This evaluation covers all lichenized fungi and a few other fungi traditionally studied by lichenologists that have been reliably reported from the UK.
The publication in 1997 of the Red Data Books of Britain and Ireland: Lichens, by Church et al., provided for the first time a widely accessible evaluation of the conservation status of a selection of lichens from Britain using the internationally recognized IUCN threat categories. Since that work was completed a considerable amount of new survey work has been undertaken, providing a more complete picture of the status of a number of species. A 'Biodiversity Action Plan' approach to the conservation of lichens (and other species and habitats) has been developed. Hallingbäck et al. (1998) and Palmer et al. (1997) offered additional guidance on the application of IUCN categories to lower plants and the IUCN themselves have revised their categories and criteria for establishing threat status (IUCN 2001).
A new checklist of British and Irish lichens was published by Coppins (2002a); this highlighted new interpretations of the concept of a few species, enumerated a significant number of nomenclatural and taxonomic changes, as well as adding 190 taxa to the list. In addition, the original 'Red Data Book' account of British lichens by Church et al. (1997) was also by no means comprehensive. For all these reasons the current authors considered it appropriate to conduct a re-evaluation of the conservation status of all the lichens of England, Scotland, Wales and the Isle of Man (but excluding the Channel Islands, which are phytogeographically better considered with France). Those results were published by the British Lichen Society in 2003 in a report entitled A Conservation Evaluation of British Lichens.
Since 2003 there have been further changes in taxonomy, many adopted in the now standard identification guide The Lichens of Great Britain and Ireland (Smith et al. 2009). In addition, a number of new species have been discovered and our knowledge of lichens and lichenicolous fungi has increased, permitting the conservation status of some of them to be determined for the first time or requiring a revision of status for others. As a consequence this new edition has been prepared.