SSSI
Over fifty hectares of the south face of the Hill are a Site of Special Scientific Interest owing to its chalk grassland habitat. Grazing ceased in the early 1950s, and consequently the site was gradually invaded by scrub, mostly hawthorn, dogwood, and wild privet. An intensive restoration programme funded by the Countryside Commission and Portsmouth City Council was initiated in 1995; large areas of scrub have now been cleared by machine, and flowers and grasses allowed to regenerate naturally. Scrub re-encroachment is controlled by cattle and horses which graze overwinter.
Several species of butterfly became extinct owing to the loss of habitat to scrub, notably the Adonis Blue, Silver-studded Blue, Dingy Skipper, and Dark Green Fritillary. Others such as the Chalkhill Blue and Small Blue were at the brink of extinction, but are now flourishing again. Indeed, the hill has now probably the largest metapopulation of the Small Blue in the UK.
Portsdown also gave its name to an Army estate in Singapore. Long after the British army moved out (1967) the Portsdown estate continues to thrive, with Portsdown Rd the main road running through the middle.
Read more about this topic: Portsdown Hill