This volume presents a synthesis of new information about the responses of bryophytes and lichens to changing environmental conditions, particularly those brought about by human activities. Bryophytes and lichens are often treated independently, but as they commonly exist in association they are here described together. Both groups are sensitive indicators of environmental conditions; at various times the use of one group or the other has been recommended to indicate the presence of particular mineral deposits (geological prospecting), soil and site conditions (forestry), level of atmosphere and aquatic pollutants (biomonitoring), ages of rock surfaces (lichenometry), and historical continuity of forests cover (bioindication). Topics covered in this book include physiology, distribution, ecological function, and response to pollution and land management of these organisms.