INKLE MOOR: a forgotten fen in a corner of Yorkshire.
Inkle Moor on the western periphery of Thorne Moors SSSI is a site long known to naturalists as one from which a number of Red Data Book invertebrates have been recorded. An opportunity arose in 2011 for collaborative working to deliver an Invertebrate Survey of the ‘arrow shaft’ section of Inkle Moor as part of a wider habitat creation scheme on reclaimed agricultural land.
The impetus to undertake an invertebrate survey was the re-discovery of a much reduced remnant population of Lathyrus palustris (Marsh Pea). This species was known from the Thorne Moors area but the number of plants had dropped significantly since 1986 to around 30 in 2011 which triggered a clarion call for action to halt the decline.
The lagg fen surrounding lowland raised mires is a habitat which has rarely survived in Britain as drainage and cutting for peat has largely lead to its conversion to arable or at best rough pasture. At Thorne in South Yorkshire these processes around and on the once extensive peatlands of Thorne Moors and the contiguous areas of Crowle and Goole Moors have been further exacerbated by the practice of warping, the embankment and flooding with silt-rich waters from the adjacent rivers to raise the land for farming (Lillie 1997). Warping was extensive and virtually ubiquitous around what is now the Thorne Moors NNR and it is surprising that a single narrow strip adjacent to Durham’s Warping Drain on the west side of the Moors escaped flooding with nutrient-rich sediment from the Turnbrigg Dike. At the risk of being accused of romanticising perhaps it was a Yorkshire woman either too financially stretched to afford the engineers levy or keen that the site retain its interesting nature and landscape value as a local ‘cable’?
Known as Inkle Moor (Inclesmor), this small fragment of approximately 5.9 hectares or 14.59 acres of a once more extensive area of degraded lag fen, which until drainage, extended north westwards to the levees of the river Went and later to the artificial course of the Turnbrigg Dike. To the south, former arable on warp has recently been put down to a ley of clover and grasses, grazed by sheep, and northwards both pasture and arable abuts the overgrown hawthorn hedges which fringe the site. Westwards the boundary is influenced by the embankment and ballast of the former rail connection to Thorne Colliery, and a bank of clay silt, part of the warping process, separates the site from Thorne Moors to the east. The absence of warp means that Inkle Moor lies up to 0.5m below the adjacent land but the pumping down of adjacent ditches has until recently precluded the ingress of nutrient-rich waters from arable and pasture onto the site and it has maintained much of its poor fen vegetation.
Inkle Moor is terminated at its western end by an ‘arrowhead’ which has been formed by the junction between the Thorne Colliery branch-line and the railway line between Hull and Doncaster. The construction of this railway and the associated embankments has meant that the man-made drainage system in this area has been damaged. This has resulted in the water table here being backed-up behind (East) of the railway lines. The area which is drained by the former network of drains under the railway is known as Whaley Balk and most of this land is now drained via Black Drain Internal Drainage Board’s (IDB) system of drains which take water away to the River Don, two miles away to the west. However, a substantial proportion of the water now makes its way South, around Thorne Colliery and into the Doncaster East IDBs drainage district. The fact that the drainage has been impeded by the railway lines here, combined with the fact that Inkle Moor remained un-warped (the process of allowing the area to flood at high tide allowing silt to accumulate on the land) has led to this area of ground becoming wetter than the surrounding farmland and has encouraged the growth of reeds and willows along the shaft of the arrow. The arrowhead itself has a tall embankment along the north side on which a tramway was in use at one time. This raised linear feature ensures that the hydrology of Whaley Balk is separate from that of the Durham’s Warping Drain sub-catchment to the north. Because of its isolation and lack of warping and draining, Inkle Moor is now the only remaining area of the once much larger area of lagg fen that once surrounded Thorne Moors. Inkle, as a result, is a unique relic of the past and contains a number of relict species that probably existed in the lagg fen that once surrounded the mire.
An intensive invertebrate survey took place over a six month period. Authorisation, approval and access permissions to undertake the survey was through the management service provision of the local Internal Drainage Board and Natural England. Although Inkle Moor is a Site of Special Scientific Interest (SSSI) it is not part of the National Nature Reserve as it is privately owned. This fact may well have been key to the preservation of the habitats and perhaps more importantly the species present on this small but important area of lagg fen. Eventually, the owner was traced and also gave consent for the survey.
Every week a series of pitfall and aerial traps were emptied and reset and the material sorted. Supplementary collecting added material to the mass which was at the end of the season dispatched to experts for determination. The statistics are quite astonishing, the Coleoptera (beetles) involved in excess of 7000 specimens which resulted in 248 species being identified. A number of species of conservation interest were identified including Agabus striolatus. This species was added to the Thorne Moors list by Hammond and Merritt in 2008 and this water beetle is only otherwise known from small areas of fen carr in the Norfolk Broads (Foster 2000) which are at risk from saline inundation. Examples dissected by Foster (1982) showed poorly developed flight muscles and current populations probably descend from those noted in mid-Holocene deposits by Whitehouse (1997) in basal peat less than a kilometre north of Inkle Moor. The remaining population therefore has considerable significance in terms of any microevolutionary study utilising their DNA. A. striolatus is classified as ‘Vulnerable’ by Foster (2010) in the latest revision of UK conservation status of water beetles.
The samples of Auchenorrhyncha included a new species to Britain – the Cicadellid Streptanus okaensis. In addition the samples also appear to have provided the first Yorkshire record of the Cicadellid Athysanus argentarius (a nationally scarce species that has extended its range considerably in Britain over the last several or more years) and the fourth Yorkshire record for the Local Delphacid Paraliburnia adela. Also present was another nationally scarce Cicadellid – Agallia brachyptera previously recorded from Inkle Moor (and the only previous VC63 record) by Peter Skidmore in 1990.
Inkle Moor had long been recognised as an important remnant lag fen. The re-locating of Marsh Pea and the significance of the water beetle assemblage which included Agabus striolatus endorsed this assessment, in addition that a number of other Red Data species identified from the survey and a new British species really did highlight the need for the site to be safeguarded. This was recognised by CCT, who were as the conservation charity best placed to act and Trustees stepped up to the mark and purchased the site to ensure that this special landscape feature and its inhabitants are safeguarded for the future. The few words which inform of his acquisition make such actions sound easy. It was not, but where there is a will there is a way as they say and Ian Carstairs and others worked behind the scenes to deliver tangible conservation. No fund raising appeal, no grand gesture just careful negotiations with the absentee landowner who was fortunately sympathetic to the case. Funds were found from CCTs own reserves as Trustees believed that it was crucial that this site was acquired and managed sympathetically for the special interest briefly alluded to in this case study information.