Recording the epiphytic lichen flora in Amsterdam on 576 trees distributed over eight common lane tree species shows that the urban epiphytic diversity alone is considerable, representing 15.2%, or 100 species, of the total lichen diversity in the Netherlands. The species recorded include many rarities and some that can be viewed as urban opportunists. Trees bear 15 lichen species on average but are greatly influenced by local factors. Species-specific bark qualities such as water-holding capacity, texture and bark-shedding, influence species richness greatly but are often overshadowed by dominant environmental factors. Tree species with a higher water-holding capacity and texture generally bear the highest species richness. Bark qualities are more indicative of species richness than tree species, showing few significant differences between species richness linked to tree species. Platanus × hispanica is the only observed species whose frequent bark shedding causes it to consistently have the lowest lichen species richness, regardless of environmental factors. In general, bark desiccation and eutrophication are the most dominant factors in influencing urban epiphytic lichen diversity, resulting in xerophytic and nitrophytic lichen species being the most common. Pollution is no longer observed to be the main limiting factor for urban lichen diversity as it was in the past. Instead, bark desiccation associated with the Urban Heat Island (UHI) and low air humidity (drought) is the most damaging factor in contemporary urban conditions in Amsterdam, but it rarely reduces species richness to zero or near zero levels. Areas in which eutrophication and desiccation are much less dominant were repeatedly observed. Such areas sometimes showed local dominance of acidophytes or other distinctive communities. In line with long-term improvements to Dutch air quality, the city now offers a niche to a wider range of species. Three ecological groups (acidophytic, lithophytic-minerotrophic, xerophytic-nitrophytic) are described in this context to characterize reoccurring lichen communities in the city that are indicative of contemporary urban conditions. The term ‘lithification’ is proposed in an ecological context to describe the frequently observed urban phenomenon of tree bark taking on the properties of rock and consequently bearing lithophytic communities. Additionally, we show the potential use of lichen species and ecological groups to monitor urban climate factors such as the UHI on a very local and accurate scale.