Reconstructing environmental changes since the Last Glacial Maximum (LGM) in the Geba Basin, Northern Ethiopia, by geomorphic process interpretation and land management evaluation

Abstract

The palaeoenvironmental evolution of the Geba Basin in Northern Ethiopia since the Last Glacial Maximum (LGM) certainly is a good indicator for the climatic conditions, but there is evidence that climate has been affected by the interference of humans with the hydrological cycle, especially since the second half of the Holocene. Before -15 cal ley BP, Ethiopia knew a dry climate in the lower parts and cold and also dry conditions in the Simen and Bale Mountains, in phase with the LGM. But while elsewhere in Ethiopia the cold/dry conditions continued till -10-11 cal ley BP, the Geba Basin enjoyed moist conditions from -15 cal ley BP onwards and no clear explanation can be given for this. These conditions continued in Tsigaba till -3 cal ky BP and in many valley bottoms, till 50 years ago or even nowadays. This article presents evidence suggesting that the 'arid environmental conditions' which started in some places as early as -5 cal ky BP, in other places only very recently, are more a human-induced than an astronomically steered phenomenon. Our research indicates that man has the necessary tools to bend off the present tendency towards aridification.