Threats to the upper Glaven ecological network: Dong Energy cable route
River Glaven Conservation Group
The Upper Glaven system consists of a mosaic of very valuable aquatic, semi-aquatic and terrestrial wildlife habitats. In addition it harbours many important species of high conservation importance.
Combinations of habitat loss (hedgerows, hedge margins, meadow, wet and ancient woodland), associated habitat fragmentation and high potential for water pollution (due to soil and nutrient loss to watercourses) make the proposed Dong Energy cable a major threat to wildlife, not just locally, but for the wider Glaven ecological system, including its highly designed estuary.
This document makes a preliminary attempt at outlining these threats and in turn the need for careful planning and consultation with local landowners and stakeholder groups. To avoid serious damage to species diversity, landscape aesthetics and indeed public relations in this beautiful and ecologically sensitive part of Norfolk, considerable efforts need to be made to minimise the risks of environmental damage both during the construction phase and afterwards. In this respect we urge dong to take the HVDC approach to power transmission for the cable, hence minimising severe damage to very high quality environments, peoples enjoyment of the area and overall well- being and in turn preserving Dong’s good environmental reputation. We strongly feel that dong will suffer considerable reputational damage is the HVDC approach is not taken and if the cable corridor is wide and under construction for a long time. Key factors are the size of the disturbed area and the length of time that the works will last, both of which need to be minimised. We also propose that considerable financial resources will need to be put into mitigation works and compensatory habitat creation and restoration along and close to the proposed route.
River Glaven Conservation Group (RGCG)
The River Glaven Conservation Group (RGCG) is an award-winning local conservation group which was formed in 1999. The group is composed of local inhabitants, naturalists, scientists, fishermen and landowners, all of whom are concerned about the well-being of this beautiful Norfolk river and its tributaries. The aims of the group are to protect the River Glaven from pollution and degradation, improve river water quality and conserve and restore important habitats for wildlife within the river corridor. The RGCG’s mission
statement is to “work in friendly collaboration with landowners, farmers and conservation organisations to conserve all aquatic habitats in the Glaven catchment”.
The Glaven catchment
The River Glaven (17 km in length), is a lowland (<100 m a.s.l.) calcareous river set in a catchment dominated by arable agricultural land, with an associated mosaic of semi-natural habitats, including patches of ungrazed and grazed fen, wet floodplain meadows and a mix of deciduous and coniferous woodland. The catchment (Figure 1) contains several on- stream and near-stream artificial lakes (dug during the last three centuries), networks of drainage ditches, and 100s of small (generally <40 m diameter) farmland ponds (largely marl pits), excavated in the eighteenth-nineteenth centuries. Aquatic habitats and species in the Glaven system face an array of threats common to many catchments in lowland Europe: nutrient-enrichment, habitat disturbance, excessive siltation, reduced connectivity and invasive species. Similarly, linked terrestrial habitats have been compromised and continually threatened by agricultural intensification (and associated habitat loss), fragmentation and use of agro-chemicals. In this paper the Glaven catchment (hereafter called the Glaven system) is seen as an inter-connected ecological landscape (Sayer, 2014), where boundaries between headwater and coastal habitats and between aquatic and terrestrial places are blurred – an integrated approach increasingly favoured in modern-day conservation planning, including the North Norfolk Local Development Framework (2008). This approach reflects both an improved understanding of how natural environments functioned prior to major human disturbance and a recognition of the high pressure placed on land due to development and agricultural expansion.
Figure 1. River Glaven catchment (North Norfolk, eastern England) showing the distribution of Eurasian otter and European eel. Location of the Norfolk Rivers Trust and RGCG Upper Glaven project as illustrated in Figure 7 is shown by the inset box close to the village of Bodham
Over many years the Glaven ecological system has been the focus of intensive conservation efforts, driven in particular by the RGCG. More recently, working with the RGCG, the Norfolk Rivers Trust (NRT) have organised several aquatic conservation projects, while farmland ponds in the catchment have been the focus of landscape-scale restoration work as part of the Norfolk Ponds Project (NPP), a partnership project which includes the University College London (UCL) Pond Restoration Research Group, Norfolk Wildlife Trust, Norfolk Farming and Wildlife Advisory Group, NRT and many other partners in Norfolk.
Despite many environmental pressures and to a large extent propped up by high existing connectivity and habitat integrity, the Glaven system possesses a number of key habitats and species. Much research and fieldwork has gone into the following analysis of the Glaven’s ecology, which is especially focused on headwaters in the Baconsthorpe-lower Bodham area which will be affected by the Dong Energy cable route. An important consideration in what follows is that the quality of the Glaven’s headwaters both in terms of terrestrial and aquatic habitat and land-use, directly influence the quality of its highly designated estuary at Cley-Blakeney. The area has been even been used to illustrate the potential of an “aquatic landscapes” approach to nature conservation (Sayer, 2014).
The Glaven headwaters
The upper Glaven system in the Baconsthorpe-Lower Bodham region is an extremely scenic area. Despite being dominated by arable agriculture, it is unusual for Norfolk (and indeed N. Norfolk) in being dominated by small fields surrounded by tall, old hedges, giving the area an “old rural feel”. Indeed, a recent (February-March 2017) survey in the lower Bodham area around Pine Farm (TG 1175 3950) revealed an astonishing density of hedge still present (Figure 2). In addition the upper Glaven possesses several (50+) small and old (generally >200 years) farmland ponds, most of which have their origins as marl-workings of the eighteenth-nineteenth centuries (Sayer et al. 2013).
There are two small Glaven tributaries in this this area which converge below Selbrigg Pond, the northernmost of which starts at Franklins Farm (TG 1280 3900) and the southern of which emerges from springs at Pond Farm (TG 1330 3860). The southern tributary flows through Baconsthorpe Wood (TG 1250 3850), a linear fragment of wet ancient woodland, which recent surveys (2017) show to be of exceptionally high importance from a botanical perspective in Norfolk (Figure 3). In particular, the upper part of the wood supports extensive populations of Bluebell (Hyacinthoides non-scripta), Early Purple Orchid (Orchis mascula), Wood Anemone (Anemone nemorosa), Townhall Clock (Adoxa moschatellina) and of particular importance Herb Paris (Paris quadrifolia). The latter plant that has undergone a major decline in England since the 1930s (Jacquemyn et al. 2008), giving it the status of “Least Concern” according to IUCN Red List criteria. Similarly valuable ancient woods fragments are also present at “Alder Carr” (TG 1280 3810) where Herb Paris has also been recently (2007) recorded, Hempstead Wood (TG 1140 3840), along an old Loke that follows the edge of a field to the North of Beckett’s Farm (from TG 1085 3785 to TG 1085 3835 and Figure 4) and importantly just to the south of Pine Farm (small woodland fragment no name – TG 1160 3925), within the path of the proposed bale route Thus, despite considerable agricultural intensification, a network of ancient wet woodland habitats persist in this area, in turn forming an ecological corridor closely associated with the southern tributary, and other small streams and seepages that feed the Glaven.
Figure 2. Survey of hedgerows and hedgerow structural composition in the Bodham-Lower Bodham area, in close proximity to the Dong Energy cable route (RGCG Spring, 2017). The proposed cable route as of this time in marked
Figure 3. Baconthorpe Wood – a sensational strip of ancient woodland containing the eastern- most tributary of the River Glaven (upper) with extensive populations of Wild Garlic Allium ursinum (middle) and the rare plant Herb Paris Paris quadrifolia (lower)
Figure 4. Old Loke to the North of Beckett’s Farm Pond (from TG 1085 3785 to TG 1085 3835) – an avenue of coppiced hazel lined with bluebell Hyacinthoides non-scripta and other ancient woodland plants
As well as possessing important old woodland habitat, this area harbours a mosaic of important wetland habitats, including Baconsthorpe Castle Moat and several marl-pit ponds, five of which have recently (post-2011) been successfully restored by the NPP (see Figure 5 for an example). In particular recent fish surveys as part of the Heritage Lottery Fund (HLF) funded Glaven eel project and the Norfolk Crucian Project (Sayer et al. 2011) show Baconsthorpe Castle Moat to contain good populations of the Critically Endangered
European Eel (Anquilla anquilla) and the Crucian Carp (Carassius carassius), a Biodiversity Action Plan (BAP) species in Norfolk. European eel is also present at Hill House Farm Pond (TG 11298 39469) very close to the cable route. Crucian carp populations are also found in three other farmland ponds in Bodham (n=2) and nearby Hempstead (n=1) respectively. Farmland ponds in the upper Glaven area, especially those already restored by the NPP, are of high importance from the perspective of the European protected Great Crested Newt (Triturus cristatus) with some 13 pond populations known for the area around Bodham- Baconsthorpe (Sayer, 2014; Sayer & Shilland, unpublished data), likely making it a key centre for the species in Norfolk. Some of these ponds are very close to the cable route, with one pond (at TG 11722 38740) located within the proposed route, and many others very close to it. In addition, extensive recent surveys by the UCL Pond Restoration Research Group show the upper Glaven pond network to be of high importance to many other biological groups, including aquatic plants, dragonflies (some 24 species), farmland birds and bats which use ponds as key sources of insects during the breeding season. In particular pond restoration work has resulted in a major enhancement of pond landscape ecological quality in this area (Sayer, 2014). It should be noted that the proposed cable route goes straight through some of these ponds and other ponds are also very close to the route (see below).
Figure 5. Shooting Close Pond (TG 1135 3780), Upper Glaven system in 2017 – a pond restored to open water, plant-dominated conditions by the Norfolk Ponds Project in 2014. This pond supports a large population of Great Crested Newt Triturus cristatus
Finally, according to local people, the streams above Selbrigg Ponds were known to support the endangered White-clawed Crayfish (Austropotamobius pallipes) at least until the 1970s.
The River Glaven currently holds the largest self-sustaining population of white-clawed crayfish in south-east England and is consequently of European importance for the species. Responding to the loss of crayfish from the upper Glaven, and as part of the thriving Essex, Suffolk and Norfolk white-clawed crayfish project, white-clawed crayfish was returned to upper river above TG 1070 3890 in September 2014 with some 100 individuals stocked into the river from a donor site at Little Thornage. This upper Glaven “Ark” site may be of crucial significance to the survival of the white-clawed crayfish in the wider Glaven catchment and indeed Norfolk more generally, given the ever present threat of signal crayfish invasion (see below).
Thus, for multiple reasons, from the perspectives of landscape quality, ecological connectivity and protected species, the upper Glaven system is of crucial importance and needs to be protected and enhanced in future years. Currently, a designated Glaven Valley Conservation Area (GVCA) extends as far as Hawksmere Lake (Figure 6), but a section of forest and wet woodland links this area directly to the upper Glaven as described here. Indeed a wet woodland corridor (especially Baconsthorpe Wood – Figure 6) and a series of farmland ponds provide high connectivity with the GVCA and the lower Glaven and in a visual and landscape sense with the Norfolk Coast Area of Outstanding Natural Beauty (AONB). There is a very strong case for expanding the GVCA and the RGCG are currently lobbying in this direction, especially encouraged by Policy EN9 in the North Norfolk Local Development Framework – Core Strategy (2008). This policy states that all development proposals should “minimise the fragmentation of habitats” and in turn aims to “maximise opportunities for restoration, enhancement and connection of natural habitats”. Clearly the Dong Energy cable provides major potential threats in respect to this policy. Appendix B of the North Norfolk Local Development Framework – Core Strategy (2008) highlights priorities for a North Norfolk Ecological Network celebrates the ecological network ideas that are at the heart of this document. It recognises that North Norfolk comprises several distinctive landscapes and to the east of the region “arable landscape that comprises more woodland (including ancient woodlands) with ancient hedgerows, veteran trees and ponds”. This wording epitomises the upper Glaven as outlined here. Hence there is a strong strategic planning lead to minimise damage to this aesthetically, ecologically and indeed culturally important area.
A further important project, from the perspectives of ecological connectivity and linkages between the upper and lower Glaven is the “Upper Glaven” component of the NRT Nine Chalk Rivers Project. This important project aimed to reduce silt and nutrient pollution to the Glaven through the creation of silt traps, buffers and various agri-environment measures in the Lower Bodham-Baconsthorpe area (see Sayer, 2014 and inset in Figure 1). It also had the aim of increasing habitat connectivity in the area around the proposed Dong cable route as illustrated in Figure 2 (and again discussed in Sayer, 2014). In this respect and with much landowner goodwill, meadow restoration, installation of buffers and pond restoration led to the creation of a green corridor and enhanced connectivity between ponds, the stream and meadow habitats. The Dong cable also greatly threatens these above conservation efforts.
Figure 6. Glaven Valley Conservation Area (from North Norfolk Local Development Framework – Core Strategy, 2008)
Figure 7. Bodham area in the upper reaches of the River Glaven (Norfolk, eastern England) in 2004 (a) and in 2014 after landscape-scale conservation measures (b). See inset in Figure 1 for location of the “Upper Glaven Project” in the Glaven catchment
Dong energy cable and threats to the upper Glaven system
The proposed Dong energy wind-farm development poses a number of clear threats to the quality and ecological integrity of the upper Glaven’s landscape and wildlife. Some of these concerns are outlined in a previous RGCG letter (dated 27/3/17) and are expanded upon here.
Fine sediment pollution
Firstly, as stated in the recent 2017 RGCG strategy document (Shepherd, 2016), perhaps the greatest threat to the ecology of the River Glaven is fine sediment pollution, with headwater areas of crucial significance to this problem. A key issue here is the in-wash of topsoil (and associated nutrients and pollutants) from arable fields to the stream system especially from bare and or recently harvested fields in winter. In general fine sediment finds its way to the stream system during high rainfall events via a dense network of small rural roads – a common issue in lowland agricultural areas of the UK. Fine sediment pollution is likely responsible for many ecological negatives in the lower Glaven, including fish kills and population declines, as documented by a number of recent studies (Champkin et al. in press) and importantly by Environment Agency fish monitoring. Of particular note in this respect is a section of river between Selbrigg Pond and Hawksmere lake, where a 2016 survey as part of the Glaven eel project (Perrow et al. unpublished data) revealed a complete lack of river fish, including key species such as Brown Trout (Salmo trutta) and European Bullhead (Cotus gobio) that would normally be resident in this area. Recently, documented major fine sediment pollution events (2010, 2013, 2016) are likely responsible for this fish decline and also threaten the white-clawed crayfish, including the recently established upper Glaven White-Clawed Crayfish “Ark” (see above).
The RGCG is very concerned regarding likely issues of silt run-off into river tributaries after heavy rainfall events when the land is opened for cable burial. This is of particular concern
where two important upper Glaven tributaries are crossed at Lower Bodham and Baconsthorpe close to Pine Farm (TG 1175 3950). We know that the contours at Lower Bodham are vulnerable to run-off into the river, with several major silt run-offs documented by the RGCG and local landowners over the last 20 years. Moreover, there is a recent history of wind farm cable-induced pollution with a major sediment loss event documented by the RGCG and the Environment Agency in response to the activities of Carillion in 2010 (Figure 8). Note that white-clawed crayfish introduction site is are found just 1.5-2 km downstream of this point, where the Bodham-Baconsthorpe tributaries coalesce below Selbrigg Pond (TG 1065 3895).
Nutrient-enrichment and pollution
In addition to fine sediment pollution the upper Glaven also sets the tone for the river and its associated lakes and estuary in terms of nutrient-enrichment pressures. Diffuse pollution in the upper Glaven, especially by nitrate, but also by phosphate, which is supplemented by inputs from a small sewage treatment works above Baconsthorpe Castle is of key importance to water quality in the Glaven. The ill effects of eutrophication in the Glaven system, include blooms of phytoplankton and in particular mass surface coverings of filamentous algae (especially Cladophora sp. aka “blanketweed”) in on-stream lakes and ponds, resulting in declines in macrophytes and hence conservation value. In the river eutrophication results in dense growths of filamentous algae on gravel and silt substrates and in turn a decline in the quality of invertebrate and fish spawning habitat, with this especially the case in low flow years. Additionally, eutrophication is responsible for ecological degradation in some of the Glaven’s most highly prized conservation sites including the Blakeney Freshes grazing marshes SSSI (a mosaic of freshwater ditches) where duckweed-dominance of ditches is a prominent and negative feature (Goldsmith et al. 2004; Sayer et al. unpublished data 2017) and the Glaven’s much-designated estuary – Blakeney Pit (Glaven estuary), which failed to achieve Good Environmental Status (GES) under the EU Water Framework Directive (WFD) in 2015. High nutrient concentrations in Blakeney Pit are associated with blooms of toxin-producing planktonic algae (Campos et al. 2017) and upper Glaven nutrients will undoubtedly contribute to this problem. Notably, and again with strong potential links to poor water quality and fine sediment ingress to the upper Glaven system Blakeney Harbour Shellfishery has failed to comply with Guideline faecal coliform standards under Shellfish Water Protected Areas (England and Wales) Directions since 2011 (Environment Agency 2015 as stated in Campos et al. 2017).
The Dong cable works, in potentially disturbing soil and exacerbating diffuse pollution (as in Figure 8) therefore poses a major threat to the water quality of the entire freshwater and estuarine system. Key issues here are the scale of the cable trench, length of time that the works take place (both need to be minimised) and the degree to which careful measures are put in place to reduce soil and nutrient loss.
Fragmentation of habitats for key species
Many species migrate or ideally need to move over large areas to access sufficient habitat or to complete life cycles. As a consequence, the state of the upper Glaven is critical to the health of populations of several key species in the wider system. In particular, given the high density of farmland ponds in this area, there can be no doubt that the upper Glaven is of high importance to populations of dragonflies and amphibians at the catchment-scale. As an example of how this effect may work, June 2017 saw a hatch of 50 or more Emperor
Dragonfly (Anax imperator) individuals at NPP restored Beckett’s Farm Pond (TG 1110 3765) and given that any one pond is unlikely to support more than a few individuals of this large species, a landscape-scale colonisation event can clearly be envisioned. Among many other wetland and farmland birds, the upper Glaven also supports Barn Owl (Tyto alba), Kingfisher (Alcedo atthis) (especially associated with ponds) and Common Snipe (Gallinago gallinago), affording important contributions to the survival of these species in the wider Glaven system. Further, many important mammals use the upper Glaven corridor as key habitat including Eurasian otter (Lutra lutra) (Almeida et al. 2012) and Red Deer (Cervus elaphus).
Species potentially affected by habitat fragmentation linked to the Dong cable are many. The area supports a large number of mature oak trees, many of which will be on the cable route. Certainly the area is of high the importance to amphibians and reptiles. Great Crested Newt, Smooth Newt (Triturus vulgaris), Common Frog (Rana temporaria), Common Toad Bufo bufo) will use hedgerow and woodland habitat as corridors through the farmland and are widely associated with the many farmland ponds in the area (and see above). In addition Adder (Vipera berus) is found in Bodham Woods (regularly seen by local people) and Bodham Common that again links directly to upper Glaven corridor (Figure 2). The Dong cable will again directly disturb Adder and Adder habitat. Important mammals that can be expected to suffer due to the works are Eurasian Otter and Red Deer, both of which are commonly seen in the upper Glaven area, with otter using the farmland pond network in the area (Almeida et al. 2012, 2013) and Red Deer especially associated with Baconsthorpe Wood corridor, where the species is regularly seen by local people. The protected Water Vole (Arvicola amphibius) has also been recorded in the area very recently, especially close to Pine Farm (TG 1175 3950), which will be directly affected by the proposed cable route. In addition the Bodham-Lower Bodham area, due to a high density of old hedges (Figure 2) and mature oak trees, is likely of high importance for bats and in this respect the RGCG and NPP are organising some preliminary surveys.
Figure 8. One of a number of major silt pollution events associated with the Sheringham shoal cable laying works (undertaken by Carillion plc) in 2010 (right hand photo below taken on 23/2/2010). Location: stream flowing into Baconsthorpe Castle Moat (Photos C. Sayer).
Loss of old hedgerow and woodland habitat
As outlined above the upper Glaven area has the character of old Norfolk countryside, due to a high density of tall and old hedges that surround generally small agricultural fields and pastures. In particular, the proposed cable corridor will remove considerable amounts of old hedgerow (and associated hedgebanks), many prize oak trees (the area is renowned for its mature oaks) which will not be suitably replaced by new hedge planting after the works are completed. In addition the cable route will result in a major break in the important Baconsthorpe Wood ecological corridor, resulting in degradation to woodland habitat (plants and invertebrates) and interrupting the migration of many species (see above).
In short the highly connected upper Glaven ecological corridor links directly to the lower Glaven and GVCA and the Cromer-Holt ridge, a key and distinctive landscape unit that majorly defines the Norfolk Coast AONB. Key habitats and key species will undoubtedly be greatly affected by the proposed Dong cable route as it intersects the upper Glaven and many existing conservation projects aimed at enhancing the connectivity and ecological quality of the upper Glaven (Upper Glaven Project of the RGCG, Norfolk Ponds Project) and the Glaven catchment more generally will be directly compromised. Given these very strong landscape and ecological grounds, we are keen to see minimisation of the works area and equally the time it takes to undertake the works. HENCE WE URGE DONG TO TAKE THE HVDC APPROACH TO POWER TRANSMISSION FOR THE CABLE, HENCE MINIMISING SEVERE DAMAGE TO VERY HIGH QUALITY ENVIRONMENTS, PEOPLES ENJOYMENT OF THE AREA AND OVERALL WELL-BEING AND IN TURN PRESERVING DONG’S GOOD ENVIRONMENTAL REPUTATION. WE STRONGLY FEEL THAT DONG WILL SUFFER CONSIDERABLE REPUTATIONAL DAMAGE IS THE HVDC APPROACH IS NOT TAKEN AND IF THE CABLE CORRIDOR IS WIDE AND UNDER CONSTUCTION FOR A LONG TIME. We also recognise that similar, very strong arguments, can be made for other parts of the cable route as it intersects the Rivers Bure and Wensum and we will be working with interested parties in these systems too. Equally we are keen to see a high level of mitigation and habitat creation and restoration as compensation. Finally, the RGCG would like to be included as a full consultee as part of the planning process.
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