Railway lineside habitat audit

For the purposes of this audit railway linesides are the vegetated lands that lie adjacent to operational above-surface railways. Closed railway routes - those that are no longer in railway ownership - are not included. Vegetated lineside land may include embankments, cuttings, areas around stations and by junctions, above tunnel-mouths, and derelict sidings and marshalling yards. The habitats present are predominantly grassland, scrub, woodland and ruderal vegetation - wetlands are noticeable by their virtual absence - the key link is that they are all on land owned and/or managed as part of the railway network.

The railway network in London was largely created between 1836 and 1936, both stimulating and reacting to the rapid urban growth of the capital. Although the network cut rudely into open countryside when it was first built, most has subsequently become part of the urban landscape and, through the process of natural colonisation, now provides significant areas of wildlife habitat.

There are approximately 795km (492 miles) of open operating railway corridors in London, not including closed railway lines such as Horniman Railway Trail in Lewisham and Parkland Walk in Haringey, which are managed for nature conservation and/or amenity. The open corridors are owned predominantly by two companies; Railtrack Plc and London Underground Limited (LUL) and a number of corridors are used by both underground and surface rail trains. Smaller lengths of railway are owned and/or managed by Docklands Light Railway (DLR), Tramlink in Croydon and a few private industries.

Changes to the railway network and land area have been significant since the mid-1980s, and with privatisation development pressure may result in further land-take, particularly on derelict marshalling yards (although the growing trend for increased rail freight traffic may prevent this on certain routes). New railway projects have led to corridors being created, often at the expense of semi-natural habitat (e.g. Addington Hills in Croydon), but such projects now require environmental assessments and with heightened public sensitivity are unlikely to proceed without considerable ecological compensation.

The railway network supports significant areas of biodiversity importance in London. A total of 838 ha of lineside have been identified as Sites of Importance for Nature Conservation to date by the London Ecology Unit (LEU) (see Map a). The range of habitats (from chalk cliffs to early successional wastelands), together with their relative lack of human disturbance, provides a diversity of fauna and flora that in some areas can be relatively rich. In inner London they often support the only significant woodlands and rough grasslands. Sunny grass embankments may be havens for butterflies, grasshoppers, slow-worm and kestrel, whilst woodlands can support great tit, great spotted woodpecker and sparrowhawk. Derelict marshalling yards with a free-draining, alkaline substrate often support a diverse range of ruderal plants, before succeeding towards birch scrub and woodland. Temple Mills and Feltham are two fine examples, with a new species of spider to the UK, Zodarion rubidum, being recorded at the former site in 1999.

Well-vegetated linesides will act as `green corridors' and the combined network of railways will help to permit movement of some species along them between adjoining sites - either through direct movement (e.g. mammals) or dispersal assisted by the movements of trains (e.g. seeds of plants). Thus railway linesides will add to and benefit from the ecological integrity of adjacent SINCs and other open green space. The value of green corridors has been recognised in PPG9, in that they "help form a network to ensure the maintenance of the current range and diversity of our flora [and] fauna" (para. 15).

A few lineside areas such as Gunnersbury Triangle in Chiswick, Gillespie Park in Islington and New Cross Gate Cutting in Lewisham are actively managed as nature reserves.

Although it is unlikely that any of London's railway corridors will be managed primarily for wildlife, there is significant room to enhance their value for biodiversity. In recent years, management guidance produced by the railway companies has begun to take account of ecological issues (e.g. Maintaining the Track Environment, LUL, 1995), and this should be encouraged to progress further. Seeking to restore grassland habitats and manage graded woodland edges, for example, need not compromise the railway companies meeting their operational standards and obligations. Therefore identification of the most important stretches for nature conservation (which will require some further survey) and preparing 'Conservation Zone Plans' as guidelines for their management by contractors, should be seen as priorities. This would help to target limited management resources effectively. However, the screening and landscape value of tree stands and woodlands should not be under-estimated, and a Habitat Action Plan should take these into account where appropriate. There has been some limited tree-planting on railway land in recent years (e.g. Wandsworth Common), but in light of the priorities to expand the grassland element this should be restricted to identified areas. There may also be opportunities for habitat creation similar to the new ponds created by Railtrack for amphibians at Selhurst.

There is also the potential to seek the creation of more lineside nature reserves managed in partnership between railway companies and conservation groups. These can provide local involvement in lineside habitat management. A number already exist, but there is the opportunity for more throughout London, although it must be recognised that local groups are rarely in a position to manage them without adequate resources.

Railway linesides are seen by many hundreds of thousands of travellers on a daily basis, and for many they are places where they can see the colour and spontaneity of wildlife. Their linear character emphasises the feeling of more or less uninterrupted countryside, almost into the centre of the city. However, there is very little information on railway wildlife or the value of London's linesides and the potential for raising the awareness of their biodiversity is considerable. This may be through on-train information, station interpretation, lineside signs and leaflets.