Your Special Site and its Future is part of our commitment to improve the way we work with Site of Special Scientific Interest (SSSI) owners and occupiers. In it, we explain what is special about the wildlife and geology on your site, and what care is needed to look after its features into the future.
All SSSIs are considered to be of national importance and we recognise the crucial role that owners and occupiers play in their management and protection. We need you to share your views and knowledge of this site with us to help safeguard it. We hope that you will find Your Special Site and its Future interesting and helpful. Please contact us if there is anything about the site and its management that you would like to discuss.
What is special about the wildlife on Wallis Moor SSSI?
Wallis Moor SSSI has numerous special features:
- Lowland wet heath
- Marshy grassland
- Marsh fritillary butterfly
- River habitat
A scattered patchwork of different vegetation types covers this whole site. Freely draining areas have dry heath, a shrubby mixture of bell heather, common heather and western gorse. Peaty ground that dries out a bit in the summer has the more interesting and unusual habitat of wet heath. Various types of heather alongside bog-moss carpets and the golden spikes of bog asphodel identify these areas. Speciality plants that also grow here are the beautiful little ivyleaved bellflower as well as the rare slender green feather-moss.
Elsewhere, species rich marshy grassland has developed over a large portion of the site. Some areas are dominated by rush pasture and brightened by tall herbs such as the white flowered wild angelica and the pungent meadowsweet. The finely cut leaves of the equally distinctive but smaller ragged robin are also found, along with the aromatic water mint and marsh St Johns wort. Although areas that are rush dominated tend to be less species rich due to increased grazing pressure. However much of this area is punctuated with waterlogged peaty ground where fen has developed, often with bogbean and marsh cinquefoil amongst the more obvious species. Stands of greater tussock-sedge spread from the overgrown channels that the flushes convene towards, resulting in the diverse river side habitats of interest that we see.
Marshy grassland habitat can also consists of large tussocks of purple moor-grass, usually where less grazing has taken place. Indicative species are the yellow flowered greater birdsfoot trefoil and the delicate white marsh bedstraw. Ubiquitous also with this type of pasture is the devils-bit scabious, the food plant for the larvae of another of the sites features, the marsh fritillary butterfly.
The rocky tors are regarded as a special geological feature. The scattered out crops and large boulders are the habitat of various lichens and the english stonecrop. Around these areas where thin soils have developed and grazing has been continuous, acid grassland has developed displaying a short turf of various grasses studded with the occasional small yellow flowers of tormentil. As well as the primary features listed, it can be seen that Wallis Moor has many habitats that are essential to the maintenance of its special wildlife interest. These include the mixture of semi-improved acid grassland, willow scrub and wet deciduous woodland, fen and swamp, flushes, dry heath and bracken, together with any straight lined or individual structures such as hedgerows, streams, ponds and even old ditches in some cases. This diversity of habitats similarly supports a wide range of species and these too are a key component of the special interest of the site. Unless it is specified below, management of this site should aim to look after all these habitats as well as the listed features of interest.
What do we want Wallis Moor SSSI to look like?
The following is a summary of our vision for the special features:
Lowland Wet Heath
CCWs aim for the wet heath is to see it cover at least its current extent and displaying a range of typical wet heathland plants and invertebrates. As well as having an abundance of purple moor-grass and heathers including cross-leaved heath. Most of the heath should be short and open enough for plants such as bog asphodel, tormentil, Sphagnum moss and short sedges to grow. As a general guide, most of the special vegetation types are at their best when the vegetation varies between ankle-height and knee-height.
Marshy Grassland
Marshy Grassland is a very rare habitat, found on more waterlogged ground. Much of the remaining marshy grassland that has not been lost during the 20th century in Britain is found in Wales. Therefore we have a special responsibility for its conservation. It is rich in plant species, and is particularly important for a number of rare butterflies, such as the marsh fritillary.
Our vision for this habitat is to see it covering roughly half of the site and displaying a colourful range of typical marshland plants and invertebrates. At least one third to a half of this will need to be dominated by purple moor-grass. The majority of these areas should be kept as an uneven, low sward, open enough for smaller plants to establish and thrive, for example the heath-spotted orchids. Bog mosses carpet the damp ground with a variety of small grasses, sedges and heathers. Herbs such as devil’s-bit scabious, tormentil and the golden spikes of bog asphodel are a colourful feature in summer, the ivy-leaved bellflower also favours this habitat. Flea sedge and carnation sedge should be found where the soil is more alkaline. Wild angelica or other tall herbs should grow among larger moor-grass tussocks in wetter areas, along with occasional marsh cinquefoil. Small runnels or soakways should support marsh St John’s wort and bog pondweed. The remainder of the marshy grassland should have an abundance of sharp-flowered rush, with plenty of marsh bedstraw and greater bird’s-foot trefoil. Some taller areas of yellow-flag iris, marsh willowherb or meadowsweet should also be present.
Marsh Fritillary
CCW aim is to maintain a large, healthy population of the marsh fritillary butterfly across a network of sites in Pembrokeshire, one of which is Wallis Moor. These rare butterflies require marshy grassland with an uneven, low sward with an abundance of leafy devil’s-bit scabious, the food plant for the caterpillars. At least one third of this marshy grassland needs to be of a type suitable for the marsh fritillary.
River Habitats
Our aim is to maintain the present distribution and extent of all semi-natural river habitats, including Wallis pond; and to ensure that a range of characteristic species is present and capable of regenerating naturally. The pond is the largest area of open water on the site and a valuable and accessible landscape feature that has significant value not only for the site’s dragonfly and damselfly populations but also for the local community as a whole.
What management is needed on Wallis Moor SSSI, and why?
Although Wallis Moor is an excellent place for wildlife, the vegetation cover we see today is not entirely ‘natural’. In fact it is the product of many decades of management. If we want to achieve the vision outlined above, it will be essential to continue management and our priority is to work with you to achieve this.
What does this mean in practice?
Some management is essential to conserve the special features. Other management actions could damage the features within a very short time. These we regard as the most important:
Grazing
Extensive grazing in spring and summer is ideal. Grazing of the marshy grassland should aim to keep the soft rush (‘reed’) and purple moor-grass tussocks in check, and maintain an uneven patchwork of short and long vegetation. Most of the marshy grassland should be kept between ankle-height and knee-height, with moor-grass tussocks grazed down short, and rush-pasture and iris or meadowsweet beds left taller. Hardier breeds of beef cattle or ponies are ideal grazers, but sheep are not as they graze the smaller flowering plants and young heather rather than the tougher grasses and scrub. The marshy grassland and wet heath should be rested in winter (provided that these areas are sufficiently grazed during the summer) to avoid excessive poaching and the need for supplementary feeding.
Burning
Winter burning is sometimes used as a traditional method of keeping coarser plants like heather, gorse, bracken and moor-grass in check, or as a traditional method of rejuvenating taller heathland areas. CCW advise against large burns on this site because of the impact this could have on the marsh fritillary butterfly. Any small patch-burning should be carried out to a plan agreed with CCW. It also causes increased dominance of purple moor-grass and western gorse, and the layer of Sphagnum moss and underlying peat could be damaged. Accidental summer burns are very damaging, and every effort should be made to prevent these from occurring.
Scrub Cutting
Some cutting of tall gorse and willow is desirable, to keep it from spreading over the areas of marshy grassland and wet heath. It would be best to cut a little each year between October and February. Herbicide treatment of stumps should not be necessary, as the current aim would be to prevent scrub from spreading rather than to remove it entirely: Willow scrub is a rich habitat and it provides shelter for the marsh fritillary butterfly in places. Should it spreads across the site the younger growth needs to be controlled by grazing or occasional cutting.
Nutrient Enrichment
Where possible, fertiliser use on land adjoining the SSSI should be limited, to avoid enriching the water that drains on to the marshy grassland and wet heath from outside the site. Other activities that could lead to enrichment problems, such as supplementary stock-feeding or storage of cut vegetation, should not take place within the SSSI.
Drainage
The marshy grassland and wet heath is dependent on the maintenance of a natural or traditional drainage pattern. No new drainage systems will be put in place, and any maintenance of existing drainage systems should be done carefully with guidance from CCW. Maintenance of the pond should also be conducted in a similar sensitive manner with guidance from CCW.
Water Quality
Good water quality is a fundamental attribute of the river habitats, directly and indirectly affecting all the plants and animals that use the river. Water crowfoot habitat and their associated aquatic plants are particularly sensitive to raised levels of nutrients (soluble reactive phosphorous and nitrates) and sediment in the water. CCW will work with relevant partners including landowners and occupiers to minimise the risk of pollution of the rivers by nutrients, silt, organic matter and chemicals.
With assistance from other organisations CCW will ensure that the water quality within the SSSI and further down the watercourse fulfils the ecological requirements of the Cleddau River Special Area of Conservation (SAC). Where appropriate, consideration should be given to the creation of buffer strips along the river to reduce the input of nutrients and sediments from adjacent land.
Water Level
The water level in the river influences a range of factors of critical importance in these seminatural river habitats including current velocity, dissolved oxygen levels, concentrations of pollutants and available habitat for associated plants and animals.
The water crowfoot habitat is susceptible to drying out in the summer during periods of low flow. Increased water levels, for instance during flood conditions, lead to high current velocities that can damage or uproot aquatic plants that compose this habitat. CCW will work in partnership with relevant organisations to ensure that there is sufficient water in the channel at all times to provide adequate conditions. Any planned works need to be discussed with us in order that we may ensure that rare plants or insects will not be affected. Existing and proposed abstractions and discharges will be assessed for their impact on the flow regime in the river.
Riverside Habitat Management
All the features of the river rely on good quality bankside and channel habitat. Good riverside habitat management should usually concentrate on preserving, and where necessary, restoring natural channel features such as gravel beds, pools, meanders and backwaters. At Wallis Moor, the watercourses are natural and should therefore be left to meander unrestricted through the site, as they currently do. Engineering works, such as highway maintenance, bridge repairs, flood defence works and the maintenance of weirs have the potential to cause significant damage to the river habitats and the water crowfoot plant community. Flood defence and other works may also adversely affect the natural features of the river by widening, deepening or straightening the channel or by the removal of sand, gravel or boulders and increasing sediment and erosion and altering the flow regime.
The water crowfoot habitat is particularly sensitive to changes in the management of the riverside habitat, for example alterations to the grazing regime. Trampling of the river bed by livestock, especially at stock crossing or cattle drinks, can damage or uproot aquatic plants and may lead to widening of the channel and subsequent lowering of the water level. Livestock also graze on water crowfoot and other aquatic plants. However, the grazing levels that have been set on the moor should not create a problem.
Modification of the river channel, excessive shading by bankside trees and changes in land drainage near the river may also affect the riverside habitats. CCW should be consulted before management operations are carried out on the riverside habitat and pond.
Bracken
Bracken continues to spread. Particularly around the rocky tors of the site and on other shallow soils near to the river. Dense bracken reduces both the wildlife interest and the forage value, and further spread should be prevented if possible. Selective herbicide application could be considered. However grazing with heavy stock in July is regarded as being the best way of keeping the bracken in check in the long term.
Recreational activities
Recreational activities are not currently thought to affect the special wildlife interest here, but increases in the number of walkers since open access could cause localised pinch point disturbance. Special attention needs to be paid to works that could impact on the special features of this site.
Finally
Our knowledge and understanding of geology and wildlife is continually improving. It is possible that new issues may arise in the future, whilst other issues may disappear. This statement is written with the best information we have now, but may have to change in the future as our understanding improves. Any information you can provide on the wildlife of your site, its management and its conservation would be much appreciated.
If you would like to discuss any aspect of your SSSI, or have any concerns about your SSSI, please contact your local CCW office.
Countryside Council for WalesLlanion House
Llanion Park
Pembroke Dock
Pembrokeshire
SA72 6DY
Tel: 01646 624000
Fax: 01646 684527