Geopedology Reports Historical Changes in Climate and Agroecology: A Case Study from Northwestern Iran

Global warming is claimed to be the cause of climate change, which is often held responsible for water shortage. Let geopedology represents the complex process of soil formation, out of which much can be learnt about paleoecology; soil formation being a dynamic interaction between the atmosphere, biosphere, lithosphere, and the hydrosphere. In a multidisciplinary sustainability-oriented study in northwestern Iran, geopedologic data were analyzed and cross-referenced with some historic and archaeological information to reconstruct paleoecologic conditions in several time periods, through which the changes both in climate since upper Pleistocene, and in landuse and their consequences in terms of land degradation could be concluded. The occurrence of a (sub-) surface layer of travertine, dated 27,000 y BP that is coated by a thin organic layer with traces of rancienite (mineral), dated 13,000 y BP, implies a humid environment, corresponding with the pluvial uppermost Würm. The geopedologic survey, supported by soil micromorphology, revealed that between 6,000 and 2,600 years ago the area was subject to cycles of erosion and sedimentation that have led to glacis formation. A type of climate that is characterized by the alternation of wet and dry periods is also supported by the occurrence of Petrocalcic and Argillic horizons in the soils. Cultivating rice, tobacco and cotton, which was practiced until over a century ago, also implies relatively wetter conditions. The study concludes that aridification has never been as degrading as it is today, due to the over-exploiting of the non-renewable fossil groundwater.