Historical overview - Recent studies
As far as we are concerned, we [P. Diederich and E. Sérusiaux] assumed to carry on the lichenological exploration of Belgium and Luxembourg early in the eighties, starting with the epiphytic communities, and then the saxicolous ones, and trying to identify all species encountered, focusing especially on crustose species and lichenicolous fungi. We could rely on the experience of J. Lambinon, who shared with us his experience and collections, on the help of many colleagues and friends from abroad who helped us in the identification of critical taxa, and on several Dutch colleagues who are very interested in the lichen flora of our countries, especially P. P. G. van den Boom and A. M. Brand. We must not forget to mention the diligent mapping of the distribution of macrolichens in Luxembourg by E. Wagner-Schaber (1987), the recent studies conducted by students of the University of Gent (especially the PhD thesis of M. Hoffmann on epiphytic lichens and communities in western parts of Flanders, presented in 1993), and the exploration of the lichens of calcareous outcrops in the Belgian Meuse district by D. Ertz (2003).
The paradox of the past fifteen years of research is obvious: on one hand, we have been able to highlight an unsuspected lichen biodiversity in the study area, including rare or poorly known species and even several which turned out to be new to science; and on the other hand, we have witnessed a major decrease and impoverishment because of the very strong impact of human activities on the environment and natural and semi-natural habitats. During that period, air pollution has dramatically changed: acid pollution has strongly decreased, but high levels of nitrates and summer-time ozone are now common, especially north of the line Sambre-Meuse-Vesdre. Almost complete obliteration of many sites of high interest has occurred; forestry management is now much more intensive and is a major threat to the lichen diversity within the study area. For dozens of species first discovered during this work, population level is so low (sometimes reduced to a few individuals only) that any stochastic event can jeopardize their future. May this internet site attract attention upon the little-known organisms that lichens and their lichenicolous fungi are: they are amongst the best indicators of our environmental quality.