account of the local nature recovery strategy for the area.
• Whether opportunities to restore habitat, as opposed to merely avoid harm, were considered at all.

That last point is the one most often missed. The duty covers restoration, so a decision that treats avoiding harm as the ceiling has arguably not engaged with it.

How it appears in officer reports

Most reports handle it with a short paragraph near the end, under a heading about other matters. Look at what that paragraph does. A report that names the habitats affected, refers to the ecological evidence and explains the weight given has discharged the duty. A report that recites the section number and asserts compliance has not, and saying so in a representation before the committee meets is more useful than saying it afterwards.

Where ecological evidence is thin, the more productive argument is usually about the evidence rather than the duty. If the application lacks a preliminary ecological appraisal on a site with obvious habitat, ask for one. Authorities are generally reluctant to determine an application with an evidence gap once it has been pointed out in writing.

Reporting obligations on authorities

Local authorities in England now have to publish biodiversity reports describing what they have done and what they plan to do, on a repeating cycle. Check the current Defra guidance for the timetable, because the dates have moved.

Those reports are useful documents for anyone making representations. They set out the authority's own stated objectives, and an argument that a decision cuts across what the council published about its own biodiversity priorities carries more weight than a general appeal to the duty. And unlike most planning evidence, they are short.

Using the duty in a representation

Keep it specific and keep it short. A paragraph that works looks roughly like this: identify the habitat or species feature affected, name the evidence that establishes it, point to the relevant local nature recovery strategy priority or the council's own published objective, and ask for a particular action, such as a survey, a redesign of the layout or a condition with defined monitoring.

Avoid three things. Asserting that the duty prevents the development. Treating it as a substitute for development plan policy, which carries more weight in the decision. And relying on it where the real problem is that the ecological survey was done in the wrong season, which is a straightforward evidence point.

Where habitat creation is proposed as mitigation, the deliverability of that habitat is fair game. Planting failures are common and the timing constraints are real, as habitat creation, planting seasons and failure sets out. Similarly, errors in the metric are worth checking before assuming the numbers are right, and the recurring ones are described in biodiversity metric errors councils find most often.

The limits of the duty in decision taking

Be realistic about what it achieves. The duty has rarely been the sole ground on which a planning decision has been overturned. It is most effective as a reinforcing argument alongside development plan policy and the national framework, and as a reason for the authority to seek better information before deciding.

Its strongest use is probably at plan making stage rather than on individual applications, because that is where policies, allocations and the nature recovery network are set. Representations at a local plan consultation are read by fewer people but change far more.

There is a second practical use worth knowing about. Councils are themselves landowners and developers, and the duty applies to their own schemes and their own estate management. A representation that points to the authority's grass cutting regime, its verge policy or its treatment of a council-owned site is harder to deflect than one aimed at a private applicant, because the authority cannot answer that it has no control over the land.

Enter your postcode on PlanScope to see which ecological reports a site is likely to need.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.