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.
