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.
Wormley-Hoddesdonpark Wood North is a 143.9 hectare woodland area in Hertfordshire which has been designated as a biological site of Special Scientific Interest. The site is listed as Grade 1 in A Nature Conservation Review, and is also designated a Special Area of Conservation. It is in Hoddesdon in the borough of Broxbourne, but part of the site is in East Hertfordshire.
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.
Rye Meads is a 58.5 hectare 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.
Ruislip Woods is a Site of Special Scientific Interest and national nature reserve covering 726 acres (294 ha) in Ruislip in the London Borough of Hillingdon. The woods became London's first national nature reserve in May 1997. Ruislip Local Nature Reserve at TQ 090 899 is part of the national nature reserve.
Frays Farm Meadows is a 28.2-hectare (70-acre) biological Site of Special Scientific Interest near Denham in the London Borough of Hillingdon. It was notified as an SSSI in 1981, and has been managed by the London Wildlife Trust on behalf of Hillingdon Council since 1999. It is part of the Colne Valley Regional Park.
Denham Lock Wood is a 6.3-hectare (16-acre) biological Site of Special Scientific Interest (SSSI) next to the Grand Union Canal, and near Denham in the London Borough of Hillingdon. It was notified in 1986 and is managed by the London Wildlife Trust on behalf of Hillingdon Council. It lies within the Colne Valley Regional Park.
Mid Colne Valley is a 132 hectare biological Site of Special Scientific Interest in Harefield in the London Borough of Hillingdon and Denham in South Buckinghamshire. Its main importance lies in its extensive diversity of birdlife in lakes in former gravel pits.
Collinpark Wood is a 66.69-hectare (164.8-acre) biological Site of Special Scientific Interest in Gloucestershire, notified in 1966, revised in 1974 and renotified in 1983. There was a boundary change in 1983. There are seven units of assessment. Unit 1 is a 15-hectare (37-acre) area owned and managed by the Gloucestershire Wildlife Trust. The trust purchased this part of the wood in 1979 with grant aid from WWF. The site is listed in the 'Forest of Dean Local Plan Review' as a Key Wildlife Site (KWS).
Gutteridge Wood and Meadows is a Local Nature Reserve (LNR) in Yeading in the London Borough of Hillingdon, which is owned by Hillingdon Council and managed by the London Wildlife Trust (LWT). It is also part of the Yeading Brook Meadows Site of Metropolitan Importance for Nature Conservation, which includes two neighbouring reserves managed by the LWT, Ten Acre Wood and Yeading Brook Meadows LNRs.
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.
Sawbridgeworth Marsh is a 6.3 hectare biological Site of Special Scientific Interest (SSSI) near Sawbridgeworth in Hertfordshire, apart from a small area in the north which is in Essex. It is managed by the Essex Wildlife Trust. The planning authorities are East Hertfordshire District Council and Uttlesford District Council.
Balls Wood is a 58.5 hectare nature reserve managed by the Herts and Middlesex Wildlife Trust in Hertford Heath in East Hertfordshire. The wood was purchased by the Trust from the Forestry Commission.
Uxbridge Alderglade is a 2.9 hectare nature reserve in Uxbridge in the London Borough of Hillingdon. It is managed by the Herts and Middlesex Wildlife Trust.
Hill End Pit is a 0.7 hectare nature reserve on the site of a former chalk pit, in St Paul's Walden in North Hertfordshire. It was formerly managed by the Herts and Middlesex Wildlife Trust (HMWT). In February 2016 HMWT announced that three sites, Barkway Chalk Pit, Hill End Pit and Pryor's Wood, which HMWT managed on behalf of their owner, North Hertfordshire District Council, were to return to Council management as the Trust was no longer able to meet the cost. It has the largest colony of Azeca goodalli snails in Hertfordshire. Plants include viper's bugloss, cowslip and marjoram, there are butterflies such as common blue and gatekeeper, and many birds including woodpeckers.
Fir and Pond Woods is a 29 hectare nature reserve in Potters Bar in Hertfordshire. It is managed by the Herts and Middlesex Wildlife Trust. It is two separate woods, with Fir Wood connected by a short footpath to the large Pond Wood to the south.
Gobions Wood is a 36 hectare nature reserve managed by the Herts and Middlesex Wildlife Trust in Brookmans Park in Hertfordshire. The site was formerly owned by the Gobions Woodland Trust, a registered charity which was closed down in 2013 because it had ceased to exist.
