Barnsley Warren (grid reference SP055064) is a 61.3-hectare (151-acre) biological Site of Special Scientific Interest in Gloucestershire, notified in 1954 and renotified in 1984.

[6] Pasqueflower (Pulsatilla vulgaris) is found in larger quantities here than anywhere else in the Cotswolds, which are at the western limit of this species' European range.

[6] Other notable plants found at the site include man orchid (Aceras anthropophorum), musk orchid (Herminimum monorchis), slender bedstraw (Galium pumilum), chalk milkwort (Polgala calcarea), round-headed rampion (Phyteuma tenerum) and bastard-toadflax (Thesium humifusum).

[7] The diverse range of flowers and grasses is ideal for many downland insects and the reserve has particular good butterfly and bug populations.

[6] The plant community in which the pasqueflower grows is CG5 (Bromus erectus - Brachypodium pinnatum grassland) in the British National Vegetation Classification[7]