Lichens play a major role in shaping the natural world, both physically and biologically. One such role, as biological agents in soil development, used to be considered only in a geological context, but recent research has shown that lichens are capable of biodeteriorating stone substrata within a relatively short time-scale. Chemical alteration of the substratum is brought about by the disruptive action of many species, particularly those capable of producing oxalate(s) at the thallus-substratum interface. Raman microscopic analysis has proved invaluable in the interpretation and characterisation of the physical and chemical nature of this interface. The oxalate contributes significantly to the bulk and composition of the thallus itself and persists after the lichen.

Key words: Biodeterioration, Lichens, Oxalates, Raman microscopic analysis