The bulldozer scars are old, but somebody's been here recently. Someone's been scraping away with hand tools on a terrace above the San Pedro River, where the Hohokam built villages and fortifications centuries ago.

"The San Pedro is ground zero for preservation archaeology," said Andy Laurenzi of Archaeology Southwest, which is trying to ensure that archaeological areas on the river that have been long spared from development remain that way.

This site, near the town of Mammoth, was accessible to off-road vehicles until barriers were installed. Now you have to walk, and the disturbance has been lessened, but not eradicated

"Ah, that sucks," said Laurenzi, as he spied a series of small holes, scraped by hand or stick, most likely by someone looking for the fragments of pottery or arrowheads.

"Are we doing a lot of damage here? Nah, not really, but it's death by a thousand cuts," Laurenzi said.

It used to be worse. Before 1979, it wasn't illegal to disturb archaeological sites on public land. Now there are federal laws and fines to deter looters.

Constant threat

Our archaeological treasures are under constant assault, said Bill Doelle, president of Archaeology Southwest, whose mission is to both preserve and interpret archaeological sites.

Pot-hunters can do a great deal of damage over time, said Doelle.

Erosion of river banks and burrowing animals also contribute to the degradation of our archaeological heritage.

Archaeology can even be threatened by archaeologists, who sometimes put too much emphasis on "digs" and field schools and too little on curation of objects and publication of results, Doelle said.

The big threat, though, remains development.

In the Salt River Valley, many Hohokam sites were long ago demolished as Phoenix and its sister cities grew. Around Tucson, development gobbled up archaeological wonders long before they were deemed worth saving.

"The wonderful thing about the San Pedro is that it's so untouched it's hard to believe you're so close to Tucson," said Doelle.

There are ranches and farms in this river valley east of the Rincon Mountains. There are a few rural subdivisions, but the area remains remote, still served by dirt roads. Much of it is state land, Doelle said, which affords it greater protection but still leaves it vulnerable to occasional plans to build highways and other infrastructure.

Big mound bulldozed

When the San Pedro flooded in 1993, workers rushing to protect mining company water lines bulldozed a mound called "Big Bell," where legendary archaeologist Emil Haury had uncovered a copper bell in the 1920s.

Thousands of years of history were pushed into the river in a day's work, said Doelle.

After that incident, Doelle found grants and led a mostly volunteer preservation effort through what was then called the Center for Desert Archaeology. In January, the center changed its name to Archaeology Southwest.

The San Pedro area had been explored by archaeologists since the late 1800s, and they found layers of civilizations in its flood plain and the terraces above it.

The most famous are in the Upper San Pedro, where mammoth bones and the spear points of the hunters called "Clovis people" show evidence of human habitation up to 12,000 years ago.

The Lower San Pedro, where digs over the years have uncovered evidence of habitation and agriculture dating back 4,000 years, had been occasionally excavated but never systematically mapped.

The center's volunteer crews surveyed and mapped the entire stretch from north of Benson to its confluence with the Gila River near Winkelman, finding a village on the cliffs above the river bed about every three or four miles.

They are mostly Hohokam sites, dating from A.D. 500. Around A.D. 800, six formal ball courts - ancient fields of sport - were built along the river. Larger villages and intricate canal systems were added, and the area was inhabited by these groups until about A.D. 1450.

There are also sites that show the influence of migrants from the north - kivas associated with the Pueblo people of the Kayenta region of Northeastern Arizona.

Crews dug survey trenches at the 29 largest sites to uncover information and artifacts.

They made a list of areas most in need of preservation.

Several sites acquired

Now the goal in the San Pedro for Archaeology Southwest is to be a steward of those sites and to continue uncovering the story of its early settlement.

It has already acquired 12 of the most important properties, including the most recent addition - a ballcourt site that had been in a rancher's family for generations and just recently came up for sale.

The site was well-protected by generations of ranchers, said Laurenzi, but who knows what the future holds. Laurenzi's job, as field representative for Southwest Archaeology, is to make sure the sites are protected in perpetuity.

Laurenzi, who has done similar work for the Sonoran Institute and the Nature Conservancy, keeps his eyes and ears open for changes of ownership, talks to land owners about conservation easements, works with the many land managers along the San Pedro and finds stewards who will visit the sites occasionally and watch for signs of looting.

Doelle said the guiding principle of Archaeology Southwest is "preservation archaeology."

"We are not anti-excavation," he said, but excavation needs to be done in a way that "minimizes impact to the archaeological record."

The science of archaeology improves yearly, he said, and less invasive techniques can be applied to sites. Much can be learned by using the new science on objects collected decades ago.

The foundation also gives grants for resurrecting work done years ago that was never published and sets aside half of its project budgets for permanent curation of objects and publication of results, Doelle said.

"We try to push toward minimizing excavation and maximizing what's left in the ground."

THE SAN PEDRO OF LONG AGO

SO YOU KNOW

Archaeology Southwest, which adopted its new name in January, is a private nonprofit organization that, according to its mission statement, "explores and protects the places of our past across the American Southwest and Mexican Northwest."

It has been around in some form since 1982, operating for much of that time under the name Center for Desert Archaeology.

It was often confused with the for-profit Desert Archaeology Inc., said Bill Doelle, who is president of both entities.

Shortly after the foundation moved into its new headquarters in the former Mountain Oyster Club on Stone Avenue downtown, the organization's board decided to adopt the name of its quarterly magazine, "Archaeology Southwest."

The name better reflects its interest in the archaeology of the region, Doelle said.

The nonprofit has grown over the years from a single employee to 12 and now operates with a $4 million endowment, donated over the years by benefactors with an interest in archaeology.

Contact reporter Tom Beal at tbeal@azstarnet.com or 573-4158.