Adrian Davies / Orange coloured Seashore Lichens (Xanthoria parietina) and Sea Ivory (Ramalina siliquosa) UK, August

Alex Hyde / Lichen (Xanthoria parietina) photographed on a white background. This species is very resistant to air pollution. Peak District National Park, UK, January.

Alex Hyde / Lichen (Xanthoria parietina) found growing on a twig, showing mass of apothecia (cup-shaped fruiting bodies). This species is very resistant to air pollution. Peak District National Park, UK, January.

Adrian Davies / Orange coloured Seashore Lichens (Xanthoria parietina) and Sea Ivory (Ramalina siliquosa) UK, August

Adrian Davies / Orange coloured Seashore Lichens (Xanthoria parietina) and Ochrolechia parella. UK, August

Adrian Davies / Beard Lichen (Usnea subfloridana) a good indicator of clean air, UK

Stephen Dalton / Peppered moth [Biston betularia} normal grey form and dark melanistic form. Dark form is better camouflaged in areas of pollution where lichen is absent, UK

Stephen Dalton / Peppered moths {Biston betularia} normal white and melanistic black forms. Melanistic form is better camouflaged in areas where lichen growth is inhibited by industrial pollution

Adrian Davies / Lichen {Xanthoria parietina} on flint wall, UK, a useful monitor of pollution levels.

Adrian Davies / Seashore lichens Xanthoria parietina (orange) and Ochrolechia parella (grey), UK