Human influence on bogs, including air pollution, causes changes in vegetation leading to the degradation of an ombrotrophic bog ecosystem into a more uniform transitional mire-like system. We have hypothesized that intensive atmospheric alkaline pollution will cause an increase in water pH and convergence of bryophyte species composition among microforms. We also expected that bog-specific acidophilic species will be replaced by species indigenous to neutral pH habitats. Through GLM and DCA analyses, we found that although natural acidic bogs are more species poor than polluted bogs, the increase in pH can lead to a decrease in bogspecific vegetation. In polluted bogs, the species composition in different bog microforms will become similar; in particular bog-specific Sphagnum mosses will be increasingly replaced by more tolerant brown mosses, particularly in lawns.