Brazil's forest floor reveals stunning designs

RIO BRANCO, BRAZIL - Edmar Araujo still remembers the awe.

As he cleared trees on his family's land decades ago near Rio Branco, an outpost in the far western reaches of the Brazilian Amazon, a series of deep earthen avenues carved into the soil came into focus. "These lines were too perfect not to have been made by man," said Araujo, 62, a cattleman.

According to stunning archaeological discoveries in recent years, the earthworks on Araujo's land and hundreds like them nearby could potentially upend the conventional understanding of the world's largest tropical rain forest. The deforestation that has stripped the Amazon since the 1970s has also exposed a long-hidden secret lurking underneath thick rain forest: flawlessly designed geometric shapes spanning hundreds of yards in diameter.

Alceu Ranzi, a Brazilian scholar who helped discover the squares, octagons, circles, rectangles and ovals that make up the land carvings, said these geoglyphs found on deforested land were as significant as the famous Nazca lines, the enigmatic animal symbols visible from the air in southern Peru.

"What impressed me the most about these geoglyphs was their geometric precision, and how they emerged from forest we had all been taught was untouched except by a few nomadic tribes," said Ranzi, a paleontologist who first saw the geoglyphs in the 1970s and, years later, surveyed them by plane.

New revelations

For some scholars of human history in Amazonia, the geoglyphs in Acre State and other archaeological sites suggest that the forests of the western Amazon, previously considered uninhabitable for sophisticated societies partly because of the quality of their soils, may not have been as "Edenic" as some environmentalists contend.

In addition to parts of the Amazon being "much more thickly populated than previously thought," Mann, the author of "1491," a groundbreaking book about the Americas before the arrival of Columbus, said "these people purposefully modified their environment in long-lasting ways."

As a result, South America's colossal forests may have been a lot smaller at times, with big areas resembling relatively empty savannas.

Such revelations do not fit comfortably into today's politically charged debate over razing parts of the forests, with some environmentalists opposed to allowing any large-scale agriculture to advance further into Amazonia.

Scientists say other swaths of the tropics, notably in Africa, could potentially benefit from strategies once used in the Amazon to overcome soil constraints. "If one wants to recreate pre-Columbian Amazonia, most of the forest needs to be removed, with many people and a managed, highly productive landscape replacing it," said William Woods, a geographer at the University of Kansas who is part of a team studying the Acre geoglyphs. "I know that this will not sit well with ardent environmentalists, but what else can one say?"

Denise Schaan, an archaeologist at the Federal University of Para in Brazil, said radiocarbon testing indicated that they were built 1,000 to 2,000 years ago, and might have been rebuilt several times during that period.

Initially, Schaan said, researchers, pondering the 20-foot depth of some of the trenches, thought they were used to defend against attacks. But a lack of signs of human settlement within and around the earthworks, like vestiges of housing and trash piles, as well as soil modification for farming, discounted that theory.

For Brazil's scientists, Schaan said, the earthworks are "one of the most important discoveries of our time." But the repopulation of this part of the Amazon threatens the survival of the geoglyphs, after being hidden for centuries.

Forests still cover most of Acre, but in cleared areas where the geoglyphs are found, dirt roads already cut through some of the earthworks. People live in shacks inside others. Electricity poles dot the geoglyphs. Some ranchers use their trenches as watering holes for cattle.