Nutrient Neutrality – a long term perspective?

Tuesday 19th July, 2022

In an article published last week in DTA Ecology’s Habitats Regulations Assessment Journal, Afonydd Cymru’s CEO Gail Davies-Walsh writes about the concept of “nutrient neutrality” and how it relates to rivers in Wales.


Afonydd Cymru is the umbrella body for the six rivers trusts in Wales. It has been working to support the restoration of rivers in Wales for 10 years, focussing predominately in the beginning on habitat and ecological restoration. The organisation provides advocacy for the rivers trusts and has been pinnacle in establishing delivery of river restoration to meet the requirements of the Plan of Action for Salmon and Sea Trout in Wales.

In 2019, Herefordshire Council applied a planning moratorium in Herefordshire as a result of phosphate failure in the county against targets on the River Lugg, a tributary of the River Wye. The Wye & Usk Foundation was at the forefront of calling the excessive levels of nutrients to media attention on the River Wye, having sadly witnessed the river becoming pea green soup. The Foundation are members of the Wye Nutrient Management Board and Technical Advisory Groups, and have been supporting Herefordshire Council on development of solutions ever since.

The ”pea soup” that is the Wye’s water for much of the time between late spring and early autumn.

In 2021, Natural Resources Wales published its phosphorus compliance reports for Wales against revised Joint Nature Conservation Committee (JNCC) targets for Special Areas of Concern (SAC) rivers which has resulted in five SAC rivers in Wales (the Usk, Cleddau, Twyi, Teifi and Dee) also failing, and forcing local authorities on these rivers to also apply planning moratoriums.

This article reflects on the work being undertaken by rivers trusts in Wales, who have a long-term history of providing solutions and delivering projects on the ground to restore our iconic rivers.

Nutrient neutrality

In 2018 Natural England coined the phrase ‘nutrient neutrality’, meaning that development could not proceed in a SAC which is failing to achieve its water quality targets due to nutrients unless it was deemed to be neutral (i.e. that mitigation was provided to offset the load of nutrient created from the proposed new development). This approach was Natural England’s response the ruling of the Court of Justice of the European Union in the Dutch Nitrogen Case which identified that the capacity for further growth was ‘necessarily limited’ under such circumstances. The nutrient neutrality approach has had widespread impact in the UK, causing first the Solent, then the Wye and now numerous other rivers to require nutrient neutrality for development to continue.

It is the responsibility of the local authority to ensure that planned development does not impact the features of the designated site. The nature conservation advisers, Natural England and Natural Resources Wales, have advised the local authorities in their role as “Competent Authorities” that mitigation measures forming part of a Habitats Regulation Assessment (HRA) 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’.

What’s the problem?

The first issue? Well, for those of us working in the world of fixing things, the first step is to identify what causes the problem.  But even here we fall over.  Decision-makers use a tool called SAGIS – Source Apportionment Geographical Information System – to understand where nutrients in a river catchment come from and the proportion that can be assigned to each sector.  It works on the basis of permitted discharges to the watercourse, so assumes the maximum permitted volume from water industry discharges and industry.  Sounds good? But, that surely assumes that all discharges are permitted, which they are not.  It also assumes that because it’s permitted there is a maximum known amount of nutrient discharged – but sadly, this isn’t the case as many permits aren’t permitted for nutrients, and so a generic, best estimate is applied. 

The difference between the monitored nutrient levels in the river and these discharges is then assumed to come from the agricultural sector.  Although source apportionment has been applied for a while now, it doesn’t mean these models were available on every river and they all needed updating for the new targets, new monitoring data and better assumptions for unpermitted sites.  But, it shows some significant results. On the River Wye, contribution from nutrients is at 72% from agriculture, 23% from Welsh Water discharges. On the River Usk, the split is 67% agriculture and 21% Welsh Water. We expect to see similar proportions on other rivers.

The phosphorus attached to soils is not captured in regulatory monitoring nor in any source apportionment. Agriculture’s true contribution to nutrient levels in rivers might much higher than modelling suggests.

It is possible that agriculture’s contribution to ‘P’ levels in rivers is being underestimated

 So, that’s where it comes from sorted then? Well, perhaps not. The first problem is ‘P’ exists in many forms, particulate and dissolved, phosphate and phosphorus.  Regulatory monitoring of phosphorus in rivers in measured in the form of Total Reactive Phosphorus (referred to by Environment Agency and Natural Resources Wales as orthophosphate as P), river targets are set in Soluble Reactive Phosphorus and wastewater discharges are set to Total Phosphorus.  The most significant issue, given the conclusion on source apportionment above, is that orthophosphate represents only a part of the total picture.  The other part is predominately particulate and levels in soils are intrinsically linked to the application of nutrients through fertiliser, slurry or land spreading, i.e. the agricultural impact may be even more.

On the River Wye, Lancaster University have been studying the phosphorus use through a project called RePhokus (Withers, Rothwell, Forber and Lyon, May 2022). This research has recently concluded the following key findings:

  • Environment Agency/Natural Resources Wales water quality monitoring programmes are not considered adequate to capture river quality impacts of short-term or small area changes in agricultural practice. Similarly, the general provision of up-to-date census data is not at a sufficiently fine resolution to accurately quantify spatially distributed P input pressure in catchments. These are both generic problems confounding provision of robust evidence of cause and effect.
  • Water quality in the Wye catchment, and many other livestock-dominated catchments, will not greatly improve without reducing the agricultural P surplus and drawing-down P-rich soils to at least the agronomic optimum. This will take many years.
  • Farming generates an annual P surplus (i.e. unused P) of ca. 3000 t (17 kg P ha-1) in the Wye catchment, which is accumulating in the agricultural soils. This P surplus is nearly 60% greater than the national average, and is driven by the large amounts of livestock manure produced in the catchment.

This legacy P is not therefore captured in regulatory monitoring nor in any source apportionment assessment, but significantly impacts the balance of nutrients in the catchment. Given the similarities in agricultural type across Wales, a wider research project on failing SAC rivers would surely show the same conclusion.


The phosphorus attached to soils is not captured in regulatory monitoring nor in any source apportionment. Agriculture’s true contribution to nutrient levels in rivers might much higher than modelling suggests.

What’s the problem?

Here’s where it begins to get interesting.  In 2022, there are still no mitigation options which have been offered by either regulator.  Natural Resources Wales and Natural England have issued nutrient advice and a generic methodology to affected planning authorities but there’s no UK approved register of mitigation activities, with a confirmed mitigation value and nutrient loading saved.  Local authorities, housing developers and those seeking solutions have been left to wander through the literature and research and try to establish what could be classified as a mitigation option and tentatively offer up solutions to try and get the housing market moving again and our rivers improved.

But the Habitats Directive requires us to operate ‘beyond reasonable scientific doubt’ which implies a necessary degree of ‘certainty’. The types of mitigation measures required on the agricultural side are covered in detail in the River Dee Catchment Phosphorous Reduction Strategy(1).  It can include a range of measures such as buffer strips, riparian corridors, stock exclusion, fencing and restoration – activities that rivers trusts are well practised in delivering.  But monitoring of these solutions has never been funded and the evidence base for their effectiveness is low, so how can they be used for nutrient neutrality? Farmscoper, an Environment Agency model which assigns loading removal to different agricultural interventions, could be an accepted tool for this but has long been questioned in terms of its accuracy. So, how can we define mitigation measures which will meet the obligations required to satisfy the Directive?

The Habitats Directive requires that nutrient mitigation measures for SAC rivers must have a degree of certainty

Afonydd Cymru are currently working on the promotion of wetlands for nutrient removal.  Regulatory position statements have been published by both Environment Agency and Natural Resources Wales on their use, but the statements raise more questions than they answer. We believe that in the case of enhanced treatment of a water works discharge, wetlands designed specifically for nutrient removal could be promoted for nutrient neutrality purposes.

However, agricultural wetlands are much more difficult to evidence given the lack of monitored data, the implications for permitting at the site and the sheer unviability of implementing a wetland in some agricultural settings.  There are currently no wetlands permitted in the UK for nutrient removal purposes and as it stands no regulatory permitting process in place to achieve this, although the Wye & Usk Foundation continue to work hard to achieve this with the Environment Agency.  In short, both regulators need to address the issue that the current permitting process does not meet the needs for nature-based solutions despite this being a key objective for both the English and Welsh Governments.

Wetlands designed specifically for nutrient removal from WWTW discharges could be promoted for nutrient neutrality purposes but for agricultural sources, may not be as effective.

What we cannot lose focus on, however, is what bought us to nutrient neutrality in the first place and what it means in the long-term. Nutrient offsetting is a short-term fix, designed to allow the housing market and economic growth to recommence.  The solution needed is to get all SAC rivers back to favourable condition status, meeting their designated requirements.  We need to be careful that nutrient neutrality measures are not an alternative to SAC compliance. Government guidance (2) in England and Wales is clear that the integrity of a site will be adversely affected if a proposal might ‘prevent or disrupt restoration work, or the potential for future restoration, if it undermines the site’s conservation objectives’; the potential for nutrient neutrality approaches to compromise or disrupt the achievement of restoration objectives will also need to be subject to careful review.  

The principles of the Polluter Pays Principle also need to be achieved on all rivers. Enshrined in the EU Directive 2004/35/EC on Environmental Liability with regard to the prevention and remedying of environmental damage, the aim of the Directive is to ensure that a company causing environmental damage is liable for it and takes the necessary remedial or preventative action.  We need to ensure that each sector is responsible for their own piece in the jigsaw and that actions and measures are in place to meet SAC compliance before any trading can commence towards nutrient neutrality.

Salmon and sea trout in Wales have declined significantly over the last 30 years, with NRW now classifying populations on every river as ‘at risk’ or ‘probably at risk’. This means that numbers of these iconic fish in Wales are now below sustainable levels and on a downward trend.

The recommendations include using range of measures to reduce the impacts of fish eating birds

Of particular concern is the impact of fish eating birds on migrating smolts in the Spring, especially during low flows. On their way out to sea, the young salmon and sea trout tend to gather in pools and behind weirs where they make easy targets for predators 

A joint statement by Afonydd Cymru, The Angling Trust, WildFish Wales and the Game and Wildlife Conservation Trust Wales has been released today.  

For the last two years Natural Resources Wales have co-ordinated the Fish-eating Birds Advisory Group. Participants have included Afonydd Cymru, The Angling Trust, WildFish Wales (formerly Salmon & Trout Conservation Wales), The Game and Wildlife Conservation Trust (GWCT) Wales, as well as the Royal Society for the Protection of Birds (RSPB), British Trust for Ornithology, Welsh Ornithological Society.

The group’s primary purpose was to review current scientific evidence and establish expert opinion regarding the risks that populations of fish-eating birds (specifically cormorants and goosanders) pose to conserving Wales’s threatened populations of wild Atlantic salmon (Salmo salar) and sea trout (Salmo trutta).

On the 13th of July 2022 the group put 19 recommendations to NRW’s Board for policy in relation to fish-eating birds in Wales, with the primary aim of aiding the recovery of depleted fish stocks.

We are pleased to report that the Board has accepted each recommendation in full.

NRW will now be urged to put resources in place to implement and deliver this new more effective fish-eating birds management policy to help salmon and sea trout populations to return to sustainable conservation levels.

Why is this important?

Populations of salmon and sea trout in Wales have declined significantly over the last 30 years, with NRW now classifying populations on every river as ‘at risk’ or ‘probably at risk’. This means that populations of these iconic fish in Wales are now below sustainable levels and on a downward trend.

With the aim of restoring healthy and more sustainable populations of Welsh salmon and sea trout, NRW published their ‘Salmon and sea trout plan of action for Wales 2020’. A key component of the 2020 plan was to review the current scientific evidence surrounding the impact of cormorants and goosanders on juvenile salmon and trout in particular. The review concluded that fish-eating birds are one of a number of pressures on salmon and sea trout populations and that they could reduce the chance of recovery.

Of particular concern was the impact of fish-eating birds during Spring, when the young salmon and trout migrate downstream and out to sea as “smolts.” In low flows especially they can be held up in pools and behind weirs making them easy prey for fish-eating birds.

The recommendations…..

 The Group made nineteen recommendations to the NRW Board, which can be summarised as:

  • Given the protracted decline in salmon and sea trout stocks there is a need for increased targeted actions to counter fish predation by fish-eating birds, particularly in catchments where fish stocks are vulnerable
  • Predation by fish-eating birds on salmonid smolts is of primary concern and requires particular efforts to mitigate predation pressure when impacts are greatest
  • A combination of non-lethal and lethal measures is likely to be most effective
  • Catchment or area-based licences could provide a more strategic approach to licensing and facilitate adaptive resource management where interventions can be applied more flexibly
  • Interactions between fish stocks and fish-eating birds are complex and large key evidence gaps persist
  • Greater transparency on the licensing of fish-eating birds is needed.

While acceptance of the advisory group’s recommendations has been welcomes, Natural Resources Wales must, of course, do their utmost to resolve other pressures affecting Welsh salmon and sea trout, including water quality issues. 

Chris Mills, Afonydd Cymru’s Chairman said: “We were pleased to be party to this review and welcome NRW’s decision to allow increased measures to minimise the predation of migratory salmonids by fish eating birds.”

He added: “It is important that all the biodiversity of our rivers is conserved. However, salmon and sea trout populations have crashed dramatically in recent years and previous research has shown that smolts are particularly vulnerable to predation by cormorants and goosanders. This dramatic decline in our stocks of salmon and sea trout requires urgent and priority action to protect these increasingly endangered fish. The rivers trust movement in Wales would welcome the opportunity to work with NRW and other stakeholders to determine the most effective ways to minimise this predation.”

Posted: July 19, 2022