By Stuart Munro-Hay
The work of the geomorphologist Karl Butzer (1981) has suggested that the climate of northern Ethiopia may have changed for the worse just after the Aksumite period. The measurement of the Nile flood levels, recorded in Egypt, indicates that after a long period of excellent rainfall, more erratic precipitation ensued; this seems to have been after the abandonment of the city. However, if the land had reached a state of advanced degradation during the late Aksumite period, even the heavier rains, though theoretically ideal for the growth of the crops, would have contributed to the erosion on the slopes above the city and in the surrounding fields. What had been an advantage before had become another element in the vicious circle of the decay of the resources. It was the material brought down by the runoff caused by the rains from the hillsides that began to cover the buildings in the town as they were abandoned and fell into ruin.
Butzer’s figures suggest that until about 750AD floods were high in Egypt, then poorer with very low levels from the mid-tenth to late eleventh centuries, the period when the kingdom, after the invasion of the queen of the Bani al-Hamwiyya, had decayed almost to the point when the Zagwé dynasty could take over (Ch. 4: 8.3). The low-water levels after 730, in part following the spring rains in the Aksumite region, were already averaging below normal. It may be going too far to say that insufficient `little’ rains (the March to May rains) combined with erosion caused by the action of strong June-September rains on the denuded land both to shorten the growing season and remove the topsoil. Nevertheless, climatic factors may have had their part to play in the abandonment of Aksum.