Along the northern coast of Africa into Tunisia and Algeria we read the record of the granary of Rome during the empire -- by surveying a cross section from the Mediterranean to the Sahara Desert, from 40 inches of rainfall to 4 inches, from Carthage on the coast to Biskra at the edge of mysterious Sahara.

In Tunisia we found that it rains in the desert of North Africa in wintertime now as it did in the time of Caesar -- in 44 B. C. Caesar complained of how a great rainstorm with wind had blown over the tents of his army encampment and flooded the camp. It rained hard enough to produce flash floods in the wadies. At one place muddy water swept across the highway in such volume that we decided to wait for the flash flow to go down before proceeding.

We stood on the site of ancient Carthage, the principal city of North Africa in Phoenician and Roman times -- the city that produced Hannibal and became a dangerous rival of Rome. In 146 B. C., at the end of the Third Punic War, Scipio destroyed Carthage, but out of the doomed city he saved 28 volumes of a work on agriculture written by a Carthaginian by the name of Mago.

Mago was recognized by the Greeks and Romans as the foremost authority on agriculture in the Mediterranean area. These works of Mago on agricultural subjects were translated by such Roman writers as Columella, Varro, and Cato. The translations tell us that the traditions of conserving soil and water discovered on the slopes of ancient Phoenicia had been brought there by colonists. We suspect these measures furnished the basis of the great agricultural production that was so important to the Romans during the empire.

Over a large part of the ancient granary of Rome we found the soil washed off to bedrock and the hills seriously gullied as a result of overgrazing. Most valley floors are still cultivated but are eroding in great gullies fed by accelerated storm runoff from barren slopes. This is in an area that supported many great cities in Roman times.

We found at Djemila the ghosts of Cuicul, a city that once was great and populous and rich but later was covered completely, except for about 3 feet of a single column, by erosion debris washed off the slopes of surrounding hills. For 20 years French archaeologists had been excavating this remarkable Roman City and had unearthed great temples, two great forums, splendid Christian churches, and great warehouses for wheat and olive oil. All this had been buried by erosional debris washed from the eroding slopes above the city. The surrounding slopes,once covered with olive groves, are now cut up with active gullies.

The modern village houses only a few inhabitants. The flat lands are still farmed to grain but the slopes are bare and eroding and wasting away. What is the reason for this astounding decline and ruin?