The English metric uses ‘distinctiveness’ where ‘conservation value’ would be a better term. ‘Distinctiveness’ is a potentially misleading term in this context and would be best avoided in a Scottish metric. For example, species-poor agriculturally improved grassland (NVC MG7), rhododendron scrub, dense Sitka spruce plantation and patches of Himalayan balsam or giant hogweed are undoubtedly distinctive but of low biodiversity interest and, in various ways, ecologically undesirable. So are supermarket car parks and six-lane motorways.
Some of the English metric’s habitat categories are broad enough to encompass considerable variation in rarity, species-richness, occurrence of notable species, and so on. A single conservation value level applied to such habitat categories can therefore lead to unrealistic or inappropriate scorings in some cases. Subdivision of metric habitat categories, based largely on the NVC, helps to fine-tune conservation value scores. Ideally, it would be good to have flexibility of scoring beyond just the habitat category, as there can be instances of varied ecological significance within a single NVC community or even sub-community – for example, the presence of a rare species, or some other ecologically interesting aspect of the habitat. It is acknowledged, of course, that attempting to incorporate such details could get very complicated.
In Appendix 3 we have suggested conservation value scores for use in Scotland that differ from those (distinctiveness values) given in the current English metric. These are discussed below (VL = very low; L = low; M = medium; H = high; VH = very high, VH+ = very high with especially notable significance):
Upland acid grassland is given a M score in the English metric but is a very varied category including montane snowbeds and summit heaths (NVC U7-14) of high ecological interest and conservation value, worthy of VH/VH+, and species-rich acid grasslands (NVC U4c/5c/4F/6R) also worthy of VH.
Lowland dry acid grassland UK BAP priority habitat scores VH in the current English metric, but from our experience of it in Scotland we think H is more appropriate here – otherwise it scores higher than such things as some fine examples of upland calcareous grassland scoring H.
Among the Other neutral grassland, all of which currently scores M in the English metric, Lolium-Cynosurusneutral grassland (NVC MG6) and Elytrigia repens grassland (no NVC), both of which are in some way artificial and species-poor, seem more worthy of L. Also, among Other neutral grasslands that currently score M, Schedonorus arundinaceus vegetation (NVC MG12), which is not very common here, appears worthy of H.
Upland calcareous grassland currently scores H in the English metric, but the uncommon montane/northern forms (NVC CG12-14), including Dryas heath, and also the rare upland examples of the more southern NVC CG2 community, seem worthy of VH.
Lowland calcareous grassland currently scores H in the English metric, but VH seems more appropriate through Britain generally, except perhaps for tall (less species-rich) southern forms (NVC CG3-6) and, in Scotland, examples belonging to NVC CG10 – we have suggested H for these.
Tall herb communities score H in the English metric, but given its small total extent, high species diversity, naturalness and, in many places, presence of rare species, a VH score appears more realistic.
Bracken currently scores L in the English metric, but we suggest M – otherwise it scores the same as agriculturally improved grasslands (which are less semi-natural than bracken stands).
Native pine woodlands scores H in the English metric, but given the obvious importance of this habitat, surely VH+ would be more appropriate.
Upland birchwoods, Upland oakwoods, Upland mixed ashwoods, Wet woodland, Lowland mixed deciduous woodland and Lowland beech/yew woodland all currently score H in the English metric, but these UK BAP priority habitats have a high degree of naturalness when compared with unwooded habitats at these altitudes. With this in mind, as well as the generally accepted need for us to greatly value and look after our remaining examples of semi-natural woodland, we think VH is more appropriate. Indeed, we also suggest VH+ for all examples that are forms of temperate rainforest.
Aspen woodland currently has to be placed in Other woodland; broadleaved, scoring M in the English metric, but given the known high biodiversity value of aspen stands we suggest that this habitat is given a separate category and a VH score.
Felled woodland currently scores H in the English metric, but we have suggested L in Appendix 3.
Montane willow scrub currently scores VH in the English metric; we have suggested a higher VH+ score because it is so rare and vulnerable, and is one of the more natural forms of upland vegetation.
Upland heathland scores H in the English metric, but this category is very varied, including species-poor burned/degraded heath (NVC H9) for which we suggest M, and species-rich or otherwise notable upland heaths (H10d, H21b, M14, M15a, M15c with dwarf juniper, non-NVC Calluna heath with mesotrophic herbs and non-NVC calcicolous Arctostaphylos uva-ursi heath) for which we suggest VH (indeed, VH+ for H21b because of the international significance of its oceanic liverwort assemblages).
Lowland heathland scores H in the English metric, but some rare forms restricted to parts of southern England could be more worthy of VH.
Juniper scrub does not yet have a score because there is no English metric category for it; we consider it to be worthy of a VH score.
Hawthorn scrub currently scores M in the English metric, but the geographically restricted and relatively species-rich southern NVC sub-community W21d seems worthy of H.
Hazel scrub is given a M score in the English metric, but H seems more appropriate and indeed VH+ for rainforest examples, which can be of great international importance for oceanic bryophytes and, especially, lichens.
Willow scrub scores M in the English metric but is a habitat of high conservation value and more than just a precursor to taller woodland; a score of H or VH seems more appropriate.
Non-native sea buckthorn scrub currently scores L in the English metric, but it can still have a considerable semi-natural element and is perhaps worthy of M, especially given that native sea buckthorn scrub, which can be floristically similar, scores H.
Rhododendron scrub scores L in the English metric, but we think VL is more appropriate because this invasive alien shrub has such a damaging effect on various habitats including internationally important western temperate rainforest.
Other types of non-native scrub have no current score in the English metric; we suggest L or, in the case of Rosa rugosa (quite seriously invasive in places) VL.
Raspberry and ivy underscrub have no score because they have no current place in the English metric; we suggest M for these.
Modified bogs score VH in the English metric; we suggest H because they are ecologically poorer than active bogs in good condition.
Fen (upland and lowland) has a VH score in the English metric but is a very varied category that includes species-poor Molinia (NVC M25a/b) for which a lower score of M seems more appropriate.
Reedbeds score H in the English metric, but we suggest VH unless they show signs of eutrophication (as in NVC S26), in which case H. Phragmites swamps in shallow water appear reasonably natural, and Phragmitesfens belonging to NVC S24/25 (and S27 with abundant Phragmites) can be of great botanical interest.
Inundation herb communities do not seem to have a clear place in the current English metric but seem worthy of recognition with scores of M or, in the case of rare southern forms, VH.
Coastal cliff and Coastal sand dune habitats currently score H in the English metric but given their ecological interest and naturalness we think VH is more appropriate.
Ruderal/ephemeral vegetation currently scores L in the English metric, but it can be of great interest, so we think M is more suitable.
Winter stubble currently scores L in the English metric but could be M because it can be good habitat for birds.
Some urban habitats (Allotments, Bioswale, Rain garden, Sustainable drainage system, Vacant or derelict land and Vegetated garden) score L in the English metric but could be worthy of M because they can make a significant contribution to biodiversity.
These suggested changes to conservation value scores are not based on the English metric’s stated criteria for defining the various categories but are based on a more general assessment of scarcity, naturalness and richness. The current criteria as stated in the English metric’s documentation, with much reference to the Natural Environment and Rural Communities (NERC) Act, Priority Habitat and Red List categories, might seem logical but they lead to some scoring that doesn’t seem right when looked at from a more general ecological perspective.
Key Criteria for Measuring Conservation Value
Habitat Size: Larger habitats generally support more species and have higher resilience.
Distinctiveness: Assesses the rarity of the habitat type and its species, often on a national or international level.
Condition: Evaluates the quality of the habitat, including species diversity, structure, and functionality.
Connectivity: Measures how well the habitat is linked to other areas, crucial for species movement.
Strategic Significance: Considers the location and its importance within local, regional, or national nature strategies.
Threat of Human Interference: Assesses vulnerability to disturbance or loss.
Methods and Tools
Biodiversity Metric 4.0/3.1: The standard tool for evaluating changes in habitat value, calculating scores based on the factors listed above.
Site Surveys: Expert ecological assessments determine the ecological condition and species diversity on the ground.
NVC survey by Ben and Alison Avis
Remote Sensing/GIS: Used to map habitat extent, fragmentation, and connectivity. (John Cassidy)
For assessing biodiversity at Dun Coillich, high-resolution UAV/drone imagery (LiDAR, multispectral) is best for mapping habitat structure and vegetation types, while satellite data (Copernicus) provides landscape-level change detection. Thermal imaging drones can track wildlife, and passive acoustic monitoring (AI-paired) helps identify species. These tools enable non-invasive monitoring of habitat restoration, species distribution, and environmental stress over time.
Key Remote Sensing Technologies for Dun Coillich:
LiDAR (Light Detection and Ranging): Mounted on drones to create high-resolution 3D structural models of woodland/heathland, allowing precise habitat mapping, tree height measurement, and vegetation structure assessment.
Multispectral & Hyperspectral Imaging (Drones/Satellite): Captures near-infrared data to identify different vegetation species, assess vegetation health (phenology/physiology), and distinguish between habitat types.
Thermal Imaging (Drones): Useful for surveying wildlife, such as deer or ground-nesting birds, especially in challenging terrain or dense vegetation.
Satellite Data (e.g., ESA Sentinel-2): Suitable for large-scale, long-term monitoring of reforestation progress, habitat changes, and land-use changes over time.
Passive Acoustic Monitoring (PAM): Uses sensors to record sounds in the environment, which can be analyzed using AI to identify species presence and diversity.
These methods provide essential data for monitoring biodiversity, especially for tracking restoration progress at sites like Dun Coillich
Extra information about - Remote Sensing
Indicator Species: Monitoring specific, sensitive species to represent overall habitat health.
Suitable biodiversity indicator species for Dùn Coillich in Highland Perthshire, a site with upland, woodland, and grassland habitats, include species representative of Scottish upland biodiversity. Key indicators to track restoration and ecosystem health are likely to include heather moorland species, breeding birds, and specific woodland wildflowers
.
Key Potential Indicator Species:
Upland & Moorland Habitats:
Heather/Ling (Calluna vulgaris): Monitors heathland condition and regeneration.
Bilberry (Vaccinium myrtillus): Indicates woodland ground flora and upland heath health.
Meadow Pipit & Skylark: Indicators of open, upland mosaic habitats.
Woodland & Scrub Restoration:
Downy Birch (Betula pubescens) & Oak (Quercus robur): Monitoring young woodland development (W4/W10 communities).
Rowan (Sorbus aucuparia): Indicates colonization and successional change.
Woodland Birds (e.g., Willow Warbler): Indicators of scrub and new woodland establishment.
Grassland & Special Habitats:
Limestone Grassland Flora: Species like Wild Thyme (Thymus polytrichus) or Saxifrages, indicating base-rich soils.
Butterflies and Bees: Indicators of species-rich grassland connectivity and wildflower abundance.
Peatland Areas:
Bog Mosses (Sphagnum spp.): Indicators of peat health and hydrology.
These species are selected based on the varied habitats present at Dùn Coillich, which include young native woodland, upland, limestone outcrops, and calcareous grasslands. Monitoring these species can provide insights into habitat changes following conservation efforts
Freshwater Burns (Goulandie Burn and others)
Based on the habitat restoration, woodland regeneration, and conservation activities occurring at Dùn Coillich in Highland Perthshire, biodiversity indicator species for a burn (stream) would focus on water quality, habitat connectivity, and the return of woodland/wetland riparian zones.
Suitable indicator species and groups, based on local reports and Scottish upland monitoring, include:
1. Invertebrates (Water Quality Indicators)
Freshwater invertebrates are excellent indicators of stream health. A healthy, oxygen-rich burn on Dùn Coillich would support species sensitive to pollution and low oxygen.
Stonefly Nymphs (Plecoptera): Indicate high oxygen levels and low pollution.
Mayfly Nymphs (Ephemeroptera): Specifically, species that thrive in clean, fast-flowing upland streams.
Caddisfly Larvae (Trichoptera): Diverse communities indicate a stable, healthy ecosystem.
(Freshwater Pearl Mussel (Margaritifera margaritifera): While rare, their presence (or suitability of habitat) indicates very high water quality, though they are endangered. )
2. Mammals & Birds (Riparian and Aquatic Ecosystem Health)
Species that depend on the burn for food and habitat indicate a functioning food web.
Otter (Lutra lutra): A key indicator of healthy river ecosystems with ample fish/invertebrate populations. They are active in the area.
Water Vole (Arvicola amphibius): Indicates high-quality bankside habitats (wetland/grassy) and a lack of mink.
Common Heron (Ardea cinerea): Regularly seen and indicates fish or amphibian presence.
Grey Wagtail (Motacilla cinerea): A bird specialized in nesting and feeding along fast-flowing, rocky burns.
3. Riparian Flora (Stream-bank Health)
Plants that indicate a healthy,, un-browsed, or regenerating riparian edge, supporting the work done to reduce deer/sheep damage.
(Marsh Saxifrage (Saxifraga hirculus): A rare species for which Dùn Coillich has potential habitat not yet planted.)
Globeflower (Trollius europaeus): Indicates damp, ungrazed, nutrient-rich flush areas.
Marsh Marigold (Caltha palustris): A key indicator of wet,, boggy banks.
Water Avens (Geum rivale): Typical of wet,, base-rich woodland burns.
Bog Cotton (Eriophorum spp.): Indicates acidic, waterlogged areas adjacent to the burn.
4. Riparian Woodland Indicators
As the burn sides are part of the woodland restoration project, these plants show the successful return of a shaded burn ecosystem.
Rowan (Sorbus aucuparia): Extensively regenerating, providing habitat for insects.
Downy Birch (Betula pubescens): A key tree species returning to the riparian corridor.
Wood Ants (Formica spp.): Their presence indicates the return of mature wooded areas, often foraging along the edge of burns.
Monitoring these species, particularly via invertebrate kick-sampling or recording otter/vole signs, would provide strong data on the health of the burns as Dùn Coillich continues to recover.
Measuring Biodiversity Net Gain (BNG) on the 1100-acre Dun Coillich community hill land is best achieved by using the statutory Biodiversity Metric tools (as described on the GOV.UK website) to establish a baseline and future targets, focusing on habitat size, quality, distinctiveness, and connectivity. Given its Scottish location, utilizing emerging NatureScot guidelines is essential for assessing upland habitats like peatland and moorland, ensuring improvements exceed a 10% gain.
Key Steps for Measuring BNG at Dun Coillich:
Establish Baseline Habitat Units: Use a qualified ecologist to map existing habitats across the 1100 acres, assigning distinctiveness and condition scores to calculate total baseline biodiversity units.
Apply the Correct Metric: While the DEFRA tool is standard in England, Scottish-specific approaches (as described in this NatureScot document should be used to evaluate peatland, woodland, and moorland habitats on the site.
Assess Condition and Type: Measure habitat quality (distinctiveness, condition, and strategic significance) as these factors strongly influence the unit value rather than just the area.
Create a BNG Plan: Develop a strategy to achieve at least a 10% increase, focusing on enhancing existing habitats or creating new ones, such as native woodland regeneration or peatland restoration.
Monitor Progress: Use consistent, repeated surveys to track changes in biodiversity units over time, comparing post-intervention results against the initial baseline.
Genetic diversity within a species, low genetic diversity can result in low resilience to environmental change. Tools evaluating genetic diversity within populations are too constrained to provide a useful means of calculating biodiversity as a whole.
Abundance of priority species
Number of individuals of a priority species (e.g. red list species - see below for some Dun Coillich Details). For most species a complete census is not feasible, and an estimate is derived from a standardised sampling protocol. Estimates can vary, particularly for mobile species, and can show significant temporal variation. Focus on monitoring priority species can result in trade-offs between species.
Species richness
The number of species present. This is often targeted to a particular taxon or functional group (e.g. the number of species of vascular plants or insect pollinators) and many standard protocols encompass both identifying and quantifying species. This involves using standardised methodology and data can feed into the UK biodiversity indicators. As with metrics relating to species abundance these metrics can show significant temporal variation.
Indicator species
Here the focus is on indicator species that reflect habitat quality – indicators could be both positive or negative. For example, plant species associated with high quality species rich grasslands, or invertebrates that reflect water quality. Constraining the species list to indicator species can reduce the level of ecological expertise required in addition to time in the field.
Ecosystem health/ function
Measurement of the health of an ecosystem and its ability to function and provide ecosystem services.
Functional/or response diversity
Here information on species occurrence is integrated with information on the traits of the species present. Response diversity focusses on a wide suite of traits and measures the ability of a community to respond to environmental change. Functional diversity focusses on traits related to a particular ecosystem function (e.g.pollination services). Functionally diverse communities are perceived to promote ecosystem resilience under environmental change, ensuring the ecosystem processes in question persists. Metrics related to functional or response diversity are reliant on the existence of comprehensive trait databases which are lacking for many taxa.
Irreplaceable habitats
The occurrence of habitats of conservation concern (e.g.Annex 1 habitats) or irreplaceable habitats (e.g.Raised bog)
Habitat extent
The total area of habitat/habitats. This measure is easily upscaled from site to landscape level, and could draw on spatial data derived from remote sensing. However, the value of habitats to biodiversity varies considerably depending on their condition.
Habitat extent and condition
The total area of habitat/habitats alongside a measure of their condition (i.e.habitat quality). Condition is usually based on collection of a variety of metrics relating to habitat structure and in some instances the occurrence of key indicator species and management information. Collecting on the ground data on habitat condition provides more detailed information on the biodiversity value of habitats. However, on the ground collection of data requires more time for baseline and follow-up monitoring.
Habitat extent, condition and distinctiveness
In addition to encompasses extent and condition this metric recognises that not all habitats are equal with respect to their biodiversity value. Distinctiveness of a habitat provides a measure of habitat rarity and importance and may be dependent on its rarity (at national, international level), proportion protected, and priority status (national, international level). Once underlying scores on distinctiveness have been derived, this metric would involve similar effort to metrics based on habitat extent and condition.
Ecological connectivity
This metric takes into account the spatial arrangement of habitats in the landscape. Restoring ecological connectivity is a key priority to ensure that nature can thrive in the face of environmental change. Enhancing connectivity between habitats through the creation of corridors and stepping stones is fundamental to the Scottish government's ambitions of creating a Nature Network. In the Central Scotland Green Network area, network modelling has spatially identified opportunity areas for some habitats where the creation of new habitat will optimise connectivity. However, this mapping is geographically constrained.
Dùn Coillich community woodland, located near Schiehallion in Highland Perthshire, has undergone significant ecological restoration from a former deer farm, resulting in the presence a number of red-listed bird species of conservation concern by year three of monitoring
The site hosts a mosaic of habitats supporting a variety of species, including several threatened with extinction in Scotland.
Red-Listed and Protected Species Found on Dùn Coillich:
Birds: The site supports species listed on the Birds of Conservation Concern (BoCC) Red List, including:
Hen harrier, Golden eagle, Merlin, Black grouse, Woodcock, Peregrine, Common sandpiper, Garden warbler, Kestrel, Osprey, Skylark, Tawny owl, Curlew, Lapwing
Mammals: The site has attracted Red Squirrels and is home to Pine Martens and Water Voles. Beavers were present.
Butterflies: The rare Pearl-bordered fritillary has been recorded, along with the Northern Brown Argus
Flora:
Montane Scrub: Rare "wee trees" such as Mountain willow are present.
Habitat Restoration: The site hosts uncommon species like Shady Horsetail (Equisetum pratense) and Round-leaved Sundew.
Rare Plant Initiatives: The Royal Botanic Garden Edinburgh has surveyed the site for introducing other threatened species, including Oblong Woodsia, Small Cow Wheat, Whorled Solomon's Seal, Alpine Blue Sowthistle, and Marsh Saxifrage.
Oblong Woodsia and Marsh Saxifrage have not yet been planted.
The site is managed to encourage biodiversity, including the protection of adders and the creation of habitats for insects and woodland birds
Tayside Local Biodiversity Action Plan
Key species in the Tayside BAP include:
Mammals
Red Squirrel: A major focus of conservation efforts, particularly in Perthshire and Angus woodlands.
Water Vole: Monitored and protected, especially in Strathardle and the Angus Glens, due to local declines.
Otter: Protected along rivers and in the Tay Reedbeds.
Pine Marten: Monitored with den boxes at sites like Loch of the Lowes.
Scottish Wildcat: Identified as a key, critically endangered species in the area.
Bats: Key species include the Pipistrelle, Daubenton’s, Natterer’s, and Brown Long-eared Bat.
Other: Mountain hare, Hedgehog, and Brown Hare.
Birds
Farmland & Woodland: Barn Owl, Tree Sparrow, Yellowhammer, Linnet, Grey Partridge, Lapwing, Corn Bunting, and Skylark.
Wetland/Reedbed: Reed Bunting, Bearded Tit, Water Rail, Sedge Warbler, Marsh Harrier, and Osprey.
Upland: Golden Eagle, Snow Bunting, Black Grouse, Peregrine, Raven, and Ptarmigan.
Coastal: Pink-footed and Greylag Geese, seabirds.
Invertebrates
Butterflies: Small Blue (Angus coast), Northern Brown Argus (Angus Glens/Perthshire), Pearl-bordered and Small Pearl-bordered Fritillary, Dark Green Fritillary, Scotch Argus, and Grayling.
Moths: Dark Bordered Beauty, Cinnabar, Six-spot Burnet, and Lunar Hornet Moth.
Bees: Osmia inermis (Mason Bee).
Other: Freshwater Pearl Mussel (South Esk), White-clawed Crayfish.
Plants & Trees
Trees: Aspen (a focus of the Tayside Aspen Project).
Flora: Slender Naiad (found in local lochs), Twinflower, Alpine Sow-thistle, Alpine Forget-me-not, and Various Alpine/Montane lichens.
Amphibians & Fish
Amphibians: Common Toad, Palmate Newt.
Fish: Brown Trout
Birds at Dun Coillich that are on the UK red list
Birds of Prey & Owls
Hen Harrier (Circus cyaneus)
Merlin (Falco columbarius)
Short-eared Owl (Asio flammeus)
Seabirds & Gulls
Herring Gull (Larus argentatus)
Common Gull (Larus canus) – Added in 2024
Garden, Farmland & Woodland Birds
Greenfinch (Carduelis chloris)
Linnet (Linaria cannabina)
Redpoll (Acanthis flammea/cabaret)
House Martin (Delichon urbicum)
Tree Pipit (Anthus trivialis)
Twite (Linaria flavirostris)
Spotted Flycatcher (Muscicapa striata)
Starling (Sturnus vulgaris)
Grasshopper Warbler (Locustella naevia)
Waders
Curlew (Numenius arquata)
Thrushes
Ring Ouzel (Turdus torquatus)
Fieldfare (Turdus pilaris)
Mistle Thrush (Turdus viscivorus)