Slate - Slate Ecology.

• Contrary to what one would expect, the slate areas support a very rich ecological variety as various surveys have shown. In 1995, Cynefin Environmental Ltd. published an environmental statement on the Rhosydd and Conglog Quarries at Blaenau Ffestiniog. This survey was undertaken using the standard methodology of the Nature Consultancy Council Phase 1 habitat survey, which is a standardised system for classifying and mapping units of land in all parts of Britain. The habit classification is based principally on vegetation, as it is simple to observe, identify and record, as opposed to animals, being mainly small, fugitive and mobile are therefore more difficult to record and use as indicators. The habitat recorded was:-
  
  

  acid grassland;  marshy grassland;  continuous bracken;  acid dry dwarf shrub heath;  wet dwarf shrub heath;  wet dwarf shrub heath/acid grassland mosaic;  acid flush;  valley mire;  basin mire;

  swamp;  standing water (oligotrophic);  running water (oligotrophic);  natural rock exposure;  slate spoil;  buildings.

Plant communities

The vegetation of the area was recorded using the methodology developed for the British National Vegetation Classification from small representative sample areas, called quadrants.

Ornithology

Cwmorthin and surrounding the hills are particularly important ornithologically for their upland bird population.

Bird species ranked roughly in order of interest:-

• chough;
• peregrine; 
• raven; 
• ring ousel; 
• twite; 
• buzzard; 
• dunlin; 
• merlin; 
• wheatear; 
• whinchat; 
• common sandpiper; 
• dipper; 
• grey wagtail; 
• cuckoo; 
• grey heron; 
• little grebe; 
• goosander.

Mammalian ecology

It is likely that the palmate newts (Tritinus helvetceuis) occur in this area as well as the common frog (Rana temporaria). In general, though, the whole area is likely to be too cool with too little sun for ecothermic vertebrates like reptiles. The virtual lack of heather (Calluna vulgaris and Erica spp) further mitigates against, for example, the presence of adders (Vipera beris). However, it is quite possible that grass snakes (Natrix natrix) occur, especially in the vicinity of the lake, and slow worms (Anguis fragilis) might be found, especially near the ruined buildings.

The almost complete absence of trees and shrubs (except those associated with derelict buildings which are discussed below) mitigates against the presence of bats, except for the Pipistrelle (Pipistrellus pipistrellus), which probably occurs in the area. The exposed conditions are probably unfavourable for small mammals generally. The ground is almost certainly too wet throughout the year for hedgehogs (Erinaceus europea), moles (Talpa europea), and rabbits (Oryctolagus cuniculus). The only small mammal that is likely to be common and widespread is the field vole (Microtus afratis), with perhaps the pygmy shrew (Sorex minutus), and common shrew (S. araneus). However, the absence of heather means the habitat is not good for either of the species.

The stream, nant Conglog, feeding Llyn Cwmorthin looks suitable for the water shrew (neomys fodiens) but the almost complete absence of cover means that the large mammals are likely to be absent from this area, and neither the weasel (Mustela nuralis) nor polecat (Mustela putorius) are likely to occur in the area because of the high altitude and the lack of trees.

Plas Cwmorthin and other built structures

There are several built structures in the valley and in the vicinity of Rhosydd Quarry. Plas Cwmorthin is largely roofless, but might nevertheless provide possible sheltering sites for bat species. There are approximately 24 mixed mature broad-leaved and coniferous trees in its surrounds including larch (Larix decidua), Scots pine (Pinus sylvestris), ash (Fraxinus excelsor), sycamore (Acer pseudoplatanus) and beech (Fagus sylvatica). Two other built sites in the valley also have trees nearby, at the south-eastern end of Llyn Cwmorthin and at Capel Rhosydd. Only the former is likely to provide a significant habitat, as the chapel site has just 2 very isolated and exposed pines.

The Plas Cwmorthin site, particularly, is a haven, an island of shelter in an area that is generally very inhospitable for vertebrates generally. Bat species in Great Britain, apart from the Pipistrelle, requires trees and it impossible that conditions at Plas Cwmorthin could meet the requirement of two or more bat species. Furthermore, such sites with shelter from trees might act as islands for other mammal species not found elsewhere in the area. In particular, the bank vole (Clethrionomys glareolus) and the wood mouse (Apodemus sylvaticus) might occur. Some of the larger mammals mentioned elsewhere in the statement might find havens there. At some time in the past, all areas of human habitation would have contained populations of house mouse (Mus domesticus) and common rat (Rattus norvegicus), but both will now almost certainly be extinct in the study area due to the abandonment of habitation. As well as an unusually wooded and sheltered habitat for some mammal species, Plas Cwmorthin especially is an island habitat in bleak grassland for several species of bird.

The upland areas, including Rhosydd Quarry

Generally, the bleakness of both of the semi-natural, sheep-grazed, wet and acid grassland of the abandoned quarry workings and buildings at Conglog and Rhosydd mean that very few non-avian vertebrate species will be found. Fox (Vulpes vulpes) and stoat (Mustela erminea) will, however, regularly hunt over the high country, and these uplands lie within the Welsh range of the nationally rare pine marten (Martes martes) which may be found in open moorland here. It is conceivable that the old quarry buildings and mine workings might serve as sheltering places for one or more species of bat, although this is considered unlikely because of the lack of trees, and high altitude and climatic characteristics of this upland area.

Invertebrate ecology

Cwmorthin

From the southwestern end of Llyn Cwmorthin, the existing agricultural track passes an area covered by a mosaic of wet heath and acid grassland and further on, before the gate chain age 520m, it bisects an extensive area of mire. The mire area, although far from pristine due to disturbance mainly from heavy grazing by sheep, is likely to be one of the more important habitat types in terms of the inveterate fauna represented. A similar but more isolated upland valley mire at Llyn Pencraig, Caernarfon (NGR SH775585) at 295m AOD, which adjoins old lead workings was surveyed by the NCC in 1988 as part of the Welsh Peatland Invertebrate Survey, and the results have recently been published. (Holmes et. Al., 1995). Although in general, the invertebrate interest at the study area was limited, certain nationally rare, or scarce, species could be present in the mire habitat in the Rhosydd Quarry survey area. J. Sursumflexus is considered to be widespread in Welsh peatlands, and the prescence of bottle sedge at the western margin of the mire might support a population of S. litoralis.

In terms of abundance, flies (Diptera) account for a large proportion of the invertebrates which emerge from upland bogs and mires. Craneflies (Tipulidae) whose larvae, leather jackets are generally highly prone to desiccation are particularly abundant….At the time of visiting the survey area large numbers of Tipulidae were observed emerging from parts of the mire and wet heath and acid grassland habitats. Populations of upland insectivorous passerine birds, such as meadow pipits (Anthus pratensis) and whinchats (Saxicola ruberta) can be highly dependent upon the food source provided by the characteristically high emergence of tipulids from acid upland wetlands….The presence in the vicinity of the survey area of raptors such as peregrine falcon (Falco peregrinus), which prey upon passerines such as meadow pipits and whinchats, could be indirectly linked to the abundance of emergent tipulids from mires such as those near Llyn Cwmorthin.

Conglog and Rhosydd Workings

The majority of the land in both of these areas consists of heavily grazed acid grassland. This type of habitat is probably the most estensive in the uplands of north Wales. The characteristic invertebrate fauna are of little or no conservation interest. There is however, an extensive area of inaccessible dry heath that is apparently sparsely grazed situated on the natural rock outcrops to the east of Rhosydd Quarry. The scarcity of well established heath in north Wales probably renders this area of some importance. Many invertebrate species are associated with heather or the closed canopy heathland habitat and do not occur in more heavily grazed habits where heather is replaced by grassland.

Twll East and Twll West

Due to adverse weather conditions at the time of the site visit, only the extensive mire area to the north and east of y tyllau was observed. This wetland area is considered to be of similar importance to the mire around Llyn Cwmorthin.