Biodiversity in Wales: the section 6 duty in practice

Welsh applications are not English applications with the place names changed, and biodiversity in Wales is the clearest example. There is no statutory biodiversity gain condition in Wales, no mandatory 10 per cent uplift and no legal requirement to run the statutory metric. What there is instead is the section 6 duty in the Environment (Wales) Act 2016 and a policy requirement in Planning Policy Wales for development to show a net benefit for biodiversity.

For a consultant used to English practice, the section 6 duty wales biodiversity position feels looser and is in some ways harder. A metric produces a number you can argue about. A duty produces a judgement, and the judgement belongs to the planning authority.

The section 6 duty and who it binds

Section 6 of the Environment (Wales) Act 2016 requires public authorities to seek to maintain and enhance biodiversity so far as is consistent with the proper exercise of their functions, and in doing so to promote the resilience of ecosystems. Local planning authorities are public authorities, and determining a planning application is the exercise of a function.

Two features matter in practice.

The duty binds the decision maker, not the applicant. You cannot discharge it. You can only give the authority the evidence it needs to discharge it, which reframes what your ecology chapter is for. It is not a compliance statement. It is the material on which a public body forms a judgement it has to be able to defend.

The duty also reaches beyond species and habitats to the resilience of ecosystems, which the Act and Welsh policy describe through diversity, extent, condition, connectivity and adaptability. Connectivity is the limb most often underserved in submitted documents. A scheme that creates a wildflower area with no link to anything outside the red line addresses extent and does nothing for connectivity.

Section 7 of the same Act carries the list of living organisms and habitats of principal importance for maintaining and enhancing biodiversity in Wales, which is the Welsh successor to the old section 42 list. If a section 7 habitat is present, say so by name and show what happens to it.

Net benefit for biodiversity in Welsh policy

Planning Policy Wales sets out a step wise approach and requires development to demonstrate a net benefit for biodiversity. The steps run in order: avoid harm, then minimise it, then mitigate what cannot be minimised, then compensate as a last resort, and then provide enhancement beyond that.

The sequence is doing real work here, and the common failure is to jump to the last step. A scheme that removes a section 7 hedgerow and offers three bat boxes and a hibernaculum has not worked the steps. It has bought its way to the final one.

What a Welsh authority is looking for, in the order it reads:

• Evidence that the layout was tested against retaining the features of value, with the alternatives that were considered.
• A description of what is lost, in area, length and condition terms.
• The mitigation, tied to specific drawings and specific locations.
• The enhancement, quantified in whatever units suit the habitat, with a mechanism to secure and maintain it.
• Confirmation that the resilience attributes have been considered, connectivity included.

Quantify where you can even though you are not required to. A table of habitat areas before and after, with condition described against a recognised classification, gives the officer something to report. A paragraph of adjectives does not.

Why there is no statutory metric requirement

The mandatory regime under the Environment Act 2021 is England only. The biodiversity gain condition, the 10 per cent figure, the 30 year management period and the statutory metric are English law, and applying them in Wales as though they were binding is a mistake that turns up in submitted documents more often than it should.

That does not make the metric useless in Wales. Where a Welsh authority is willing to accept it, a metric calculation is a defensible way to show net benefit, and some applicants run it voluntarily for exactly that reason. Present it as supporting evidence, not as compliance, and be clear in the text that no statutory requirement is being met. If you are working across both jurisdictions, our page on the Biodiversity Net Gain Assessment sets out the English position that does not transfer.

The honest uncertainty here is about direction of travel. Welsh Government has been consulting on environmental governance and biodiversity targets for some years, and the statutory framework may change. As at September 2026, the position is the section 6 duty plus policy, and nothing here should be read as anticipating a new duty. Check the current Welsh Government position before advising a client on a long programme.

Green infrastructure statements and what they contain

Planning Policy Wales expects green infrastructure to be considered from the outset and a green infrastructure statement to be provided with development proposals. The statement is where the section 6 material, the landscape material and the drainage material meet, and it is the document Welsh officers most often find missing or thin.

A usable statement covers:

1. The existing green infrastructure on and around the site, mapped, including trees, hedgerows, watercourses, grassland and any designated sites within a defined search area.
2. The functions those features perform, from habitat and connectivity to shading, surface water management and amenity.
3. How the proposal retains, changes or replaces each feature, cross referenced to the layout drawing.
4. The multifunctional benefits claimed for new features, stated as what they do rather than as a list of species.
5. Management and maintenance, with the responsible party named and the funding route identified.

A Green Infrastructure Plan drafted from the site survey will get you a structure. The site specific content still has to come from someone who has walked the site.

Evidence Welsh authorities expect from ecologists

The protected species law is the same across Great Britain. The Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017 apply in Wales, with licensing handled by Natural Resources Wales rather than Natural England. So the survey evidence looks familiar:

• A Preliminary Ecological Appraisal with an extended habitat survey, scoped to the site and its surroundings.
• Species specific survey where the appraisal identifies potential, within the correct seasonal windows.
• A Protected Species Survey and any European protected species licence prepared by a suitably licensed ecologist, which is a legal requirement rather than a preference.
• A landscape and ecological management plan for the post construction period.

Welsh authorities also tend to expect the ecologist's own conclusion on the section 6 duty, expressed as a view on whether the proposal maintains and enhances biodiversity. Ask your ecologist for that sentence explicitly. Officers quote it.

Securing enhancement through conditions

Without a statutory gain plan, everything rests on conditions and obligations. That puts a weight on drafting that English practice has partly removed.

Workable approaches in Wales:

• A condition requiring the approved landscape and ecological management plan to be implemented, with a defined management period and monitoring reports at stated intervals.
• A condition tying occupation to the completion of the ecological features, so the habitat is not the thing that never gets built.
• A planning obligation where off site compensation or long term funding is involved, since a condition cannot reach land outside the applicant's control.
• Reserved matters or a phasing condition that keeps the enhancement in step with the built development on a multi phase site.

Vague wording is the enemy. A condition requiring the development to provide a net benefit for biodiversity is unenforceable, because nobody can say when it has been met. A condition requiring 120 metres of new native hedgerow of stated species mix, planted in the first planting season after occupation and maintained for ten years, is enforceable.

Comparing the Welsh and English approaches honestly

England has a measurable duty on the applicant with a rigid method. Wales has a judgement duty on the authority with a flexible method. Neither is obviously better, and the practical difference for a consultant is where the argument happens. In England you argue about habitat condition scores. In Wales you argue about whether the step wise approach was properly worked.

One warning for anyone using AI assisted drafting across both jurisdictions. PlanScope's drafting is grounded in English national policy and English local plans, so a Welsh application needs the reviewer to check Planning Policy Wales, the relevant Technical Advice Notes and the adopted local development plan rather than the NPPF. Treat the draft as a structure to fill with Welsh policy, not as Welsh policy.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. For specialist technical reports, qualified professional input may be required.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.