A Lost Civilization May Shed Light on Coping with Climate Change
An innovative collaboration between scientists is discovering how, 700 years ago, a mysterious, prehistoric culture overcame its landscape's harsh constraints. The findings may tell a cautionary tale for today's Southwest.
Imagine a science in which discoveries are made after a bulldozer digs up the ground for a new highway, oil pipeline, or strip mall. That's the way most archaeological sites are unearthed today, particularly in the booming Southwest. "The vast majority of information about prehistoric people is learned this way," says Rick Moore, an associate director with the Grand Canyon Trust, an Arizona-based conservation group that has incorporated archaeology into its mission. For example, in Phoenix, which is sprawling ever faster across the Sonoran Desert, 700-year-old remnants of the ancient Hohokam settlement--everything from farming tools to subterranean pit houses--are still routinely found.
Similar evidence of other lost cultures turns up frequently all over the Southwest. The ruins--sometimes whole villages--are remarkably well preserved by the region's dry climate and often still largely intact, at least until the latest highway widening. Scientists have grown accustomed to working one step ahead of the bulldozer. "Where there is destruction of the landscape, you'll find archaeologists," says Steve Simms, an archaeologist at Utah State University. "We're like morticians of the environment."
Ecologists, who also are called to action when a species is at death's door, have the Endangered Species Act (ESA) to help them ward off extinction. The federal law can be invoked to prevent the last remaining habitat of an imperiled animal or plant from being converted into a casino or condominium development. Archaeologists have the National Historic Preservation Act to at least help them slow the backhoes. To mitigate potential damages, they get a short reprieve to document or excavate the ruins before they're lost forever.
For both wildlife and archaeology, one of the best refuges has long been public lands, as President Bill Clinton decreed when he began establishing national monuments in the mid-1990s specifically for their ecological and archaeological value. He distinguished these monuments as scientific havens and eventually grouped them into a special classification within the Bureau of Land Management (BLM) called the National Landscape Conservation System. (There are more than 100 national monuments, most of them managed by the National Park Service.) This novel breed of BLM monuments soon prompted a number of ecologists and archaeologists to step out of their separate universes and join forces.
Today that newfound familiarity has bloomed into a pioneering, collaborative venture at Agua Fria National Monument, a mosaic of canyons, mesa tops, and grasslands located in a sparsely populated, mountainous region of central Arizona. President Clinton created the monument in 2000, based largely on its 450 known prehistoric sites, which include an unusual assortment of multi-room houses made of mud and stone (known as pueblos) perched on a rocky mesa. There archaeologists and ecologists from Arizona State University (ASU) are studying the age-old ruins and the ecosystem surrounding them. The project, started in 2003 and called Legacies on the Landscape, is now yielding surprising insights about the people who lived there 700 years ago, as well as about the long-term ecological changes they wrought on the land.
Additionally, the research sheds new light on a volatile period in the Southwest, when prehistoric cultures were forced to adapt to unpredictable climate changes. Some scientists believe that the stage is being set for similar environmental conditions today, as the region contends with explosive development, cyclical droughts, and rapid water depletion. In some circles there's even a school of thought, argued recently in Jared Diamond's best-selling Collapse: How Societies Choose to Fail or Succeed, that the current rate of population growth and environmental exploitation in the Southwest is about to collide with harsher climatic conditions in ways that may soon mirror what occurred across the region in the 13th century, which archaeologists consider a period of tremendous societal upheaval. This also happens to be the time when people started moving into the forbidding, isolated moonscape that now comprises Agua Fria National Monument.
Perry Mesa, a rolling, high-desert landscape within the 71,000-acre monument, is only 40 miles north of Phoenix, but it is so remote and stretches so far toward the horizon that it might as well be the end of the earth. The monument's entrance lies just off a lonely stretch of Interstate 17. There, a winding gravel road descends three miles to the Agua Fria River before climbing through narrow valleys and grassy hills to the top of Perry Mesa, 3,500 feet above sea level.
Steep, 1,000-foot canyons cut the mesa. Right here, along several edges, sit a number of hollowed-out pueblos, some with 50 to 70 rooms. The people of Perry Mesa started constructing this settlement around 1275, stayed for most of the 1300s, and then suddenly vanished into history. The only remaining tangible clues, it would seem, are crumbling masonry walls, pottery and other artifacts excavated from the ruins, and the many rock-art images pecked onto cliff faces, including those of bighorn sheep, deer, and bizarre geometric designs.