The Dry Lands of North Africa
We traveled across North Africa southward toward the Sahara Desert into zones of less
and less rainfall. Beyond the cultivated area in Roman times was a zone devoted to
stockraising on a large scale. Thousands of cisterns were built in Roman or pre-Roman
times to catch storm runoff from the land to store it for outlying villages and for
watering herds of livestock during the dry summer seasons. Many of these cisterns were
being cleaned out and repaired by the French Government before World War II, to be used
for the same purpose as they were in ancient times. One of the modern cisterns was four
times as large, as any Roman cistern, with a capacity of 100,000 cubic feet. This cistern
was filled in 2 years and now furnishes water for the seminomads who inhabit this part of
North Africa.
Still farther toward the desert, about 70 miles south of
Tebessa, we found a remarkable
example of ancient measures for the conservation of water. At some time in the Roman or
possibly pre-Roman period, peoples of this region built check dams to divert storm water
around slopes into canals to spread it upon a remarkable series of bench terraces.
This area of unusual interest raises a number of questions we are not yet able to
answer. If these terraces were cultivated to crops in times past they are the best
evidence we have that climate has become drier since they were first built. But if they
were built for spreading water to increase forage production for grazing herds, as the
French are using them today, they are not evidence of an adverse change of climate. This
evidence alone could leave us in doubt, but other evidence indicates that water spreading
was most used here for crops.
It would be interesting to know the date and the reason for building these terraces.
They may indicate that with Roman occupation of North Africa the native tribes were driven
beyond the border of the Roman Empire and were forced to devise these refined measures for
conservation and use of water in a dry area. Or they may indicate that North Africa was so
densely populated that it was necessary to use these refinements in the conservation of
water to support the population on the margins of a crowded region.
While the land of North Africa has been seriously damaged, as one can see written on
landscape after landscape, the country is still capable of far greater than its present
production. In Roman times a high degree of conservation of soils and waters was reached
with an intensive culture of orchards and vineyards on the slopes and intensive grain
growing in the valleys.
All this depended on efficient conservation and us of the rainfall. We find numerous
references to such practices in the literature of the time. But, as nomads swept in out of
the desert, their extensive and exploitive grazing culture replaced these highly refined
measures of land use and let them fall into disuse and ruin. Erosion was unleashed on its
destructive course, and the capacity of the land to support people was seriously reduced.
The veteran student of North Africa, Professor Gautier, answered my query as to whether
climate of North Africa had changed since Roman times, in the following way: "We have
no evidence to indicate that the climate has changed in an important degree since Roman
times, but the people have changed."
We conclude that the decline of North Africa is due to a change in a people and more
especially to a change in culture and methods of use of land that replaced a highly
developed and intensive agriculture and that allowed erosion to waste away the land and to
change the regime of waters.
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