Third millennium climate in the Near East based upon pollen evidence

Third millennium BC abrupt climatic change and the Old World social collapse, as suggested from archaeological evidence, is traced in pollen diagrams from the Near East. The third millennium pollen assemblages is followed closely in a selection of pollen diagrams from various locations in the Near East. The distribution of the pollen evidence is fairly even, but only one diagram is available from the Mesopotamian area itself.

The third millennium period in general and two dry periods within this era more specifically, are defined chronologically for the pollen diagrams. The given calendar dates were converted to uncalibrated years. The chronology of the pollen diagrams is based upon uncalibrated radiocarbon dates which, together with the sedimentation rate, were used to indicate the suggested drought periods.

The behaviour of plant and tree species in relation to climate is discussed. The concept 'response time' as the period of time necessary to cause a change in the growth curve of a plant species is explained. Long living trees react upon changes with a lower frequency than short-living annuals, for instance certain crops.

Eight pollen diagrams, distributed over the Near East,have been traced for types that might be indicative for abrupt climatic changes. One pollen diagram originates from Mesopotamia, the others come from the adjoining mountains or farther away in the Near East. As the water discharge in the Euphrates and Tigris depends on rain and snow in the Anatolian and Zagros Mountains, drought will also have affected that part of Mesopotamia.

The pollen evidence does not indicate sudden drought, and no support for centuries-long dry periods is found, The only location where a dry period may have occurred is Bouara, Towards the final centuries of the third millennium peat is formed here in an otherwise open water system.