Yes / The role of lichens as environmental monitors is widely recognised. Not only are they valuable as indicators of habitat stability and enyironmental continuity, but they are also effectiye in monitoring environmental quality. more particularly air and soil (and more recently water) pollution. In the past. the main role of lichens in this context has been to monitor sulphur dioxide air pollution. especially stable and rising levels (Seaward 1993). Howeyer, it has also been shown that lichens arc effective monitors of falling levels of gaseous sulphur dioxide and indeed of other pollutants. some of which are manifesting themselves as a consequence of the reduction in the former; of particular interest in this respect is the use of lichens to detect and determine the extent of qualitative changes in air pollution such as the impact of acid rain and hypertrophication (Seaward 1997: Seaward & Coppins 2(04).