3. EVALUATION
The 358.50 ha of the reserve includes 94 ha of lowland wet grassland. The overwintering populations of white-fronted goose,gadwall and shoveler are of national importance. The site also includes 28 ha of reedbed,1% of the UK resource,which supports wintering bittern and bearded tit plus otters. The 157.50 ha of lowland heath and acid grassland is an important remnant of the Sandlings heath which has been decimated by 90% loss in the twentieth century. ( Beardall.C & Casey.D 1995 - Suffolk's Changing Countryside ). This area currently supports a nationally important breeding population of woodlarks.
The site comprises five main habitats,i.e. lowland wet grassland, reedbed, heathland,woodland and shingle beach within a relatively small area. 351 species of vascular plants have been located on the site including nine nationally scarce species. Ferns and horsetails number eight species,seven species of lichen,26 bryophytes and 159 fungi. 264 species of birds have been recorded and of these 107 have bred or attempted to breed. Twenty-nine species of mammals have been recorded,including otter,and 31 butterfly species and 18 odonata species. Extensive moth recording has revealed 17 RDB species.
Lowland Wet Grassland
This habitat comprises 97.50 ha and is dominated by an Agrostis stolonifera -Alopecurus geniculatus vegetation community. This area supports up to six species of breeding waders plus nationally important populations of wildfowl. The 10.92 km of ditches support an interesting range of aquatic plants including brackish-water crowfoot ( Ranunculus baudotii ).
Lowland Heathland
A remnant of the Sandlings heathland amounting to 157.50 ha including 60 ha of bracken and 79.00 ha of the acid grassland community of Festuca ovinaAgrostis capillaris-Rumex acetosella. The heath supports a nationally important population of breeding woodlarks plus the typical assemblage of heathland breeding birds.
Reedswamp
A Phragmites australis community of 28 ha has undergone extensive management over the past five years including lowering the bed by up to 30 cms. Bitterns and bearded tits now winter in the reedbeds and an extensive reed warbler breeding community has developed.
Woodland and Scrub
The 56.50 ha of high forest,plantation and scrub supports a typical breeding bird assemblage including turtle dove,nightingale and several species of warblers.
Shingle and Gravel
The 13 ha of beach shingle is of national importance for its vegetation community which includes extensive areas of sea pea and several other nationally scarce species. In 1995 up to 15 pairs of little terns attempted to breed on the beach which is also extensively used by the public.
The entire site is man-made with the lowland wet grassland being maintained by summer grazing with cattle and the manipulation of water levels. The reedbeds were harvested until the mid 1950's but are now extensively managed to prevent their succession to woodland. Most of the heathland areas are sheep grazed and scrub and bracken are controlled by mechanical and herbicide methods. The shingle ridge has been formed through natural processes and almost all of the plant species occurring here have resulted from natural colonisation.
The areas of lowland wet grassland,reedswamp and heathland are priority habitats within the Reserves Acquisition Strategy ( i.e scarce and declining ). The lowland wet grassland supports a large community of breeding waders particularly lapwing,snipe and redshank and garganey have also bred.. The reedbeds support wintering bittern and bearded tit and both of these species will probably breed in the near future as the condition of the habitat improves. Otters are recorded regularly and there is a breeding population of hairy dragonfly ( Brachytron pratense ). The heathland holds 22 pairs of breeding woodlarks and sizeable populations of green hairstreak and grayling butterflies. Seventeen species of RDB moths have been recorded including several reedbed species. Nine nationally scarce species of vascular plants have been recorded: Parapholis incurva,Ranunculus baudotii,cramse maritima,Trifolium ornithopodioides,Trifolium glomeratum,Trifolium suffocatum,Lathyrus japonicus,Crassula tillaea & Sonchus palustris. The botanically most important communities include U1 Festuca ovinaAgrostis capillaris-Rumex acetosella agg. grassland, S4 Phragmites australis swamp and reedbed,Hl Calluna vulgaris-Festuca ovina heath,S25 Phragmites australis-Eupatoria cannabinum fen and A3 Spirodela polyrhiza-Hydrocharis morsus-ranae. The ditch complex on the marshes satisfies qualification for SSSI selection on botanical grounds alone. They support a mean of 12.7 species of wetland plants per 20m stretch and a total of 70 wetland species in the complex.
The lowland wet grassland communities are most threatened by drainage, under/over grazing and grazingZcutting at the wrong time of year. The ditch flora and fauna require regular ditch clearance and unpolluted water to maintain diversity. Ground nesting waders and breeding/wintering wildfowl would suffer adversely from uncontrolled human access. High water levels and a supply of good quality water are essential to maintain reedbed quality. Lack of management would result in drying out and climax succession to woodland. The heathland communities are threatened by lack of management leading to succession to woodland and the loss of the typical heathland communities. Ground nesting birds such as nightjar and woodlark would be under threat from unrestricted human access. The shingle ridge is susceptible to erosion resulting from uncontrolled and excessive recreational use. The long term future of the site may be affected by sea-level rise.
The lowland wet grassland represents a small remnant typical of the wet grassland once widespread over much of East Anglia,traditionally managed by grazing and mowing. The reedbeds are a small constituent of this habitat on the Suffolk coast,dominated by the large reedbeds of Walberswick and Minsmere. The heath and acid grassland is an important component of the Suffolk Sandlings and represents one of the few remaining areas of this habitat on the Suffolk coast.
The North Warren reserve was established in 1939 when 37 ha of heath, acid grassland,reedbed and scrub were purchased outright. A further 27 ha of heath and reedbed scrub was purchased in 1950 and a small area of heath in 1958. Another 26 ha of reedbed was added in 1982 and the area known as Church Farm marshes was purchased in 1990. A 12 ha area of arable land completed the area of owned land in August 1990. In 1995 management agreements were signed for Aldringham Walks, River Hundred SSSI and The Haven LNR. At the end of the l9th century the area was considered one of the most ornithologically important areas in Suffolk. In 1912 Thorpeness Meare was dug out and most of the marshes were drained although the reedbed survived intact as the River Hundred became partially blocked and water levels were maintained. Thatching reed was harvested from the fen until the early 1950's and birds such as bittern, garganey, shoveler, Montagu's harrier and bearded tit were all regular breeding species. The Anglia Water Authority straightened the River Hundred around this time to improve the drainage of the whole area. Consequently the water table dropped,the fen began to dry out and all of the above breeding species were lost. Most of the heathland areas were grazed by sheep until the 1930's and after wartime occupation,much of the area was cultivated. Stone-curlew, whinchat and red-backed shrike have all been lost as breeding species in the last 30 years.
The marshes were reclaimed from the sea in 1912 and were then substantially drained and improved with the consequent loss of much of their ornithological and botanical importance. Each winter the sluices were kept fully open to keep the area as dry as possible and summer grazing was largely by cattle. Most of the lower,wetter areas were filled in and levelled up to the 1980's. A wide tank trap was constructed across the south marsh in the second world war to forestall any German invasion and anti-glider ditches were constructed on the north marshes. A small flock of bean geese were reported on the marshes in the 1980's although the area remained largely dry and birdless. Since the acquisition of the area by RSPB in 1990 the marshes have become nationally important for three wildfowl species.
3.8 Position in an Ecological Unit
North Warren and Aldringham Walks lies within the Suffolk Heritage Coast Area of Outstanding Natural Beauty. Within this coastal strip are several nature reserves with similar features including Walberswick and Benacre NNR's, Minsmere, Havergate and Boyton Marshes RSPB reserves and the National Trust holdings at Dunwich Heath and Orfordness. The heathland forms a sizeable part of the Suffolk Sandlings which only now exist in fragments from Ipswich to Lowestoft. The reedbeds are a small example of a network of reedbeds along the Suffolk coast including large reedbeds at Walberswick,Benacre and Minsmere. Most of the lowland wet grassland on the Suffolk coast has been drained and/or improved. North Warren represents one of the few sites that is managed specifically for its nationally important wintering wildfowl and breeding wader popoulations. There is an interchange of wintering wildfowl between all the wetland sites on the coast.
a. Habitat and Species Manaqement
The grazing marshes have probably realised their full potential for wintering wildfowl and breeding waders although a complete cessation of wildfowling at Thorpeness Meare would probably increase wildfowl usage on north marsh. ( Habitat Action LWG 3.2 ). The completion of reedbed restoration should benefit the full assemblage of reedbed breeding birds particularly bittern, marsh harrier and bearded tit ( Habitat Action REE 3.3; Species Action BI3.2 ). The removal of invasive scrub and bracken from the heath together with extended sheep grazing should benefit the typical breeding heathland assemblage particularly nightjar and woodlark and possibly stone curlew ( Habitat Action LHE 3.2 )
b. Human Use
i. General
The reserves are used by local people,visitors and RSPB members. Minimum facilities have been provided and include well-maintained trails,notice boards and an information hut in Aldeburgh from June to September. The Aldeburgh and Thorpeness area attract in excess of 100K visitors per annum. Comminications and business plans should be drawn up to look at the potential of the reserves.
The lowland wet grassland and heathland could be utilised as management showcases particularly for local landowners and other conservation bodies. The site would be ideal to show the benefits of support schemes such as Suffolk River Valleys ESA and Countryside Stewardship. Due to the wide range of habitats this site is eminently suitable to hold management and ecological training courses.
iii. Marketing
With the current level of facilities at the site marketing opportunities are severely limited. The use of an information hut on the beach throughout the summer months should help in membership recruitment. This site has the potential to attract in excess of 100X visitors per annum without impinging on the conservation value of the reserve. Admission charges for the reserve are not practical as there is an extensive network of public footpaths across the whole site.
iv. Education
Education opportunities do exist at the site although there are few facilities. It would seem appropriate to concentrate educational resources at Minsmere at the present time until facilities are considerably upgraded.
v. Public Affairs
Invitations to ministers/civil servants to visit the reserve to show the benefits of the ESA and Countryside Stewardship support schemes. Guided walks of the site for local organisations and societies to increase awareness of the reserve and its importance for important species.
Large numbers of wintering wildfowl provide a spectacle for birdwatchers, general visitors and local people. Local people also value the retention of the grazing marshes and traditional management as promoted by the RSPB. The extensive network of public footpaths across the heathland provide a delightful all-year round walk for many people although there is a slight problem with uncontrolled parking and loose dogs on Aldringham Walks.
3.11 Identification and confirmation of important features
|
Feature |
Populations 91-95 |
National importance |
Regional importance |
|
Geology |
|||
|
March/fen alluvium |
Medium |
||
|
Corraline crag |
High |
||
|
Habitat/vegetation |
|||
|
Lowland wet grassland |
Medium |
||
|
Lowland heath |
Medium |
||
|
Reedswamp |
Medium |
||
|
Woodland |
Medium |
||
|
Plants |
|||
|
Parapholis incurva |
Medium |
||
|
Ranunculus baudotii |
Medium |
||
|
Crambe maritima |
Medium |
||
|
Trifolium ornithopodioides |
Medium |
||
|
T glomeratum |
Medium |
||
|
T suffocatum |
Medium |
||
|
Lathyrus japonicus |
Medium |
||
|
Crassula tillaea |
Medium |
||
|
Sonchus palustris |
Medium |
||
|
Dactylorhiza incarnata |
High |
||
|
Ranunculus lingua |
High |
||
|
NVC communities |
|||
|
U1 Festuca ovina-Agrostis capillaris-Rumex acetosella agg grassland |
High |
||
|
S4 Phragmites australis swamp and reedbed |
High |
||
|
A3 Spirodela polyrhiza-Hydrocharis-morsus-ranae |
Medium |
||
|
Animals |
|||
|
White-fronted goose |
100 |
2% UK |
|
|
Gadwall |
100 |
2% UK |
|
|
Shoveler |
180 |
3% UK |
|
|
Bewick's swan |
40 |
High |
|
|
Brent goose |
200 |
High |
|
|
Wigeon |
1000 |
High |
|
|
Teal |
750 |
high |
|
|
Ringed plover |
100 |
High |
|
|
Dunlin |
750 |
High |
|
|
Gadwall |
10 pairs |
2% UK |
|
|
Woodlark |
15 pairs |
6% UK |
|
|
Redshank |
24 pairs |
High |
|
|
Lapwing |
42 pairs |
High |
|
|
Snipe |
7 pairs |
HIGH |
|
|
Otter |
High |
||
|
Serotine |
High |
||
|
Brachytron pratense |
High |
||
None
3.13 Oserations likely to damaqe the special features and interests as notified by Enqlish Nature ( 05.03.86 ).
1. Cultivation including ploughing,rotovating,harrowing and reseeding.
2. Changes in the grazing regime including type of stock or intensity or seasonal pattern of grazing and cessation of grazing.
3. The introduction of stock feeding including the number of animals stocked.
4. Application of manure, fertilisers and lime.
5. Application of pesticides including herbicides and weedkillers.
6. Drainage including the use of mole,tile,tunnel or other artificial drains.
7. Use of vehicles or craft likely to damage or disturb vegetation or wildlife.
3.14 Main factors influencinq the manaqement of the site
Internal
1. Low water levels and scrub invasion causing parts of the reedbed to dry out with consequent loss of nationally scarce breeding species.
2. Scrub and bracken invasion reducing available breeding areas for nightjar and woodlark, particularly on Aldringham Walks.
3. Uncontrolled public access to the heath on Aldringham Walks severely affecting breeding attempts of nightjar and woodlark.
External
1. Occasional wildfowling on Thorpeness Meare may affect usage of north marsh by wintering wildfowl. Wildfowling currently carried out at a low level once a month.
2. Occasional shooting over the arable on Aldringham Walks may affect breeding birds on the heath.
3.15 Land of conservation or strateqic importance in the reserve vicinity
1. Aldringham Walks 298ha.
A mosaic of heathland,woods,scrub and arable land currently supporting breeding nightjars,woodlarks and tree pipits. Outstanding opportunities for heathland restoration and management to create suitable breeding habitat for stone-curlews. 110ha of heath and woods in this area is currently being managed by RSPB under a management agreement.
2. Aldringham Common/Square 50 ha.
A mosaic of heathland,woods,scrub and improved grassland currently supporting breeding nightjars and woodlarks.
Thorpeness Meare 30 ha.
A strategic area of man-made lakes,islands and reedbeds currently supporting small numbers of breeding and wintering wildfowl. Outstanding opportunities for reedbed management and re-creation primarily for breeding bittern,marsh harrier and bearded tit.
4. River Hundred SSSI 17 ha
A mosaic of restored heathland,woods,scrub and river frontage currently supporting breeding sparrowhawk,kingfisher and woodlark. Good opportunities for heathland management primarily for the benefit of breeding nightjar and woodlark. Part of this area is currently being managed by RSPB under a management agreement.
Abandoned railway track now in use as a permissive footpath. Acquisition required to control access through the centre of the reserve.
6. Gorse Hill Field 7.5 ha
Acid and improved grassland bordering the acid grassland at North Warren and currently supporting breeding skylark. Good opportunities for grassland management primarily for the benefit of breeding woodlark.
7. Church Farm Caravan Site 12 ha
Important as a buffer zone against southern boundary of the reserve with excellent opportunities for visitor management.
8. Aldeburgh Marshes 187 ha
Improved grassland and arable land bordering the internationally important Alde estuary and currently supporting breeding oystercatcher,lapwing and reed warbler plus in the region of 100 wintering Bewick's swans. Outstanding opportunities for reedbed and lowland wet grassland re-creation primarily for the benefit of breeding bittern,marsh harrier and bearded tit plus wintering wildfowl and waders.