Nutrient neutrality and Welsh European marine sites: What developers and LPAs need to know

Natural Resources Wales (NRW) has issued interim advice following the publication of updated condition assessments for Welsh marine Special Areas of Conservation (SACs) and Special Protection Areas (SPAs). These reports reveal that several marine sites are in an unfavourable condition for both chemical and biological indicators of nutrient enrichment.

This advice places new legal obligations on Local Planning Authorities (LPAs) and has significant implications for developers, landowners, and communities across Wales.

Why is this happening now?

NRW’s June 2025 assessments concluded that the nutrient-sensitive features of sites such as Pembrokeshire Marine, Carmarthen Bay and Estuaries, and Cemlyn Bay are failing to meet conservation targets. Excessive nitrogen is contributing to algal blooms, reduced oxygen levels, and negative impacts on fish and other aquatic life.

This mirrors the position in England, where Natural England issued similar advice in 2020 (following the Dutch Nitrogen Case) to advise local planning authorities that mitigation measures forming part of a Habitats Regulations Assessment must demonstrate no adverse effect ‘beyond reasonable scientific doubt’ and that the benefits of the mitigation measures must be ‘certain at the time of the Assessment’ before consent can be granted. The advice resulted in new development being required to achieve ‘nutrient neutrality’, where the nutrient load created through additional wastewater from development had to be mitigated, either on-site or off-site. Importantly, previously consented, as well as existing schemes are caught here. This includes LPAs discharging planning conditions, approving reserved matters or granting minor amendments to existing planning consents.

The legal position under the Habitats Regulations

Under the Conservation of Habitats and Species Regulations 2017 (the Habitats Regulations), LPAs are the “competent authority”. This means they cannot lawfully grant planning permission unless they are satisfied, through an Appropriate Assessment (AA), that a proposed development will not adversely affect the integrity of a protected site.

A few key points:

• A resolution to grant planning permission is not final. Until the decision notice is issued, the LPAs duty under the Habitats Regulations remains so if new material information (such as NRW’s findings) arises they will need to reassess applications.
• Failure to carry out an AA risks legal challenge. If an LPA issues a decision without properly assessing nutrient impacts, the consent is vulnerable to being quashed by the courts.
• The courts have confirmed that AAs may also be required at the discharge of conditions stage. In CG Fry v Secretary of State [2023], the Court of Appeal held that the Habitat Regulations could require an AA at discharge of conditions stage both directly as a matter of law in the case of a SAC (or SPA) and indirectly a matter of national policy in the case of Ramsar Sites.

What does “nutrient neutrality” mean in practice?

Nutrient neutrality requires that any increase in phosphate or nitrogen discharges from new development is fully mitigated, so that there is no net increase in nutrient loading in affected catchments.

Mitigation may include:

• on-site options such as sustainable drainage systems, wastewater treatment works and habitat creation; or
• off-site options such as nutrient trading schemes, land use changes/rewilding secured by conservation covenants and upgrades to wastewater treatment works

NRW’s advice is clear: a conclusion of no adverse effect on site integrity may only be reached if nutrient neutrality can be demonstrated.

Differences between Wales and England

While the principles are aligned, there are some important differences:

• Guidance source: NRW (Wales) and Natural England (England) each issue separate advice, tailored to local catchments.
• Catchment mapping: NRW has confirmed GIS mapping of affected catchments will be published, which will guide LPAs in Wales.
• Policy context: In England, central government has proposed reforms to streamline nutrient neutrality requirements (including potential legislative changes). In Wales, there is currently no equivalent policy intervention. This means LPAs are likely to apply NRW’s advice strictly until further notice.

What should developers and landowners do now?

1. Review your sites and proposals. If you are within, or draining into, the identified marine SACs, assume nutrient neutrality may apply.
2. Engage early with LPAs. Demonstrating mitigation up front can avoid delays.
3. Factor in potential re-assessment. Even if your scheme has a resolution to grant, the decision notice cannot lawfully be issued until the AA duty is met.
4. Consider strategic solutions. Larger schemes may need to work collaboratively on mitigation strategies.
5. Take legal advice. The case law in this area is developing quickly, and each site will need careful, fact-specific analysis.

Conclusion

Natural Resources Wales’ interim advice is a turning point for planning in Wales. With marine Special Areas of Conservation now in unfavourable condition, nutrient neutrality assessments and mitigation are legal requirements. Further guidance from NRW is expected, and the Supreme Court’s decision in CG Fry may shape how these issues are dealt with at different planning stages. What is clear is that consents which do not properly address nutrient impacts risk delay or legal challenge.

We are already advising clients on these developments. If your project may be affected, our team can provide clear and practical guidance to keep it on track.