Climatic Changes in Israel during Historical Times and Their Impact on Hydrological, Pedological and Socio-Economic Systems

A change from the deposition of loess to that of sand was observed in the southern coastal plain of Israel at the end of the Pleistocene (starting ca. 20 K B.P.). This was explained by a northward movement of the ITCZ (Inter-Tropical Convergence Zone) over East Africa which reduced the number of dust rain storms with a simultaneous northward movement of the East African Monsoonal Belt, which caused a rise in the level of the Nile and with it an increase in the supply of sand to the Mediterranean. Such a change in deposition was also observed at the transition from the Byzantine to the Arab periods (ca. 650 A.D.), and thus a similar climatic change for this historical period, was also suggested. This raised the question whether, prior to this change, a more humid phase did not affect the Levant while a dry spell affected the East African monsoon belt. The environmental data from this period, such as 18O and 13C, as well as pollen of olive and oak trees in a core in the Sea of Galilee, records of the Dead Sea Level and the level of the Nile, indeed show that during the Hellenistic, Roman and Byzantine periods (from about 300 BC. to 600 A.D.) these paleo-environmental conditions existed. During the more humid period agricultural settlements expanded into the desert and vice versa.