The Past is Prologue – Drought in the South West

“We are stardust, we are golden,

We are billion year old carbon.

And we got to get ourselves back to the garden.”

— Joni Mitchell

The Salado Culture [1]

The prolonged drought in the Southwestern United States has lowered the levels of Roosevelt Lake in the Tonto Basin of central Arizona to the point that archeologists are able to investigate to a larger extent than previously possible the remains of the once thriving communities of the Salado Indian culture that inhabited the area beginning around AD 1150 until abruptly disappearing around AD 1450.

Named for their dependence on the nearby Rio Salado, or Salt River, the Salado culture took hold in the Tonto Basin where Tonto Creek joins the Salt River.  Following completion of Roosevelt Dam over a century ago in 1911, much of the evidence of the settlements and irrigation canals built by the Salado people in the Tonto Basin were submerged by the rising waters of Roosevelt Lake.

The Tonto Basin is located in what is known as the “transition zone,”
as it essentially bisects Arizona into two major geologic provinces, the Colorado Plateau to the north and the Basin and Range to the south.
The region is characterized by numerous mountain ranges separated by several basins, including Chino Valley, the Verde Valley, San Carlos Basin, the Safford Valley and Tonto Basin.

Ten to 30 million years ago tremendous forces wrenched apart the rocks of this region,
raising up huge blocks, and dropping others down in a jumbled mass of mountainous terrain through which molten rock was interjected and overlain. Corresponding with the latter millennia of the uplift was down-cutting by streams and rivers, including the Salt River, which carried debris from the uplands to the surrounding lowlands. Water erosion began to cut out the caves and alcoves now famous for the Salado cliff dwellings between 50,000 and 400,000 years ago, and by 10,000 years ago, the Salt River had carved the Tonto Basin into a landscape similar to that of today.

The Tonto Basin was inhabited by several American Indian groups with whom the Salado culture combined customs and characteristics, such as the Mogollon, whose pottery styles and burial traditions the Salado adopted, as well as the Hohokum and pueblo cultures.

The archeological evidence indicates that by the late 8^th century members of the Hohokum Culture from the lower Gila and Salt valleys (near today’s Phoenix) built permanent settlements in the Tonto Basin. For 400 years they used irrigation farming to grow corn, beans, squash, and cotton. They traded goods across a network that reached from Colorado to the Gulf of California.

Starting in 1100 the puebloan population centers to the north approached their social and economic peak. Archeological evidence indicates that in these regions drought, plant and animal depletion, and population growth pushed resource availability to critical levels. Many northern pueblo groups left their homelands, settled, then moved on, as part of their quest to find permanent homelands. Migration took them to what are now western New Mexico and central, southern, and eastern Arizona, including the Tonto Basin. By 1275 thousands of people lived in Tonto Basin.

Around 1300 a dramatic change occurred in the region’s climate. The region became more arid. The changing climate decreased farming and increased hunting and gathering, severely impacting the ecosystem. Important plants and animals declined or disappeared. By this time, the population had grown so large that demand and overuse led to a scarcity of resources. The 1300s were also marked by catastrophic flooding of the Salt River that destroyed lowland farms and villages as well as many of the irrigation canals, rendering hundreds of acres of farmland useless. Competition for dwindling resources created stress among the villagers and the quality of life declined. By 1450 those struggling to maintain their way of life gave up and left the area.

We don’t know the Salado people’s beliefs or culture—they left no written records. Their story is told largely through the interpretation of the artifacts and features found at places they lived. They likely did not understand and were unable to respond to the challenges brought about by population growth, natural disasters and climate change.

The American Southwest has always been relatively dry. Weather cycles known as El Niño and La Niña, caused by oceanic current oscillations in the Southern Hemisphere that primarily affect the Pacific Ocean and its coasts, also affect decade-long rainfall cycles in the Southwest that have caused, for example, the droughts of the 1300’s that affected the Salado, the 1930s (the Dust Bowl) and 1950s.
The current drought that is bringing more of the ruins of the Salado Culture to light as the water level in Roosevelt Lake declines, however, is likely the beginning of a period of even longer and more intense droughts—megadroughts—resulting from Anthropomorphic Climate Change (ACC). We now have scientific evidence that ACC will override the shorter-term weather cycles and create permanent drought conditions over this region of the United States [2], [3],[4]

Just as earlier drought conditions affected the Salado, the severe and prolonged drought will undoubtedly force drastic changes in lifestyles for the people currently living in the Southwest, including Arizona and the Phoenix area. The difference is that the knowledge and means to meet or even avert the crisis is available to the current residents. Unfortunately, it appears that the present culture has yet to evolve to the point where it likely will effectively deal with the climate consequences it produces.

1. Tonto National Monument: Saving a National Treasure; Teaching With Historic Lesson Plans, National Park Service, Department of the Interior

2. Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America by Richard Seager, and others
Science, v. 316, p. 1181-1184, 25 May 2007

3. Extended megadroughts in the southwestern United States
by Peter J. Fawcett, and others
Nature, v. 470, p. 518-521, 24 February 2011

4. Observational and model evidence of global emergence of permanent, unprecedented heat in the 20th and 21st centuries
by Noah Diffenbaugh and Martin Scherer
Climatic Change Letters, v. 107, n. 3-4, p. 615-624, 7 June 2011