The epiphytic lichen vegetation of 20 sites around Thessaloniki (Macedonia,
northern Greece) surveyed in 1987 was sampled again in 1997 to monitor any
changes in lichen communities and consequently in air duality. A general i
mpoverishment in lichen communities was recorded in the 10-year period, pre
sumably chiefly due to changes in the air pollution status. A small increas
e in lichen species diversity was recorded in some stations, probably as a
result of the buffering capacity of airborne dust.