01.10.2012 - Natural Sciences Sector

Learning from ancient droughts

CC, Wikimedia Commons. Agricultural scene from the tomb of Nakht, 18th Dynasty, Thebes

A project involving the geoscience community, but also biologists, archaeologists, historians, meteorologists and astrophysicists looked far into our past to examine how quickly ecosystems and civilizations are able to recover from catastrophic events. Working in unison, they pieced together the events that brought pharaohs to their knees, and how Egypt bounced back.

Some 11,300 years ago, the Sahara was dotted with lakes. Giraffes, hippopotamuses, lions, elephants, zebra, gazelles, cattle and horses roamed across grasslands that may have received ten times more rainfall than the same area today.

By 9,000 years ago, pastoralists had colonized much of the Sahara. They prospered for another 3,000 years, until a shift in the monsoon belt to lower latitudes steered potential rains away from the continent, causing catastrophic droughts. The pastoralists took refuge in the Sahel, Saharan highlands and Nile Valley, where they gave rise to numerous African cultures, including that of Pharaonic Egypt.

Those who settled in the Nile Valley were forced to abandon nomadic pastoralism for lack of summer rains. Instead, they adopted an agricultural way of life. Small sedentary communities gradually coalesced into large social groups. About 5,200 years ago, the first pharaoh managed to unify Upper and Lower Egypt into a single state with Memphis as its capital. A long period of prosperity followed, characterized by bountiful Nile floods that produced abundant grain harvests. Successive pharaohs took advantage of this prosperity to launch ambitious pyramid-building programmes to give themselves a tomb worthy of their rank. The pharaohs asserted their authority over the population by claiming the power to intercede with the gods to ensure the Nile River flooded each year. This strategy worked perfectly – until about 4,200 years ago when the harvests failed for six long decades. Brought about by a drop in rainfall at the Ethiopian headwaters during a prolonged El Niño cycle, this drought was so long and so severe that the Nile could be crossed on foot. With the pharaoh powerless to prevent the resulting famine, regional governors seized control.

It took 100 years for Egypt to reunify and thereby bring to an end a century of political and social chaos known as the First Intermediary Period. The return to stability heralded the advent of the Middle Kingdom. This time, the pharaohs would not make the same mistake. To avoid suffering the fate of their improvident predecessors, they would invest massively in irrigation and grain storage.

This work was part of an International Geoscience Programme (IGCP) project on the Role of Holocene Environmental Catastrophes in Human History (IGCP project 490). The project focused on the inter-disciplinary investigation of Holocene geological catastrophes, which are of importance for civilizations and ecosystems. The objective was to examine how quickly ecosystems and civilizations are able to recover from catastrophic events. With the growing recognition that major natural events can have abrupt global impacts, this project is a timely opportunity to assess the sensitivity of modern society to extreme natural threats.

Suzanne Leroy
This article was first published in A World Of Science, Vol. 10, n°3 - July September 2012




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