Aldbury Nowers is a 19.7 hectares biological Site of Special Scientific Interest (SSSI) in the Chiltern Hills, north-east of Tring in Hertfordshire. The site was notified in 1990 under the Wildlife and Countryside Act 1981. It is managed by the Hertfordshire and Middlesex Wildlife Trust. The site, formerly known as "Duchie's Piece," comprises two areas of hillside, linked by The Ridgeway. The calcareous meadow element of the site hosts the flowers of chalk grassland and has butterfly habitats with thirty-four different species of butterfly recently recorded, including the Duke of Burgundy, hairstreaks and the Essex skipper. The site also includes a "beech hanger", a type of upland ancient woodland, and is considered one of the best examples of this feature in Hertfordshire.
Pegsdon Hills and Hoo Bit is a 79-hectare (200-acre) nature reserve in Pegsdon in Bedfordshire. It is managed by the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire. The site is on the border between Bedfordshire and Hertfordshire, and it covers Pegsdon Hills and part of the adjacent Deacon Hill in Bedfordshire, and Hoo Bit in Hertfordshire. It is in the Chilterns Area of Outstanding Natural Beauty, and part of the site is designated by Natural England as the Deacon Hill SSSI.
Water End Swallow Holes is a biological site of Special Scientific Interest in Hertfordshire, south-east England. Located in Welham Green and under the planning authority of Welwyn Hatfield District Council, it has an area of 11.3 hectares.
Rye Meads is a 58.5-hectare (145-acre) biological Site of Special Scientific Interest (SSSI) in Rye House, Hoddesdon, Hertfordshire. It is one of series of wetlands and reservoirs situated along the River Lea, to the north-east of London. It is part of the Lea Valley Ramsar site and a Special Protection Area.
Fancott Woods and Meadows is a 13.3-hectare Site of Special Scientific Interest near the hamlet of Fancott in Bedfordshire. It was notified under Section 28 of the Wildlife and Countryside Act 1981, and the local planning authority is Central Bedfordshire Council. The site is managed by the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire.
Moor Mill Quarry, West is a 0.16-hectare (0.40-acre) geological Site of Special Scientific Interest in How Wood in Hertfordshire. The local planning authority is St Albans City and District Council. It was notified in 1992 as representing the former Moor Mill Quarry SSSI, which was lost to landfill operations. It is listed by the Geological Conservation Review.
Croxley Common Moor is a 39.5-hectare (98-acre) biological Site of Special Scientific Interest (SSSI) and Local Nature Reserve in Croxley Green, Hertfordshire. It is owned by Three Rivers District Council and managed by the council together with the Countryside Management Service and the Friends of Croxley Common Moor. Most of it is a registered common.
Frogmore Meadows is a 4.6-hectare (11-acre) biological Site of Special Scientific Interest in Hertfordshire and Buckinghamshire, north of the village of Chenies. It consists of two meadows in the Chilterns Area of Outstanding Natural Beauty, next to the River Chess, one of which is a Hertfordshire and Middlesex Wildlife Trust nature reserve. The planning authorities are Three Rivers District Council, Dacorum Borough Council and Chiltern District Council.
Sarratt Bottom nature Reserve in Hertfordshire is a 3.2-hectare (7.9-acre) biological Site of Special Scientific Interest. 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. The site has hedgehogs and a wide variety of wetland birds and invertebrates.
Roughdown Common is a 3.6-hectare (8.9-acre) biological Site of Special Scientific Interest in Hemel Hempstead in Hertfordshire. The planning authority is Dacorum Borough Council. The site is Common land, and it is owned by the Box Moor Trust having been officially brought by the trust in April 1886 from the Dean and Chapter of St Paul's. It is part of the Chilterns Area of Outstanding Natural Beauty. The Common is a steeply sloping chalk hill in south Hemel Hempstead.
Hunsdon Mead is a 34 hectare biological Site of Special Scientific Interest (SSSI) west of Harlow and east of Roydon in Essex. The site is partly in Essex and partly in Hertfordshire, and it is jointly owned and managed by the Essex Wildlife Trust and the Herts and Middlesex Wildlife Trust. The SSSI also includes part of the neighbouring Roydon Mead. The planning authorities are East Hertfordshire District Council and Epping Forest District Council. Hunsdon Mead is registered common land.
Benington High Wood is a 20.7-hectare (51-acre) biological Site of Special Scientific Interest in Benington, Hertfordshire. The planning authority is East Hertfordshire District Council.
Blagrove Common is a 4.0 hectare Site of Special Scientific Interest in Green End near Sandon in Hertfordshire. It is managed by the Hertfordshire and Middlesex Wildlife Trust, and the planning authority is North Hertfordshire District Council.
Thorley Wash or Thorley Flood Pound is a 17.3-hectare biological Site of Special Scientific Interest in Thorley, south of Bishop's Stortford in Hertfordshire. It was formerly a flood pound for the Stort Navigation, which was decommissioned in 2004 and converted to a more natural state. It was purchased by the Herts and Middlesex Wildlife Trust from the Environment Agency in 2011.
Poker's Pond Meadow is a 1.9-hectare (4.7-acre) biological Site of Special Scientific Interest south of Stoke Hammond in Buckinghamshire.
Temple Island Meadows is a 14.1-hectare (35-acre) biological Site of Special Scientific Interest on the Buckinghamshire bank of the River Thames. It is north of Henley-on-Thames and opposite Temple Island, an island in the Thames.
Greywell Fen is a 38-hectare (94-acre) biological Site of Special Scientific Interest in Greywell in Hampshire. It is a Nature Conservation Review site, Grade 2, and an area of 13 hectares is a nature reserve called Greywell Moors, which is managed by the Hampshire and Isle of Wight Wildlife Trust.
Hazeley Heath is a 180.8-hectare (447-acre) biological Site of Special Scientific Interest west of Farnborough in Hampshire. It is part of Thames Basin Heaths Special Protection Area for the conservation of wild birds.
