“…However, their occurrence and development are restricted by local environmental conditions, such as substratum instability, rock type and surface texture, permanent shading from direct solar radiation, excessive exposure to strong and abrasive wind action, mineral particles and ice crystals and, in the close proximity of bird colonies, the impact of disturbance and toxic levels of certain chemical elements (Smith, 2007). Some species are abundant and form distinct communities in habitats receiving nutrient enrichment (especially from nitrogenous compounds in meltwater run-off and in aerosol form) from seabird colonies (Jablonski, 1986); although lichens may develop dense stands even in some nutrient-deficient habitats (Albuquerque et al, 2012).…”