North Somerset and Mendip Bats special area of Conservation (SAC)-Guidance on Development. Draft Supplementary Planning Document

Annex

Annex 1:  Details on the North Somerset and Mendip Bats Special Area of Conservation

A1.1     The North Somerset and Mendip Bats SAC is made up of 7 component Sites of Special Scientific Interest (SSSI):

  • Compton Martin Ochre Mine SSSI (B&NES)
  • Banwell Caves SSSI (NSC)
  • Banwell Ochre Mine SSSI (NSC)
  • Brockley Hall Stables SSSI (NSC)
  • King’s Wood and Urchin Wood SSSI (NSC)
  • The Cheddar Complex SSSI (SCC & SDC)
  • Wookey Hole SSSI (SCC & MDC)

A1.2     This site in south-west England is selected on the basis of the size of population represented (3% of the UK Greater Horseshoe bat Rhinolophus ferrumequinum population) and its good conservation of structure and function, having both maternity and hibernation sites. This site contains an exceptionally good range of the sites used by the population, comprising two maternity sites in lowland north Somerset and a variety of cave and mine hibernation sites in the Mendip Hills. The limestone caves of the Mendips provide a range of important hibernation sites for Lesser Horseshoe bat Rhinolophus hipposideros.

A1.3     Greater Horseshoe bats are long lived (over 30 years in some cases) with the bats remaining faithful to these important roosting sites, returning year after year for generations.

A1.4     In terms of physical area, the SAC designation applies to a very tiny element of the habitat required by the bat population (the maternity roosts and entrances to their hibernation sites).  It is clear that the wider countryside supports the bat populations because of the following combination of key elements of bat habitat:

A1.5    The area has to be large enough to provide a range of food sources capable of supporting the whole bat population; the bats feed at a number of locations through the night and will select different feeding areas through the year linked to the seasonal availability of their insect prey:

SAC bats regularly travel through the administrative areas of the Somerset authorities between feeding sites and their roosts via a network of established flyways. Radio tracking of Greater Horseshoe bats[1] has shown that they also travel greater distances between Brockley Hall Stables and Cheddar Gorge and further afield to the Bath and Bradford on Avon Bat and Mells Valley Bat SACs

  1. at certain times of the year, for example, in the spring and autumn between hibernacula and maternity sites, and in the autumn to mating sites occupied by single males. Bats need a range of habitats during the year in response to the annual cycle of mating, hibernating, giving birth and raising young;
  1. It follows that SAC bats need to be able to move through the landscape between their roosts and their foraging areas in order to maintain ‘Favourable Conservation Status’. They require linear features in the landscape to provide landscape permeability. Compared to most other bat species, the echolocation call of the Greater Horseshoe bat attenuates rapidly in air due to its relatively high frequency. This means it cannot ‘see’ a great distance and is one reason why it tends to use landscape features to navigate, such as lines of vegetation (e.g. hedgerows, woodland edge, vegetated watercourses, etc.). The Greater Horseshoe bat will tend to commute close to the ground up to a height of 2 metres, and mostly beneath vegetation cover. Radio tracking studies[2] and observations in the field confirm that Greater Horseshoe bats will regularly use the interconnected flyways associated with lines of vegetation. Further studies[3] have shown that landscapes with broadleaved woodland, large bushy hedgerows and watercourses are important as they provide habitat continuity. Habitat is therefore very important to SAC bats in terms of quality (generation of insect prey) and structure (allowing them to commute and forage);
  1. SAC bats are sensitive to light and will avoid lit areas[4]. The interruption of a flyway by light disturbance, as with physical removal/ obstruction, would force the bat to find an alternative route which is likely to incur an additional energetic burden and will therefore be a threat to the viability of the bat colony. In some circumstances, an alternative route is not available and can lead to isolation and fragmentation of the bat population from key foraging areas and/or roosts. The exterior of roost exits must be shielded from any artificial lighting and suitable cover should be present to provide darkened flyways to assist safe departure into the wider landscape[5].
  2. The feeding and foraging requirements of the Greater Horseshoe bat have been reasonably well studied in the south west of England and Europe[6]. From this work we know that most feeding activity is concentrated in an area within 4km of the roost (juvenile bats will forage within 3km at a stage in their life when they are most susceptible to mortality). The most important types of habitat for feeding have been shown to be permanent pasture grazed by cattle or sheep, hay meadows, and wetland features such as stream lines and wet woodland. Depending upon the availability of suitable flyways and feeding opportunities, most urban areas will provide limited Greater Horseshoe bat habitat. The North Somerset and Mendip Bats SAC situation is unusual in that the wintering Greater Horseshoe bat population mainly hibernates in caves in Cheddar Gorge and Wookey Hole, which are located close to urban areas and are subject to visitor disturbance. Commuting routes follow the urban edge, the Cheddar Yeo and within the urban area of Cheddar.[7]

A1.6     The populations of bats from the North Somerset and Mendips SAC are currently under particular stress from a number of factors, particularly the number of development applications and proposals on the urban edges of Yatton, Congresbury, Nailsea and Cheddar.  

Greater Horseshoe Bat (Photo Frank Greenaway: Courtesy Vincent Wildlife Trust)

 

___________________________________________________________

[1] Billington, G. 2001. Radio tracking study of Greater Horseshoe bats at Brockley Hall Stables Site of Special Scientific Interest, May – August 2001. Peterborough: English Nature

[2] Radio tracking studies have been undertaken by NE in the following research reports R344, R496 & R573.

[3] A L Walsh & S Harris, (1996), Foraging habitat preferences of vespertilionid bats in Britain. Journal of Applied Ecology, 33, 508 – 518

[4] http://www.batsandlighting.co.uk/

[5] see EN research reports R174

[6] R D Ransome and A M Hutson, (2000), Action plan for the conservation of the greater horseshoe in Europe (Rhinolophus ferrumequinum), Convention on the Conservation of European Wildlife and Natural Habitats, Nature and Environment No 109. http://www.swild.ch/Rhinolophus/PlanII.pdf  Also see EN research reports R174, R241, R341 & R532

[7] Rush, T. & Billington, G. 2013. Cheddar Reservoir 2: Radio tracking studies of greater horseshoe and Lesser Horseshoe bats, June and August 2013. Witham Friary: Greena  Ecological Consultancy

Annex 2: Bat Consultation Zones

A2.1     The Bat Consultation Zone density Band widths will vary from species to species depending on its characteristic use of its home range. Those for Greater and Lesser Horseshoe bats are given in the Table below. As both these species use a single focus for a population, a roost, they are likely to occur at a decreasing density in the landscape the further removed from the centre (e.g. see Rainho & Palmeirim, 2011; Rosenberg & McKelvey, 1999[1]).

A2.2     Around Cheddar it was reported that Greater Horseshoe bats spent most of time roaming along hedgerows whilst foraging, moving onto different hedgerows after visiting several in their ‘patch’. Individuals use foraging areas that could be over 200 or more metres in length or over 6 to 7 hectares. Within these foraging areas each bat has localised feeding spots of about 0.35 hectares.  In Germany they visit 11 – 25 such areas per night.

A2.3     A similar study of frequency of home range use away from a maternity roost site was carried out by Bontadina & Naef-Daenzer (2002) [2] at Grisons in Switzerland. It showed a higher frequency of use than would be expected at 1.2 to 1.6km distance when compared with uniform spatial use over the whole foraging range up to 4km. Above 4km the trend in spatial use declined up to the maximum range of 7.4km. In a radio tracking study carried out  by Rossiter et al (2002) [3] at Woodchester Manor, overlaps in core foraging areas were nearly all within 1km of the roost with only two overlaps recorded at ~2km and then both corresponded to a mother / daughter pair.

A2.4     The bands in the above table for a maternity roost of Greater Horseshoe bats are derived from radio tracking distances carried out by Billington (2001)[4] of the Brockley Hall Stables Greater Horseshoe bat roost in North Somerset. Although the Swiss study (Bontadina & Naef-Daenzer, 2002) [5] found greatest spatial density at 1.2 to 1.6km it is considered that 2.2km is used to determine the width of Band A in this case derived from Duvergé (1996)[6]. Billington notes that there has been deterioration in habitat near to the Brockley Hall roost where hedgerows have been removed, poorly managed or neglected. Duvergé (1996) carried out radio tracking studies in North Somerset where the summer foraging areas of adults were found to be located within 3 – 4 km of maternity roosts, and the mean adult range in one extensive study was 2.2km. About 75% of the foraging areas are located within the mean adult range. A number of radio tracking studies have shown the maximum foraging range for most Greater Horseshoe bats is 4km and this distance is quoted in the requirements of habitat conservation from a roost site.[7] Billington (2001) tracked the maximum distance travelled by bats at Brockley Hall as 6.8km, discounting one bat which travelled 10.2km to Shipham and then subsequently day roosted in Cheddar Gorge. However, measuring the distances in GIS the furthest recorded bat fix was 7.8km (“as the crow flies”).The Band widths for the non-breeding and winter roosts are derived from a radio tracking study of non-breeding roosts of Greater Horseshoe bats in Dorset carried out by Flanders (2008).[8] A comparison of foraging ranges from various studies on Greater Horseshoe bats is given in Appendix 1.

Table 2: Band Widths for Horseshoe Bats

Band

Greater Horseshoe bat (metres)

Lesser Horseshoe bat (metres)

Maternity

Other

Maternity

Other

A

0 – 2200

 

0 - 600

 

B

2201 - 4000

0 - 610

601 - 2500

0 - 300

C

4001 - 8000

611 – 2440

2501 -  4100

301 - 1250

A2.5     The Band widths for Lesser Horseshoe bats are derived from the radio tracking study carried out by Knight (2006)[9] for a lowland study area (as opposed to high quality and upland landscapes) which was located in North Somerset. The maximum distance travelled in this study was 4.1km for an adult female and 4.5km for a nulliparous female. The mean maximum range was 2.2km. Bontadina et al (2002)[10], whose study found a similar maximum foraging range, recommended that conservation management should be concentrated within 2.5km of the roost with special consideration within 600 metres of the roost where the colony foraged half the time. The same result was found for the North Somerset study.

A2.6     Radio tracking of Lesser Horseshoe bats carried out by Bontadina et al (2002) [11] estimated the density of Lesser Horseshoe bat foraging in their study area was 5.8 bats per hectare within 200 metres of the maternity roost, decreasing to 1 bat per hectare at 390 metres and 0.01 bats per hectare at 1200 metres. Knight (2006) [12] when carrying out a radio tracking for a Lesser Horseshoe bat roost of 200 individuals in North Somerset estimated a foraging density of 0.13 bat/hectare within 2 km of the roost and, like the Bontadina et al study, density declined sharply within the first kilometer in two of the study sites and subsequently at a lower rate out to the extent of the recorded foraging distance. A third study site in a high quality landscape showed a steadier rate of decline in density throughout the range.

A2.7     The Band widths for the non-breeding roost are derived from England radio-tracking of Lesser Horseshoe bats carried out in the winter. This study revealed that they foraged on average to a maximum distance of 1.2 kilometers from the hibernation site. One bat travelled to an absolute maximum distance of 2.1 kilometers. The winter foraging range appears to be approximately half that of the distance covered in the summer months. (Bat Conservation Trust/BMT Cordah, 2005)[13] For the purposes of this study the ranges are similarly halved. A comparison of foraging ranges is given in Appendix 1.

 

 

 

 

Lesser Horseshoe Bat (Photo: Frank Greenaway. Courtesy Vincent Wildlife Trust)

 

[1] Rainho, A. & Palmeirim, J. W. 2011. The Importance of Distance to Resources in the Spatial Modelling of Bat Foraging Habitat. PLoS ONE, April 2011, 6, 4, e19227; Rosenberg, D. K. & McKelvey, K. S. 1999. Estimation of Habitat Selection for Central-place Foraging Animals. Journal of Wildlife Management 63 (3): 1028 -1038.

[2] Bontadina, F. & Naef-Daenzer, B, 2002. Analysing spatial data of different accuracy: the case of Greater Horseshoe bats foraging. PhD Thesis, Universität Bern

[3] Rossiter, S. J., Jones, G., Ransome, R. D. & Barratt, E. M. 2002 Relatedness structure and kin-based foraging in the Greater Horseshoe bat (Rhinolophus ferrumequinum). Behav. Ecol. Sociobiol. (2002) 51: 510-518

[4] Billington, G. 2001. Radio tracking study of Greater Horseshoe bats at Brockley Hall Stables Site of Special Scientific Interest, May – August 2001. Peterborough: English Nature.

[5] Bontadina, F. & Naef-Daenzer, B, 2002. Analysing spatial data of different accuracy: the case of Greater Horseshoe bats foraging. PhD Thesis, Universität Bern

[6] Duvergé, L. 1996 quoted in Roger Ransome. 2009. Bath Urban Surveys: Dusk Bat Surveys for horseshoe bats around south-western Bath. Assessments Summer 2008 & Spring 2009. Bat Pro Ltd.

[7] See Appendix 1; e.g. also see Duvergė, P. L. & Jones, G. 1994. Greater Horseshoe bats - Activity, foraging behaviour and habitat use. British Wildlife 6, 2, 69 -77; Ransome, R. D. 1996. The management of feeding areas for Greater Horseshoe bats. Peterborough: English Nature; Ransome, R. 2009. Bath Urban Surveys: Dusk Bat Surveys for horseshoe bats around south-western Bath. Assessments Summer 2008 & Spring 2009. Bat Pro Ltd..

[8] Flanders, J. R. 2008. Roost use, ranging behaviour and diet of the Greater Horseshoe bat Rhinolophus ferrumequinum in Dorset: in Flanders, J. R. 2008. An integrated approach to bat conservation: applications of ecology, phylogeny and spatial modelling of bats on the Isle of Purbeck, Dorset. PhD Thesis, University of Bristol.

[9] Knight, T. 2006. The use of landscape features and habitats by the Lesser Horseshoe bat (Rhinolophus hipposideros). PhD thesis. University of Bristol.

[10] Bontadina, F., Schofield, H. & Naef-Daenzer, B. 2002. Radio-tracking reveals that Lesser Horseshoe bats (Rhinolophus hipposideros) forage in woodland. J. Zool. Lond. (2002) 258, 281-290.

[11] Bontadina, F., Schofield, H. & Naef-Daenzer, B. 2002. Radio-tracking reveals that Lesser Horseshoe bats (Rhinolophus hipposideros) forage in woodland. J. Zool. Lond. (2002) 258, 281-290.

[12] Knight, T. 2006. The use of landscape features and habitats by the Lesser Horseshoe bat (Rhinolophus hipposideros). PhD thesis. University of Bristol.

[13] Bat Conservation Trust / BMT Cordah. 2005. A Review and Synthesis of Published Information and Practical Experience on Bat Conservation within a Fragmented Landscape. Cardiff: The Three Welsh National Parks, Pembrokeshire County Council, Countryside Council for Wales

Annex 3: Survey Specification for Surveys for Planning Applications Affecting SAC bat Consultation Zones.

A3.1    Three types of survey are required to inform the impact of proposed development. These are:

  • Bat Surveys
  • Habitats / Land use Surveys
  • Light Surveys

Bat Surveys

A3.2    The following sets out the survey requirements for development sites within the Bat Consultation Bands A and B in part based on the guidance given by the Bat Conservation Trust (2016)[1] and on the advice of consultants experienced in surveying for horseshoe bats. Note that the objective is to detect commuting routes and foraging areas rather than roosts.

A3.3     The following specification is recommended in relation to development proposals within Bands A and B of the Bat Consultation Zone. It is also worth mentioning the difficulty associated with detecting the Greater Horseshoe bat’s echolocation call compared to most other British bat species due to the directionality and rapid attenuation of their call. This fact emphasises the requirement for greater surveying effort and the value of broadband surveying techniques. It is recommended that the most sensitive equipment available should be used. It is also recommended that the local planning authority ecologist be contacted with regard to survey effort.

(i) Surveys should pay particular attention to linear landscape features such as watercourses, transport corridors (e.g. roads, sunken lanes railways), walls, and to features that form a linear feature such as hedgerows, coppice, woodland fringe, tree lines, ditches and rhynes and areas of scrub and pasture that may provide flight lines.

(ii) The main survey effort should be that using automated detectors. Automatic bat detector systems need to be deployed at an appropriate location (i.e. on a likely flyway). Enough detectors should be deployed so that each location is monitored through the survey period in order that temporal comparisons can be made. The period of deployment should be at least 50 days from April to October and would include at least one working week in each of the months of April, May, August, September and October (50 nights out of 214; ≈25%). For development within Band B of the Bat Consultation Zone of hibernation roosts winter surveys may be required.

(iii) The number of automated detectors will vary in response to the number of linear landscape elements and foraging habitat types, the habitat structure, habitat quality, used by horseshoe bats and taking into account their flight-altitude. Every site is different, but the objective would be to sample each habitat component equally[2]. Generally:

  • With hedges it depends on the height and width, and also whether they have trees, as to how many detectors might be needed to ensure the coverage is comprehensive no matter what the wind decides to do.
  • With grassland, the number depends on whether the site is grazed or not; if it is we need a comparison of the fields with livestock and the fields without.
  • In a woodland situation a sample with three detectors: one on the woodland edge, two in the interior with one in the canopy and one at eye-level.
  • The open areas of a quarry are sampled with two detectors reflecting the un-vegetated and vegetated cliffs so the two can be compared.

(iv) Results from automated detectors recording should be analysed to determine whether the site supports foraging or increased levels activity as this affects the Band used in calculating the amount of replacement habitat required to mitigate losses to horseshoe bats.

(v) Manual transect surveys[3] should be carried out on ten separate evenings; at least one survey should be undertaken in each month from April to October[4], as the bats’ movements vary through the year. Transects should cover all habitats likely to be affected by the proposed development, including a proportion away from commuting features in field. Moreover, manual surveys only give a snap shot of activity (10 nights out of 214; ≈5%) and less effective at detecting horseshoe bats therefore automated bat detector systems should also be deployed see section (ii).

(vi) Surveys should be carried out on warm (>10 °C but >15°C in late summer), still evenings that provide optimal conditions for foraging (insect activity is significantly reduced at low temperatures; see commentary below). Details of temperature and weather conditions during surveys should be included in the final report.

(vii) Surveys should cover the period of peak activity for bats from sunset for at least the next 3 hrs.

(viii) Transect surveys should preferably be with most sensitive equipment available. Digital echolocation records of the survey should be made available with the final report; along with details of the type and serial number of the detector.

(ix) Surveys should be carried out by suitably qualified and experienced persons. Numbers of personnel involved should be agreed beforehand with the appropriate Somerset authority or Natural England, be indicated in any report and be sufficient to thoroughly and comprehensively survey the size of site in question.

(x) Surveys should also include desktop exercises in collating any records and past data relating to the site via Bristol Environmental Records Centre (BRERC) or Somerset Environmental Records Centre (SERC), local Bat Groups etc.

(xi) All bat activity should be clearly marked on maps and included within the report.

(xii) Basic details of records for the site should be passed to BRERC and/or SERC after determination of the application.

A3.4     Survey effort in Band C is dependent on whether commuting structure is present and the suitability of the adjacent habitat to support prey species hunted by horseshoe bats. Nonetheless this should be in accordance with Bat Conservation Trust guidelines (Collins, 2016[5])

Habitats Surveys

A3.5     Phase 1 habitat surveys should be carried out for all land use developments within the Bat Consultation Zone and be extended to include the management and use of each field, e.g. whether the field is grazed or used as grass ley, and the height, width and management of hedgerows in the period of bat activity. Information can be sought from the landowner. If grazed, the type of stock and management regimes should be detailed if possible.  Habitat mapping should include approximate hectarage of habitats to inform the methodology for calculating replacement habitat required.

Lighting Surveys

A3.6     Surveys of existing light levels on proposed development sites should be undertaken and submitted with the planning application. This should cover the full moon and dark of the moon periods so that an assessment of comparative horseshoe bat activity on a proposed site can be ascertained. Light levels should be measured at 1 metre above ground level. This survey data can then be used to inform the masterplan of a project.

A3.7     A lux contour plan of light levels down to 0.5 Lux, modelled at 1 metre above ground level, should be submitted with the application.

 

 

 

[1] Collins, J. (ed). 2016. Bat Survey Guidelines for Professional Ecologists: Good Practice Guidelines. (3rd Edition) London: Bat Conservation Trust

[2] Pers. Comm. Henry Andrews, AEcol, 23/09/2016

[3] Collins, J. (ed). 2016. Bat Survey Guidelines for Professional Ecologists: Good Practice Guidelines. (3rd Edition) London: Bat Conservation Trust

[4] The active bat season can vary e.g. shortened by prolonged cold winters and lengthened by warm  ‘Indian summers’

[5] Collins, J. (ed). 2016. Bat Survey Guidelines for Professional Ecologists: Good Practice Guidelines (3rd Edition). London: Bat Conservation Trust

Annex 4: Habitat Requirements of Greater and Lesser Horseshoe bats

Greater Horseshoe Bats

Prey

A4.1     Dietary analysis of Greater Horseshoe bat droppings shows three main prey items: cockchafer Melolontha melolontha; dung beetles Aphodius sp. (Coleoptera: Scarabaeidae); and moths (Lepidoptera). Of these moths form the largest part of the diet but the other two are important at certain times of year.[1] They are conservative in their food sources. Three secondary prey sources are also exploited: crane flies (Diptera: Tipulidae), ichneumonids (Hymenoptera: Ichneumonidae) of the Ophian luteus complex, and caddis flies (Trichoptera) [but less so at Brockley Hall Stables].[2]

General

A4.2     Greater Horseshoe bat populations are sustained by a foraging habitat which consists primarily of permanently-grazed pastures interspersed with blocks or strips of deciduous woodland, or substantial hedgerows. Such pasture/woodland habitats can generate large levels of their favoured prey, especially moths and dung beetles, but also tipulids and ichneumonids. Preferably pastures should be cattle-grazed, as their dung sustains the life-cycles of the most important beetles to Greater Horseshoe bats, but sheep and horse grazing can also be beneficial in a rotation to reduce parasite problems. Sheep-grazing, which results in a short sward, may also benefit the life-cycles of tipulids and cockchafers.

A4.3     The periods through the year when these prey species are hunted is outlined below:

  • The preferred key prey in April for all bats that have survived the previous winter is the large dung beetle Geotrupes.
  • In May, the preferred key prey is the cockchafer Melolontha melolontha.
  • In April and May, in the absence of sufficient key prey, bats switch to secondary prey such as tipulids, caddis flies and the ichneumonid Ophion. As a last resort they eat small dipterans.
  • In June and early July, pregnant females feed on moths, their key prey at that time, and continue to do so after giving birth, until late August. They usually avoid Aphodius rufipes even when they are abundant, as long as moths are in good supply. If both are in poor supply they switch to summer chafers (Amphimallon or Serica).
  • Moth supplies usually fall steadily in August and September, due to phonological population declines, or rapidly at a particular dawn or dusk due to temporary low temperatures. If either happens adult bats switch to secondary, single prey items, or combine moths with them. Tipulids are often the first alternative, but Aphodius rufipes is also taken. In very cold spells ichneumonids, of the Ophion luteus complex are consumed. They are common prey in October and through the winter as they can fly at low ambient temperatures. However in summer they are used as a last resort.
  • Juvenile bats do not feed at all until they are about 29 or 30 days old, when they normally feed on Aphodius rufipes, which is their key prey. This dung beetle species is a fairly small (90mg), easily-caught and usually abundant prey, which reaches peak numbers at the time that the young normally start to feed in early August.[3]

A4.4     The top five feeding areas for Greater Horseshoe bats over the active period in North Somerset include:

  • pasture with cattle as single stock or part of mixed stock (38.6%);
  • ancient semi natural woodland (16.6%);
  • pastures with stock other than cattle (10.3%);
  • meadows grazed by cattle in the autumn (9.4%); and
  • other meadows and broadleaved woodland (4.9%).[4]

A4.5     These habitats are not used according to the fore listed proportions throughout the year but change with the seasons. Woodlands and pasture adjoining wood are used in spring and early summer. As summer progresses, feeding switches to areas further away and tends to be fields used for grazing cattle and other types of stock.  Meadows that have been cut and where animals are grazing are also used. A balance of woodland and pasture of about 50% and 50% provides optimum resources for Greater Horseshoe bats.[5] Billington (2000)[6] identified that there were four principal habitat types: scrub, meadow, deciduous woodland and grazed pasture.

A4.6     Within suitable habitat, a range of three roosts types must be present for a colony to exist. A single maternity roost, with many surrounding night roosts nearby (usually up to 4 km, but exceptionally up to 14 km) for resting between foraging bouts and a range of suitable hibernacula within a 60 km radius. Three types of hibernaculum have been identified which should be as close as possible, but within 15 km of the maternity roost.[7]

Grassland

A4.7     The most important factor for supporting Greater Horseshoe bat populations is grazed pasture[8]. Cattle are preferred to smaller grazers, since they create the ideal structural conditions for perch-hunting bats in hedgerows and woodland edge. Within 1 kilometre of the roost the presence of permanent grazed pasture is critical for juvenile Greater Horseshoe bats. A high density of grazing animals should be present giving high presence of dung. Within the remainder of the roost foraging range grazing regimes can be more flexible provided adequate pasture is available.[9]

A4.8     Aphodius beetles live in cow, sheep and horse dung. Short grazed habitat, such as produced by sheep, benefits Melontha and Tupilid species which require short grass to oviposit. Sheep dung also provides dung based prey. Large dung beetles, Geotrupes spp., can provide a major dietary component of Greater Horseshoe bats. Most favour cattle dung, but some also use sheep dung.

A4.9     Longer swards benefit the larvae of noctuid moths.[10] The main species of moth eaten by Greater Horseshoe bats at Woodchester in Gloucestershire are Large Yellow Underwing; Small Yellow Underwing; Heart and Dart; and Dark Arches. The former two species are on the increase whilst the latter two are in decline.[11]

  • Large Yellow Underwing are found in a range of habitats, including agricultural land, gardens, waste ground, and has a range of food plants including dandelion, dock, grasses and a range of herbaceous plants both wild and cultivated, including dog violet and primrose. It will also visit flowers such asBuddleia, ragwort, and red valerian. The larva is one of the ‘cutworms’ causing fatal damage at the base of virtually any herbaceous plant, including hawkweeds, grasses, plantains and dandelions and a range of cultivated vegetables and flowers. This moth flies at night from July to September and is freely attracted to light.
  • Small Yellow Underwing are found on flower-rich grassland, including meadows, roadside verges, open woodland and grassy embankments. The food plants are as for those listed for the Large Yellow Underwing but also include foxglove, sallow, hawthorn, blackthorn and silver birch. The larvae feed on the flowers and seeds of mouse-ear (Cerastium spp.), especially common mouse-ear. This moth flies in May and June in the daytime so may be gleaned at night.
  • Heart and Dart are found in agricultural land, meadows, waste land, gardens and places where their food plants grow. Food plants include dock, plantain, chickweed, fat hen, turnip, sugar beet and many other herbaceous plants. The larvae feed on various wild and garden plants. The moth flies from May to July, when it is readily attracted to light.
  • Dark Arches are found in meadows and other grassy place and food plants include cocksfoot, couch grass and other grasses. The larvae feed on the bases and stems of various grasses. The moth is on the wing from July to August and is readily attracted to light.[12]

Woodland

A4.10   Rides and footpaths are used by Greater Horseshoe bats when flying in woodland feeding areas. Grassy rides and glades in woodland increase the range of food and provide opportunity for perch hunting.[13]

A4.11   Woodland supports high levels of moth abundances. Macro (and micro) moths are densest where there is grass or litter, less so where there are ferns, moss, bare ground or herbs. They are richer where there is native tree diversity and trees with larger basal areas. Species such as oak, willow and birch have large numbers of moths, whereas beech has small numbers even when compared to non-native species such as sycamore. Uniform stands of trees are poorer in invertebrates than more diversely structured woodland.[14]

A4.12 Greater Horseshoe bats feedthrough the winterwhen prey species become active, for example when Ophian wasps swarm in woodlands above 5˚C. They have been found to spend significant times in woodland, being sheltered, often warmer at night, and insects are much more abundant than in open fields. However, in another study Billington (2000) carried out in the summertime found that there was limited foraging of adults recorded in woodlands, of only a few minutes duration, except during medium-heavy rainfall when most of the foraging time was spent in broadleaf and coniferous woodland. Use, therefore, is likely to be dependent on season and weather conditions.[15]

Hedgerow

A4.13   Larger hedgerows are required for commuting as well as foraging by Greater Horseshoe bats. Continuous lines of vegetation of sufficient height and thickness to provide darkness when light levels are still relatively high are needed for commuting bats. Ransome (1997) recommended the retention of existing hedgerows and tree lines linking areas of woodland, encouraging hedgerow improvement to become 3 to 6 metres wide, mean 3 metres high with frequent standard emergent trees.[16]

A4.14   Substantial broad hedgerows with frequent emergent trees can provide suitable structure for foraging conditions for Greater Horseshoe bats if woodland is scarce. Cattle are preferred to smaller grazers, since they create the ideal structural conditions for perch-hunting bats in hedgerows and woodland edge. A tall thick hedgerow is a very efficient way of producing a maximum level of insect prey using a minimum land area and important creators of physical conditions that enhance insect concentrations and reduce wind speeds for economical hunting flight. The vast majority of insects (over 90%) found near hedge lines do not originate in the hedge but come from other habitats brought in on the wind.[17]

Scrub

A4.15   Scrub also seems to be an important foraging habitat for Greater Horseshoe bats. Billington (2000) records the frequent use by the species during radio tracking carried out for the Mells Valley SAC in June. Scrub in disused quarries is important.[18]

A4.16   Large Yellow Underwing moths are attracted to Buddleia or Butterfly Bush. Butterfly Bush grows in abundance in limestone quarries and flowers from July to September, when demands on lactating female horseshoe bats are high. There is potential to deprive horseshoe bats of a foraging ground by restoring large areas of butterfly bush scrub all in one hit and at the wrong time of year.[19]

A4.17   However, similarly to Lesser Horseshoe bats, large areas of continuous scrub are likely to be avoided by Greater Horseshoe bats.[20]

Others

A4.18   Ditches and rhynes are used as flight corridors to access foraging areas in the Somerset Moors south of Cheddar, flying below ground level. This is also likely to be the case in North Somerset. They have also been radio tracked flying straight across the open water of Cheddar Reservoir.[21]

A4.19   Tipulid larval development is favoured by damp conditions. Therefore, any aquatic environments and/or marshes can provide a secondary prey source.  Aquatic environments could also favour the production of caddis flies in certain months, such as May and late August / September when other food supplies may be erratic. There is significant caddis fly consumption at roosts close to extensive river or lake habitats.[22]

A4.20   In Devon the River Dart, a large river system, mostly banked by broadleaved woodland was also found to be a key habitat.[23]

A4.21   Habitats which are of little use to Greater Horseshoe bats include urban areas, arable land and amenity areas such as playing fields. Lights, such as street lights or security lamps, are strong deterrents to Greater Horseshoe bats, both when they emerge from roosts, and when they forage. However, radio tracking shows that bats regularly pass through urban areas of Cheddar and will fly along hedgerows adjoining arable areas to reach hunting grounds. It is suspected that they will fly through (but not along) a line of street lights, probably at the darker points between lamps, as evidenced by radio tracking. In North Somerset they have been recorded within urban areas but here lights are switched off after midnight.

A4.22   During the winter period Greater Horseshoe bats are likely to forage closer to roost sites than during the summer and in areas sheltered from the wind, and on south and southwest facing slopes.[24]

Lesser Horseshoe Bats

 

Prey

A4.23   The diet of the Lesser Horseshoe bat consists mostly of Diptera of the crepuscular sub-order Nematocera. Families of Nematocera Diptera recorded in the diet include Tipulidae (crane-flies), Ceratopogonidae (biting midges), Chironomidae (non-biting midges), Culicidae (mosquitoes), and Anisopodidae (window midges). Lepidoptera (moths), Trichoptera (caddis-flies) and Neuroptera (lacewings) are also eaten.[25]

A4.24   Due to their small body size they cannot cope with large prey, such as cockchafers. By comparison they eat smaller moth species than the Greater Horseshoe bat. The principal prey species for Lesser Horseshoe bats, using data collected at Hestercombe House SAC are from the Diptera and Lepidoptera families. At this location there were seven major prey categories comprised over 70% of the diet: Tipulidae (crane flies), Anisopodidae (window gnats), Lepidoptera (moths), Culicidae (mosquitoes), Hemerobiidae (brown lacewings), Trichoptera (caddis flies) and Ichneumonidae (ichneumon wasps)[26]

 General

A4.25   ‘The primary foraging habitat for Lesser Horseshoe bats is broadleaf woodland where they often hunt high in the canopy. However, they will also forage along hedgerows, tree-lines and well-wooded riverbanks.’[27] Lesser Horseshoe bats are primarily a woodland feeding bat using deciduous woodland or mixed coniferous woodland and hedgerows. It has been found that landscapes that were most important contained a high proportion of woodland, parkland and grazed pasture, linked with linear features, such as overgrown hedgerows.

Woodland

A4.26   In the Wye valley in Monmouthshire studies revealed that Lesser Horseshoe bats significantly spend the majority of their time foraging in woodland. Broadleaved woodland predominated over other types of woodland and was shown to be a key habitat for the species. In the core foraging areas used by bats woodland accounted for 58.7 ± 5.2% of the habitats present. Although Lesser Horseshoe bats prefer deciduous woodland as foraging habitat they will occasionally hunt in conifer plantations. However, the biomass in coniferous woodland is smaller, but where smaller blocks are surrounded by habitat productive in insect prey they will be used.[28]

A4.27   The Ciliau SSSI, designated for its Lesser Horseshoe bats, and also the River Wye, is surrounded by predominately pastoral habitats, with cattle grazing on lowlands and sheep grazing on higher areas. There are, however, high densities of broadleaved woodland, especially along watercourses, and some conifer plantations. Again Lesser Horseshoe bats foraged predominately in broadleaved woodland along the banks of the River Wye and its tributary streams. Woodland with watercourses has more importance. They were also recorded foraging in conifer plantations.[29] 

A4.28   Furthermore, radio tracking carried out in the spring also revealed that coniferous woodland appeared to be more used for foraging than deciduous woodland and that coniferous woodland close to maternity colonies may provide refuge in certain weather conditions[30]

A4.29   Although Lesser Horseshoe bats prefer woodland in which to forage there is a further requirement as to the structure of the woodland. In Bavaria, except in one area, the distance between trees was large and in dense stands no activity was recorded. In Belgium it was found that the density of taller trees, either broadleaved or coniferous, must be low enough to allow the development of an under storey of shrub and coppice.[31]  

 

Grassland

A4.30   Radio tracking research of Lesser Horseshoe bats shows that in foraging over pasture cattle must be actively grazing the field.  Once cattle are removed from a field foraging by Lesser Horseshoe bats ceases immediately. However, pasture in such use offers a valuable and predictable food source at a time of year when bats are energetically stressed (pre- to post-weaning), because they are feeding their young. The report recommended a grazing density of 0.5 -1 cows per hectare. Scatophagidae can be one of the major prey categories in the diet of Lesser Horseshoe bats. The larvae of the Yellow Dung-fly Scatophaga stercoraria develop in cattle dung. The presence of pasture is also indispensable to the larval stage of development for certain species (Tipulids), which form a significant proportion of the prey hunted by Lesser Horseshoe bats.[32]

 

Hedgerows

A4.31   Belgian research similarly showed that the feeding grounds for Lesser Horseshoe bats were deciduous woodland along with copses or mixed coniferous woodland. Woodland occupied 25% of the area within 1 kilometre of the roost. However, some foraging was observed in hedgerows. Hedgerows had an average density of 47 metres per hectare. Generally, bats selected areas that were of undulating countryside with hedgerows, tree lines and woodland in preference to flat open intensively farmed areas. In Austria hedgerows, tree lines and streams were only exploited where there was less forest.[33]

A4.32   Commuting corridors, such as tall bushy hedgerows, are important features for Lesser Horseshoe bats as they avoid crossing open areas and are vulnerable to the loss of these corridors. In Belgium no bat was recorded more than 1 metre from a feature. Stonewalls have been reported in use as commuting routes in Ireland.[34]

A4.33   At Ciliau SSSI Lesser Horseshoes only crossed the River Wye when fully dark. Lesser Horseshoe bats have been observed crossing roads where the tops of trees have touched.[35]

Scrub

            A4.34   Lesser Horseshoe bats avoid dense scrub cover[36].

 

 

[1] Ransome (1996) carried out dietary analyses of Greater Horseshoe bats in June and July and found that 60 – 80% of their diet was moths.

[2] Ransome, R. D. 1997. The management for Greater Horseshoe bat feeding areas to enhance population levels: English Nature Research Reports Number 241. Peterborough: English Nature.

[3] Ransome, R. D. & Priddis, D. J. 2005. The effects of FMD-induced mass livestock slaughter on greater horseshoe bats in the Forest of Dean. English Nature Research Reports Number 646. Peterborough: English Nature.

[4] Duvergė, P. L. & Jones, G. 1994. Greater Horseshoe bats - Activity, foraging behaviour and habitat use. British Wildlife Vol. 6 No 2

[5] Ransome, R. D. 1996. The management of feeding areas for Greater Horseshoe bats. Peterborough: English Nature; Bontadina, F. & Naef-Daenzer, B, 2002. Analysing spatial data of different accuracy: the case of Greater Horseshoe bats foraging. PhD Thesis, Universität Bern

[6] Billington, G. 2000. Radio tracking study of Greater Horseshoe bats at Mells, Near Frome, Somerset. Peterborough: English Nature

[7] R D Ransome and A M Hutson, (2000), Action plan for the conservation of the greater horseshoe in Europe (Rhinolophus ferrumequinum), Convention on the Conservation of European Wildlife and Natural Habitats, Nature and Environment No 109. http://www.swild.ch/Rhinolophus/PlanII.pdf

[8] Ransome, R. D. 1997. The management for Greater Horseshoe bat feeding areas to enhance population levels: English Nature Research Reports Number 241. Peterborough: English Nature.

[9] Ransome, R. D. 1996. The management of feeding areas for Greater Horseshoe bats. Peterborough: English Nature

[10] Ransome, R. D. 1996. The management of feeding areas for Greater Horseshoe bats. Peterborough: English Nature; Ransome, R. D. 1997. The management for Greater Horseshoe bat feeding areas to enhance population levels: English Nature Research Reports Number 241. Peterborough: English Nature

[11] Jones, G., Barlow, K., Ransome, R. & Gilmour, L. 2015. Greater Horseshoe bats and their insect prey: the impact and importance of climate change and agri-environment schemes. Bristol: University of Bristol.

[12] Ransome, R. D. 1996. The management of feeding areas for Greater Horseshoe bats. Peterborough: English Nature; http://ukmoths.org.uk/species/noctua-pronuba/; http://ukmoths.org.uk/species/panemeria-tenebrata/; http://ukmoths.org.uk/species/agrotis-exclamationis; http://ukmoths.org.uk/species/apamea-monoglypha/

[13] Duvergė, P. L. & Jones, G. 1994. Greater Horseshoe bats - Activity, foraging behaviour and habitat use. British Wildlife Vol. 6 No 2; Ransome, R. D. 1996. The management of feeding areas for Greater Horseshoe bats. Peterborough: English Nature; Bontadina, F. & Naef-Daenzer, B, 2002. Analysing spatial data of different accuracy: the case of Greater Horseshoe bats foraging. PhD Thesis, Universität Bern.

[14] Ransome, R. D. 1997. The management for Greater Horseshoe bat feeding areas to enhance population levels: English Nature Research Reports Number 241. Peterborough: English Nature; Fuentes-Montemayor, E.,Goulson, D., Cavin, L., Wallace, J.M. & Park, K. J. 2012. Factors influencing moth assemblages in woodland fragments on farmland: Implications for woodland management and creation schemes. Biological Conservation 153 (2012) 265–275; Kirby, K. J. (ed). 1988. A woodland survey handbook. Peterborough: Nature Conservancy Council.

[15] Ransome, R. D. 1996. The management of feeding areas for Greater Horseshoe bats. Peterborough: English Nature; Billington, G. 2000. Radio tracking study of Greater Horseshoe bats at Mells, Near Frome, Somerset. Peterborough

[16] Ransome, R. D. 1996. The management of feeding areas for Greater Horseshoe bats. Peterborough: English Nature; Ransome, R. D. 1997. The management for Greater Horseshoe bat feeding areas to enhance population levels: English Nature Research Reports Number 241. Peterborough: English Nature

[17] Ransome, R. D. 1996. The management of feeding areas for Greater Horseshoe bats. Peterborough: English Nature; Bat Conservation Trust. 2003. Agricultural practice and bats: A review of current research literature and management recommendations. London: Defra project BD2005

[18] Billington, G. 2000. Radio tracking study of Greater Horseshoe bats at Mells, Near Frome, Somerset. Peterborough: English Nature

[19] Pers. comm. Henry Andrews. AEcol, 22/09/2016

[20] Schofield, H. W. 2008. The Lesser Horseshoe Bat Conservation Handbook. Ledbury: The Vincent Wildlife Trust.

[21] Jones, Dr. G. & Billington, G. 1999. Radio tracking study of Greater Horseshoe bats at Cheddar, North Somerset. Taunton: English Nature; Rush, T. & Billington, G. 2013. Cheddar Reservoir 2: Radio tracking studies of greater horseshoe and Lesser Horseshoe bats, June and August 2013. Witham Friary: Greena  Ecological Consultancy

[22] Ransome, R. D. 1997. The management for Greater Horseshoe bat feeding areas to enhance population levels: English Nature Research Reports Number 241. Peterborough: English Nature

[23] Billington, G. 2003. Radio tracking study of Greater Horseshoe bats at Buckfastleigh Caves, Site of Special Scientific Interest. Peterborough: English Nature.

[24] Ransome, R. D. 2002. Winter feeding studies on Greater Horseshoe bats: English Nature Research Reports Number 449. Peterborough: English Nature

[25] Vaughan, N., Jones, G. & Harris, S. 1997. Habitat use by bats (Chirpotera) assessed by means of a broad-band acoustic method.  Journal of Applied Ecology 1997, 34, 716-730; Boye, Dr. P. & Dietz, M. 2005. English Nature Research Reports Number 661: Development of good practice guidelines for woodland management for bats. Peterborough: English Nature

[26] Boye, Dr. P. & Dietz, M. 2005. English Nature Research Reports Number 661: Development of good practice guidelines for woodland management for bats. Peterborough: English Nature; Knight Ecology. 2008. Hestercombe House, Taunton, Somerset:  Lesser Horseshoe bat Diet Analysis. Clutton: Knight Ecology

[27] Schofield, H. W. 2008. The Lesser Horseshoe bat Conservation Handbook. Ledbury: The Vincent Wildlife Trust.

[28] Bontadina, F., Schofield, H. & Naef-Daenzer, B. 2002. Radio-tracking reveals that Lesser Horseshoe bats (Rhinolophus hipposideros) forage in woodland. J. Zool. Lond. (2002) 258, 281-290; Schofield, H. W. 2008. The Lesser Horseshoe bat Conservation Handbook. Ledbury: The Vincent Wildlife Trust.

[29] Schofield, H., Messenger, J., Birks, J. & Jermyn, D. 2003. Foraging and Roosting Behaviour of Lesser Horseshoe bats at Ciliau, Radnor. Ledbury: The Vincent Wildlife Trust; Barataud, M., Faggio, G., Pinasseau, E. & Roué, S. G. 2000. Protection et restauration des habitats de chasse du Petit rhinolophe. Paris : Société Français pour l’Etude et la Protection des Mammifères.

[30] Bat Conservation Trust. 2005. A Review and Synthesis of Published Information and Practical Experience on Bat Conservation within a Fragmented Landscape. Cardiff: The Three Welsh National Parks, Pembrokeshire County Council, Countryside Council for Wales

[31] Holzhaider, J., Kriner, E., Rudolph, B-U. & Zahn, A. 2002. Radio-tracking a Lesser Horseshoe bat (Rhinolophus hipposideros) in Bavaria: an experiment to locate roosts and foraging sites. Myotis, 49, 47-54; Motte, G. & Libois, R. 2002. Conservation of the Lesser Horseshoe bat (Rhinolophus hipposideros Bechstein, 1800) (Mammalia: Chiroptera) in Belgium. A case study in feeding requirements. Belg. J. Zool., 132 (1): 47-52.

[32] Cresswell Associates. 2004. Bats in the Landscape Project. The National Trust, Sherborne Park Estate; Knight,T. 2006. The use of landscape features and habitats by the lesser horseshoe bat (Rhinolophus hipposideros). PhD Thesis: University of Bristol

[33] Holzhaider, J., Kriner, E., Rudolph, B-U. & Zahn, A. 2002. Radio-tracking a Lesser Horseshoe bat (Rhinolophus hipposideros) in Bavaria: an experiment to locate roosts and foraging sites. Myotis, 49, 47-54; Motte, G. & Libois, R. 2002. Conservation of the Lesser Horseshoe bat (Rhinolophus hipposideros Bechstein, 1800) (Mammalia: Chiroptera) in Belgium. A case study in feeding requirements. Belg. J. Zool., 132 (1): 47-52.

[34] Motte, G. & Libois, R. 2002. Conservation of the Lesser Horseshoe bat (Rhinolophus hipposideros Bechstein, 1800) (Mammalia: Chiroptera) in Belgium. A case study in feeding requirements. Belg. J. Zool., 132 (1): 47-52; Biggane, S. & Dunne, J. 2002. A study of the ecology of the lesser horseshoe colony at the summer roost in Co. Clare, Ireland: In European Bat Research Symposium (9, 2002, Le Havre). Abstracts of presentations at the 9th European Bat Research Conference, August 26-30 at Le Havre, France. Bat Research News 43(3): 77.

[35] Schofield, H., Messenger, J., Birks, J. & Jermyn, D. 2003. Foraging and Roosting Behaviour of Lesser Horseshoe bats at Ciliau, Radnor. Ledbury: The Vincent Wildlife Trust;

[36] Schofield, H. W. 2008. The Lesser Horseshoe Bat Conservation Handbook. Ledbury: The Vincent Wildlife Trust.

Annex 5: Methodology for Calculating the Amount of Replacement Habitat Required

Introduction

A5.1     The method used to calculate the amount of habitat required to replace that lost to a horseshoe bat population due to development is based on the requirements for maintaining that needed to support viable populations. It uses an approach similar to the Habitat Evaluation Procedures (HEP) developed by the U.S. Fish and Wildlife Service (1980) to provide ‘…for mitigation and compensation that can allow fair use of the land and maintain healthy habitats for affected species’.[1] HEP is structured around the calculation of Habitat Units (HU), which are the product of a Habitat Suitability Index (quality) and the total area of habitat (quantity) affected or required[2].

A5.2     A key assumption is that habitat type, amount and distribution influence the distribution of associated animal species. It is also important to recognise that Habitat Suitability Index (HSI) models predict habitat suitability, not actual occurrence or abundance of species populations.[3]

A5.3     The HEP uses the Integrated Habitat System (IHS) developed by Somerset Environmental Records Centre, described below. It requires a Habitat Suitability Index for the horseshoe bat species scored on IHS descriptions, which are given in Appendices 2 and 3.

A5.4     Such methods are necessary to obtain an objective quantitative assessment that provides improved confidence that the mitigation agreed is likely to be adequate; and that a development will not significantly reduce the quantity or quality of habitat available to a horseshoe bat population; whereas current ecological impact assessments are often based on subjective interpretations. In Somerset they have been used since 2009 including for effects on Greater and Lesser Horseshoe bats to inform the adequacy of replacement habitat provided by the developer. The method has gone through planning inquiries including for a Nationally Significant Infrastructure Project.

A5.5     The methodology has also been reviewed and further developed with the Bat Conservation Trust.

Integrated Habitat System Mapping

A5.6     The Integrated Habitat System coding is used as a basis for describing and calculating habitat values used as a base in applying scores in Habitat Suitability Indices. The Integrated Habitat System (IHS)[4] classification comprises over 400 habitat categories, the majority drawn from existing classifications, together with descriptions, authorities and correspondences arranged in a logical hierarchy that allow application for different purposes. The classification can be customised for a geographical area or special project use without losing data integrity.

A5.7     The IHS represents a coded integration of existing classifications in use in the UK with particular emphasis on Broad Habitat Types, Priority Habitat Types, Annex 1 of the Habitats Directive and Phase 1[5].

A5.8     Standard habitat definitions from these classifications are combined into a hierarchy starting at the level of Broad Habitat Types, through Priority Habitat types, Annex 1 to vegetation communities which are coded. These are the Habitat Codes.

A5.9     Within IHS Habitat Codes are hierarchical with the numbers in the code increasing as the habitat becomes more specific. Descriptions of habitats can be found in IHS Definitions (Somerset Environmental Records Centre)[6]. For example:

  • WB0 Broadleaved, mixed and yew woodland (Broad Habitat Type)
  • WB3 Broadleaved woodland
  • WB32 Upland mixed ashwoods (Priority Habitat Type)
  • WB321 Tilio-Acerion forests on slopes, screes and ravines (upland) (Annex 1 Habitat)

A5.10   As well as Habitat Codes IHS provides Matrix, Formation and Land Use/Management Codes which are added as a string to the main Habitat Code to provide further description.

A5.11   Ideally habitat information for the whole of the geographic area of the Somerset authorities should be mapped in a GIS programme, such as MapInfo or ArcGIS. However, when used in ecological impact assessment for calculating the value of impacts of habitat change on a species population then at minimum it is only necessary that IHS coding is applied to the habitat types present on the proposed development site to enable the use of Habitat Suitability Indices in the HEP metrics.

Habitat Suitability Indices

Introduction

A5.12   A form of Habitat Suitability Indices (HSI) has been used in the United States and Canada since the early 1980s as a way of assessing the impacts of development on species' populations and distributions. In addition, they have been used to predict what replacement habitat needs to be created to maintain species' populations. The process assumes that the suitableness of habitat for a species can be quantified - the HSI. The overall suitability of an area for a species can be represented as a product of the geographic extents of each habitat and the suitability of those habitats for the species[7].

Description

A5.13   In constructing the HSI the index scores are applied to each Habitat, and Matrix, Formation and Land Use / Management codes in the Integrated Habitat System (IHS) based on analysis of the ecological requirements, from existing literature and professional judgement, for each species assessed or mapped.

A5.14   Each IHS ‘Habitat’ category is scored on a scale of 0 to 6 (as defined below) using a potential or precautionary approach as a starting point, e.g. Broadleaved, mixed and yew woodland is assumed to be the Annex 1 broadleaved woodland habitat unless otherwise proved not. The score will be the same across each of the hierarchical levels of the IHS Habitat coding (e.g. poor is scored as 1 whether this is at broadest habitat level or priority habitat level unless there is discernible differences in the type of habitat used, e.g. oak or beech woodland)[8]. This means that the full range of scoring is used before the modifiers (the IHS Formation and Management codes) are applied.

A5.15   The Habitat Code scoring is considered in combination with the IHS Matrix codes[9]. These are either added or subtracted from the Habitat code, e.g. grassland score 3 + scrub score 2 would equal 5. This is to account for species, for example that use grassland with a matrix of scattered scrub or single trees, which would otherwise avoid open grassland habitat.[10] Habitat Codes have a range of 0 to 6 but when considered in combination must not exceed a score of 6 or fall below a score of 0, Where there is no effect from a Matrix type then a default score of 0 is used.

A5.16   All other Codes are scored between 0 and 1 and are multipliers. Where there is no effect from Formation, Management then a default score of 1 is used.

Table 3: Example of HSI Calculation

 

Habitat Code

Matrix Code

Formation Code

Land Use / Management Code

HSI Score

Code

GI0

SC2

-

GM12

 

Description

Improved Grassland

Scattered Scrub

-

Sheep Grazed

HSI Score

3

1

1

0.75

3

A5.17   Scores will be applied such that a precautionary approach or 'potential' approach is taken, e.g. if a species requires grassland which is most valuable when grazed then grassland scores the top score. This potential score will take into account a combination of the Habitat and Matrix codes. The management modifier would then maintain the habitat score at this high level by a multiplier of 1. If the management is not grazed a decimal multiplier is applied to reduce the value of the habitat. For example a grassland habitat is valued at 6 but by applying the relevant management code, i.e. either mown or other management type, the value of the habitat will be reduced. Only one management code is allowed. An example (non-horseshoe bat) is set out in Table 3 above.

 

A5.18   The definition of poor, average, good and excellent habitat is adapted from the ‘Wildlife Habitat Handbook for the Southern Interior Ecoprovince’, British Columbia, Ministry of Environment[11] and expanded, in consultation with the Bat Conservation Trust, as follows:

 

Excellent - provides for essential life requisites, including feeding, reproduction or special needs and supports a relatively high population density, implied >70% chance of occurrence, can support positive recruitment. Can be a critical life-cycle association.

Very good - provides for essential life requisites, including feeding, reproduction or special needs and supports a relatively high population density, implied 50 - 70% chance of occurrence, can support positive recruitment.

Good - provides for a life requisites, including feeding, reproduction or special needs and supports a relatively high population density, implied 40 -50% chance of occurrence, can support a stable population.

Average - provides for moderately required life needs, including feeding, reproduction or special needs and supports a relatively moderate population density, implied 25 - 40% chance of occurrence, can support a stable population.

Marginal - provides for marginally required life needs, including feeding, reproduction or special needs and supports a relatively modest population density, implied 15 - 25% chance of occurrence, can support a small population.

Poor - provides for a non-essential life needs, including feeding, reproduction or special needs and supports a relatively low population density, implied <15% chance of occurrence.

A5.19   It is recognised that not all habitat patches of the same type have equal value in terms of resource to a species, for example see Dennis, 2010[12]. However, in scoring the overall HSI, i.e. including all Habitat, Matrix, Formation codes, etc., it is considered that a higher value is given as a precaution. However, there is a factor in the HEP taking into account survey results which is partly aimed to account for variability in habitat quality.

A5.20   No allowance for seasonal variations, i.e. due to the availability of prey species at different times of year, has been made in developing the HSI. It is considered a habitat valued at 6 at a particular period but not at other times will remain at a value of 6 being necessary to support that species at that time of year when other prey or other resources may not be so readily available.

A5.21   The HSI score arising from the above calculation can be joined into a GIS base habitat map and displayed using thematic mapping to give a graphical representation of the value of a landscape to horseshoe bats.

A5.22   The Habitat Suitability Index for Greater Horseshoe Bats can be found in Appendix 2 and that for Lesser Horseshoe bats in Appendix 3.

Validation

A5.23   A HSI model can be reviewed against occurrence data held by the biological records centre. The Gulf of Maine HSI work[13] established the principle of producing several HSI models for one species and retained the model, which had the best association with known occurrences. The mapping is produced and matched with species data at the biological records centre and the model refined to fit the records with a view to errors of omission and commission.

A5.24   Garshelis (2000)[14] concluded that the '...utility of the models is to guide further study or help make predications and decisions regarding complicated systems; they warrant testing but the testing should be viewed as a never-ending process of refinement, properly called bench-marking or calibration.'  The validation should be seen as a continuous refinement process and HSI scoring should be reviewed from time to time and up dated[15].

A5.25   In this study HSI have initially been researched and scored by the author. However, the scores can be varied through review, further research findings or to reflect local conditions based on survey. Where varied by consultants the reason for the variation should be given and supported by evidence.

Density Band

A5.26   The HSI score is multiplied by the location of the proposed site in relation to that of the horseshoe bat roost. The Consideration Zone (CZ) is divided into three Density Bands.  The three Bands are, ‘A’ closest to the record, ‘B’ and ‘C’ furthest from the record valued at 3, 2 and 1 respectively. The values are given in Table 4 below.

Table 4: CZ Band

Band

Score

A

3

B

2

C

1

A5.27   When two Bands occur within one field take the higher value as the score. The Density Band widths can be found in Table 1 above.

A5.28   Following ecological surveys for horseshoe bats carried out for the proposed development the Density Band score may be modified up depending on whether feeding activity was recorded or not or whether absence is recorded. This reflects uneven use of a home range and refines the value of the habitat for a species (e.g. see Bontadina & Naef-Daenzer, 2002[16]). Note that sufficient automated detectors should be deployed

A5.29   The following criteria should be used to modify the Band following the results of site surveys and applied to the whole of the proposed development site:

  • Not present – Where potential habitat is present reduce the Band score down by 0.5, e.g. at A from 3 to 2.5; at B from 2 to 1.5; except at C where it reduced to 0.
  • Commuting only – as the Band the site falls within
  • Commuting and Foraging – increase the band score by 0.5 e.g. at C from 1 to 1.5; at B from 2 to 2.5; A stays as it is.

A5.30   The identification of ‘foraging’ (i.e. a higher level of activity) for horseshoe bat species is defined as:

  • An average of 1 pass per night on one automated detector in any one of the monthly recording periods over the total survey year

 

Calculating the Habitat Unit Value

A5.31   For information the value of the proposed site to a horseshoe bat species in Habitat Suitability value is calculated by using the HSI Score and the Density Band (See Table 5). The outcome of the Habitat Suitability Units used in the HEP is on a scale of 0 to 18[17].

Table 5: Matrix Combining Habitat Suitability Score and Density Band

 

Habitat Suitability Score

Poor

 

1

Marginal

 

2

Average

 

3

Good

 

4

Very Good

 

5

Excellent

 

6

Band

A (3)

 

3

6

9

12

15

18

B (2)

 

2

4

6

8

10

12

C (1)

 

1

2

3

4

5

6

A5.32   The habitat replacement value required is calculated by multiplying the score by the hectarage of the habitat affected (hectares x [HSI x Band]) giving figure in Habitat Units. For example a HSI x Band score of 12 for an area of 1.50 hectares would give a value of 18 Habitat Units.

A5.33   The resultant total of Habitat Units for the whole proposed development site could then be divided by 18 (6 [HS] x 3 [Band]) to arrive at the minimum area in hectares of accessible replacement habitat required to develop the proposed site

A5.34   Hedgerows and some watercourses are not mapped as separate polygons in OS Mastermap and if a width is not known a default width of 3 metres is used and multiplied by the length to give an area in hectares. These values are usually small and do not significantly affect the overall area of a site, and for simplicity’s sake and considering their value to wildlife are not deducted from the area of bordering fields, compartments or OS Mastermap polygons. If preferred calculations can be carried out separately for these features using linear measurements but the end result is the same, especially if a direct replacement value of the hedgerow or watercourse is required.

A5.35   Nonetheless hedgerow and other commuting structure should be seen as having a functional role, and should normally be maintained or replaced to maintain horseshoe bat commuting across a proposed development site.

A5.36   HEP calculations for development sites should be made on the basis that the total site area would be lost to a species and would therefore produce a maximum replacement requirement to develop the site. This saves a separate calculation for the value of the existing habitat on which enhanced habitat is created. Where habitat remains unchanged and is retained by the development it is not included in the calculation.

A5.37   To calculate the amount of replacement habitat provided as mitigation within a master plan for a proposed development site the same procedure as described above is used for each area of created or enhanced habitat. These habitats should in the first instance be aimed at providing optimal foraging habitat for horseshoe bats (although it is unlikely that some habitats such as grazed pasture would be possible to re-create within a development site).

A5.38   Standard prescriptions that can be used for replacement habitats can be found in Annex 6. Habitats will need to be accessible and undisturbed by introduced lighting to count towards mitigation. As all habitats are considered optimal the HSI score would automatically be 6.

A5.39   In addition to the standard calculation described above Fraction Multipliers are also applied to the calculation to allow for temporal effects and the difficulty in restoring or creating a habitat (See below).

 

Fraction Multipliers

A5.40   In delivering the replacement habitat there may also be an issue or risk with delivering a functional offset and the timing of the impact.  A loss in biodiversity would result and there could potentially be a risk to maintaining a species population during the intervening period even though it would recover in time. Therefore, it is important and desirable that where feasible replacement habitat is in place and functional just before development commences on site. However, functionality may not be achieved until several years after replacement habitat has been created and there is a risk that it may fail due to the difficulty in recreating or restoring. To account for these possibilities Fraction Multipliers are used. These are usually applied only once to the calculation for the value of the habitat lost to horseshoe bats. However, in some circumstances the Fraction Multipliers may be applied to habitat created as replacement for that lost where this has been designed and there are multiple habitat types. In this case they are not applied to the habitat lost calculation.  

 

A5.41   The aim of a multiplier is to correct for a disparity or risk. In practice this is very difficult to achieve, not least because of uncertainty in the measurement of the parameters and the complexity of gathering the required data.[18] In order that any habitat creation or enhancement would functionally replace habitat lost to development (and the need to take a precautionary approach in the case of horseshoe bats, as features of European sites and European protected species) a ‘fraction multiplier’ is applied to the resultant Habitat Units needed to replace habitat lost to development in order to provide robust mitigation, e.g. to maintain ‘favourable conservation status’.

A5.42   ‘There is wide acknowledgement that ratios should be generally well above 1:1. Thus, compensation ratios of 1:1 or below should only be considered when it is demonstrated that with such an extent, the measures will be 100% effective in reinstating structure and functionality within a short period of time (e.g. without compromising the preservation of the habitats or the populations of key species likely to be affected by the plan or project.[19] The Environment Bank recommend a two for one ratio where habitats are easily re-creatable contiguous to the development or on similar physical terrain as a minimum.[20]. In many other situations a significantly higher multiplier may be appropriate[21]. The conclusion of the BBOP [Business Biodiversity Offsets Programme] paper (Ekstrom et al, 2008) is that where there are real risks around the methods and certainty of restoration or creation then the Moilanen framework is applicable; but for some other situations, (averted risk ...and where restoration techniques are tried and tested), lower ratios can be used.[22]

A5.43   Appendices 4 and 5 give a guide to difficulty in creating and restoring habitats and the time frame required to reach maturity or functionality.

Delivery Risk

A5.44   As different habitats have different levels of difficulty in creation or restoration there will be different risks associated with each. ‘Once there is an estimate of the failure risk, it is possible to work out the necessary multiplier to achieve a suitable level of confidence (Bill Butcher pers com; Moilanen, 2009; Treweek & Butcher, 2010). The work of Moilanen provides a basis for different multipliers of various levels of risk. We have used this work to come up with categories of difficulty of restoration/expansion, and associated multipliers, as set out in [Table 6] below.’[23]

A5.45   In most cases a multiplier will be applied to the calculation of the habitat lost on the development site and the figure (≥1) shown in middle column of Table 6 below will be used. This assumes that the optimal habitat for horseshoe species will be created. The resultant figure can either be checked against that provided in the Master Plan to confirm that there is sufficient to mitigate the loss or then be used to design the area into a Master Plan.

A5.46   Where the replacement habitat has been designed, and includes several types, in an offsite location, for example, this needs to be checked to ensure that adequate mitigation habitat has been provided. In this case, due to the nature of the calculation the multiplier is inversed (≤1) as shown in the right hand column of Table 6 and applied to the replacement habitat not the lost habitat.  

Table 6: Multipliers for different categories of delivery risk (Defra, 2011)

Difficulty of recreation/restoration

Multiplier

Multiplier

(Where the replacement site has been designed and  consists of multiple habitat types )

Very High

10

0.1

High

3

0.33

Medium

1.5

0.67

Low

1

1

A5.47   For information Appendix 4 gives an indicative guide to risk levels which have been assigned to habitats to these broad categories using expert opinion by Defra (2011). Factors such as substrate, nutrient levels, state of existing habitat, etc. will have an impact on the actual risk factor, which may need to be taken into account.

Temporal Risk

A5.48   In delivering replacement habitat there may be a difference in timing between the implementation of the development and the functionality and maturity of the replacement habitat in terms of providing a resource for the affected species

.           This time lag would be minimised by calculation of existing habitat value in the pre application stage and implementation of the habitat creation and / or restoration in consultation with the local authority and other nature conservation organisations. In some cases the replacement habitat may be planted or managed concurrently with that of the site development.

A5.49   Where a time lag occurs a multiplier will be applied to take account of the risk involved to the ‘no net loss’ objective. These are set out in Table 7 below.  Appendix 5 gives general guidance on how long different habitats would be expected to reach maturity. The actual multiplier used needs to be judged on a case by case basis. As with Delivery Risk the multiplier in the left hand column is likely to apply in most cases (see paragraphs A5.45 and A5.46 above).

A5.50   It is considered that some priority habitats cannot be recreated due to the length of time that they have evolved and the irreplaceability of some constituent organisms, at least in the short and medium terms. It is also considered that in the medium and longer terms the management of any replacement habitat may be uncertain. Therefore Table 7 has been constrained to a maximum period of 20 years. In some cases the time lag for the development of a habitat to support a population may be too long to be acceptable.

Table 7: Multipliers for different time periods using a 3.5% discount rate

Years to target condition

Multiplier

Multiplier

(Where the replacement site has been designed and  multiple habitat types )

5

1.2

0.83

10

1.4

0.71

15

1.7

0.59

20

2.0

0.5

A5.51   An Excel spread sheet in which figures used in the calculation for the HEP just as an example is shown in Appendix 6. It is likely that a full spread sheet will be made available by the Council..

Summary

A5.52   The total replacement habitat required therefore comprises the following metric for each habitat type within a proposed development site. The whole proposed development site should be included in the calculation.

The HSI = Habitat Code (Range 0 to 6) + or – Matrix Code (Range 0 to 6, Default 0) x Formation Code (Range 0 to 1) x Management Code (Range 0 to 1)

 

HSI x Band x hectares x Delivery Risk x Temporal Risk = Habitat Units required.

 

Habitat Units divided by 18 = hectares required

Off Site Replacement Habitat

A5.53   Where there are residual offsets, i.e. where the replacement habitat cannot be created within the proposed development sites red line boundary an allowance is calculated for the value of the existing habitat on the intended habitat creation site as this will be lost or included in the value of any enhancement. Where replacement habitat is located offsite then the value of that site needs to be taken into account. The formula applied to offset losses of existing habitat at the offset site is:

Area Equivalent of Habitat Units Needed to Offset from Development

(Habitat Value of Desired Habitat Type – Habitat Value of Offsite Habitat Creation Site)

A5.54   This figure is then added to the Habitat Units derived from the calculation from the proposed development site and the total divided by 18 to find the amount of offsite replacement habitat required. For example the proposed development requires 32HUs to replace that lost to horseshoe bats. The habitat to be created is valued at a suitability score of 6 and the field intended for the creation of replacement habitat at 1. The calculation would be 32/ (6-1) + 32 = 38.4HU (or, divided by 18, 2.13 hectares).

A5.55   It is critical that the replacement site where habitat has been enhanced is accessible to the population of horseshoe bats affected.


 

 

[1] http://www.fort.usgs.gov/Products/Software/HEP/

[2] U. S. Fish and Wildlife Service. 1980. Habitat Evaluation Procedures ESM102. Washington, D. C.: Department of the Interior.

[3] Dijak, W. D. & Rittenhouse, C. D. 2009. Development and Application of Habitat Suitability Models to Large Landscapes: in Millspaugh, J. J. & Thompson, F. R. 2009. Models for Planning Wildlife Conservation in Large Landscapes. London: Academic Press.

[4]   http://www.somerc.com/integrated+habitat+system/

[5] Phase 1 (JNCC, 1993) habitat mapping can be converted to IHS by using the software provided by Somerset Environmental Records Centre.

[6] http://www.somerc.com/integrated+habitat+system/

[7] http://www.fort.usgs.gov/Products/Software/HEP/

[8] The 1 to 6 scale matches Defra's habitat distinctiveness range used in its metric.

[9] IHS considers that patches of scrub and single trees are matrix habitat acting in combination with main habitats types rather than separate habitats in their own right. It is possible that further sub codes be added to the grassland habitat codes, e.g. calcareous grassland with scattered scrub, etc. but this would lead to a proliferation of coding and current IHS GIS mapping would need amending to take this into account. Therefore by providing a positive multiplier the needs of those species which require a mosaic of grassland and scrub is taken into account.

[10] IHS considers that patches of scrub and single trees are matrix habitat acting in combination with main habitats types rather than separate habitats in their own right.

[11] For example http://www.env.gov.bc.ca/wld/documents/techpub/r20.pdf

[12] Dennis, R.L.H. 2010. A Resource-Based Habitat View for Conservation. Butterflies in the British Landscape. Chichester: Wiley-Blackwell.

[13] http://www.fws.gov/r5gomp/gom/habitatstudy/Gulf_of_Maine_Watershed_Habitat_Analysis.htm

[14] Garshelis, D. L. 2000. Delusions in Habitat Evaluation: Measuring Use, Selection, and Importance: in Boitam, L. & Fuller, T. K. (eds.) 2000. Research Techniques in Animal Ecology: Controversies and Consequences. New York: Columbia University Press.

[15] http://www.fws.gov/r5gomp/gom/habitatstudy/Gulf_of_Maine_Watershed_Habitat_Analysis.htm

[16] Bontadina, F. & Naef-Daenzer, B. 2002. Analysing spatial data of different accuracy: the case of Greater Horseshoe bats foraging: in Bontadina, F. 2002. Conservation Ecology in Horseshoe Bats.  PhD thesis. Universität Bern.

[17] This range is in line with that used for the habitat metric used by Defra in its pilot projects 2012 -2014.

[18] Defra. 2011. Biodiversity Offsetting. Technical paper: proposed metric for the biodiversity pilot in England. London: Department for Environment, Food and Rural Affairs.

[19] European Communities. 2007. Guidance document on Article 6(4) of the'Habitats Directive' 92/43/EEC: Clarification of the concepts of: alternative solutions, imperative reasons of overriding public interest, compensatory measures, overall coherence, opinion of the commission. Brussels: Office for Official Publications of the European Communities.

[20] Briggs, B., Hill, D. & Gillespie, R. 2008. Habitat banking – how it could work in the U.K. http://www.environmentbank.com/docs/Habitat-banking.pdf

[21] Moilanen, A., Van Teeffelen, A., Ben-Haim, Y. & Ferrier, S. 2009. How much compensation is enough? A framework for incorporating uncertainty and time discounting when calculating offset ratios for impacted habitat. Restoration Ecology 17, 470-478.

[22] Defra. 2011. Biodiversity Offsetting. Technical paper: proposed metric for the biodiversity pilot in England. London: Department for Environment, Food and Rural Affairs.

[23] Defra. 2011. Biodiversity Offsetting. Technical paper: proposed metric for the biodiversity pilot in England. London: Department for Environment, Food and Rural Affairs.

Annex 6: Habitat Creation Prescriptions

A6.1     The following are standard prescriptions that can be used as replacement habitat both on development sites and at off-site locations. They are all considered to be scoring 6 in terms of HSI.

Greater Horseshoe Bats[1]

            Pasture

A6.2     Ideally grazed pasture should be created or existing enhanced for Greater Horseshoe bats. It is unlikely that a grazing regime could continue within a development site and the following is more likely to constitute off site enhancements. Ransome (1996) set out prescriptions for grazing regimes: 

Enhancement within 3 kilometres of the roost preferably revert arable to grassland managed to be improved by non-hazardous methods to provide high levels of grass productivity to cope with high densities of livestock between July and September. Where currently grazed the existing regime should be adjusted so that between March and May these pastures should be stocked with cattle, sheep and possibly a few horses at 1.4 cattle/ha or 8 sheep/ha as the weather permits and rotated between cattle and sheep in specific fields to keep a short, but not seriously damaged sward. The fields should be rested in June to allow grass growth to recover, which is likely to be necessary, Silage cutting should not be permitted. From the first of July until mid-September grazing should be at least at 2-3 cattle/ha or cattle mixed with 11-16 plus sheep/ha (maximum level depending on quality and quantity of grass). If weather permits, continue grazing at lower levels into early October. From July onwards primarily mature cattle, in either beef or milking herds, should be used. NB stocking levels may need to be adjusted in the light of climatic conditions influencing the growth of grass in a particular summer.

Grazing has been shown to have a detrimental effect on moth abundance. Outside the 3 kilometres zone in the wider roost sustenance zone cattle may be grazed at 1/ha and sheep at 5/ha. At these lower grazing rates longer swards are likely to be maintained to the benefit of Noctuid moths.

Ivermectin is a broad spectrum antiparasitic drug approved for the use in cattle, sheep and horses. The drug is absorbed systemically after administration and is excreted mainly in the faeces. Being insecticidal, residues of ivermectin in cow dung can reduce the number of dung beetles, appearing to inhibit larval development and/or prevent pupation from taking place and thus could reduce prey availability to Greater Horseshoe bats.[2] In one study higher numbers of Aphodius sp. were found in dung in long swards from cattle treated with ivermectin[3]. However, it appears that smaller numbers emerge from the dung, compared with the dung of untreated cattle, as the number of eggs per female A. rufipes can be significantly reduced but the magnitude of the decline is not large[4].

.

However, it must be emphasised there are inherent issues in using third parties to create new pasture as replacement habitat in perpetuity in terms of reasonableness and enforceability. These were highlighted in the Churston Golf Club planning appeal which was refused as grazing could not be sustained.[5]

            Grassland

A6.3     The creation of species rich grassland is likely to be more feasible in response to providing replacement habitat to mitigate the impacts of a development. This will need to be managed to produce a long sward to support an abundance of Noctuid moths, one of the main prey items hunted by Greater Horseshoe bats. Specified seed mixes should include food plants, as well as grasses, such as dandelion, dock, hawkweeds, plantains, ragwort, chickweed, fat hen, mouse-ear and red valerian and other herbaceous plants. Buddleia and bramble in particular, and other scrub species may be planted within or on the edges of the grassland. The grassland should be divided into parcels and cut in rotation once a year in October and the cuttings removed. Where grassland is established as a field margin this should be at least 6 metres wide.

                        Woodland

A6.4     Again off-site the replacement of coniferous woodland with broad-leaved woodland would benefit Greater Horseshoe bats. This should be carried out gradually over a period of time to avoid extensive clear-felling. Macromoth abundance is higher at the edge of woodland than in the interior. All woodlands should be permeated by grassy rides, and contain grassy glades. They should be managed without insecticide treatments. Glades probably need to be 10 - 15 metres across before they will be used by the bats for feeding. Macromoth abundance and species richness were positively affected by tree species richness and by the relative abundance of native trees in a woodland patch. Of dominant ground types, ‘grass’ and ‘litter’ had higher abundances and species richness than bare ground, herbs, moss or ferns. Woodland size is positively related to macromoth abundance.

Woodlands over 5ha have the highest values of moth diversity and abundance. However, relatively small patches (e.g. woodlands between 1 and 5 ha) seem to contain relatively large moth populations.

However, when creating woodland for horseshoe bats the target species should be considered as the specification will be different (see Lesser Horseshoe bats below)

Hedgerow

A6.5     Hedgerow acts as commuting structure and provides feeding perches for Greater Horseshoe bats. Over 90% of prey caught by bats is brought in on the wind from adjacent habitats. New hedge lines could be planted off-site to divide up large grazed fields into smaller units and link them to blocks of woodland. Hedgerows should be 3 to 6 metres wide and 3 metres high with standard trees planted frequently along its length. The provision of trees increases moth abundance. Cutting should be restricted to the minimum needed to ensure visibility or retain hedgerow structure. Hedgerows are best cut every 2-3 years, working on only one part or side at any time.

A6.6     A species-rich grass strip, a minimum of 6 metres wide, with a long sward, managed as described above, should accompany hedgerow creation as this will enhance moth abundance[6].

 

 

Lesser Horseshoe Bats[7]

 

Woodland with Water

A6.7     Lesser Horseshoe bats hunt a variety of insects which are generally smaller than those consumed by Greater Horseshoe bats. These include micromoths, gnats, midges, mosquitoes, craneflies, brown lacewings, caddis flies and ichneumon wasps. Barataud et al (2000) found the woodland associated with water was the most preferred habitat by Lesser Horseshoe bats.

A6.8     Micromoth abundance is positively related to the relative abundance of native trees[8] and unlike macromoths the percentage cover of understory in a woodland patch. Micromoth abundance was higher within the woodland interior than at the edge. The shape of the woodland patch was important particularly for woodland micromoth species, indicating that patches of compact shapes (with proportionally less edge exposed to the surrounding matrix) sustain a larger number and larger populations of woodland species of micromoths. This highlights the importance of designing patches of compact shapes, especially when the patch to be created is small. Brown lacewings can be found amongst conifers. Woodland trees and shrubs should be planted in naturalistic non-linear patterns. Scalloped edges and bays will provide sheltered areas with higher insect concentrations. Provide a variety of types of vegetation from trees to shrubs and rough grass. Overhanging branches and bushy shrubs should be left to provide cover. Woodland edges can be used both by bats that fly in woodland and in the open. When developed the woodland should not be coppiced.

A6.9     Mosquitoes and caddies fly larvae are aquatic, as can be gnat larvae. Gnats and midges also use damp places near water to breed. Therefore the incorporation of ponds in association with the woodland habitat is likely to increase their value to Lesser Horseshoe bats. Ponds with permanent water should be created. It is possible that these could form attenuation features as part of the surface water mitigation for a development. They should be designed so that water is maintained within them throughout the year.

A6.10   Variation on the banks of ponds favours high insect and structural diversity. Design in as many natural features as possible, including varied depths, diverse aquatic and bankside vegetation, and overhanging trees. Grassy margins, scrub and overhanging vegetation provide excellent conditions for insects. Habitat diversity can often be achieved simply through allowing growth of taller vegetation. Where bank management is necessary, restrict it to a small area and work on one bank at a time. Carry out management sensitively, aiming to enhance variation in vegetation. Use fencing to prevent livestock from causing excessive damage to water margins.

                        Grassland

A6.11   Long sward grassland is also of benefit to Lesser Horseshoe bats as that described above for Greater Horseshoe bats. The management of grassland should be as that fro Great Horseshoe bats. Rough grassland and scrub is an important predictor of micro moth abundance

Hedgerow

A6.12   Hedgerow acts as commuting structure and provides feeding perches for Lesser Horseshoe bats. Over 90% of prey caught by bats is brought in on the wind from adjacent habitats. New hedge lines could be planted off-site to divide up large grazed fields into smaller units and link them to blocks of woodland. Hedgerows should be 3 to 6 metres wide and 3 metres high with standard trees planted frequently along their length. The provision of trees increases moth abundance.

 

 

[1] Derived from Ransome, R. D. 1996. The management of feeding areas for greater horseshoe bats. English Nature research report No.174. Peterborough: English Nature; Fuentes-Montemayor,E., Goulson, D.,Cavin, L., Wallace, J. M. & Park, K. J. 2012. Factors influencing moth assemblages in woodland fragments on farmland: Implications for woodland management and creation schemes. Biological Conservation 153 (2012) 265–275; Merckx, T. & Macdonald, D. W. 2015. Landscape-scale conservation of farmland moths: in Macdonald, D. W. & Feber, R. E. (eds) 2015. Wildlife Conservation on Farmland. Managing for Nature on Lowland Farms.   Oxford: Oxford University Press; Fuentes-Montemayor, E., Goulsion, D.& Park, K. J. 2010, The effectiveness of agri-environment schemes for the conservation of farmland moths: assessing the importance of a landscape-scale management approach. Journal of Applied Ecology 48, 532-542

[2] http://jncc.defra.gov.uk/page-2736

[3] Foster, G., Bennett, J. & Bateman, M. 2014. Effects of ivermectin residues on dung invertebrate communities in a UK farmland habitat. Insect Conservation and Diversity, 7 (1): 64-72; Beynon, S.A., Peck, M., Mann, D.J. & Lewis, O.T. 2012.  Consequences of alternative and conventional endoparasite control in cattle for dung-associated invertebrates and ecosystem functioning. Agriculture, Ecosystems & Environment, 162, 36-44.

[4] O’Hea, N.M., Kirwan, L., Giller, P.S. & Finn, J.A. 2010. Lethal and sub-lethal effects of ivermectin on north temperate dung beetles, Aphodius ater and Aphodius rufipes (Coleoptera: Scarabaeidae). http://repository.wit.ie/1974/2/Bioassays_final.pdf

[5] See paragraphs 41 to 50 of Appeal Ref: APP/X1165/A/13/2205208 Land at Churston Golf Club, Churston, Devon, TQ5 0LA. https://acp.planninginspectorate.gov.uk/ViewCase.aspx?Caseid=2205208&CoID=0

[6] Merckx, T. & Macdonald, D. W. 2015. Landscape-scale conservation of farmland moths: in Macdonald, D. W. & Feber, R. E. 2015. Wildlife Conservation on Farmland. Managing for Nature on Lowland Farms. Oxford: Oxford University Press.

[7] Derived from Barataud, M., Faggio, G., Pinasseau, E. & Roué, S. G. 2000. Protection et restauration des habitatas de chasse du Petit rhinolophe (Rhinolophus hipposideros) Année 2000. Paris: Ministère de l’Environnement – Direction de la Nature et des Paysages ; Fuentes-Montemayor,E., Goulson, D.,Cavin, L., Wallace, J. M. & Park, K. J. 2012. Factors influencing moth assemblages in woodland fragments on farmland: Implications for woodland management and creation schemes. Biological Conservation 153 (2012) 265–275; Chinery, M. 2007. Insects of Britain and Western Europe. London: A & C Black; Fuentes-Montemayor, E., Goulsion, D.& Park, K. J. 2010, The effectiveness of agri-environment schemes for the conservation of farmland moths: assessing the importance of a landscape-scale management approach. Journal of Applied Ecology 48, 532-542; Entwistle, A. C., Harris, S., Hutson, A. M., Racey, P. A., Walsh, A., Gibson, S. D., Hepburn, I. & Johnston, J. 2001. Habitat management for bats: A guide for land managers, land owners and their advisors. Peterborough: Joint Nature Conservation Committee.

[8]Many native tree species (e.g. Betula sp., Quercus sp. and Salix sp.) have large numbers of moth species associated

with them (i.e. feeding on them), although this is not always the case and there are native trees (e.g. Fagus sylvatica) which support relatively few moth species, comparable in number to those supported by non-native trees (e.g. Acer pseudoplatanus; Young, 1997)’ [Fuentes-Montemayor,E., Goulson, D.,Cavin, L., Wallace, J. M. & Park, K. J. 2012. Factors influencing moth assemblages in woodland fragments on farmland: Implications for woodland management and creation schemes. Biological Conservation 153 (2012) 265–275];  Entwistle, A. C., Harris, S., Hutson, A. M., Racey, P. A., Walsh, A., Gibson, S. D., Hepburn, I. & Johnston, J. 2001. Habitat management for bats: A guide for land managers, land owners and their advisors. Peterborough: Joint Nature Conservation Committee.

Annex 7: Application of the Habitats Regulations

A7.1     The Habitats Regulations protect identified sites by designation as Special Areas of Conservation.  However, the Habitats Regulations also protects habitat which is important for the Favourable Conservation Status of the species.[1] 

A7.2     Achieving Favourable Conservation Status of a site’s features “… will rely largely on maintaining, or indeed restoring where it is necessary, the critical components or elements which underpin the integrity of an individual site.  These will comprise the extent and distribution of the qualifying features within the site and the underlying structure, functions and supporting physical, chemical or biological processes associated with that site and which help to support and sustain its qualifying features”.[2]

A7.3     Regulation 61 Habitats Regulations states that:

 A competent authority, before deciding to undertake, or give any consent, permission or other authorisation for, a plan or project which –

  • is likely to have a significant effect on a European Site … (either alone or in combination with other plans or projects), and
  • is not directly connected with or necessary to the management of that site must make an appropriate assessment of the implications for that site in view of that site’s conservation objectives.

A7.4     Regulation 61 therefore describes a two-stage procedure: a screening stage where the “competent authority” has grounds to conclude whether a plan or project is likely to have a significant effect on a European site, and the appropriate assessment stage if it concludes that a significant effect is likely.

A7.5     In accordance with Regulation 61 information submitted with a planning application will be used by the Somerset Authorities to determine whether the proposal is likely to have a significant effect on the SAC. The Somerset authorities will apply a “Test of Likely Significant Effect” for proposals which involve or may involve:

  • the destruction of a Greater Horseshoe and/or Lesser Horseshoe bat roost (maternity, hibernation or subsidiary roost);
  • loss of foraging habitat for SAC bats
  • fragmentation of commuting habitat for SAC bats
  • increase in luminance in close proximity to a roost and/or increase in luminance to foraging or commuting habitat
  • impacts on foraging or commuting habitat which supports the SAC bat populations structurally or functionally

A7.6     When considering whether a project is likely to have a significant effect on a European site, the competent authority should take account of mitigation measures which are built into the project. Mitigation measures are measures which are designed to avoid or reduce adverse effects on a European site. It is important to distinguish these from compensatory measures which are designed to compensate for unavoidable adverse effects on a European site and follow the “3 tests”[3].  Compensatory measures will not be taken into account at the Test of Likely Significant Effect stage.

A7.7     The precautionary principle underpins the Habitats Directive[4] and hence the Habitats Regulations and must be applied by the local planning authority as Competent Authority as a matter of law.[5] It is clear that the decision whether or not an appropriate assessment is necessary must be made on a precautionary basis.[6] In addition, the Waddenzee judgement[7] requires a very high level of certainty when it comes to assessing whether a plan or project will adversely affect the integrity of a European site. The judgement states that the competent authority must be sure, certain, convinced that the scheme will not adversely affect the integrity of the site. It goes on to state that that there can be no reasonable scientific doubt remaining as to the absence of adverse effects on the integrity of the site.

A7.8     For the Somerset authorities to be able to conclude with enough certainty that a proposed project or development will not have a significant effect on the SAC, the proposal or project must therefore be supported by adequate evidence and bespoke, reasoned mitigation. Where appropriate a long term monitoring plan will be expected to assess whether the bat populations have responded favourably to the mitigation. It is important that consistent monitoring methods are used pre- and post-development, to facilitate the interpretation of monitoring data.

A7.9     Mitigation, an Ecological Management Plan and, (where required) monitoring during and / or post development, will be secured through either planning conditions or a S106 agreement or both. Data from monitoring will be used by the Somerset Authorities to determine how the bat populations have responded to mitigation and to increase the evidence base.

________________________________________________

[1] See European Site Conservation Objectives for Bath and Bradford on Avon Bats Special Area of Conservation at Annex [ ]

[2] Natural England Standard: Conservation Objectives for European Sites in England Standard 01.02.2014 V1.0 http://publications.naturalengland.org.uk/publication/6734992977690624

[3] See ODPM circular 06/2005

[4] Council Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and  flora (known as the ‘Habitats Directive’)

[5] Assessing Projects under the Habitats Directive: Guidance for Competent Authorities 2011, CCW p.15

[6] ODPM Circular 06/2005 para13

[7] ECJ judgement: C-127/02 [2004] ECR-I