Marshland Habitat Audit
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the complete Audit
Summary
The term `marshland' has been chosen to cover the following
wet terrestrial habitats: bog, swamp, fen, wet marginal
vegetation, wet marshy grassland and ditches. The following
habitats also occur in association with marshland but are
covered by other audits: fen carr (Woodland); floodplain
grassland (Grazing Marsh and Floodplain Grassland); and
reedswamp (Reedbed).
Marshland
habitat has been highlighted as a priority for nature conservation
in the UK due to dramatic declines in area and distribution
throughout Europe during the last century. Marshland habitat
within London is now relatively rare and fragmented. There
are approximately 273 ha of marshland in Greater London.
Marshland areas are more frequent in outer London boroughs
and are effectively absent from the inner London boroughs.
London's marshlands support a rich diversity of plant and
animal communities.
The
main present day threats to London's marshland resource
are development, water abstraction, pollution and lack of,
or inappropriate, management. Fen
and bogs will be particularly threatened by drying out and
succession to woodland, whereas wet marginal vegetation
can be seriously affected by water-borne pollution, development
and unsympathetic maintenance, for example vegetation clearance
at inappropriate times of the year. Wet marshy grassland
can be very easily damaged or destroyed by relatively minor
drainage schemes, particularly those associated with `improvements'
to agricultural land, golf courses, parks and other amenity
land.
Existing
degraded marshland habitats can be enhanced or new marshland
habitats created when designing new flood-defence projects
or refurbishing existing ones by incorporating schemes which
aim to reduce the incidence of flooding by reducing direct
run-off through containment of floodwaters in balancing
ponds and flood-storage lagoons.
Marshlands can also be restored or rehabilitated as part
of the after use of mineral workings. At present many existing
gravel pits are restored as deep-water pits or returned
to agricultural use.
Existing
high quality marshland habitats can be conserved by the
preparation of Water Level Management Plans which identify
the water budget for a particular site and how this can
be effectively managed with respect to conflicting demands.
At
many smaller sites, the biggest threat to marshlands · drying
out and succession · can be tackled relatively inexpensively
by control of water levels.
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the full audit - this is only a summary
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