Many would agree that there are situations where a local or regional increase of rainfall and evaporation might be expected to follow afforestation. When the problem cannot be resolved by experiments, probably the next best approach is by using computer simulation models. These should be based on the physical systems involved, using as much real data as possible, and be tested against real catchment systems. This innovation for assessing the effect of land use change on climate has provided the thrust of this book. It is an objective way of combining our present knowledge to produce the best current predictions.
Irrational outputs indicate our limitations in understanding the system and a lack of data.
Sensitivity analyses show which parameters of the land surface, the atmosphere, and the radiation and water balances have insufficient precision. An interdisciplinary approach involving atmospheric physicists together with plant physiologists, hydrologists, and microclimatologists is needed to achieve the understanding and precision required to detect land use effects on regional climate. Scientists studying exchange processes at the earth's surface and those investigating general atmospheric circulation have been brought together by the workshop. Very few situations have been simulated and those that have generally represent extreme changes. It is to be hoped that we are poised to assess to realistic degrees the significance to regional and local climate of man's manipulation of the earth's vegetative mantle.