extinction risk

Fox, R., Warren, M.S., Brereton, T.M., Roy, D.B. & Robinson, A. (2011) A new Red List of British butterflies. Insect Conservation and Diversity, 4, 159-172.
Walker, K.J. & Preston, C.D. (2006) Ecological Predictors of Extinction Risk in the Flora of Lowland England, UK. Conservation, 15, 1913-1942.