Lichens make excellent material for field studies throughout the year and are valuable for the detection and mapping of pollution. This book provides an overview of the value of lichens for monitoring a range of potentially harmful substances including sulphur dioxide, fluorides, PCBs, metals and radioactive elements. In each section background information is provided and case studies briefly described to enable the reader to appreciate the potential applications of lichens for monitoring each type of environmental pollutant. To help with the problems of identifying lichens, coloured illustrations are provided of species that commonly grow on trees together with an identification key and direction to more advanced texts for lichens growing on other surfaces.