SSSI Condition Change Briefing Note Somerset Levels and Moors May 2021 BRIEFING NOTE SOMERSET LEVELS AND MOORS SSSI – CONDITION STATUS PURPOSE This note communicates the latest information Natural England holds on the condition of the Somerset Level and Moors (SLMs), Sites of Special Scientific Interest (SSSI) following recent monitoring and review of evidence. The overall condition across all Somerset Level and Moors SSSIs* is ‘Unfavourable Declining’ due to evidence of failing water quality, most notably high Phosphate levels. * (Catcott, Edington and Chilton Moors, Curry and Hay Moors, King’s Sedgemoor, Langmead and Weston Level, Moorlinch, North Moor, Shapwick Heath, Southlake, Tealham and Tadham Moors, West Moor, West Sedgemoor, Westhay Heath, Westhay Moor, Wet Moor). IMPORTANCE OF THE SOMERSET LEVELS AND MOORS The SLMs SSSIs are internationally important as they host an abundance of waterfowl during winter months such as Wigeon, Teal, Golden Plover, Lapwing and Snipe. The SLMs are also designated as a Ramsar site for the resident invertebrates and Special Protection Area (SPA) status for the wintering birds. The SLMs are one of the most important locations in southern Britain for breeding waders. There is a variety of water dependent habitats across the SLMs, such as wet grassland, mire, lowland fen as well as rhynes and ditches that separate grazing pastures and hay meadows. These habitats are sensitive to hyper-eutrophication, a condition caused by excessive nutrient enrichment. ADVICE TO LOCAL PLANNING AUTHORITIES ON PHOSPHATES Natural England advised the planning authorities last year (letter 17/8/2020) that the unfavourable water condition of the SLMs Ramsar site, should be given due consideration before determining a planning application that may give rise to additional phosphates within the catchment. This advice reflected existing legislation and recent caselaw, including the judgement known as ‘Dutch Nitrogen’. This has significant implications for development across the catchment and Natural England is working with the planning authorities, developers and other partners to ensure that development proposals can achieve ‘phosphate neutrality’. EVIDENCE OF HIGH LEVEL OF PHOSPHATES IN THE CATCHMENTS It has long been known that the rivers flowing into the SLMs are significantly nutrient enriched, though the evidence for indisputable adverse effects on the SSSI ditch systems is relatively recent. The Environment Agency’s assessment under the Water Framework Directive (WFD) classes the majority of the SLMs water bodies as less than ‘good’, with many having ‘poor’ status for phosphates [1]. The Common Standards Monitoring Guidance (CSM) for the assessment of ditch SSSIs [2], state that, total Phosphorus (P) concentrations in water feeding these sites, and within the ditches themselves, should be less than 0.1mg P/l to be in “favourable condition”. Above this concentration there is a high risk that the adverse biological effects of nutrient enrichment will occur. While many of the SSSIs have been recorded as being in unfavourable condition or at risk in relation to water quality for some time, Natural England considers that all of the SLMs SSSIs are in unfavourable condition based on the latest available evidence: ▪ Monitoring and modelling work conducted by Wessex Water, and agreed with the Environment Agency, demonstrates that the annual mean concentrations of Phosphate in the river inputs into the SSSIs, are at least 3 times the CSMG target in numerous locations. ▪ Detailed survey work within the ditch systems of the SSSIs reflects the situation found in the feed rivers, with very high levels of total Phosphorus. (e.g. PhD research conducted by the University of Plymouth [3]. ▪ The evidence of adverse biological effects of this nutrient enrichment is becoming ever more widespread and obvious (explained further below). www.gov.uk/natural-england BRIEFING NOTE SOMERSET LEVELS AND MOORS SSSI – CONDITION STATUS EFFECTS OF NUTRIENT ENRICHMENT ON DITCH ECOLOGY Excessive nutrients lead to the overgrowth of duckweed and algae on the water’s surface, and the vigorous growth of dominant plant species on the ditch margins. The increase in duckweed and algae smothers other plant species, and creates heavy shading of the water column, depriving submerged plant species of light. This causes a decrease in plant diversity and a declining quality of habitat for animals such as invertebrates. Shading from heavy duckweed growth prevents submerged plants from photosynthesising, lowering the level of dissolved oxygen in the water, which in severe cases can kill animals requiring oxygen rich conditions such as fish. The accumulation of dying algal and plant matter on the ditch bed further contributes to deoxygenation. Figure 1. Schematic showing the effects of nutrient enrichment on ditch ecology Algae and duckweed blooms are becoming increasingly common and severe on the SLMs (Figures 2-3), quite possibly exacerbated by climate change [4]. The Internal Drainage Board have noted that ditch maintenance needs to be carried earlier in the year because of the prolific plant and algal growth blocking the ditch systems. It therefore seems that the extent of nutrient enrichment is now affecting the traditional management practices on the SLMs, quite apart from the deterioration of the nature conservation interests. Further work is required to understand better the effect of the nutrient enrichment problem on wintering and breeding birds. Whilst clear cause and effect relationships have yet to be established it seems entirely feasible that the excessive nutrients, combined with climate change, could lead to a situation where it is far more difficult, if not impossible, to maintain the supporting habitats of these bird species. www.gov.uk/natural-england BRIEFING NOTE SOMERSET LEVELS AND MOORS SSSI – CONDITION STATUS Figure 2&3. Photographs taken at King’s Sedgemoor SSSI (summer 2020) which show extremely thick mats of duckweed. It is clear there is an excessive algal and duckweed growth on the surface, an indicator of nutrient enrichment found in the SLMs. SOURCES OF PHOSPHORUS POLLUTION The relative importance of different sources varies across SSSIs. Looking across the SLMs catchments, the largest contributions are currently from the agricultural sector and water industry discharges. Pollution from urban run- off and settlements that are on non-mains sewerage may also play a significant role, especially in localised situations. Figure 4. Sources of Phosphate (Location Above Pomparles Bridge – South Drain). Percentage of phosphate sources in 2009 & predicted percentage sources in 2024 (following significant investment by Wessex Water) Historically, effluents from sewage treatment works were the largest source of Phosphates to the SLMs; in 2011 it was estimated they were responsible for c. 70% of phosphate pollution overall. However, considerable improvements have been made over the last 2 decades, and by 2024, further reductions by Wessex Water will have been implemented through investment. www.gov.uk/natural-england BRIEFING NOTE SOMERSET LEVELS AND MOORS SSSI – CONDITION STATUS The challenge now is to reduce nutrient inflow arising from agricultural practices. There is strong evidence suggesting that inputs from this sector will be proportionally greater that those from the water industry by 2024. Work is underway to systematically study agricultural sources across the SLMs catchments including major sources such as intensive dairy farming and maize growing. REMEDIES TO ADDRESS THE ISSUE The unfavourable condition of SSSIs requires ‘Remedies’ to be identified to address the water quality issue. A remedy consists of the mechanism that can be used to deliver favourable/ recovering condition; the organisations which can put these in place; and the date for implementation. To restore the SSSIs of the SLMs a multi-disciplinary and collaborative approach is required across government agencies, partners and stakeholders. This will require improved use of existing regulatory tools and incentives alongside new and innovative approaches (e.g. the EnTrade catchment markets) which will allow landowners to be appropriately rewarded for the ecosystem services they provide. However, this needs to be delivered within a setting of compliance with existing regulatory requirements. The task of reducing nutrient pollution should be dovetailed with flood risk management activities building on ‘slow the flow’ principles which are now well established in the SLMs catchments. Existing networks and partnerships are likely to play a key role in bringing remedy owners together with partners and stakeholders. New inputs of nutrients that are subject to permitting processes, such as those described above for planning applications, need to be rendered ‘neutral’ through mitigation approaches like those being developed by the Somerset Local Planning Authorities. Changing the condition status across the SLMs will facilitate further action to be taken and enable organisations to prioritise funding and workplans accordingly. It will give a clear message that nutrient pollution needs to be addressed urgently , or it will continue to negatively affect the ditch communities and associated wildlife, and without which, the situation is likely to deteriorate further as nutrient enrichment interacts with the effects of climate change. Agri-environment schemes can provide financial support to farmers and landowners to make changes to their agricultural practices. Catchment Sensitive