The consideration of time in environmental research allows new insights into the fundamentals of the environmental sciences. Considering temporalities, rhythms and time scales as well as their interdependencies with environmental science enables us to acquire a better understanding of such basic principles as irreversibility, persistence, disturbance, damage or resilience. Time scales and rhythms are of special importance for these principles and considerations. With regard to their persistence, especially the critical substances demonstrate reactivities which are so low that they are stable enough for application, although these reactivities are still seen to be present to a certain degree and they reveal a rate of transport which is not too high. In this manner, persistence is a factor which is dependent on the particular circumstances. Whether changes are to be classified as reversible or irreversible is dependent on the particular time period and the specific systems, their description and the parameters hereby selected. A prerequisite for the continuing existence of a system is, among other things, that this system must demonstrate a specific rate of development and must take into account the interconnectedness of the various time scales. Ecological systems can continue to develop according to their own dynamics if disturbances can be avoided which lead, compared to their own time scales, to rapid alterations and consequently to critical fluctuations. The duration of such disturbances should be as short as possible in order to minimize the rapid anthropogenic changes in an ecosystem as compared with the systems own time scales.