EVAPORATION RESEARCH - A CRITICAL-REVIEW AND ITS LESSONS FOR THE ENVIRONMENTAL SCIENCES

There have been few significant advances in our knowledge of evaporation on an environmental scale during the past 4 decades, a state of affairs linked to the concurrent sterility of research in hydrology and the related environmental sciences. Furthermore, almost none of the advances have been used successfully in practice. This means that we can provide only trivial or dubious answers to important environmental questions. A critical review, based on a quarter century of research on evaporation, has indicated that much of the superficiality of the environmental sciences can be attributed to inappropriate methodologies and the application of linear cause-and-effect ways of thinking to the cybernetic feedback mechanisms that prevail in environmental systems. The resultant problems are particularly evident in the application of small-scale processes to large, environmentally significant areas and in the application of mechanistic concepts to the interactions between plants and their environments. A discussion of examples from studies in evaporation leads to the suggestion that we need a completely new approach that would recognize that a biological system can differ from a physical system, that a large-scale system can differ from the sum of its individual components, and that a forest is not just a collection of trees. Such an approach is exemplified in the Gaia hypothesis, in the accomplishments of the Bergen School of Meteorology during the 1920s and in the development of the complementary relationship between potential and actual areal evaporation.