Changes to nutrient neutrality in England

DOI: https://doi.org/10.58248/PN755

In 2019 and 2022, Natural England issued planning advice to 74 local planning authorities for 31 sites spanning 27 river catchments in unfavourable condition due to nutrient pollution. Building projects and plans may only go ahead if they will not cause additional pollution, referred to as ‘nutrient neutrality’.

Nutrient neutrality does not seek to reduce the nutrient pollution levels affecting protected sites, but to limit future increases from development. The Commons Library briefing Nutrient neutrality and housing development explains how the previous government proposed to reduce the effects of nutrient pollution on protected sites.

Excess nitrogen and phosphorus nutrients arising from point sources, such as sewage effluent, and diffuse sources, such as agricultural activities, affect soil, wildlife, air and water quality as they move through the environment, as well as emitting greenhouse gases. This includes impacts on freshwater and coastal habitats protected under the Habitats Regulations.

The Planning and Infrastructure Bill provides for a new approach to nutrient neutrality by creating Environmental Delivery Plans, funded by levies paid into the Nature Restoration Fund.

Trends in nutrient pollution sources and effects

The Environment Agency says that phosphorus pollution levels in England’s rivers and lakes are the main cause of eutrophication (excessive algae growth affecting water quality and ecology). However, in some waterbodies, nitrogen pollution levels may increase eutrophication risks, either alone or in combination with phosphorus pollution.

Research suggests that treated sewage effluent, emitted as a ‘point source’ of water pollution, may have historically had the greatest effect on water quality in some catchment areas. However, diffuse sources of water pollution are now having a greater effect; this trend may become increasingly dominant.

The Environment Agency suggests that phosphorus pollution from agriculture and rural land use, rather than sewage effluent, is one of the main causes of waterbodies failing to meet the relevant water quality criteria. Agriculture and rural land use is also the main source of nitrogen pollution.

Proportions and patterns of nutrient pollution sources vary between and within catchments, but are apportioned using modelling with uncertainties at this scale.

Current nutrient neutrality mitigation requirements

Developers must calculate the excess nutrients (‘nutrient load’) created by a proposed development using catchment nutrient calculators, which compare the development with previous land uses. Mitigation measures must remove this excess amount, either on the development site or within the same catchment.

Nutrient removal by mitigation project schemes is assessed and accredited by Natural England, which has set out the evidence for measures with sufficient mitigation certainty. Schemes must be maintained and monitored for the lifetime of a development (usually 80 to 125 years). Examples include constructed wetlands, which reduce nutrient loads from sewage effluent or agricultural activities.

In catchments with these mitigation project schemes, some of which are led by local authorities or Natural England, developers can pay to offset their nutrient loads. Schemes supply credits which are considered the mitigation equivalent of 1 kilogram of nitrogen or phosphorus emitted per year.

Reducing nutrient pressures on protected areas

Research suggests that setting overall nutrient load caps for catchments can reduce nutrient loads, but that reducing loads may also require an improved understanding of nutrient flows. Reducing flows at a catchment scale is challenging, as interactions occur across water, soil, sediments and air, and include legacy nutrient pollution sources in soil and groundwater.

Natural England will take a catchment-scale strategic mitigation approach to Environmental Delivery Plans, implementing the existing nutrient neutrality scheme measures upstream of protected areas. Research suggests that, if Environmental Delivery Plans are to be successful, measures should be tailored to specific catchments and affected protected areas, including their physical and natural features, and N and P pollution sources.

Nature markets, where private investment funds environmental restoration by paying for the benefits generated, may provide additional opportunities for nutrient mitigation projects. The Environmental Audit Committee has suggested that the state-run Nature Restoration Fund may create uncertainty for nature markets.

Contributors raised other concerns about the limitations and impacts of existing approaches and Environmental Delivery Plan proposals, including holistically managing trade-offs between policy objectives.

Acknowledgements

This briefing was produced in consultation with experts and stakeholders, who are listed at the end of the briefing. POST would like to thank everyone who contributed their expertise.