List of Sites of Special Scientific Interest in Hertfordshire

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Tring Reservoirs at sunrise
Tring Reservoirs at sunrise

Hertfordshire is a county in eastern England. It is bordered by Bedfordshire to the north, Cambridgeshire to the north-east, Essex to the east, Buckinghamshire to the west and Greater London to the south. The county town is Hertford. As of June 2014, the county has a population of 1,154,800[1] in an area of 634 square miles (1,640 km2).[2]

As of January 2016, there are 43 sites designated within this Area of Search, 36 of which have been designated for their biological interest and 7 for their geological interest.[3] In England the body responsible for designating SSSIs is Natural England, which chooses a site "because of its flora, fauna, or geological or physiographical features".[4]

The data in the table is taken from Natural England's website in the form of citation sheets for each SSSI.

Key[edit]

Sites[edit]

Site name Photograph B G Area[a] Public
access
Location[a] Other
classifications
Map[a] Citation[a] Description
Aldbury Nowers Aldbury Nowers Green tickY 19.8 hectares (49 acres) YES Tring
51°48′43″N 0°37′19″W / 51.8120°N 0.6219°W / 51.8120; -0.6219 (Aldbury Nowers)
SP951135
HMWT[5] Map Citation The site hosts the flowers of chalk grassland and has butterfly habitats with several different species of butterfly including the Duke of Burgundy, hairstreaks and the Essex skipper. There are also large areas of woodland and calcareous grassland.[6][7]
Alpine Meadow Alpine Meadow Green tickY 0.8 hectares (2.0 acres) YES Berkhamsted
51°46′57″N 0°34′04″W / 51.7826°N 0.5677°W / 51.7826; -0.5677 (Alpine Meadow)
SP989103
HMWT[8] Map Citation This steeply sloping small meadow is a rare example of unimproved chalk grassland. Grass species include upright brome, false brome and sheep's fescue, and there are many orchids, especially common twayblade and common spotted orchid.[9]
Amwell Quarry Amwell Quarry Green tickY 37.1 hectares (92 acres) YES Amwell
51°47′52″N 0°00′16″W / 51.7978°N 0.0045°W / 51.7978; -0.0045 (Amwell Quarry)
TL377129
HMWT,[10] SPA, SPA[11] Ramsar[12] Map Citation This is an internationally important site for wintering wildfowl, and is Britain's most important site for dragonflies. Plants include marsh dock and hairlike pondweed, both nationally rare. Amwell has a quarter of all British species of molluscs.[13][14]
Ashridge Commons & Woods Pitstone Common Green tickY 627.3 hectares (1,550 acres) YES Little Gaddesden
51°48′42″N 0°35′14″W / 51.8116°N 0.5871°W / 51.8116; -0.5871 (Ashridge Commons & Woods)
SP975135
CAONB,[15] NT[15] Map Citation Ths site is mainly semi-natural vegetation, with has extensive areas of woodland, grass and scrub. There are many species of breeding birds, including some which are rare nationally, such as firecrests. Other species which are rare in Hertfordshire are redstart, nightingale and wood warbler.[16]
Ashwell Springs Ashwell Springs Green tickY 0.3 hectares (0.74 acres) YES Ashwell
52°02′32″N 0°08′59″W / 52.0421°N 0.1497°W / 52.0421; -0.1497 (Ashwell Springs)
TL270398
Map Citation The site consists of a series of freshwater springs, which provide a habitat for cold water, invertebrate animals, some of which are rare. The site is particularly important for flatworms, including Crenobia alpina and the Polycelis felina.[17]
Benington High Wood Benington High Wood Green tickY 20.7 hectares (51 acres) YES Benington
51°53′43″N 0°08′02″W / 51.8952°N 0.1339°W / 51.8952; -0.1339 (Benington High Wood)
TL285235
Map Citation The site is ancient woodland, described by Natural England as "one of the best remaining examples in the county of the pedunculate oak-hornbeam of the ash-maple variety". Shrub species include field maple and hazel, with a higher ground flora diversity in clearings and rides.[18]
Blagrove Common Blagrove Common Green tickY 5.0 hectares (12 acres) YES Sandon
51°59′12″N 0°04′13″W / 51.9868°N 0.0704°W / 51.9868; -0.0704 (Blagrove Common)
TL326338
HMWT[19] Map Citation The site is one of the few areas of unimproved marshy grassland in east Hertfordshire. It is crossed by a stream and has a rich diversity of vegetation, including a variety of orchids.[20] Kestrels often hunt mice and voles, which are common on the site.[21]
Bricket Wood Common Bricket Wood Common Green tickY 75.5 hectares (187 acres) YES Bricket Wood
51°41′47″N 0°21′59″W / 51.6964°N 0.3664°W / 51.6964; -0.3664 (Bricket Wood Common)
TL130010
Map Citation The common is a remnant of a lowland heath, with much it on the heavy soils of boulder clay which have poor drainage and wet habitats. There are also areas of ancient woodland and dry heath. In drier heath areas there are heather, purple moor-grass and heath milkwort.[22]
Castle Lime Works Quarry Castle Lime Works Quarry Green tickY 1.4 hectares (3.5 acres) NO South Mimms
51°42′31″N 0°13′22″W / 51.7087°N 0.2227°W / 51.7087; -0.2227 (Castle Lime Works Quarry)
TL229026
GCR[23] Map Citation Natural England states: "This reveals extensive piping in the top of the chalk resulting from solution at the Chalk - Tertiary sediment interface. Believed to have formed during the Tertiary and Pleistocene, it is the finest exposure of clay-filled pipes in the Chalk Karst of England."[24]
Croxley Common Moor Croxley Common Moor Green tickY 39.6 hectares (98 acres) YES Croxley Green
51°38′33″N 0°26′11″W / 51.6425°N 0.4363°W / 51.6425; -0.4363 (Croxley Common Moor)
TQ083949
LNR[25] Map Citation The site is mainly grass heathland with some ancient woodland and hazel coppice. Over 250 species of plants have been recorded, including sheep sorrel, common bent and sheep's fescue. There are many ant hills made by yellow meadow ants.[26][27]
Downfield Pit, Westmill Downfield Pit Green tickY 0.3 hectares (0.74 acres) YES Ware
51°49′51″N 0°02′37″W / 51.8308°N 0.0437°W / 51.8308; -0.0437 (Downfield Pit, Westmill)
TL349165
Map Citation The site provides an example of the complex sequence of Pleistocene gravels and clays laid down by the River Thames when it flowed through the Vale of St Albans before the river was diverted south by the Anglian ice age around 450,000 years ago.[28]
Frogmore Meadows Frogmore Meadows Green tickY 4.6 hectares (11 acres) YES Chenies
51°40′47″N 0°31′29″W / 51.6796°N 0.5247°W / 51.6796; -0.5247 (Frogmore Meadows)
TQ021989
CAONB,[29] HMWT,[30] Map Citation The site has marshy areas and fens next to the river, damp grassland and drier, more acidic areas. The river bank has water voles, and damp areas are dominated by meadow foxtail and Yorkshire fog, with some marsh marigold and marsh bedstraw.[31][32]
Great Hormead Park Great Hormead Park Green tickY 15.0 hectares (37 acres) YES Great Hormead
51°56′36″N 0°03′42″E / 51.9432°N 0.0616°E / 51.9432; 0.0616 (Great Hormead Park)
TL418292
Map Citation The site is coppiced ancient woodland on boulder clay. It has diverse tree species, including wych elm and hornbeam, resulting in a rich ground flora. Dog's mercury is dominant over most of the woodland floor, with plants such as angelica sylvestris and tufted hair grass in wetter areas.[33]
Hertford Heath Hertford Heath Green tickY 29.1 hectares (72 acres) YES Hertford Heath
51°46′53″N 0°02′14″W / 51.7813°N 0.0372°W / 51.7813; -0.0372 (Hertford Heath)
TL355110 &
TL350106
HMWT[34] Map Citation The heath is dominated by heather, and there are grass snakes and slow worms. Sphagnum mosses and creeping willow are found in wetter areas. Ponds support the rare water violet and a rich invertebrate fauna such as great crested and smooth newts, the water spider and eight species of dragonfly.[35][36]
Hillcollins Pit Hillcollins Pit Green tickY 0.2 hectares (0.49 acres) YES Furneux Pelham
51°55′16″N 0°05′43″E / 51.9211°N 0.0954°E / 51.9211; 0.0954 (Hillcollins Pit)
TL442268
GCR[37] Map Citation This disused gravel pit is the type site for the Westland Green Gravels, which were laid down by the ancestral River Thames 1.6 to 1.8 million years ago, and which show the river's ancient course.[38]
Hunsdon Mead Hunsdon Mead Green tickY 34.2 hectares (85 acres) YES Harlow
51°46′47″N 0°03′15″E / 51.7797°N 0.0541°E / 51.7797; 0.0541 (Hunsdon Mead)
TL418110
HMWT[39] Map Citation This is unimproved grassland which is subject to winter flooding. Notable grass species include meadow brome and the quaking grass briza media, and there are other unusual flora such as pepper saxifrage and green-winged orchid.[40]
Knebworth Woods Knebworth Woods Green tickY 128.8 hectares (318 acres) YES Stevenage
51°53′09″N 0°13′02″W / 51.8857°N 0.2172°W / 51.8857; -0.2172 (Knebworth Woods)
TL228223
Map Citation The wood is ancient in origin and ecologically diverse. The dominant trees are oak and hornbeam. Ponds have unusual plant species, and the site is rich in fungi and bryophytes. Breeding birds include nightingales.[41]
Little Heath Pit Little Heath Pit Green tickY 1.2 hectares (3.0 acres) YES Potten End
51°45′48″N 0°31′40″W / 51.7633°N 0.5278°W / 51.7633; -0.5278 (Little Heath Pit)
TL017082
GCR,[42] NT[43] Map Citation The lowest layer is gravel dating to the beginning of the Pleistocene 2.6 million years ago. A higher layer of gravel was laid down some 20,000 years ago, when the last ice age was at its maximum, and the site was cold tundra like western Siberia today.[44]
Moor Hall Meadows Moor Hall Meadows Green tickY 24.0 hectares (59 acres) YES Ardeley
51°55′16″N 0°04′03″W / 51.9211°N 0.0674°W / 51.9211; -0.0674 (Moor Hall Meadows)
TL330265
Map Citation The site has a variety of types of meadows, with marshy grassland being the most extensive. Its rich flora makes it one of the most important grassland sites in the county. There is also a small ancient woodland which has a variety of breeding birds.[45]
Moor Mill Quarry, West Moor Mill Quarry Green tickY 0.2 hectares (0.49 acres) NO How Wood
51°42′43″N 0°21′02″W / 51.7119°N 0.3506°W / 51.7119; -0.3506 (Moor Mill Quarry, West)
TL141027
GCR[46] Map Citation The pit displays the advance of ice during the Anglian glaciation around 450,000 years ago, which diverted the Thames south to its present course. The site is regarded by Natural England as of fundamental importance as the only one which demonstrates the diversion of the Thames from its pre-Anglian course.[47]
Northaw Great Wood Northaw Great Wood Green tickY 224.3 hectares (554 acres) YES Cuffley
51°43′22″N 0°08′54″W / 51.7228°N 0.1483°W / 51.7228; -0.1483 (Northaw Great Wood)
TL280043
LNR[48] Map Citation The site has one of the county's most exensive areas of ancient hornbeam woodland, with other trees including oak and silver birch. Glades, streams and springs add to the biodiversity.[49]
Oddy Hill and Tring Park Tring Park Green tickY 36.0 hectares (89 acres) YES Tring
51°47′20″N 0°38′50″W / 51.7890°N 0.6473°W / 51.7890; -0.6473 (Oddy Hill)
SP934109
51°47′01″N 0°39′22″W / 51.7837°N 0.6561°W / 51.7837; -0.6561 (Tring Park)
SP928103
RHPG.[50] Map Citation This is one of the most extensive areas of unimproved chalk downland in Hertfordshire. The site has diverse grass and flowering plant species Orchids include common spotted-orchid, common twayblade, greater butterfly-orchid and southern marsh-orchid.[51]
Oughtonhead Lane Oughtonhead Lane Green tickY 1.0 hectare (2.5 acres) YES Hitchin
51°57′19″N 0°17′45″W / 51.9552°N 0.2959°W / 51.9552; -0.2959 (Oughtonhead Lane)
TL172299
GCR[52] Map Citation The site probably dates to the Hoxnian interglacial 420,000 to 300,000 years ago. It was then a marsh fed by springs, and it has a tufa which contains fossil land snails and mammal bones which show the climate and local environmental conditions.[53]
Patmore Heath Patmore Heath Green tickY 8.5 hectares (21 acres) YES Albury
51°54′43″N 0°05′47″E / 51.9120°N 0.0965°E / 51.9120; 0.0965 (Patmore Heath)
TL443258
HMWT[54] Map Citation The site is home to a large amount of dry grass, as well as marshy-areas. Much of the turf is dominated by Deschampsia, as well as occurrences of Anthoxanthum odoratum. Uncommon plants are heath rush and heath grass. There are a wide variety of dragonfly, including the emperor dragonfly.[55]
Plashes Wood Plashes Wood Green tickY 73.2 hectares (181 acres) YES Standon
51°52′01″N 0°00′21″E / 51.8669°N 0.0058°E / 51.8669; 0.0058 (Plashes Wood)
TL382206
Map Citation The site is mainly oak and hornbeam woodland near the northern limit of its natural distribution. It has varied ground flora on soils from damp heavy clay to light gravels. There are also ponds and extensive clearings dominated by bracken, and other flora including hoary cinquefoil.[56]
Redwell Wood Redwell Wood Green tickY 52.6 hectares (130 acres) YES South Mimms
51°42′29″N 0°14′45″W / 51.7081°N 0.2459°W / 51.7081; -0.2459 (Redwell Wood)
TL213025
Map Citation The site has ancient and secondary woodland, heath and scrub. The woodland canopy is dominated by pedunculate oak. Ground flora include bluebells and enchanter’s-nightshade, while heathland species include heather and the rare creeping willow.[57]
Roughdown Common Roughdown Common Green tickY 3.7 hectares (9.1 acres) YES Hemel Hempstead
51°44′25″N 0°29′06″W / 51.7402°N 0.4850°W / 51.7402; -0.4850 (Roughdown Common)
TL047057
CAONB[58] Map Citation This is one of the few examples of unimproved calcareous grassland in Hertfordshire. The dominant grasses are meadow fescue and meadow oat-grass, and there are colonies of orchids. It is the only site in the county where common juniper regenerates naturally.[59][60]
Rye Meads Rye Meads Green tickY 60.3 hectares (149 acres) YES Rye House
51°46′34″N 0°00′22″E / 51.7760°N 0.0061°E / 51.7760; 0.0061 (Rye Meads)
TL385105
Ramsar,[61] SPA[11] RSPB,[61] HMWT[62] Map Citation Part of this site is an ancient flood meadow which has a variety of habitats including reedbed, marshy grassland and fen. It is grazed by ponies and water buffalo.[63] There are also ponds which have kingfisher, snipe, green sandpiper, shoveler, gadwall and tufted duck.[64]
Sarratt Bottom Sarratt Bottom Green tickY 3.5 hectares (8.6 acres) NO Sarratt
51°40′46″N 0°30′37″W / 51.6794°N 0.5102°W / 51.6794; -0.5102 (Sarratt Bottom)
TQ031989
Map Citation The site is a meadow beside the River Chess. It is an example of damp grassland which has been traditionally managed for grazing. There are also areas of swamp and marsh. The main plants in grassland areas include sweet vernal grass and meadow foxtail, and marsh horsetail and common spike-rush are common in damper areas.[65]
Sawbridgeworth Marsh Sawbridgeworth Marsh Green tickY 6.2 hectares (15 acres) YES Sawbridgeworth
51°49′15″N 0°09′48″E / 51.8209°N 0.1634°E / 51.8209; 0.1634 (Sawbridgeworth Marsh)
TL492158
EWT[66] Map Citation The site is a river valley marsh close to the River Stort, which has a varied wetland flora. Grazing and cutting of the marsh in rotation maintain biological diversity. The site also has an important wetland fauna and many moth species.[67]
Sherrardspark Wood Sherrardspark Wood Green tickY 74.4 hectares (184 acres) YES Welwyn Garden City
51°48′37″N 0°13′02″W / 51.8102°N 0.2172°W / 51.8102; -0.2172 (Sherrardspark Wood)
TL230139
LNR[68] Map Citation The site is an ancient semi-natural sessile oak and hornbeam wood on acid soils. There are also swallowholes fed by streams, and a woodland ride provides a habitat for invertebrates.[69]
Tewinbury Tewinbury Green tickY 7.3 hectares (18 acres) NO Tewin
51°48′34″N 0°10′04″W / 51.8095°N 0.1679°W / 51.8095; -0.1679 (Tewinbury)
TL264139
HMWT[70] Map Citation The site borders the River Mimram. It has alluvial meadows and marshes which are rare in lowland Britain. There are areas of swamp and tall fens, with plants including butterbur and angelica. Otters have been observed on the riverbank, in possibly the only site in the county.[71][72]
Therfield Heath Therfield Heath Green tickY 146.5 hectares (362 acres) YES Therfield
52°02′32″N 0°03′18″W / 52.0423°N 0.0549°W / 52.0423; -0.0549 (Therfield Heath)
TL335400
LNR,[73] SM[74][75] Map Citation This site is described by Natural England as describing some to the richest chalkland in England. It is unimproved pasture which has a wide variety of plants including the rare pasque flower. There is a diverse insect fauna.[76]
Thorley Flood Pound Thorley Flood Pound Green tickY 17.3 hectares (43 acres) YES Thorley
51°50′36″N 0°09′41″E / 51.8434°N 0.1615°E / 51.8434; 0.1615 (Thorley Flood Pound)
TL490183
HMWT[77] Map Citation Habitats include tall wash grassland, which is now rare, marsh and waterlogged grassland. It has a wide variety of plant species, including reed sweet-grass and meadowsweet. There are flowers such as fen bedstraw and early marsh orchid. Breeding birds include snipe and water rails.[78]
Tring Reservoirs Tring Reservoirs Green tickY 100.0 hectares (247 acres) YES Tring
51°48′49″N 0°40′06″W / 51.8135°N 0.6683°W / 51.8135; -0.6683 (Tring Reservoirs)
SP919136
SP905131
HMWT[79] Map Citation These four reservoirs are on the sites of ancient marshes, and their diverse fauna and flora include some dating back to their marshland origins. The site is important for breeding and wintering birds, including nationally important numbers of shovelers. The site is also significant for invertebrates.[80]
Tring Woodlands Tring Woodlands Green tickY 24.1 hectares (60 acres) YES Tring
51°46′52″N 0°40′20″W / 51.7812°N 0.6721°W / 51.7812; -0.6721 (Tring Woodlands)
SP917100
CAONB[81] Map Citation The wood has a rich flora, showing that it is well established. It is one of the best examples of semi-natural beech woodland in Hertfordshire. Plants include woodruff, wood anemone and dog's mercury, and there is a variety of woodland birds.[82]
Turnford and Cheshunt Pits Cheshunt Pit Green tickY 174.4 hectares (431 acres) YES Cheshunt
51°42′32″N 0°01′07″W / 51.7090°N 0.0186°W / 51.7090; -0.0186 (Turnford & Cheshunt Pits)
TL370030
SPA[11] Map Citation This site includes ten former gravel pits, which are of national importance for wintering gadwalls and shovelers. It is also valuable for invertebrates, especially grasshoppers and bush-crickets.[83]
Wain Wood Wain Wood Green tickY 19.0 hectares (47 acres) YES Preston
51°54′56″N 0°17′09″W / 51.9155°N 0.2858°W / 51.9155; -0.2858 (Wain Wood)
TL180255
Map Citation The wood lies on a north-east facing slope of decalcified boulder clay. The woodland area is also home to Pedunculate Oak and Quercus petraea, with much of the south of the area consisting of acidic grassland. There are many butterfly species, including Thecla quercus.[84]
Water End Swallow Holes Water End Swallow Holes Green tickY 11.1 hectares (27 acres) YES Welham Green
51°43′26″N 0°13′14″W / 51.7239°N 0.2206°W / 51.7239; -0.2206 (Water End Swallow Holes)
TL230043
Map Citation The site covers more than fifteen sinkholes, the only ones in chalk which are a permanent feature of the landscape. Next to the holes is a swamp area of willow carr which is biologically important, and in deep water there is Reed Sweet-grass. The site also has areas of woodland and grassland.[85]
Westwood Quarry Westwood Quarry Green tickY 0.1 hectares (0.25 acres) NO Watford
51°40′56″N 0°27′08″W / 51.6823°N 0.4523°W / 51.6823; -0.4523 (Westwood Quarry)
TQ071993
GCR[86] Map Citation This site throws light on the early history of the River Thames, when it flowed through the Vale of St Albans, before it was diverted south to its present course during the Anglian Ice Age around 450,000 years ago.[87]
Whippendell Wood Whippendell Wood Green tickY 66.7 hectares (165 acres) YES Watford
51°40′07″N 0°26′44″W / 51.6687°N 0.4455°W / 51.6687; -0.4455 (Whippendell Wood)
TQ076978
Map Citation This is ancient woodland, and the main trees are oak, ash, hazel and hornbeam. Ground flora include Yorkshire Fog, bluebells and honeysuckle. There are diverse species of fungi, invertebrates and birds.[88]
Wormley-Hoddesdonpark Wood North Hoddesdonpark Wood Green tickY 143.9 hectares (356 acres) YES Hoddesdon
51°45′32″N 0°02′33″W / 51.7589°N 0.0425°W / 51.7589; -0.0425 (Wormley-Hoddesdonpark Wood North)
TL352085
TL325075
NNR,[89] WT,[89] NCR,[90] HMWT,[91] SAC[92] Map Citation The site is oak and hornbeam on acid gravel. The ground flora is diverse, including dog’s mercury and yellow archangel. Small ponds and streams are important for bryophytes, and invertebrates include the green tiger beetle.[90]
Wormley-Hoddesdonpark Wood South Wormley-Hoddesdonpark Wood South Green tickY 196.2 hectares (485 acres) YES Cheshunt
51°44′39″N 0°04′25″W / 51.7441°N 0.0735°W / 51.7441; -0.0735 (Wormley-Hoddesdonpark Wood South)
TL331068
NNR,[93] NCR,[94] SAC[92] Map Citation The site is oak and hornbeam woodland mainly on London clay. Plants in the variable ground flora include brambles, wood anemones and bluebells. Other habitats include marshland and acidic grassland.[94]

See also[edit]

Notes[edit]

  1. ^ a b c d Maps and citations for each site are taken from the Natural England database. The area and location of the site is shown on the citation. The listing is as in January 2016.

References[edit]

  1. ^ "Resident Population". Hertfordshire Local Information System. Retrieved 29 July 2015. 
  2. ^ "Area Measurements". Hertfordshire Local Information System. Retrieved 10 February 2015. 
  3. ^ "Designated Sites View - Hertfordshire". Natural England. Retrieved 12 January 2016. 
  4. ^ "Guidelines for selection of biological SSSIs". Joint Nature Conservation Committee. Retrieved 12 January 2016. 
  5. ^ "Aldbury Nowers". Herts and Middlesex Wildlife Trust. Retrieved 11 January 2016. 
  6. ^ "Aldbury Nowers" (PDF). Natural England. Archived from the original (PDF) on 20 March 2009. Retrieved 21 February 2006. 
  7. ^ "Aldbury Nowers". Herts and Middlesex Wildlife Trust. Retrieved 2011-01-07. 
  8. ^ "Alpine Meadow". Hertfordshire and Middlesex Wildlife Trust. Retrieved 21 December 2014. 
  9. ^ "Alpine Meadow citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 21 December 2014. 
  10. ^ "Amwell". Hertfordshire and Middlesex Wildlife Trust. Retrieved 19 December 2014. 
  11. ^ a b c "Lee Valley". Joint Nature Conservation Committee. Retrieved 16 January 2016. 
  12. ^ "Lee Valley". Ramsar Sites Information Service. Retrieved 19 December 2014. 
  13. ^ "Amwell". Hertfordshire and Middlesex Wildlife Trust. Retrieved 19 December 2014. 
  14. ^ "Amwell Quarry citation" (PDF). Sites of Special Scientific Interest. Natural England. Retrieved 19 December 2014. 
  15. ^ a b "Ashridge Commons and Woods citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 4 January 2016. 
  16. ^ "Ashridge Commons & Woods citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 19 December 2014. 
  17. ^ "Ashwell Springs citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 12 January 2015. 
  18. ^ "Benington High Wood citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 3 January 2015. 
  19. ^ "Blagrove Common". Hertfordshire and Middlesex Wildlife Trust. Retrieved 12 January 2015. 
  20. ^ "Blagrove Common citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 12 January 2015. 
  21. ^ "Blagrove Common". Hertfordshire and Middlesex Wildlife Trust. Retrieved 12 January 2015. 
  22. ^ "Bricket Wood Common citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 7 December 2014. 
  23. ^ "Castle Lime Works Quarry (Karst)". Joint Nature Conservation Committee. Retrieved 11 January 2016. 
  24. ^ "Castle Lime Works Quarry citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 15 January 2015. 
  25. ^ "Croxley Common Moor". Local Nature Reserves. Natural England. 13 March 2013. Archived from the original on 9 August 2014. Retrieved 10 December 2014. 
  26. ^ "Croxley Common Moor citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 10 December 2014. 
  27. ^ "Croxley Common Moor". Local Nature Reserves. Natural England. 13 March 2013. Archived from the original on 9 August 2014. Retrieved 10 December 2014. 
  28. ^ "A Geological Conservation Strategy for Hertfordshire" (PDF). Hertfordshire RIGS Group. 2003. p. 43. Retrieved 4 February 2015. 
  29. ^ "Frogmore Meadows citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 11 December 2014. 
  30. ^ "Frogmore Meadow". Herts and Middlesex Wildlife Trust. Retrieved 11 December 2014. 
  31. ^ "Frogmore Meadows citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 3 March 2016. Retrieved 11 December 2014. 
  32. ^ "Frogmore Meadow". Herts and Middlesex Wildlife Trust. Retrieved 11 December 2014. 
  33. ^ "Great Hormead Park citation" (PDF). Sites of Special Scientific Interest. Natural England. Retrieved 19 February 2015. 
  34. ^ "Hertford Heath". Herts and Middlesex Wildlife Trust. Retrieved 15 February 2015. 
  35. ^ "Hertford Heath citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 15 February 2015. 
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  37. ^ "Furneux Pelham Gravel Pit (Hillcollins Pit) (Quaternary of the Thames)". Joint Nature Conservation Committee. Retrieved 18 February 2015. 
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