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					                             Bristol, Avon Valleys
                                  and Ridges



                               A Nature Conservation Profile
                               English Nature
                               July 1997




English Nature (Somerset Team)
Roughmoor
Bishop's Hull
TAUNTON
Somerset
TA1 5AA

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CONTENTS
1.      Introduction....................................................................................................................4
        1.1        Background ........................................................................................................4
        1.2        Context: Natural Areas and the UK Biodiversity Action Plan ..........................4
        1.3        The Bristol, Avon Valleys and Ridges Natural Area.........................................5
2.      Geological Features .......................................................................................................6
        2.1        Introduction........................................................................................................6
        2.2        Devonian - Carboniferous Interest.....................................................................6
        2.3        Triassic Interest..................................................................................................6
        2.4        Jurassic Interest..................................................................................................7
        2.5        Quaternary Interest.............................................................................................7
        2.6        Mineralogical Interest ........................................................................................7
        2.7        Key Geological Features....................................................................................7
        2.8        Key Geological Management Issues..................................................................8
        2.9        Key Objectives...................................................................................................8
3.      Key Wildlife Habitats ....................................................................................................8
        3.1        Introduction........................................................................................................8
        3.2        Ancient Woodland .............................................................................................9
                   3.2.1      Significant Species...............................................................................10
                   3.2.2      Key Issues ............................................................................................10
                   3.2.3      Key Objectives.....................................................................................11
        3.3        Lowland Farmland ...........................................................................................11
                   3.3.1      Significant Species...............................................................................12
                   3.3.2      Key Issues ............................................................................................13
                   3.3.3      Key Objectives.....................................................................................13
        3.4        Urban Areas .....................................................................................................14
                   3.4.1      Significant Species...............................................................................15
                   3.4.2      Key Issues ............................................................................................15
                   3.4.3      Key Objectives.....................................................................................16
        3.5        Open Water and Riparian Habitat....................................................................16
                   3.5.1      Significant Species...............................................................................17
                   3.5.2      Key Issues ............................................................................................17
                   3.5.3      Key Objectives.....................................................................................18
        3.6        Parklands..........................................................................................................18
                   3.6.1      Significant Species...............................................................................19
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                      3.6.2      Key Issues ............................................................................................19
                      3.6.3      Key Objectives.....................................................................................19
           3.7        Carboniferous Limestone Gorge......................................................................20
                      3.7.1      Significant Species...............................................................................20
                      3.7.2      Key Issues ............................................................................................21
                      3.7.3      Key Objectives.....................................................................................21
           3.8        Limestone Grassland........................................................................................22
                      3.8.1      Significant Species...............................................................................22
                      3.8.2      Key Issues ............................................................................................22
                      3.8.3      Key Objectives.....................................................................................23
           3.9        Neutral Grassland.............................................................................................23
                      3.9.1      Significant Species...............................................................................24
                      3.9.2      Key Issues ............................................................................................24
                      3.9.3      Key Objectives.....................................................................................24
4.         Significant Species.......................................................................................................25
5.         The Future....................................................................................................................26
Acknowledgements..................................................................................................................27
Bibliography ............................................................................................................................28




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1.      Introduction
1.1     Background
The Bristol, Avon Valleys and Ridges Natural Area encompassing the city of Bristol has a
complex and varied landscape. Although there is a gradual transition to the Cotswolds in the
south west, the boundary becomes more sharply defined against the Cotswold scarp edge to
the north west. The area adjoins the Mendip Hills to the south and overlooks the North
Somerset levels and moors and the Seven Estuary to the west.

The great scenic and nature conservation diversity of the area is due in part to the range of
rock types found and a complexity of erosion and earth movements. Rock types include
sandstones, mudstones, clays, limestones and shales. In general the higher ground on the
ridges is underlain by limestones and sandstones with mudstones, with clays and alluvium in
the shallow valleys.

Onto this complex geological framework human activities have altered ‘natural’ animal and
plant communities, through agriculture, settlement, infrastructure and industry. Whilst in
some cases the resultant habitats have significant wildlife interest (eg semi-natural woodlands
and reservoirs) in other cases the change has been more fundamental and the opportunities for
wildlife exist in pockets or corridors of green space (eg within large urban and industrial
areas).

The nature conservation interest of this Natural Area lies in its range of habitats including
internationally valuable types and its diversity of rare and uncommon flora and fauna,
together with the more ‘commonplace’ habitats and species. In combination these many
elements contribute to the overall biodiversity of the Natural Area. As indicated above this
interest is a result of the past and continuing interplay between human activities and the
environment. What is critical is that we understand this dynamic process, identify what is
characteristic and special about this Natural Area and endeavour to promote its conservation.
That is the basic aim of this profile: to describe the key physical, wildlife and land use
features of the Natural Area, to outline the main issues affecting them and illustrate the need
for action. It also identifies objectives through which the nature conservation value of the
Natural Area can be maintained and enhanced.

1.2     Context: Natural Areas and the UK Biodiversity Action Plan
In June 1992 the Prime Minister and over 150 other Heads of State or Governments signed
the Convention on Biological Diversity at Rio de Janeiro. They did so to express a shared
believe that action must be taken to halt the world-wide loss of animal and plant species and
genetic resources. At the same time they agreed to draw up national plans and programmes
and to share resources to help implement them. This resulted in the first UK Biodiversity
Action Plan published in 1994 (Box 1).

Box 1 UK Goals, principles and objectives

•   Overall goal
to conserve and enhance biological diversity (the variety of life) within the UK and to contribute to
the conservation of global biodiversity through all appropriate mechanisms.


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• Underlying principles
1. Where biological resources are used, such use should be sustainable.
2. Wise use should be ensured for non-renewable resources
3. The conservation of biodiversity requires the care and involvement of individuals and
   communities as well as Governmental processes
4. Conservation of biodiversity should be an integral part of Government programmes, policy and
   action.
5. Conservation practice and policy should be based upon a sound knowledge base.
6. The precautionary principle should guide decisions.

•  Objectives and conserving biodiversity
1. To conserve and where practicable enhance
   a) the overall populations and natural ranges of native species and the quality and range of
       wildlife habitats and ecosystems
   b) internationally important and threatened species, habitats and ecosystems
   c) species, habitats and natural and managed ecosystems that are characteristic of local areas
   d) the biodiversity of natural and semi-natural habitats where this has been diminished over
       recent past decades
2. To increase public awareness of, and involvement in, conserving biodiversity.
3. To contribute to the conservation of biodiversity in a European and global scale.

The Plan commits the Government to the objectives of the Convention but, just as its
production required a wide ranging and vigorous contribution from people and organisations
who care about our natural environment, so delivering it will require active participation.
The Government can take a lead and establish a framework but whether, in the end, we and
our children enjoy a country which is richer or poorer in species and habitats depends on all
of us (Department of the Environment, 1994).

English Nature, as the Government’s statutory advisors on nature conservation in England,
have a key role to play in stimulating action. The development of the Natural Areas concept
is an important part of that role (Box 2).

Box 2             The Natural Areas concept

•     A Natural Area is a tract of the countryside (incorporating urban areas) which can be identified by
      its physical, wildlife and land use features.

•     Physical features are determined by the geology, landform, soils, climate and drainage

•     Wildlife features are determined by the habitats and species of flora and fauna

•     Land use features are derived from past and present management activities.

A Natural Area is not a designation, but a broad area of land characterised by its unique
combination of physical attributes, wildlife, land use and culture. These features give a
Natural Area a “sense of place” and a distinctive nature conservation character which we can
seek to sustain (EN, 1993 (1)).

1.3       The Bristol, Avon Valleys and Ridges Natural Area
The many varied features of this Natural Area do not give it a single distinctive character
throughout the area. It is perhaps most easily defined by those Natural Area’s bordering it.
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However, it can be said to be characterised by alternating ridges and broad valleys with some
steep wooded slopes and open rolling farmland. The large urban expanse of the city of
Bristol, with its dramatic gorge of the River Avon, dominates the central part of the Natural
Area as can be seen from the map.

2.      Geological Features
2.1     Introduction
This Natural Area has considerable geological interest as outlined below. The area has a
varied topography which is related both to the nature of the underlying rocks and to the
amount of erosion to which they have been subjected. In general , the harder Paleozoic rocks
form areas of moderately high relief (such as Broadfield Down) which exceed 125 metres
Above Ordnance Datum. The solid geology consists mainly of Upper Palaeozoic (Devonian
- Carboniferous) and Mesozoic (Triassic - Middle Jurassic) rocks. There are also important
Silurian rocks with igneous intrusions in the extreme north of this Natural Area.

The area also has considerable interest in the history of the development of geology as a
science. William Smith (the ‘father of geology’) based some of his founding geological
principles upon strata and features exposed within the area.

2.2     Devonian - Carboniferous Interest
The oldest strata are late Devonian aged (approximately 370 million years old) and these out
crop in a series of inliers along the Clevedon - Portishead ridge. Beds of reddish fluvial
sandstones, siltstones and conglomerates are exposed along the Portishead coast whilst
sediments at Woodhill Bay contain important fossil fish faunas. Marine conditions spread
across the area in early Carboniferous times (about 355 to 335 million years ago) and resulted
in the deposition of thick grey limestones which are now visible in the Clevedon - Portishead
ridge, Broadfield Down (Kingswood - Lulsgate) and along the Avon Gorge. Many of the
limestone beds yield coral, brachiopod and crinoid fossils.

Sedimentation and uplift during Early Carboniferous times converted most of the area into
land containing large rivers and extensive swamps. Here flourished the great ‘Coal Measure
Forests’ whose rotting debris accumulated as thick layers of peat, which ultimately became
compressed and lithified to form coal seams. The Coal Measures are mainly of late
Carboniferous age (approximately 310 to 295 million years old) and out crop in the Radstock
district (the Somerset Coalfield), eastern Bristol and around Nailsea. The coal was formerly
extensively mined but the last pit closed in 1971 and exposures today are usually confined to
small scrapes on disused, landscaped tips. Writhlington is a notable exception and fossil Coal
Measure plants and insects can still be collected from the shales. Thick deltaic/fluviatile
sandstones above the productive Lower Coal series are referred to as the Pennant Series.

2.3     Triassic Interest
A period of earth movements and folding/erosion/non-deposition then occurred over the area
and the next sediments encountered are of mid to late Triassic age (approximately 240 to 210
million years old). Marginal deposits consisting of breccias, conglomerates and coarse
sandstones which accumulated against higher slopes and as outwash fans. These Dolomitic


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Conglomerates are well exposed along the Portishead coast where they lie unconformably
over Devonian strata. Elsewhere thick deposits of red marls (the Mercia Mudstones,
formerly the ‘Keuper Marl’) accumulated in arid, lacustrine conditions.

The youngest Triassic strata (210 to 208 million years old) are referred to as the Penarth
Group or the Rhaetic. These deposits (and the overlying Jurassic Lower Lias) form much of
the underlying country around the south and the east of Bristol (Stony Easton-Radstock-
Farmborough-Keynsham) and within the Horfield area of Bristol itself. The Penarth Group
consists of black shales passing up into buff, thinly-bedded limestones and shales which in
turn are overlain by grey alternating limestones and shales. These beds mark the transition
from arid terrestrial environments to shallow marine seas. The Rhaetic contains a restricted
fossil bivalve fauna, rich in numbers of individuals but low in diversity.

2.4      Jurassic Interest
Lower Jurassic sediments (approximately 208 to 190 million years old) are assigned to the
lower Lias (with the Blue Lias’ at the base). The strata consists of alternating grey clays and
limestones (which weather yellowish) becoming clay dominated in higher parts. These beds
are fully marine and contain a rich fossil fauna including ammonites, nautiloids, bivalves,
brachiopods, belemnites and marine reptiles such as ichthyosaurs. The area around
Keynsham is famous for its ‘Blue Lias’ fossils.
During early Jurassic times parts of the Natural Area remained as islands and Lower Lias
deposits occurred here. The youngest Jurassic sediments exposed in the area are
approximately 190 to 175 million years old and out crop on Dundry Hill. Here Middle-Upper
Lias siltstones and limestones are capped by pale oolitic limestones. These marine sediments
are well known for their abundant and well preserved ammonite and brachiopod fossils.

2.5      Quaternary Interest
The youngest sediments present in the Natural Area are Quaternary in age. Extensive alluvial
deposits extend from Clapton Moor to Avonmouth (and northwards); in places along the
River Avon, First and Second Terrace Gravel deposits can be distinguished. Alluvial sands
and gravels at Weston-in-Gordano are fluvioglacial and interglacial in origin.

2.6      Mineralogical Interest
The mineralogical interests of the Natural Area lie mainly in iron mineralisations (goethite,
haematite, ‘ochre’ or various sulphides) with some copper, zinc and occasional arsenic. The
mineralisation tends to be associated with porous/permeable strata (such as Triassic aged
Dolomitic conglomerate) or within veins related to faults and cross-cutting neptunian dykes.

Ochre deposits are particularly notable and often occur in carbonate-hosted form within cave
deposits. Associated minerals include quartz lined geodes (‘potato stones’), barytes (barite)
and barytocalcite.

2.7      Key Geological Features
•     Silurian - Tortworth inlier.

•     Devonian stratigraphy and sedimentology of the Portishead beds, including fossil fish
      faunas.
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•     Lower Carboniferous (‘Avonian’) stratigraphy in the Avon Gorge.

•     Coal Measure fossil communities including plants, insects and arthropods, eg.
      Writhlington tips.

•     Lower Lias stratigraphy and sedimentology (‘Blue Lias’ and ‘marginal’ facies).

•     Inferior oolite sequences on Dundry Hill.

•     Fluvioglacial and interglacial Pleistocene/Quaternary gravels.

2.8      Key Geological Management Issues
•     Maintenance and enhancement of existing exposures.

•     The number of permanent geological exposures available and the recording of temporary
      sections.

•     Threats to coastal/foreshore exposures from engineering and coastal defence projects.

•     Threats/opportunities from quarrying/infill proposals.

•     Overuse and misuse of sensitive fossil locations.

2.9      Key Objectives
Geological

1. Maintain current geological exposures and enhance where practical.
2. Increase the number of permanent geological exposures and/or recording of temporary sections
   by encouraging joint initiatives with RIGs, local geological groups.
3. Maintain existing coastal/foreshore exposures and the operation of natural coastal processes.
4. Encourage responsible fossil collecting and contact with Taunton, Bristol and North Somerset
   museums, Rigs groups and local geological groups.
5. Encourage quarry operators and prospective waste operators to maintain and enhance exposures.
6. Encourage greater educational/interpretive use of appropriate sites.


3.       Key Wildlife Habitats
3.1      Introduction
A wide range of wildlife habitats are represented within this Natural Area. The principal
types are described within this profile and are categorised under the following headings:

•     Ancient Woodland

•     Lowland Farmland

•     Urban Areas

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•     Open Water and Riparian Habitats

•     Parklands

•     Limestone Gorge

•     Limestone Grassland

•     Neutral Grassland

Under each of these headings the main features of interest are outlined. Following this the
significant species are listed (defined in section 4) and the key issues and objectives briefly
set out. The aim is not to provide a comprehensive documentary on all that is found within
the Natural Area but to provide a contextual framework within which decisions on wildlife
conservation measures can be developed.

Hedgerows, whilst a recognised feature of interest, have been included within the section on
Lowland Farmland as it is considered that this is the most appropriate section under which
they can be assessed.

A number of documents relating to nature conservation within the old county and districts of
Avon have provided useful source information. These are listed in the Bibliography together
with a limited number of other references.

3.2      Ancient Woodland
Ancient woodlands are those which are believed to have had continuous woodland cover
since at least 1600 AD, although they may have temporarily been cleared for underwood
and/or timber production. Since these woodlands have existed for so long they have

developed a very rich and diverse flora, which in turn can support a very wide variety of
insect and other invertebrate species. These woods also provide food, shelter and breeding
sites for many birds and mammals.

Ancient woodland is found throughout this Natural Area in small patches but has major
concentrations at Leigh Woods, to the north east of Congresbury (Kings and Urchin Wood
SSSI) and at Lower Woods SSSI near Wickwar.

Most of the ancient woodland in this Natural Area is dominated by pedunculate oak and ash
with hazel and field maple as an under storey. Ground flora species include dogs mercury,
bluebell, wood anemone and wood sorrel. Small leaved lime is a tree which is only ever
found on ancient woodland sites and it is a characteristic tree of many of the woods on ridges
to the south and south east of Bristol. Damper woods or areas along the edges of streams
may support more moisture tolerant species such as willow and alder. This type of woodland
is not very common but small areas are found fringing Blagdon and Chew Valley lakes.
Where more acidic conditions prevail sessile oak and birch occur because of their preference
for such soils for example at Bickley Wood.

One of the finest ancient woodlands within this Natural Area is Leigh Woods near Bristol.
This supports a high number of restricted plant species including nationally rare and endemic

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whitebeam species. Part of the woodland is a National Nature Reserve and part has been put
forward as a Candidate Special Area of Conservation under the Habitats Directive 1992. See
also section 3.7. on the Avon Gorge.

Another outstanding wood is Lower Woods at Wickwar in the far north of the Natural Area.
These woods are the most extensive ancient woodlands in the area with the SSSI extending to
280 hectares.

3.2.1   Significant Species

•       Purple gromwell
•       Angular Solomons seal
•       Bath asparagus
•       Yellow star of Bethlehem
•       Lily of the valley
•       Common cow wheat
•       Ivy broomrape
•       Southern polypody
•       Whitebeams - Sorbus rupicola, S.eminens, S.aria x torminalis.
•       Large leaved lime
•       Small leaved lime

•       Dormouse
•       Greater horseshoe bat
•       Bat species generally

•       Brown hairstreak
•       White letter hairstreak
•       White admiral
•       Clytra quadripunctata (beetle)

3.2.2   Key Issues

•       Expanding roe deer and muntjac population affecting coppice regrowth and
        regeneration/planting.

•       Lack of appropriate management - particularly coppicing and control of invasive
        species.

•       Removal of old and dead trees and fallen deadwood reducing niche availability.

•       Past coniferisation of ancient woodland sites and continuing to plant conifers
        adversely affecting woodland flora and fauna.

•       The Forest of Avon - opportunities for new planting and protection of existing species
        rich grasslands.

•       Inadequate incentives and markets for coppice products.


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•         Inappropriate management for rare and uncommon species.

•         Planting of inappropriate species.

•         Lack of provision for informal recreational use of woodlands and problems of
          overuse.

3.2.3     Key Objectives

Ancient Woodland

•     Maintain the existing area of ancient semi natural woodland and improve its condition through
      appropriate management where necessary assisted by grants schemes.

•     Promote coppicing management within woodlands where there is a history of such management.
      Encourage appropriate incentives and markets for coppice produce.

•     Promote management which maintains or enhances populations of significant species. Key sites
      being Avon Gorge cSAC , other woodland SSSIs and County Wildlife Sites.

•     Look to establish minimum intervention areas in suitably large areas of woodland (eg over 30
      hectares and possibly part of a larger site).

•     Promote the planting of new native woodland in appropriate parts of the Community Forest area -
      particularly where it links with existing areas of ancient woodland and does not damage species
      rich grasslands.

•     Ensure planting stock is from locally collected seed to maintain genetic integrity.

3.3       Lowland Farmland
The farmed landscape of this area is tremendously varied ranging from large fields with
intensive arable cropping to small pastures with dense hedges.
Farm buildings can have value to wildlife. Specifically barn owls and bats have made use of
such buildings in the absence of natural shelters such as hollows and cavities in old tree
trunks.

The improvement of fields for agriculture through re seeding, use of artificial fertilisers or
conversion to arable use has reduced these areas ability to support a diverse wildlife
community. As a result much of the wildlife interest is restricted to field edges (or
headlands). Such edges can form the last refuge for arable weeds, some of which were once
widespread but now restricted due to modern intensive agricultural practices.

Hedgerows surrounding these fields are important habitats in their own right and have
suffered primarily through removal (due to requirement for increased field size) and neglect
or poor management. Hedgerows form vital linear features or ‘stepping stones’ for many
species of flora and fauna. In this landscape of generally scattered woodlands they provide a
‘woodland edge’ of considerable value to birds, mammals and invertebrates. These species
find the right conditions here for feeding, nesting and shelter. The importance of certain
hedgerows has been recognised on a statutory basis recently with the production of the
Hedgerows Regulations 1997 (SI No. 1160). It must be stressed that in an intensively farmed
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landscape hedgerows that might fall outside the scope of the regulations could still be of
wildlife value. Even single trees have some value and where such trees are old this value can
increase significantly (see section 3.6. for value of veteran trees).

Within improved grassland the heavy use of fertilisers reduces species diversity to a low level
dominated by competitive grasses and a few common broad leaved plants. Such grassland
generally has an impoverished fauna. However where machinery is used less frequently and
grazing levels are low such grassland might support ground nesting birds such as lapwing and
skylark.

Grass verges adjacent to fields, hedges or roads can harbour a range of plants and animals
where management is sympathetic to wildlife. For example with appropriate cutting regimes
and freedom from pesticide, herbicide and fertiliser use. Verges can harbour rare species
including orchids, and provide hunting for birds such as kestrel and barn owl

A considerable area of farmland has also been lost to development, notably at areas such as
Emersons Green, Bradley Stoke and Cribbs Causeway. In addition to actual land take there
are potential knock on impacts on nature conservation; for example from increased demand
for water, waste water disposal, waste disposal and quarried materials. The nature
conservation losses might in some individual circumstances seem slight but the overall
cumulative impact on biodiversity could be considerable.

3.3.1   Significant Species

•       Bath asparagus
•       Corn parsley
•       Small flowered catchfly
•       Bithynian vetch
•       Some orchid species

•       Dormouse
•       All bat species
•       Brown hare
•       Badger

•       Skylark
•       Lapwing
•       Song thrush
•       Grey partridge
•       Corn bunting
•       Tree sparrow
•       Bullfinch
•       Turtle dove
•       Spotted flycatcher
•       Barn owl

•       Great crested newt
•       Grass snake
•       Adder

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3.3.2   Key Issues

•       Loss of land to development, piecemeal erosion of wildlife resource.

•       Poor management of field margins.

•       The Forest of Avon - opportunities for new planting and protection of existing species
        rich grasslands

•       Inappropriate use of herbicides, pesticides and fertilisers.

•       Cutting regimes unsympathetic to wildlife.

•       Hedgerow removal and inappropriate management.

•       Changing arable practices (eg spring to autumn sown cereals).

•       Field drainage.

•       Removal of ponds and ditches.

•       Increased use of horse grazing unfavourable to conservation interests.

3.3.3   Key Objectives

Lowland Farmland

•   Maintain the existing area of species rich grassland and hedgerow and improve their condition
    through appropriate management.

•   Encourage developments to non greenfield sites and ensure new large developments in the
    countryside have appropriate environmental assessments. Existing wildlife features should be
    retained where possible, impacts should be mitigated and positive works undertaken both on and,
    where appropriate, off site.

•   Ensure planting of new native woodland is in appropriate parts of the Community Forest area - ie
    where it links with existing areas of ancient woodland and does not damage species rich
    grasslands.

•   Where the conversion of farm buildings is proposed promote appropriate surveys for barn owls
    and bats and encourage sympathetic building works for these species.

•   Promote the retention and conservation of important hedgerows through appropriate incentives,
    advice and where appropriate through the Hedgerow Regulations.

•   Promote wildlife advice to farmers and land managers through FWAG, Hawk and owl Trust,
    Game Conservancy and other advisors, as well as through publications/guidelines/codes of good
    practice from EN, RSPB, NFU and MAFF.

•   Encourage appropriate incentives for environmentally sensitive farming eg. Set Aside and
    Countryside Stewardship.

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•     Target incentive schemes to areas where they enhance, buffer and link existing areas of wildlife
      importance or to sites which support significant species eg.greater horseshoe bat and rare arable
      weeds.

•     Promote a review of the CAP to encourage a shift in the direction of funds from agricultural
      commodity support to direct environmental payments.

3.4       Urban Areas
The central part of this Natural Area is obviously dominated by the large urban area of Bristol
with satellite settlements such as Nailsea to the south west and Yate/Chipping Sodbury to the
North east. ‘Green spaces’ within urban areas have an increased importance for a number of
reasons and particularly so within the large urban setting of Bristol.

The urban habitat statement in ‘Biodiversity : The UK Action Plan’ defines urban habitats as
‘ the green spaces and associated ecological niches within built up areas ‘, however it omits
buildings and hard surfaces which can support important plant and animal communities. The
statement divides ‘green space’ into four distinct categories:

•     Remnants of ancient natural systems, such as woodland, wetland, freshwater and
      estuarine.

•     Pre-industrial rural landscapes with arable land, meadows, heath land, grazing marshes
      and villages.

•     Managed green spaces. These include town parks, pocket parks, amenity grasslands,
      private gardens and planted shrubberies. They can, depending on their structure,
      management and planted species, support a large number of wild species of invertebrates
      and birds especially in the suburbs. Mammals such as badger, fox and hedgehog have
      also been able to adapt to urban situations.

•     Naturally seeded urban areas or industrial sites such as demolition sites, disused railway
      lands or unexploited industrial land. These areas can often be particularly rich in species
      reflecting a complex mixture of features.

It can be seen that urban areas such as Bristol support many habitats and species that are of
importance in the wider context as a representation of habitat types and species which are not
specifically urban eg. The Avon Gorge and Leigh Woods. However their presence within
such a setting is of particular interest because of the proximity to large numbers of people and
the different influences that are present within the urban context. Relatively commonplace
trees, shrubs and grassy open areas also have a greater importance to people in such a setting.
In addition the managed green spaces and naturally seeded urban/industrial sites provide
opportunities for species, habitat management and conservation which are uniquely divorced
from the needs of modern farming. Such areas are , however, under different pressures which
need to be addressed if the unique wildlife resource of Bristol is to be conserved.

The mosaic of high quality nature conservation sites together with specific ‘urban’ type
habitats produces this unique mix of great interest for both people and wildlife. The pressure
of development threatening to swamp wildlife rich sites is ever present but opportunities also


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abound to bring about an understanding and desire for wildlife conservation in people
sometimes focussed on their more obvious urban setting.

3.4.1   Significant Species

•       Avon Gorge species (see section 3.7).
•       Slender hares-ear
•       Bulbous foxtail
•       Narrow leaved bittercress
•       Musk storks-bill
•       Sickle medick
•       Southern polypody
•       Small flowered catchfly
•       Large leaved lime
•       Ivy broomrape
•       Moth mullein
•       Twiggy mullein
•       Broad-leaved spurge

•       Greater/lesser Horseshoe bat
•       Leislers bat
•       Pipistrelle bat
•       Badger
•       Fox

•       Peregrine falcon
•       Skylark
•       Song thrush

•       Great crested newt
•       Slow worm

3.4.2   Key Issues

•       Loss of wildlife sites to development pressures. Including piecemeal losses eroding
        wildlife corridors.

•       Management of amenity areas not benefiting wildlife.

•       Accessibility of green space to people.

•       Disturbance to wildlife sites.

•       Lack of management of sites of wildlife interest.

•       Habitat creation.

•       Lack of understanding of wildlife issues.

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•         ‘Tidying’ up wildlife sites to enhance visual aspect can damage wildlife

•         Managing gardens for wildlife

3.4.3     Key Objectives

Urban Areas

•     Maintain the existing network of wildlife habitats (including wildlife corridors) within urban
      areas and improve its condition through appropriate management

•     Promote an appreciation of the wildlife resource found within urban areas to assist in its
      conservation and management.

•     Promote further sympathetic management of publicly owned land eg amenity areas for wildlife
      conservation.

•     Increase the accessibility to wildlife for people - aim for provision of accessible ‘natural green
      space’ within 300m of every home in the urban area.

•     Promote the declaration of LNR’s and greater community involvement in wildlife sites, including
      educational use and wildlife recording.

•     Promote sympathetic gardening practices for wildlife.

•     Promote habitat creation on appropriate sites including within new developments, whilst ensuring
      retention of existing wildlife features where possible.

3.5       Open Water and Riparian Habitat
This Natural Area has a number of significant open water features together with some
wildlife rich waterways. Of particular importance is Chew Valley Lake which is a Special
Protection Area (under the EC Directive on the Conservation of Wild Birds 79/409/EEC) and
a Ramsar Site (under the Convention on Wetlands of International Importance especially as
Waterfowl Habitat - Ramsar Convention). Chew Valley Lake supports internationally
important numbers of gadwall and shoveler and nationally important numbers of teal and
tufted duck. Many other bird species also utilise this site at various times of year in
significant numbers. Additionally the surrounding fields are of botanical interest as is the
lake itself.

Blagdon Lake is also an important site and has been designated an SSSI. It has a diverse
invertebrate fauna with snails and water beetles particularly well represented and supports
large numbers of wintering wildfowl including nationally important populations of teal.
Additional interest is provided by large stands of emergent vegetation (including reed beds)
and surrounding species rich meadows.

Watercourses can provide very important wildlife corridors in what can sometimes be an
intensively farmed landscape or built up area. Within this Natural Area the River Avon
supports 2 nationally rare plant species - the greater dodder associated with the river banks
and the aquatic Loddon pondweed. The River Avon also supports important populations of
invertebrates and fish such as tench and perch. Other important water courses include the
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River Chew and the River Frome. Outwith these ‘special’ sites watercourses and water
features generally, such as ponds, provide important areas for a wide range of species and
thereby contribute significantly to biodiversity in the wider countryside.

3.5.1   Significant Species

•       Greater dodder
•       Loddon pondweed
•       Common reed

•       Gadwall
•       Shoveler
•       Teal
•       Tufted duck
•       Aquatic warbler
•       Reed bunting
•       Pochard
•       Great crested grebe
•       Bittern
•       Reed warbler
•       Cetti’s warbler

•       Water vole
•       Otter
•       Freshwater crayfish
•       Ruddy darter
•       Scarce chaser
•       Beautiful demoiselle
•       White-legged damselfly
•       Red-eyed damselfly
•       Black darter

•       Great crested newt

3.5.2   Key Issues

•       Inappropriate management of water courses/water bodies and adjacent land.

•       Cormorants affecting fish stocks and control measures

•       Possible ruddy duck control

•       Crayfish plague/alien crayfish

•       Disturbance to waterfowl

•       Water quality/quantity - pollution /abstraction



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•         Lack of appropriate habitat eg. Reedbeds, watercourse buffer strips, ponds.

•         The adverse effect of mink on native wildlife.

3.5.3     Key Objectives.

Open Water and Riparian Habitat

•     Promote the appropriate management of water bodies and watercourses to maintain and improve
      conditions for wildlife, including the creation of new habitats eg ponds.

•     Promote a wider understanding of crayfish plague and alien crayfish and adopt appropriate
      measures in order to conserve our native freshwater crayfish.

•     Promote appropriate management for wildlife along water courses and around water bodies eg.
      Pollarding willows, buffer strips, otter habitat, reed planting in order to improve conservation
      value.

•     Promote appropriate management for wildlife along water courses and around water bodies within
      new developments. This should include careful attention to water quality issues.

•     Promote wise use of farm chemicals and fertilisers to ensure no significant adverse impacts on
      water bodies/watercourse and their wildlife eg. MAFF/FWAG/NFU guidance.

•     Encourage wise public/ recreational use of water bodies which leaves refuge areas of sufficient
      size to protect and encourage wildlife.

•     Ensure the need for control measures for cormorant/ruddy duck are carefully considered,
      researched and monitored to avoid significant adverse impact on waterfowl.
•     Promote the study of water abstraction with respect to its potential impact on sites of conservation
      importance.

•     Monitor the impact of mink on wildlife. Consider whether control measures are
      advisable/possible.

3.6       Parklands
A number of parklands of conservation value can be found within this Natural Area - for
example at Dyrham Park, Doddington House, Blaise Castle and Ashton Court. Veteran trees
found at such locations can be of considerable nature conservation importance because of the
very special conditions associated with their age. Holes and hollows are important roosting
sites for woodpeckers, tits, flycatchers and other birds. Hundreds of different species of
insects and spiders depend totally on very old trees, feeding on decaying wood, on fungi and
on each other. The trees and open grassy areas of parklands can be of particular value to
various bat species for both roosting and feeding opportunities.

Only a few trees at any one time might contain the right habitat for very specialised insects
and this makes such species very vulnerable. Places such as old parkland which hold a
concentration of veteran trees and where there has been historical continuity have a vital role
to play in the conservation of such species.


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Fungi are critical in the ecology of all of the wildlife associated with old trees and, indeed, in
the health of the trees them selves. Some of these fungi are now rare and restricted to the
oldest of trees. It is these fungi which cause the trees to decay, leading eventually to them
becoming hollow and pitted with holes. This decay of the heartwood of old trees is a
perfectly natural process, important to the actual wellbeing of the tree.

Typically such veteran trees are ancient pollards of oak, beech and chestnut although other
species also reach such maturity.

3.6.1   Significant Species

•       Many saproxylic invertebrates, fungi and lichens
•       Bats

3.6.2   Key Issues

•       Lack of habitat continuity ie. no replacement trees to grow on once the present
        veteran trees finally cease standing.

•       Lack of understanding amongst parkland managers of the high wildlife value of
        veteran trees.

•       Lack of financial incentives to manage such areas appropriately for wildlife.

•       Poor knowledge of how to manage veteran trees in the most appropriate manner in
        which to maintain their wildlife interest.


•       Poor knowledge of the species to be found within the various parkland areas.

•       Inappropriate management of veteran trees for amenity, heritage and safety reasons.

3.6.3   Key Objectives

Parklands

•   Promote the value of veteran trees as wildlife features, particularly within parklands.
•   Provide advice on the value and management of existing veteran trees and the recruitment of
    replacements.
•   Collate existing and gather new information on problems faced by veteran trees.
•   Promote the targeting of incentive schemes eg. Countryside Stewardship towards the appropriate
    management of such features.
•   Promote the study of veteran trees to ensure knowledge is gained of the species associated with
    them ie. Determine the location of the trees/sites having high species diversity or holding
    particularly rare species.
•   Ensure the sites of particular scientific interest receive appropriate recognition, designation and
    protection to ensure their future continuity.
•   Ensure strong links are established with managers of heritage parklands to integrate management
    for historical, amenity and wildlife purposes.



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3.7     Carboniferous Limestone Gorge
The Avon Gorge is an outstanding nature conservation feature set at the heart of this Natural
Area. It lies on the edge of Bristol and rises about 100 metres from the tidal River Avon to
Observatory Hill on the eastern side and Stokeleigh Camp to the west.

The gorge has natural cliffs and quarry exposures of carboniferous limestone, which are of
great geological interest and together with the screes, scrub, pockets of grassland and
adjacent woodland, support an exceptional number of nationally rare and scarce plant species.
It is a Site of Special Scientific Interest and part is a National Nature Reserve. A large part of
the site has been put forward to the European Commission as a Candidate Special Area of
Conservation under the Habitats Directive 1992. Its European priority interest is described as
‘mixed woodland on alkaline soils associated with rocky slopes (Tilio-Acerion ravine forests)
for which this is considered to be one of the best areas in the United Kingdom’.

Within the Gorge and surrounding woodland can be found 10 nationally rare and 11
nationally scarce plants together with a great many other plants of conservation interest. Of
the plants, round headed leek or the Bristol onion has the gorge as its only mainland locality
for the UK whilst Bristol rock-cress is unique to this site.

Leigh Woods cover the gorge’s western side , the plateau above and the steep valley down to
the River Avon. These woods are mainly semi natural, broadleaved woodland, but the site
also includes areas of mixed and broadleaved plantation and parts are ancient woodland.

The woods and scrub have an exceptional diversity of whitebeams (Sorbus species) including
two which are unique to the Avon Gorge - Sorbus bristoliensis and Sorbus wilmottiana.

3.7.1   Significant Species

•       Sorbus bristoliensis (Bristol whitebeam)
•       Sorbus anglica English whitebeam
•       Sorbus wilmottiana Wilmott’s whitebeam
•       Sorbus porrigentiformis (a whitebeam)
•       Sorbus eminens (a whitebeam)
•       Compact brome
•       Bristol rock-cress
•       Honewort
•       Little robin
•       Nit-grass
•       Round headed leek
•       Autumn squill
•       Angular Solomon’s-seal
•       Dwarf mouse-ear chickweed
•       Dwarf sedge
•       Hutchinsia
•       Rock stonecrop
•       Western spiked speedwell
•       Spring cinquefoil


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•       Fingered sedge
•       Ivy broomrape

•       Peregrine falcon
•       Raven

•       Silky wave moth

3.7.2   Key Issues

•       Scrub encroachment adversely affecting botanically rich areas.

•       Alien plants crowding out native rare flora.

•       Peregrines nesting in gorge under threat from egg collectors/disturbance.

•       Potential damage/disturbance to flora/fauna by rock climbers.

•       Safety works to prevent rocks hitting The Portway can be detrimental to botanical
        interest due to lack of communication between conservationists and road managers.

•       Recovery of rare plants affected by grit fallout from bridge cleaning.

•       Poor public awareness of the wildlife importance of the gorge and lack of
        understanding of the need for management to maintain the botanical interest.

3.7.3   Key Objectives

Carboniferous Limestone Gorge

•   Promote a partnership approach to put into place an appropriate management scheme which will
    maintain and enhance the conservation interest of the gorge.

•   Ensure a peregrine watch takes place which will protect the nest from disturbance.

•   Liaise with climbers to ensure that no damage/disturbance occurs to the nature conservation
    interest of the site.

•   Liaise with road safety personnel to ensure nature conservation interests are fully taken into
    account prior to safety works taking place.

•   Raise public awareness of the nature conservation interest of the gorge through publicity of
    appropriate management works.

•   Monitor scarce/rare plants in the gorge and target those areas most under threat with appropriate
    management works.




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3.8     Limestone Grassland
This type of grassland has a very limited distribution within this Natural Area. It is more
characteristic of the adjacent Natural Area’s of The Mendips and The Cotswolds. Such
calcareous grassland can be extremely species rich particularly where it occurs on shallow
soils and where it is grazed or mown short. Such grasslands are dominated by red fescue and
sheeps fescue with quaking grass often present. Other species may include salad burnet,
common rockrose, fairy flax, squinancywort, dwarf thistle, wild basil and marjoram. Longer
swards, dominated by upright brome, can also be of value especially for invertebrates.

Short grazed calcareous grasslands are not as common as they used to be and many have been
ploughed up in the last 40 years or improved by fertiliser and herbicide spraying. The areas
of short calcareous grassland which remain are frequently restricted to very shallow soils or
to steep hillsides where farm machinery cannot get access to carry out such operations.

Patches of calcareous grassland occur in the Avon Gorge, at Ashton Court and Blaise Castle,
and adjacent to Cleeve Wood(Hanham). Good examples of short grazed or mown calcareous
grassland may be seen at Cadbury Camp near Tickenham, on Walton Down, on some of the
south facing slopes of Dundry Hill and at the Bristol and Clifton Golf Course. There are a
number of sites found on the broad limestone ridge running parallel to the A38 from Bristol
to Thornbury. Calcareous species are also found at Goblin Coombe which is unusual in that it
has patches of ling and bell heather. This mixture of acidic and calcareous vegetation is
known as limestone heath and is a result of the complex underlying soils.

3.8.1   Significant Species

•       Clustered bellflower
•       Lesser centaury
•       Dropwort
•       Horseshoe vetch
•       Pale flax
•       Wild clary
•       Meadow saxifrage
•       Autumn lady’s-tresses

•       Cheilothela chloropus (a moss)
•       Pleurochaete squarrosa (a moss)

•       Small blue
•       Dark green fritillary
•       Grayling

3.8.2   Key Issues

•       Loss of botanical diversity through agricultural improvement.

•       Lack of appropriate management eg. Insufficient grazing, scrub encroachment.

•       Urban fringe effects eg. large scale development, horsiculture.

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•         Forest of Avon - inappropriate planting.

•         Lack of financial incentives to manage for wildlife.

•         Insufficient advice available to encourage appropriate management.

3.8.3     Key Objectives

Limestone Grassland
As for lowland farmland:

•     Maintain the existing area of species rich grassland and hedgerow and improve their condition
      through appropriate management.

•     Encourage developments to non greenfield sites and ensure new large developments in the
      countryside have appropriate environmental assessments. Existing wildlife features should be
      retained where possible, impacts should be mitigated and positive works undertaken both on and,
      where appropriate, off site.

•     Ensure planting of new native woodland is in appropriate parts of the Community Forest area - ie
      where it links with existing areas of ancient woodland and does not damage species rich
      grasslands.

•     Where the conversion of farm buildings is proposed promote appropriate surveys for barn owls
      and bats and encourage sympathetic building works for these species.

•     Promote the retention and conservation of important hedgerows through appropriate incentives,
      advice and where appropriate through the Hedgerow Regulations.

•     Promote wildlife advice to farmers and land managers through FWAG, Hawk and owl Trust,
      Game Conservancy and other advisors, as well as through publications/guidelines/codes of good
      practice from EN, RSPB, NFU and MAFF.

•     Encourage appropriate incentives for environmentally sensitive farming eg. Set Aside and
      Countryside Stewardship.

•     Target incentive schemes to areas where they enhance, buffer and link existing areas of wildlife
      importance or to sites which support significant species eg.greater horseshoe bat and rare arable
      weeds.

•     Promote a review of the CAP to encourage a shift in the direction of funds from agricultural
      commodity support to direct environmental payments.

3.9       Neutral Grassland
These are also referred to as mesotrophic grasslands and are grasslands which are not
strongly influenced by either calcareous or acidic soil types. They are dominated by species
such as cock’s-foot, common bent, Yorkshire fog, sweet vernal grass, crested dogs tail,
timothy grass and meadow foxtail. In some case where the grass is neglected and not grazed
or mown these grasses can grow tall and rank, dominating the less competitive grasses and
forbs leading to a sward of low species richness.

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The most species rich forms of neutral grassland are those which are enclosed and are kept as
traditional hay meadows without the use of herbicides or artificial fertilisers. These
grasslands are usually mown for hay late in the summer after the flowers have set seed.
These support a typical mixture of herbs including common knapweed, oxeye daisy, meadow
vetchling, self heal, common birds foot trefoil and agrimony. Meadows like this are found,
for example, at fields near Claverham. The mowing regime prevents the grass species
completely out competing the other less vigorous herb species. Neutral grasslands which are
grazed can also be very species rich and are generally better for insects than hay meadows.
Neutral grasslands of interest can be found in the fields fringing Blagdon and Chew Valley
Lakes, at Dundry Slopes and Stockwood open space, and at fields in the vicinity of Lower
Woods, Wickwar. In the more species rich neutral grasslands species such as saw-wort,
dyers greenweed, sneezewort, devils bit scabious and betony will be found.

3.9.1   Significant Species

•       Bath asparagus
•       Bithynian vetch
•       Corky-fruited water-dropwort
•       Adders tongue spearwort
•       Green winged orchid
•       Adder’s tongue
•       Oval sedge
•       Common sedge
•       Carnation sedge

•       Marsh fritillary

3.9.2   Key Issues

•       Loss of botanical diversity through agricultural improvement.

•       Lack of appropriate management eg. Insufficient grazing, scrub encroachment.

•       Urban fringe effects eg. large scale development, horsiculture.

•       Forest of Avon - inappropriate planting.

•       Lack of financial incentives to manage for wildlife.

•       Insufficient advice available to encourage appropriate management.

3.9.3   Key Objectives

Neutral Grassland

•   Maintain the existing area of species rich grassland and hedgerow and improve their condition
    through appropriate management.

•   Encourage developments to non greenfield sites and ensure new large developments in the
    countryside have appropriate environmental assessments. Existing wildlife features should be

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                                                 24
     retained where possible, impacts should be mitigated and positive works undertaken both on and,
     where appropriate, off site.

•    Ensure planting of new native woodland is in appropriate parts of the Community Forest area - ie
     where it links with existing areas of ancient woodland and does not damage species rich
     grasslands.

•    Where the conversion of farm buildings is proposed promote appropriate surveys for barn owls
     and bats and encourage sympathetic building works for these species.

•    Promote the retention and conservation of important hedgerows through appropriate incentives,
     advice and where appropriate through the Hedgerow Regulations.

•    Promote wildlife advice to farmers and land managers through FWAG, Hawk and owl Trust,
     Game Conservancy and other advisors, as well as through publications/guidelines/codes of good
     practice from EN, RSPB, NFU and MAFF.

•    Encourage appropriate incentives for environmentally sensitive farming eg. Set Aside and
     Countryside Stewardship.

•    Target incentive schemes to areas where they enhance, buffer and link existing areas of wildlife
     importance or to sites which support significant species eg.greater horseshoe bat and rare arable
     weeds.

•    Promote a review of the CAP to encourage a shift in the direction of funds from agricultural
     commodity support to direct environmental payments.


4.       Significant Species
The preceding sections dealt with the many important habitats to be found within this Natural
Area. Within each of the habitat sections a list of ‘significant’ or ‘key’ species was given, the
purpose of this was to assist in the focussing of effort on those species which were felt to be
most important or distinctive. In reality this Natural Area (in common with all the others)
contains many species that are highly valued by wildlife conservation bodies and by the
general public. Given the existing limitations on human and financial resources, we are
unlikely to be able to focus conservation action on them all and, therefore must identify those
that might be priorities for action. It is hoped that the great majority of the remaining species
will be conserved by habitat conservation measures as highlighted in the issues and
objectives for habitats in the preceding sections.

The following table outlines the selection criteria for key species.

Selection criteria for key species

Key species for conservation attention in this Natural Area are drawn from:

1.       Species that are endemic to the UK and which have viable populations in this Natural
         Area.

2.       Species which are threatened on a global or European scale and which have
         significant populations in this Natural Area.

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3.      Species which are rapidly declining throughout Great Britain and which have a
        national stronghold in this Natural Area.

4.      Species which are threatened in Great Britain, being listed in the relevant Red Data
        Book, and which are on the extreme edge of their normal range in this Natural Area.

5.      Species which are highly characteristic of this Natural Area , being seldom found in
        such numbers elsewhere in England and/or which are popular with the general public.

Some account too has been taken of the desirability of ensuring that all the important taxa
within the Natural Area are represented, and that the species selected are spread across the
key habitats present. Some scope exists, particularly at the local or community level, to
delete or add species to the list. The hope is that it promotes conservation action which is
focussed initially on species of most concern. At this stage it is also recognised that some
taxa are poorly represented in the lists, for example, invertebrates, fungi and mosses. Over
time these lists will be amended and improved upon to incorporate missing elements.

The Bristol Regional Environmental Records Centre (BRERC) has a key role to play in
compiling information on ‘key’ species in conjunction with their collection of information on
the presence and distribution of all species in their recording area. Such data is the back bone
of effective conservation action.

5.      The Future
One purpose of this profile has been to outline some of the key habitats and species to be
found in the Natural Area. But its primary purpose has been to highlight some of the key
issues affecting this nature conservation interest and suggest some objectives for its
conservation and enhancement.

The conservation of biodiversity is an international concern and was recognised as such with
the signing of the convention at Rio in 1992 (see introduction). Within this Natural Area are
habitats and species of international, national and local importance. They all contribute
something to the overall biodiversity of our country. In this profile there is a focus on what
can be done for the conservation of biodiversity in this Natural Area. It is hoped to build on
this profile and incorporate specific targets for certain habitats and species to enable us to
assess our contribution to national biodiversity targets with local action. This process is
being replicated across the country within all the other defined Natural Area’s and will
ultimately enable us to determine how successful we have been in conserving biodiversity
across the country.

Success in such action will only be possible with the cooperation of a very diverse range of
people and organisations. It is the responsibility of all those who wish to contribute to
conservation within this Natural Area to take steps to make it happen.




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                                              26
Acknowledgements

This profile has drawn heavily upon a number of strategies and documents produced through
the hard work of various individuals and organisations. In addition it has benefited from
constructive comments from a number of individuals who have knowledge and experience
gained from many years of working in this area. English Nature is grateful to all those who
have contributed to the production of this document.




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                                            27
Bibliography
UK BIODIVERSITY STEERING GROUP. 1994. Biodiversity: The UK Action Plan
London: HMSO.

UK BIODIVERSITY STEERING GROUP 1995. Biodiversity: The UK Steering Group
Report Vols 1&2.

B R E R C. Publication 225. June 1997. 3rd Draft List of ‘Avon’ Notable Species.

ENGLISH NATURE 1993. Strategy for the 1990's: Natural Areas. Peterborough: English
Nature.

GRICE, P.V., and others. 1994. Birds in England: A Natural Areas approach. English
Nature Research Reports, No. 114.

JEFFERSON, R.G. 1996. Lowland grassland in Natural Areas: National assessment of
significance. English Nature Research Reports, No. 171.

GARDINER, A.J. 1996. Freshwater wetlands in England: A Natural Areas approach.
English Nature Research Reports, No. 204.

KING, A., and others. 1996. Earth heritage conservation in England: A Natural Areas
perspective. English Nature Research Reports, No. 158.

NATURE CONSERVANCY COUNCIL. 1991 Greater Bristol Nature Conservation
Strategy.

NATURE CONSERVANCY COUNCIL. 1990. Avon Phase 1 Survey.

Northavon Landscape and Conservation Strategy. 1992.

North Somerset Countryside Strategy. 1995.

Wansdyke - Nature Conservation and Landscape Strategy. 1995.




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