The area's geology has little variety, comprising almost entirely of Eocene clays which, prior to urbanisation, supported a heathland environment.[61][62] Patches of the original heath still remain, notably Turbary Common, a 36-hectare (89-acre; 0.14 sq mi; 0.36 km2) site, much of which is designated a Site of Special Scientific Interest.[63] This heathland habitat is home to all six species of native reptile, the Dartford warbler and some important flora such as sundew and bog asphodel.