Changing summer monsoon and environment in tropical Asia

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This research project on long-term change in summer monsoon and environment of tropical Asia was planned in response to IGBP of ICSU to clarify the relationships between global-scale environmental change and mankind activities.The first objective of this project is to restore the environmental change of tropical Asia after last interglacial with time scale of several thousand years. In order to achieve the objective, we conducted field research for microrelief, soils and vegetation in southwestern part of India, Thailand and Indonesia where have been apt to be influenced by southwestern monsoon from the Indian Ocean since last interglacial. As a result, we made synoptic chronological tables on environmental change after the late Quaternary in each region. For further reconstruction of terrestrial paleoenvironments, it is required to develop some methodology / techniques, for example, paleopedology, geomorphology and palynology.The second objective is to distinguish natural environmental change from artificial effects. We also collected data from archeological reports and historical records published by concerned institutes to clarify the relation between natural environment and human influence. Human impact on terrestrial environment, particularly that of deforestation and agriculture, was also indicated by the studies in India, Indonesia, Thailand and China, using geomorphological and palynological records.For the further study, it is necessary to elucidate the change in southwestern monsoon over wide area by comparing the data on land which we got from the field survey with the data from the analysis for core samples of deep sea drilling in the Indian Ocean and glacial fluctuation in Himalaya. From the view point of climatology, the studies of mutual relationship between high-latitude and low-latitude atmospheric circulation are necessary to understand global mechanism of environmental change.