Therfield Heath is a biological Site of Special Scientific Interest and Local Nature Reserve on the chalk escarpment just north of Therfield, Hertfordshire; since it lies south-west of the town of Royston it is also known locally as Royston Heath. The Heath is a common on which sheep are still regularly grazed. The site offers views towards the north, over the valley of the Cam as far as Cambridge.
Fowlmere is a Royal Society for the Protection of Birds nature reserve between Fowlmere and Melbourn in Cambridgeshire. It is designated a 39.9-hectare (99-acre) biological Site of Special Scientific Interest called Fowlmere Watercress Beds.
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.
Westwood Quarry is a 0.07 hectare geological site of Special Scientific Interest west of Watford in Hertfordshire. It was notified in 1987 under the Wildlife and Countryside Act 1981. The planning authority is Three Rivers District Council. It is a Geological Conservation Review site.
Dogsthorpe Star Pit is a 36.4-hectare (90-acre) biological Site of Special Scientific Interest (SSSI)) on the eastern outskirts of Peterborough in Cambridgeshire. It is also designated a Local Nature Reserve, and it is managed by the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire.
Herts and Middlesex Wildlife Trust manages over 40 nature reserves covering nearly 810 hectares north of London, in Hertfordshire and the historic county of Middlesex, part of which is divided between the London boroughs of Barnet, Enfield, Harrow and Hillingdon. It has over 21,000 members, and is one of 46 Wildlife Trusts across the UK. It is a Registered Charity, with its Registered Office in St Albans, and had an income in the year to 31 March 2014 of over £1.5 million.
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.
Northaw Great Wood is a 223.6-hectare (553-acre) biological Site of Special Scientific Interest (SSSI) near Cuffley in Hertfordshire, England. It covers Northaw Great Wood Country Park, which is managed by Welwyn Hatfield Borough Council, Well Wood, Justice Hill and Grimes Bottom. Part of the site is managed by Hertfordshire County Council as a schools' park. The country park is also a local nature reserve.
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.
Knebworth Woods is a 120.8-hectare (299-acre) biological Site of Special Scientific Interest in Knebworth, immediately south of Stevenage in Hertfordshire. The planning authority is North 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.
Tring Woodlands is a 23.8-hectare (59-acre) biological Site of Special Scientific Interest in Tring in Hertfordshire. It is part of the Chilterns Area of Outstanding Natural Beauty and the local planning authority is Dacorum District Council. The wood has a rich flora, showing that it is well established. It is a good example of a semi-natural beech wood in Hertfordshire. Plants that are abundant include woodruff, wood anemone and dog's mercury, and there are a variety of woodland birds. There is access to the wood from Hastoe Hill.
Redwell Wood is a 52.8-hectare (130-acre) biological Site of Special Scientific Interest near South Mimms in Hertfordshire. The local planning authority is Welwyn Hatfield District Council.
Downfield Pit is a 3.6-hectare (8.9-acre) geological Site of Special Scientific Interest near Ware in Hertfordshire. It is in the Geological Conservation Review in the Thames Pleistocene section, and the local planning authority is East Hertfordshire District Council.
Oughtonhead Lane is a 0.9-hectare (2.2-acre) geological Site of Special Scientific Interest in Hitchin in Hertfordshire. The local planning authority is North Hertfordshire District Council. The site has been identified as of national importance in the Geological Conservation Review.
Purwell Meadows is an 8.6-hectare (21-acre) nature reserve in Hitchin, Hertfordshire, England. It was declared a Local Nature Reserve in 1994. It is owned and managed by North Hertfordshire District Council.
Tewinbury is a 7.5-hectare (19-acre) biological Site of Special Scientific Interest near Tewin in Hertfordshire. The local planning authority is East Hertfordshire District Council, and the site is managed by the Herts and Middlesex Wildlife Trust
Ashwell Quarry and Quarry Springs is a three hectare nature reserve managed by the Herts and Middlesex Wildlife Trust near Ashwell in Hertfordshire. Ashwell Quarry is owned by a local farmer, and Quarry Springs by Hertfordshire County Council. It is a Regionally Important Geological Site.
