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IPA Factsheet - Porton Down
Site code
CountryUnited Kingdom
Administrative regionSouth East (North Hampshire), South West (South Wiltshire)
Central co-ordinates51o 7' N / 1o 41' W map
Altitude92 - 159

 Site Description Porton Down constitutes the largest uninterrupted tract of semi-natural chalk grassland in Britain, a habitat which elsewhere has declined by more than 80% in the last 50 years. As well as the grassland, juniper scrub Juniperis communis of several age classes is widespread, and constitutes about 20% of the total southern English population. The site is also noted for its outstanding assemblages of lower plants (lichens), vascular plants and invertebrates.

 Botanical Significance Vascular plant interest. Four main types of grassland have been identified. Two of the communities are particularly rare in Britain. One, in which red fescue Festuca rubra and downy oatgrass Avenula pubescens occur as pronounced tussocks with litter-choked channels between, is virtually confined to Porton Down. The second uncommon community is characterised by sheep's-fescue Festuca ovina, mouse-ear hawkweed Hieracium pilosella and wild thyme Thymus praecox and has lichens prominent in the sward, in particular Cladonia rangiformis, C. impexa and Peltigera furescens may cover 80% of the ground surface. Other grassland communities include a type characterised by sheep's-fescue and meadow oat-grass Avenula pratensis, which has a particularly rich and intimate mixture of grasses and broadleaved herbs, and a type dominated by the coarse grass upright brome Bromus erectus, which has fewer herbs and is typical of undergrazed chalk downlands.Porton Down also supports a colony of meadow clary Salvia pratensis. Other rare species include early gentian Gentianella anglica, chalk milkwort Polygala calcarea, bastard toadflax Thesium humifusum and field fleawort Senecio integrifolius, all of which are confined to the southern chalk, and dwarf sedge Carex humilis, scrub and scattered trees are a feature of much of the grassland.

 General Habitat Description

Land use

Land use% CoverLevel
agriculture (mixed)Unknown
nature conservation and researchUnknown

Threatened Species

Species NameIPA Assess.Species Assess.AbundanceData qualityCriteria

Botanical Richness

EUNIS level 2 code & nameIPA Assess.Habitat Assess.% of indicator speciesNo. SpeciesNational BiotopeData qualityCriteria
E1 Dry Grasslands2016201600unknownB

Threatened Habitats

IPA Habitat code & nameIPA Assess.Habitat Assess.AreaData qualityCriteria


DesignationProtected Area NameRelationship with IPAOverlap with IPA
Special Area of ConservationSalisbury Plainprotected area overlaps with IPA1559
Special Protection AreaPorton Downprotected area overlaps with IPA1559
Special Area of ConservationRiver Avonunknown0
Site of Special Scientific InterestBentley Woodunknown0
Site of Special Scientific InterestRiver Avon Systemunknown0
Site of Special Scientific InterestPorton Downprotected area overlaps with IPA1559
Site of Special Scientific InterestPorton Meadowsunknown0
Site of Special Scientific InterestBracknell Croftunknown0
Site of Special Scientific InterestCockey Downunknown0
Site of Special Scientific InterestFigsbury Ringunknown0


TypeDescriptionYear startedYear finishes


abandonment/reduction of land managementunknown

 Conservation Issues Intensification of military activities

Contact Information

ContactContact Type