LONDON – Peru’s ancient Nazca civilization perished because it eliminated its natural line of defense, the forests that had protected the area against devastation by the natural phenomenon known as El Niño.

That is the conclusion reached by Dr. David Beresford-Jones of the McDonald Institute for Archaeological Research at Britain’s Cambridge University and his colleagues after studying the effects of the 1998 El Niño as a model.

The 1998 El Niño submerged the modern Peruvian city of Ica under 2 meters (6½ feet) of water, and a computer-generated projection indicates that an El Niño occurring some time in the sixth century must have had an even more catastrophic effect on the Lower Ica Valley, one of the two centers of the Nazca civilization.

That civilization is best known for the Nazca lines, declared a World Cultural Heritage Site by UNESCO, which cover an area of some 500 sq. kilometers (about 193 sq. miles) about 300 kilometers (186 miles) south of Lima and are thought to have served as a gigantic map or a celestial calendar.

The Nazca could have survived the El Niño, however, and the natural catastrophe it brought, had it not been for the progressive clear-cutting of a large forested region so that the land could be used for crops like corn and cotton.

Now a desert, the Lower Ica Valley was once covered with forests of huarango, a species of acacia that can live more than 1,000 years and which, besides supplying the Nazca with lumber for construction, fulfilled an important environmental role with its deep roots that kept the land stable and impervious to erosion from wind and water.

The trees were an important line of defense against sudden floods, the British experts said, adding that their analysis of ancient pollen shows that the huarango forests began to disappear in the years preceding the collapse of the Nazca civilization due to the accelerating pace of deforestation.

With the massive cutting down of trees, the natural defenses against a particularly intense El Niño that occurred around that time had been eliminated, Beresford-Jones said.

“In time, gradual woodland clearance crossed an ecological threshold, sharply defined in such desert environments, exposing the landscape to the region’s extraordinary desert winds and the effects of the El Niño floods,” he said.

“The climate wasn’t enough to induce collapse on its own. The Nazca partly wrought their own demise,” Beresford-Jones said.

Deforestation is also believed to have contributed significantly to the collapse of other civilizations, such as that on Easter Island and of the Anasazi people in the southwestern United States.

“The mistakes of prehistory offer us an important lesson for our management of fragile arid areas in the present,” said study co-author Oliver Whaley, of the Royal Botanical Gardens, Kew. EFE