Principles of Bio-Indication

The concept indication as used in this series of papers points to making visible what is not immediately perceptible. In this case the non-immediately visible is the quality of air, water, soil and the living world which surrounds us, in short: our environment the ecosystem on which also man depends. One can try to find indicators which tell us directly something about the quality, i.e. the usefulness, resp. harmfulness for a certain purpose. However, one might be content with the indication of environmental factors which are not the quality itself, but which decide the quality indirectly such as moisture content, composition of minerals and the like.