Do something for the environment yourself! With this book, you can recognize the lichens on trees. You will learn what they indicate about the air quality. Is it in good, satisfactory, moderate, or critical condition? Through examples from Reutlingen, you will discover what can be done against air pollution and gain interesting information for clean air today and tomorrow, including why it is essential to preserve cold air currents. This is a report on 44 years of work on the quality of the air we must breathe. The book includes a map of air quality for the Reutlingen metropolitan area with explanations.