4.2 Semi-improved Grassland
Large areas of the site have in the past been used for grazing livestock and potentially there may have been some agriculture and hence input of fertilisers. These areas also include grassland for which there was some doubt as to the degree to which they may have been improvement as specified by the NCC (Blake 1989). Whilst grasses such as Cocks’ Foot (Dactylis glomerata) tend to dominate, the species composition is reasonably diverse often including herbs such as Cows’ Parsley (Anthriscus sylvestris) and Common Sorrel (Rumex acetosa). This grassland provides habitat for invertebrates such as butterflies as well as small mammals, several of which were noted during the phase 1 survey.
4.3 Unimproved Grassland
The unimproved grassland sites at Tunstall Hills generally occur in areas where topography prevented intensive agricultural use. Where possible these areas are managed by mowing to prevent invasive grasses dominating. These areas are extremely diverse relative to the improved grasslands and contain notable species such as Tor-Grass (Brachypodium pinnatum). The presence of species such as Upright Brome (Bromus Erectus) suggest these areas are predominantly calcareous, the presence of Blue Moor Grass (Sesleria albicans) suggests Magnesian limestone underlies these areas (URL 1). These areas provide important habitat to support invertebrate communities especially Lepidoptera, which in turn encourages bird life onto the site.
4.4 Woodland
The main area of woodland on site is a semi-natural Ash dominated area to the south of Rock Farm. The woodland was surveyed and the vegetation in the studied quadrates was found to be most similar to W8e (Fraxinus Excelsior-Acer campeste-Mercurialis perrennis-Geranium robertianum woodland). The goodness of fit was 72%, suggesting a good level of similarity to the standard.
By conducting the NVC survey in March identification of deciduous trees was hampered by the lack of leaves. This may explain why large amounts of Sycamore were identified when the computer software expected Field Maple, a very similar looking tree to be constant. The woodland was found to support nesting birds and also contained a large amount of dead wood making it an excellent habitat for invertebrates.
4.5 Scrubland
The scrubland is dominated by Hawthorn but contained atleast 22 other species of vascular plant. The vegetation in the studied quadrates was found to be most similar to NVC community W21 (Crataegus monogyna-Hedera scrub). The sub-community was most similar to C31.812 with a goodness of fit of 65% suggesting a fair degree of correlation with the standard samples. The scrubland provides excellent roosting and nesting habitat for birds and several species of Tit were spotted.
4. Resource Assessment –
4.1 Educational Value
The fact that part of the site is designated as an SSSI gives a clue as to it’s significance from a research and educational perspective. The geology of the site is Magnesian Limestone, which provides unique research opportunities. Due to the sedimentary nature of the rock, the site provides one of the best known areas for the study of Middle Magnesian Limestone Reef fossils. The limestone provides a time capsule of prehistoric life including examples of colour-banded gastropods (English Nature, 1995).
The area of to the south of Rock Farm provides a valuable range of habitats to demonstrate succession from grassland to mature woodland. As the area is species poor it can be used year round for teaching classes with little disturbance to wildlife. In addition there is already an extensive footpath network present. The only drawback in this area is the severity of the slope, which provides a potential hazard to young children. The site has potentially massive educational potential due to its semi-urban location, which makes it accessible to a large amount of schools. It is useful because the size of the site and the topography increase the perceived carrying capacity, which enables it to be used by multiple groups simultaneously.
4.2 Ecological Value
The ecological value of the site lies almost entirely in the unimproved and semi-improved grassland areas and the communities they support. In order to gain a full appreciation of the conservation interest at Tunstall Hills it is essential that the grassland areas are resurveyed at an appropriate time of year. Only when armed with more data about the species richness can a full assessment of the ecology of the site be made.
For the purposes of this report some attempt has been made to gauge the value of the site ecologically. However it is acknowledged from the outset that this approach is not fully objective. In order to minimise subjectivity the ‘Ratcliffe criteria’ shall be used to assess the ecological value of the site. This approach is consistent with that recommended by the Institute of Ecology and Environmental Management (Regini, 2000).
4.2.1 Size
With an area of just under 16 ha. the site would appear to be quite limited in areal extent. However when it is considered that the total national resource for Magnesian limestone grassland is only 270 ha. this puts it in perspective. The rarity of this grassland habitat means that potentially the site contains nearly 6% of the national resource. In addition the important species that are supported are not reliant on vast habitat ranges. Hence when considered in its national context the site is actually a reasonably extensive grassland site, or atleast could be with the entire site given over to grassland.
4.2.2 Diversity
The full extent of the richness of species needs to be examined by expert ecologists using more detailed survey techniques. Potentially the unimproved grasslands may have high species richness but this will not be apparent until the summer months. It is essential that the areas highlighted in the target notes have extended phase 2 surveys conducted at this time of year.
4.2.3 Naturalness
Grasslands are virtually everywhere a product of human activity, created by forest clearance and wetland drainage (NCC, 1989b). In this respect almost nowhere in the UK is truly natural. However due to the historic site use and current management practices the Tunstall Hills is especially unnatural.
4.2.4 Rarity
Magnesian Limestone grassland is categorised as nationally scarce, in addition it
is also included in the EC Habitat Directive as a habitat type of community interest (Hedley et al. 1997). Within the entire UK there is around 40000 ha. of calcareous grassland but within the Northeast region the amount of unimproved calcareous grassland is as little as 336 ha. (Hedley et al. 1997). This habitat is constantly becoming rarer, for instance semi-natural lowland grasslands in England and Wales have declined by 97% in the last 50 years (URL 2).
Within the site a number of rare species were identified all of which were found on the unimproved grassland areas particularly around Maidens Pap and the quarry site. Species of particular note include perennial Flax (Linum anglicum ssp. perenne) which is a nationally scarce plant at the northern limit of its distribution (English Nature, 1995). In addition Tor-grass (Brachypodium pinnatum) reaches its north-most limit around this region (URL 1).
One species, which is particularly rare, is the nationally scarce Blue Moor grass (Sesleria albicans). The grass is characteristic of Magnesian grasslands and is found in very few locations in the UK. In addition the grassland areas contain significant locally rare species Frog Orchid (Coeloglossum viride), Purple milk-vetch (Astragalus danicus), Lesser meadow-rue (Thalictrum minus), Mountain St. Johns Wort (Hypericum montanum) and Thrift (Armeria maritima).
4.2.5 Fragility
The fragility of lowland calcareous grasslands has long been recognised by the NNR series with 30 sites containing calcareous grasslands afforded such protection in England and Wales. In addition many lowland calcareous grassland sites will form part of the Natura 2000 network (URL 3).
Calcareous grasslands are a particularly fragile ecosystem because the vegetation is lime loving, even modest disturbances to the pH can drastically alter species composition (URL 3). The Tunstall Hills site suffers tremendously from unfettered dog walking and the input of nutrients from faces has already produced notable areas of neutral vegetation.
In addition the industrial nature of the region provides additional inputs of acid although the limestone has a good ability to buffer this. The site is also vulnerable to over use by the general public, due to its location near dense population centres. Phase 1 surveys identified many areas of vandalised rock face and trampled and burned grassland which undermines the site.
The Tunstall Hills site contains species such as Tor grass (Brachypodium pinnatum) which is at its northern limit in the region. This and other species would be especially susceptible to climatic changes. Due to the lack of connectivity with other similar sites in the area the site is vulnerable to extinction of key species. In addition because of the large amounts of improved grassland on the site the unimproved areas are vulnerable to invasion by the rapid growing Rye grass which would seriously reduce diversity.
4.2.6 Typicality
Approximately 2/3 of all Magnesian Limestone grassland in the UK occurs in the Northeast region (URL 1). Whilst species such as Blue moor grass (Sesleria albicans) are nationally rare they are actually locally quite common. In this sense the floral communities associated with the CG8 grasslands are reasonably typical of the region. The entire site at Tunstall Hills is a good example of the grassland habitats which would be expected in this area.
4.2.7 Position in geographical unit
The site forms part of a Magnesian Limestone plateau, which spreads as far south as Nottinghamshire and as far north as the Scottish border. However this area is by no means entirely grassland and what little habitat remains has become fragmented. The Tunstall Hills site is fringed by agricultural and urban areas, essentially creating an oasis in the middle of an ecological desert.
4.2.8 Potential value
As seen from the attached map, improved grassland and other areas of little ecological interest cover large areas of the site. With the topsoil removed these areas could potentially become unimproved Magnesian Limestone grasslands given enough time. This would substantially improve the ecological value of the site but would of course entail costs and forgone recreational opportunities.
4.2.9 Intrinsic appeal
Sadly to those outside the academic and ecological community the appeal of the site may be lessened by the lack of cute fluffy mammals. The intrinsic appeal to the average person of invertebrates and grasses may well be little. However the presence of wild flowers in the summer provides an attractive setting. The appeal of the site can be dramatically increased through nature interpretation and improved awareness.
4.3 Amenity value
The most common recreational activity on the site is walking especially with dogs as evident from the massive amounts of faeces. The site provides invaluable areas of flat open grassland, which can be used for multiple ball games and other sporting activities. Due to the high prevalence of CHD in the region as a whole, the importance of informal recreation for health should be given serious consideration. Recreational use of the site also provides massive social benefits to a deprived area.
5. Conclusions –
The Tunstall Hills site is a grassland area of unique geological interest, which is currently preserved through SSSI status. However phase 1 habitat surveys of the site have identified many areas of outstanding ecological value. In particular the unimproved grassland areas which contain nationally rare plant species. The site has been identified as especially vulnerable due to the lack of connectivity to other sites and the huge pressures on the site for recreational use.
Clearly the Tunstall Hills site is simultaneously providing massive benefits to the community in terms of recreation but there is potential to improve this further. Rather than impinge on recreation conservation and education at the site could actually improve the appreciation that most people derive form the site. With appropriate management the site uses need not conflict but can actually complement each other e.g. nature interpretation increasing the satisfaction of a walk for ramblers.
6. References –
Blake, C. (1989) Handbook for phase 1 habitat survey – a technique for environmental audit, Nature Conservancy Council
English Nature (1995) Tunstall Hills and Ryhope Cutting Management Statement, Sunderland City Council
Hedley, S. Clifton, S. and Mullinger, S (1997) The Durham Magnesian Limestone, English Nature Northumbria Team, No. 6
Nature Conservancy Council (1989a) Information on selected woodlands W8, W21, ENVM45 Resources Pack, University of Sunderland
Nature Conservancy Council (1989b) Guidelines for the selection of biological SSSI’s, ENVM45 Resources Pack, University of Sunderland
Regini, K. (2000) Guidelines for ecological evaluation and impact assessment, Ecology and Environmental Management in practice, 29
Treweek, J. (1999) Ecological Impact Assessment, Blackwell Science
URL References –
URL 1 – DEFRA (2002) England Rural Development Programme – North East Regional Chapter [www] http://www.defra.gov.uk/erdp/docs/nechapter/introoverview.htm
URL 2 – North East Biodiversity Forum (2000) A Biodiversity Audit of the North East [www] http://www.nebiodiversity.org.uk
URL 3 – UK Biodiversity (2001) Habitat Action Plan – lowland calcareous grassland [www] http://www.ukbap.org.uk/asp/UKPlans.aspUKListID=12
APPENDIX 3 -
Sample 1 – Scrubland
APPENDIX 4 -
Sample 2 - Woodland
Legend –
** = Species present in upper Canopy
* = Species present in lower canopy
s = sapling <2m in height
APPENDIX 5 -
Results from TABLEFIT –
Sample 1 * 5 Parameters = Nobryo Cover% Sp & c
C31.812 W21 65 | 91 59 68 75| Crat mono-Hedera scrub
C31.812 W21c 65 | 93 45 99 64| Crat mono-Hedera scrub Brach sylvatic
C31.812 W21b 65 | 86 68 62 74| Crat mono-Hedera scrub Mercur perennis
C41.41 W 8e 62 | 82 75 50 81| Fra exc-Ace cam-Mer per Geranium robert
C41.1311 W12a 51 | 79 62 43 65| Fagus syl-Merc per wood Mercur perennis
Sample 2 * 5 Parameters = Nobryo Cover% Sp & c
C41.41 W 8e 72 | 79 72 73 80| Fra exc-Ace cam-Mer per Geranium robert
C31.812 W21 60 | 82 54 72 61| Crat mono-Hedera scrub
C41.1311 W12a 58 | 79 62 61 58| Fagus syl-Merc per wood Mercur perennis
C41.32 W 8 56 | 69 68 55 70| Fra exc-Ace cam-Mer per (subcomms a-d)
C31.812 W21b 56 | 77 61 53 67| Crat mono-Hedera scrub Mercur perennis