Nutrient Neutrality

In 2023, the South Downs National Park Authority launched a new green financing brokerage service for developers looking to buy “ReNature Credits” for phosphates, nitrates and Biodiversity Net Gain.

Natural England updated their advice and guidance for calculating and therefore addressing nutrient neutrality in March 2022. It constitutes the most up-to-date scientific information regarding water quality and so must be taken into account in preparing Habitats Regulations Assessments on planning applications.

The protected sites of the Solent and River Itchen are internationally important for their wildlife. These sites are vulnerable to elevated nutrient (nitrogen and phosphorous) levels. An increase of such nutrients can cause a process called eutrophication. This is where increased nutrient levels cause excessive growth of certain plants, such as green algae, which has a detrimental impact upon protected habitats and bird species. Sources of nutrients include agriculture such as fertiliser run off, and wastewater outputs from new development.

Residential development, including new homes and other uses that provide overnight accommodation and tourism attractions of a nature that would bring people from outside the catchment, can potentially have an adverse impact on the protected sites of the Solent and River Itchen because of the wastewater they generate.

For the types of new development listed above, the Authority will need to undertake a Habitats Regulations Assessment of planning applications to be satisfied that the proposal will not have any adverse impact on the protected site or sites. These development proposals will need to be nutrient neutral to avoid detrimental harm to the ecology of the Solent and River Itchen. A Nutrient Budget will need to be prepared and submitted to demonstrate this. Natural England has provided advice on how to do this.

The advice affects three river catchments in the South Downs National Park: the East Hampshire Catchment and Chichester Catchment that drain towards the Solent SPA, SAC and Ramsar designated sites, and the Itchen Catchment, that drains towards the River Itchen SAC. It should also be noted that the Natural England advice for the Itchen Catchment also includes a requirement for phosphates to be taken into account in the nutrient budget calculations.

Natural England’s new advice for both the Solent and Itchen catchments can be found below.

Please note, these documents have been issued by Natural England.

If you use assistive technology (such as a screen reader) and need a version of this document in a more accessible format, please email enquiries@naturalengland.org.uk

Nutrient Neutrality