There is evidence that Riccia fluitans actually prefer increased nitrogen inputs. Locally intense nitrogen deposition may therefore favour this species at the expense of other bryophytes (Roelofs 1983).
Enhanced ammonia concentrations (e.g. in the vicinity of intensive poultry farms) have been shown to have negative effects on bryophyte diversity (Pitcairn 1998). Although not studied the known sensitivity of Sphagnum to nitrogen deposition (Gunnarsson & Rydin 2000, Williams et al. 1999, Baxter1992) suggests that this genus will also be affected in such situations.
The marked decline of Racomitrium lanuginosum in the southern Pennines since the industrial Revolution (Tallis 1987) may be associated with acid deposition, deposition of sulphate and sulphuric acid in rain and cloud droplets, (Ferguson & Lee 1983a, Thompson & Baddeley 1991). There is also evidence of decline in Scotland where critical loads are exceeded (Fowler et al. 2001). Direct negative effects on mosses are possible with the leaching of base cations from cell membrane s.