Wiltshire LPA BNG

Wiltshire is a chalk county: two-thirds of it lies on chalk, and the biggest block is Salisbury Plain, which holds the largest known expanse of unimproved chalk downland in north-west Europe, about 20,000 hectares of SSSI and Special Area of Conservation, and a Special Protection Area for birds that includes stone-curlew and the reintroduced great bustard. Two rivers share the name Avon: the northern one passes Bradford on Avon, while the southern one rises in the Vale of Pewsey and runs through Amesbury and Salisbury into Hampshire as a protected chalk river. Elsewhere are Savernake Forest, an ancient forest of about 4,500 acres near Marlborough, North Meadow near Cricklade, home to roughly 80% of Britain’s snake’s-head fritillaries, and the Cotswold Lakes on the Gloucestershire border. The Cotswolds, Cranborne Chase and the Marlborough and West Wiltshire Downs are national landscapes, and about 5% of the New Forest National Park lies inside the county.

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Biodiversity Net Gain became a legal requirement for major developments in England on 12 February 2024, and for small sites on 2 April 2024. Wiltshire Council is a unitary authority. Its biodiversity and development page sets out the national minimum of 10%, delivered on site, off site or through statutory credits, and lists no Wiltshire BNG Supplementary Planning Document or guidance note. The same page refers to a 20% figure proposed in the council’s draft Local Plan, but no Wiltshire plan carrying it has been adopted, so the national 10% is what applies, and the adopted plan is still the Wiltshire Core Strategy of 2015. The council says two habitat banks have been set up for developers to buy units, and the Wiltshire and Swindon Local Nature Recovery Strategy, published on 21 October 2025, supplies the mapped priorities used to judge strategic significance in the metric.

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Wiltshire also carries nutrient neutrality requirements. The council names four catchments: the Hampshire Avon, the Somerset Levels and Moors and the River Lambourn for phosphorus, and the River Test for nitrogen, and describes the Lambourn and Somerset Levels areas as very small and rural. Natural England’s advice of 16 March 2022 covers the Hampshire Avon, which drains the Vale of Pewsey and runs through Salisbury, so a scheme there can face two statutory tests at once: Biodiversity Net Gain and nutrient mitigation. In December 2023 the council secured £9.8 million of government capital funding for Hampshire Avon mitigation, to be delivered on behalf of several authorities, and it runs the Revamp Your Tank septic tank upgrade scheme with the Wessex Rivers Trust in the Upper Avon.