The past as a Key for the Future: Mutual Dependencies of Land Use, Soil Development, Climate and Settlement

It is of high actual importance to clarify historical climate variations and their impact, because it is not possible to predict future developments and its motors, if the past way of climate is not understood. The Decapolis area in northern Jordan provides excellent opportunities to investigate this question. Environmental change could have been responsible for the abandonment of the area, caused by human activities or climate variation. Recent investigations let the climatic possibility seem more and more likely, because climatic models match very well to the historical development, while mismanagement becomes less probable, as it is evident that medieval Arabs were highly skilled farmers. Our investigations revealed a very heterogeneous land use and soil development pattern, and no indicators for a sudden and general erosion event. In contrast, relic surfaces and the soil's genesis point to moister conditions in the past and differences in the soil's development point to diverse land use intensities. While it is evident that land use changed the character of the landscape and can be tracked according to soil development, it did not lead to an advance of the desert. In this context, it merely seems that desertification is related to climate change.