This section contains practical information on what to look for and what to do in relation to key road related features. It describes the typical threats and influences and the opportunities that may exist for positive action. Links are made to sources of further information and guidance.
Features covered in this section are:
Boundaries and Linear Features
Boundary and linear features have been identified as priority habitats by the UK Biodiversity Steering Group. Road networks create very long boundaries indeed. Drystone walls (dykes) are characteristic features in some parts of Scotland and represent valuable habitat. Dykes provide an important habitat for lichens, mosses, ferns and flowering plants. Small holes can form nesting sites for birds such as wrens, wheatear and wagtails. Reptiles such as adders and lizards may hunt and hide in crevices. Even old remnant walls can be good habitats for plants and insects. Hedges and dykes may have ditches associated with them, and this increases the species diversity of the habitat.
Existing hedgerows should be protected and enhanced by implementing good management practices, and new hedges should be planted using appropriate species mixes for the locality. Construction of new drystone walling, perhaps using surplus excavated materials from road works, should also be considered.
Threats and influences
Opportunities
|
Species/Groups |
Sensitivities |
Timing |
Positive Actions |
|
Reptiles |
Hibernation, basking, feeding (walls) Some protection under the Wildlife and Countryside Act |
All year |
Consider fences or artificial hibernation sites where road development threatens existing population (consult experts on appropriate measures) |
|
Northern Brown Argus - Butterfly |
Loss of habitat and larval foodplant |
All year |
Provide larval foodplant (common rockrose) and warm south facing slopes with base rich soils |
|
Lichens/mosses/ferns/invertebrates on old walls |
Habitat loss |
All year |
Leave old walls intact where possible |
Links: Cost Effective Landscape: Learning from Nature
Verges
Grass, shrub and tree verges are the main habitats alongside roads, and have the potential to make a valuable contribution to biodiversity. Their management can be adjusted to favour a particular mix of species appropriate to the area and any relevant Local BAP objectives. Invertebrates may especially benefit where the surrounding area is otherwise intensively managed farmland. As an example of the value of verges, the only known colony of narrow-bordered five spot burnet moth in Scotland is on the verge of the A711 (see Part C - NHZ 19, Dumfries and Galloway). In the Angus Glens (Cairngorms), roadside verges which have not been treated with herbicides are thought to be an important refuge for old grassland species.
The use of chemicals to control weeds can damage wildlife. Reviewing chemical use and identifying where their use can be avoided or limited can directly benefit the environment and reduce maintenance costs. There are external sources of advice and information available; for example 'Targeted Inputs for a Better Rural Environment' (TIBRE) is an initiative led by SNH to help farmers reduce their chemical use through improved technology.
Grassland and farmland
Cereal field margins are defined as 'strips of land lying between cereal crops and the field boundary, and extending for a limited distance into the crop, which are deliberately managed to create conditions which benefit key farmland species' (UK Biodiversity Steering Group 1995). They are particularly important in areas with large scale intensive farming. Cereal crops account for 44% of arable land in Scotland. This habitat can provide nesting and feeding sites for farmland birds such as grey partridge and skylark, and rare arable weeds such as cornflower and shepherd's-needle.
Field margins often form the boundary between the crop or pasture and other habitats such as hedges, drystone walls and ditches. Most field margins are composed of perennial grasses, herbs or wildflowers, but may include a 'sterile strip' of bare cultivated ground.
Improved grassland is generally low in diversity but can be of value to ground nesting birds such as skylark and waders including snipe, lapwing, curlew and redshank.
Lowland and upland hay meadows are traditionally mown areas where the pattern of management allows a rich plant community to flourish.
Grass cutting
Maintenance requirements for grassed areas, taking into account safety and operational issues, are dealt with in the Term Management Agent Contract for Trunk Road Network Management and Professional Services.
Different cutting regimes are employed for the following areas:
Safety will always be the primary consideration, and opportunities to enhance biodiversity in some areas will necessarily be limited. However, many opportunities will still exist for promoting biodiversity, often through very simple measures.
The timing of cuts can be crucial in maintaining and encouraging a variety of plant species. Too early, or too often, and desirable species may not have time to flower and set seed. Too late, or not at all, and undesirable weeds or over dominant species may take hold to the detriment of less competitive species. An occasional grass cut will be necessary to prevent scrub developing if the objective is to maintain a grass/wildflower area. Timing must also take into account other factors such as the breeding season for ground nesting birds and the emergence times of certain invertebrates (source: Roads and Nature Conservation, English Nature).
CEL:LfN - The grass verge of the M8 through Glasgow is an example of this approach, where the timing of cuts and grass length were varied to encourage a variety of wildlife and a more attractive species rich grassland.
Cuts can also be timed to benefit a particular desired species or group. Cutting in September/October, for example, allows flowering plants to set seed and many invertebrates to complete their life cycle. On many soils a single cut in late autumn is appropriate.
Soils
Fertile soils encourage grass growth (requiring more frequent cutting and hence greater maintenance costs) and reduce species diversity. A more interesting and diverse grassland may develop on poorer, thinner soils, which at the same time may need less frequent maintenance.
On vigorously growing swards, where grass is dominating less vigorous wildflowers, a close cut in March/April with removal of cuttings will remove old winter growth and reduce the vigour of grasses.
Threats and influences
Opportunities
|
Species/Groups |
Sensitivities |
Timing |
Positive Actions |
|
Birds |
Roads can be a major risk to owls because of the large population of small mammals attracted to roadside verges which provide a good feeding resource. Verges also act as hunting corridors for barn owls Kestrels have different behaviour and while still at risk, are less likely to be struck by traffic Some birds may nest along verges Illegal to disturb nesting birds |
All year Avoid disturbance during nesting season (generally between March-July) |
Discourage owls from hunting along roads to benefit biodiversity Modify planting or maintenance regimes where barn owls are at risk along road verges to change their flight paths or reduce their food sources Plant trees to raise flight path of birds above vehicles |
|
Other Mammals |
Mice/voles may colonise areas of roadside verge |
All year Encourage where owls are not at risk |
Maintain some areas of tussocky grasses |
|
Badgers |
May cross roads on well-established pathways, build setts in road embankments, and forage along verges |
All year |
Deter badgers from crossing and/or encourage use of alternative crossing routes Consider creating areas of worm rich pasture to minimise the need to cross the road in search of food. This could be in partnership with adjacent landowner |
|
Invertebrates |
Butterflies require food plants for caterpillars as well as good nectar sources. Many can only travel short distances, and rely on suitable conditions for the whole of their life cycle in a relatively restricted area. Others need continuity of habitat, and cannot cross even the smallest barrier such as a strip of bare ground |
All year |
Manage grasslands to maintain a diversity of flowering plants, particularly in sheltered locations |
|
Wild flowers |
Timing of cuts Use of chemicals |
Spring-Autumn |
Ensure grass cutting and other maintenance is timed appropriately to allow desirable species to flower and set seed Avoid or reduce use of chemical controls wherever possible Where verges are being reseeded after work, use appropriate seed mixes (refer to guidance) Modify soil characteristics (e.g. nutrient content) to benefit wildflowers and discourage overly competitive species |
Links: Cost Effective Landscape: Learning from Nature
Cutting and Embankments
Cuttings and embankments may offer opportunities for creative habitat enhancement, taking advantage of aspect and microhabitat features to diversify the interest of the site and encourage species with particular preferences, such as reptiles.
Guidance is also contained in CEL:LfN, (see Appendix 1), illustrating the fact that materials may be used on site as a resource rather than classified as a waste.
'Diversity of physical rock form and texture and the creation of niches for pioneer plant species will also result in an appropriate diversity of vegetation which is well adapted to the prevailing conditions' (source: CEL:LfN).
Where road embankments adjoin heathland supporting reptiles, suitable conditions can encourage them to make use of sunny, warm, south facing slopes with patches of bare, sandy soil. Other species, such as certain bees and wasps, will also benefit. South facing sunny slopes are especially good for butterflies, if their other requirements for nectar, egg laying sites and shelter are also met.
|
Species/Groups |
Sensitivities |
Timing |
Positive Actions |
|
Vegetation/habitats |
Slopes and cuttings (especially south facing) may have their own microclimate |
All year |
Ensure any planting is appropriate for soil/aspect etc. |
|
Adders |
Basking, egg laying, feeding locations |
All year |
Provide a range of suitable conditions (e.g. patches of bare soil) on sunny sheltered slopes |
|
Lichens |
Exposed rock faces |
All year |
Where appropriate, encourage colonisation by lichens by spraying the north face of retaining structures and rock faces with liquid manure When moving lichen covered boulders, ensure they are replaced the right way up Use local rocks in landscaping |
Links: Cost Effective Landscape: Learning from Nature.
Bridges
Bridges, culverts and road embankments over watercourses can have effects both upstream and downstream. They also impose a structural barrier to animal movements, limiting their distribution and hence the availability to them of feeding and breeding grounds.
Plans for new bridges, or bridge repairs and strengthening, are an opportunity to design crossings to incorporate the needs of species using the watercourse corridor, and thereby make a positive contribution to the diversity of the local habitat.
New structures can cause shading, so that less light reaches the watercourse and banks, influencing temperature and, indirectly, species diversity. Conversely, removing adjacent trees and vegetation decreases the available shade, raising water temperatures and potentially affecting the suitability of a stream channel for fish. Brown trout, for example, seek shade under overhanging trees and banks.
|
Species/Groups |
Sensitivities |
Timing |
Positive Actions |
|
Bats |
Protected species - it is illegal to disturb or kill them Old bridge structures (both masonry and concrete) may hold bat roosts Ivy or other plants on older bridges may support individual hibernating bats It has been suggested that the bases of bridges over rivers may interrupt the flyways of bats along river banks, limiting their available hunting grounds Bats roost in different places in summer and winter |
Oct-March - winter roost Summer breeding roosts |
Survey old bridge structures for bats Ensure bat roosts are identified in advance of work Consult/work in partnership with SNH and local bat groups Incorporate crevices into new designs Seek opportunities to build mitigation into bridge design to maintain river bank continuity Install bat boxes at appropriate locations |
|
Otters |
Protected species Bridges over rivers may interrupt the movement of otters along riverbanks
|
All year |
Seek opportunities to build mitigation into bridge design to maintain river bank continuity (see also Drainage Features) |
|
Birds |
Ivy or other vegetation may hold nests Nests may be directly on underside of bridges It is illegal to disturb breeding birds |
Nesting season March - June |
Avoid bird nesting period for repair work on old bridges For work inside nesting season search ivy etc. before removal Install bird boxes at appropriate locations Incorporate crevices into bridge designs |
Links: Cost Effective Landscape: Learning from Nature
SEPA Habitat Enhancement Initiative publication 'Watercourses in the Community - a guide to sustainable watercourse management in the urban environment' The Skye Agreement (Draft)
Drainage Features
New road schemes offer many opportunities to integrate sustainable drainage designs which cause least damage to local biodiversity and environmental quality. It may be possible for drainage features which offer greater benefits to wildlife to be retro-fitted to existing schemes, or for management practices to be amended to minimise adverse effects.
Threats and Influences
Roads and associated drainage can affect the surrounding hydrology, and may therefore have a direct effect on adjacent habitats, for instance by making them wetter or drier. This should be taken into consideration where nearby valuable or sensitive habitats are concerned.
Amphibians, hedgehogs and other small animals may get trapped in drains and gully pots (and other non-drainage features such as cattle grids). Providing escape routes can be an effective way to minimise losses. New schemes can avoid this problem through good design incorporating alternatives to gulley pots.
Opportunities
Shingle placed around filter drains can itself be attractive to wildlife. For example, Oystercatchers have been observed nesting on shingle road edges of the A75.
Ditches, small watercourses, ponds and drainage channels are all potentially valuable wildlife habitats. With appropriate management, their wildlife value can be improved while still maintaining their operational function. Careful timing and implementation of activities such as dredging ditches and cutting verges can reduce disturbance and damage to wildlife. Scottish Environment Protection Agency (SEPA) guidance on culverts (see Links) aims to:
SEPA guidance on culverting and best practice should be taken into consideration when developing proposals.
The best ditches for wildlife generally have gently sloping banks, and contain both aquatic and emergent plants. Marshy grassland alongside a ditch increases its diversity and wildlife value. A careful balance must always be maintained to ensure that the hydraulic capacity of ditches is not adversely affected in any way, as the primary safety objective of the drainage system is to avoid ponding on road surfaces. Most drainage systems can, however, serve biodiversity as well as safety objectives.
Settlement lagoons and other pollution control features can provide opportunities for enhancing wildlife value. For example, shallow areas can be planted with native wetland plants which support a variety of invertebrates and other species. SEPA has published guidance on creating and managing drainage ponds that optimise their value for wildlife without compromising their principal drainage functions, and on best practice for maintaining ditches (see Links).
Road spills following accidents can result in pollution of adjacent watercourses. Best practice guidelines should be followed, including Development of Pollution Spillage Contingency Plans for high traffic roads (e.g. SEPA, M74).
|
Species/Groups |
Sensitivities |
Timing |
Positive Actions |
|
Otters |
Otters may use drainage culverts to pass under carriageways |
All year |
Provide high water level access under bridges etc to prevent otters crossing carriageways and suffering fatalities Use fencing to encourage use of otter passes Liaise with SNH/Vincent Wildlife Trust |
|
Amphibians |
Frogs and newts can become trapped and drown in steep sided ditches or gully pots Movement to and from breeding pools, feeding and hibernation sites Great crested newts are fully protected under the Wildlife and Countryside Act 1981 |
Especially during the breeding season (spring) when populations are on the move
|
Provide escape features to allow animals to climb out Seek to maintain connections between populations where interbreeding will maintain long term genetic diversity |
|
Small Mammals |
Road kills Voles, mice and shrews for example may fall into steep sided ditches and drown |
All year |
Discourage crossing or provide crossing facilities Provide escape features to allow animals to climb out |
|
Water Voles |
Nesting and feeding along banks, water voles favour tall lush vegetation. Their places of shelter are protected by legislation |
All year |
Where known to use ditches, seek to manage vegetation to provide suitable conditions. Avoid disturbance in breeding season, and damage to habitat within 1-2 metres of bankside |
Links: Cost Effective Landscape: Learning from Nature
SEPA statement on culverts 'Culverting - an Agenda for Action'
SEPA Guidance on Pond Protection
SEPA Farming and Watercourse Best Practice Management
Water Vole Conservation Handbook (EN/EA/Oxford University)
An Inventory of Wildlife Mitigation Measures DMRB Vol. 10