PreColumbian American Southwest Went Through Cycles of Boom/Bust

The heavily studied yet largely unexplained disappearance of ancestral Pueblo people from southwest Colorado is "the most vexing and persistent question in Southwestern archaeology," according to the New York Times.

But it's not all that unique, say Washington State University scientists. Writing in the journal Science Advances, they say the region saw three other cultural transitions over the preceding five centuries. The researchers also document recurring narratives in which the Pueblo people agreed on canons of ritual, behavior and belief that quickly dissolved as climate change hurt crops and precipitated social turmoil and violence.

"The process of releasing one's self from those canons, the process of breaking that down, can occur very quickly and occurred very quickly four times in the Pueblo past," said Kyle Bocinsky, a WSU adjunct faculty member in anthropology and director of sponsored projects for the Crow Canyon Archaeological Center in Cortez, Colo. The article grew out of work toward Bocinsky's WSU doctorate.

Funded by the National Science Foundation, Bocinsky, WSU Regents Professor Tim Kohler and colleagues analyzed data from just over 1,000 southwest archaeological sites and nearly 30,000 tree-ring dates that served as indicators of rainfall, heat and time. Their data-intensive approach, facilitated by climate reconstructions run at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, gives a remarkably detailed picture of year-to-year changes.

This is particularly important as droughts of just five or ten years were enough to prompt major shifts in the small niches where Pueblo people grew maize, their major crop.

The niches, said Kohler, were "woven together with a web of ceremony and ritual that required belief in the supernatural" to ensure plentiful rain and good crops. When rains failed to appear, he said, the rituals were delegitimized.

"Then there's a point where people say, 'This isn't working. We're leaving,'" he said.

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American Southwest may Mimic Drought Conditions That Destroyed Anasazi/Ancestral Puebloans due to Global Warming

The weather patterns that typically bring moisture to the Southwest are becoming more rare, an indication that the region is sliding into the drier climate state predicted by global models, according to a new study.

"A normal year in the Southwest is now drier than it once was," said Andreas Prein, a researcher at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, who led the study. "If you have a drought nowadays, it will be more severe because our base state is drier."

Climate models generally agree that human-caused climate change will push the southwestern United States to become drier. And in recent years, the region has been stricken by drought. But linking model predictions to changes on the ground is challenging.

For the study, the researchers analyzed 35 years' worth of data to identify common weather patterns -- arrangements of high and low pressure systems that determine where it's likely to be sunny and clear or cloudy and wet.

They identified a dozen patterns that are usual for the weather activity in the contiguous U.S., then looked to see whether those patterns were becoming more or less frequent.

"The weather types that are becoming more rare are the ones that bring a lot of rain to the southwestern United States," Prein said. "Because only a few weather patterns bring precipitation to the Southwest, those changes have a dramatic impact."

The Southwest is especially vulnerable to any additional drying. The region, already the most arid in the country, is home to a quickly growing population that is putting tremendous stress on its limited water resources.

"Prolonged drought has many adverse effects, so understanding regional precipitation trends is vital for the well-being of society," says Anjuli Bamzai, program director in the National Science Foundation (NSF) Division of Atmospheric and Geospace Sciences, which funded the research. "These researchers demonstrate that subtle shifts in large-scale weather patterns over the past three decades or so have been the dominant factor in precipitation trends in the southwestern United States."

The study also found an opposite, though smaller, effect in the Northeast, where some of the weather patterns that typically bring moisture to the region are increasing.

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What Happened to the Anasazi/Ancestral Puebloans of Mesa Verde?

Vultures carve lazy circles in the sky as a stream of tourists marches down a walkway into Colorado's Spruce Canyon. Watching their steps, the visitors file along a series of switchbacks leading to one of the more improbable villages in North America—a warren of living quarters, storage rooms, defensive towers and ceremonial spaces all tucked into a large cleft in the face of a cliff.

When ancient farmers built these structures around the year 1200, they had nothing like the modern machinery that constructed the tourist walkway. Instead, the residents had to haul thousands of tonnes of sandstone blocks, cut timber and other materials down precarious paths to build the settlement, known as Spruce Tree House, in Mesa Verde National Park.

“Why would people live here? That's an important question. It's not an easy place to reach,” says Donna Glowacki, an archaeologist now at the University of Notre Dame in Indiana, as she walks among the ruins. Even more perplexing is what happened after they settled there. The villagers occupied their cliffside houses for just a short time before everyone suddenly picked up and left. So did all the other farmers living in the Four Corners region of the American Southwest, where the modern states of Colorado, New Mexico, Utah and Arizona meet.

All together, nearly 30,000 people disappeared from this area between the mid-1200s and 1285, making it one of the greatest vanishing acts documented in human history. What had been one of the most populous parts of North America became almost instantly a ghost land.

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Hat tip to Randy.

How Southwestern America's Pueblo's Fell Apart, Physically

The pueblo decomposition model: A method for quantifying architectural rubble to estimate population size

Authors:

Duwe et al

Abstract:

While most archaeological measures of population rely on material proxies uncovered through excavation (rooms, hearths, etc.), we identify a technique to estimate population at unexcavated sites (the majority of the archaeological record). Our case study focuses on ancestral Tewa Pueblo villages in northern New Mexico. Uninhabited aerial vehicle (UAV) and instrument mapping enables us to quantify the volume of adobe architectural rubble and to construct a decomposition model that estimates numbers of rooms and roofed over space. The resulting metric is applied at ten Pueblo villages in the region to ‘rebuild’ architecture, and calculate maximum architectural capacity and the maximum extent of population size. While our focus is on population histories for large Classic period (A.D. 1350–1598) pueblos in the American Southwest, the model and method may be applied to a variety of archaeological contexts worldwide and is not limited to building material, site size, or construction technique.

Might be a Neo Oligocene Climate: US may Have Megadrought in Southwest, Midwest by Century end?

The intricate sandstone ruins of Chaco Canyon, New Mexico—a once thriving settlement abandoned in the 13th century by the ancient Pueblo peoples during a decades-long “megadrought”—serve as a silent reminder to all who live in the arid regions: When water supplies dwindle, even sophisticated societies may not be able to adapt.

Now, new research suggests that the severe, 60-year drought that likely helped empty Chaco Canyon was a preview of longer, hotter dry spells to come as a result of climate change. The Chaco drought will look “quaint” compared with what computer models predict will hit the midwestern and southwestern United States over the next century, says Jason Smerdon, a climate scientist at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York, and co-author of the new study, published this week in Science Advances.

Warnings that droughts will intensify as the climate warms are not new. But this forecast gains credibility, other researchers say, because Smerdon and colleagues developed detailed forecasts of soil moisture—a key drought measure—and put those predictions into historical perspective. The study is “the most sophisticated effort I've seen by far to connect records of ancient droughts with projections of future change,” says Jonathan Overpeck, a geologist and atmospheric scientist at the University of Arizona in Tucson.

How global warming will affect specific regions is one of the thorniest questions in climate science. Previous studies have suggested that, in a warming world, existing weather patterns will intensify, causing wet regions of North America to get wetter and dry regions drier, with the Southwest experiencing the worst droughts first. To add detail to that picture, the researchers used 17 state-of-the-art climate models to forecast three different measures of soil moisture over the next 100 years as the warming climate alters rainfall and speeds evaporation. The models also took into account variables such as wind speed and humidity.

The results were striking. In nearly every climate model, the projections pointed to severe drying in the Southwest and Midwest by the end of the century if greenhouse gases continue to build up. “If models that are all constructed a bit differently all converge on the same answer, that gives us confidence that we are getting the right answer,” says co-author Benjamin Cook of the NASA Goddard Institute for Space Studies in New York City.

link.

hrm.  The precipitation sims are still not yet there.  I'd still be wary.

Maize had a Complex Path Into the American Southwest

After it was first domesticated from the wild teosinte grass in southern Mexico, maize, or corn, took both a high road and a coastal low road as it moved into what is now the U.S. Southwest, reports an international research team that includes a UC Davis plant scientist and maize expert.

The study, based on DNA analysis of corn cobs dating back over 4,000 years, provides the most comprehensive tracking to date of the origin and evolution of maize in the Southwest and settles a long debate over whether maize moved via an upland or coastal route into the U.S.

Study findings, which also show how climatic and cultural impacts influenced the genetic makeup of maize, will be reported Jan. 8 in the journal Nature Plants.

The study compared DNA from archaeological samples from the U.S. Southwest to that from traditional maize varieties in Mexico, looking for genetic similarities that would reveal its geographic origin.

"When considered together, the results suggest that the maize of the U.S. Southwest had a complex origin, first entering the U.S. via a highland route about 4,100 years ago and later via a lowland coastal route about 2,000 years ago," said Jeffrey Ross-Ibarra, an associate professor in the Department of Plant Sciences.

The study further provided clues to how and when maize adapted to a number of novel pressures, ranging from the extreme aridity of the Southwest climate to different dietary preferences of the local people.

Excavations of multiple stratigraphic layers of Tularosa cave in New Mexico allowed researchers to compare genetic data from samples from different time periods.

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Crosbysaurus: Another Occurrence of an Engimatic Norian Triassic Archosaur

The first occurrence of the enigmatic archosaur Crosbysaurus (Heckert 2004) from the Chinle Formation of Southern Utah

Authors:

Gay et al

Abstract:

Originally identified as an ornithisichian dinosaur, Crosbysaurus has been found in New Mexico, Arizona, and the type locality in Texas, the genus has been reassessed by other workers in light of revelations about the postcrania of another putative Triassic ornithischian, Revueltosaurus. The understanding of Triassic dental faunas has become more complicated by the extreme convergence between pseudosuchian archosaurus and ornithichian dinosaur dental morphologies. This new specimen does not help resolve the affinities of Crosbysaurus but does extend the range of this taxon into southern Utah. This specimen may also represent the youngest-known member of this genus

Earth Observing Satellites Note Large Methane Leaks From American SouthWest/Four Corners Regions

An unexpectedly high amount of the climate-changing gas methane, the main component of natural gas, is escaping from the Four Corners region in the U.S. Southwest, according to a new study by the University of Michigan and NASA.

The researchers mapped satellite data to uncover the nation's largest methane signal seen from space. They measured levels of the gas emitted from all sources, and found more than half a teragram per year coming from the area where Arizona, New Mexico, Colorado and Utah meet. That's about as much methane as the entire coal, oil, and gas industries of the United Kingdom give off each year.

Four Corners sits on North America's most productive coalbed methane basin. Coalbed methane is a variety of the gas that's stuck to the surface of coal. It is dangerous to miners (not to mention canaries), but in recent decades, it's been tapped as a resource.

"There's so much coalbed methane in the Four Corners area, it doesn't need to be that crazy of a leak rate to produce the emissions that we see. A lot of the infrastructure is likely contributing," said Eric Kort, assistant professor of atmospheric, oceanic and space sciences at the U-M College of Engineering.

link.

MegaDrought Almost Certain for American Southwest With Global Warming

Due to global warming, scientists say, the chances of the southwestern United States experiencing a decade long drought is at least 50 percent, and the chances of a "megadrought" – one that lasts over 30 years – ranges from 20 to 50 percent over the next century.

The study by Cornell University, University of Arizona and U.S. Geological Survey researchers will be published in a forthcoming issue of the American Meteorological Society's Journal of Climate.

"For the southwestern U.S., I'm not optimistic about avoiding real megadroughts," said Toby Ault, Cornell assistant professor of earth and atmospheric sciences and lead author of the paper. "As we add greenhouse gases into the atmosphere – and we haven't put the brakes on stopping this – we are weighting the dice for megadrought conditions."

As of mid-August, most of California sits in a D4 "exceptional drought," which is in the most severe category. Oregon, Arizona, New Mexico, Oklahoma and Texas also loiter between moderate and exceptional drought. Ault says climatologists don't know whether the severe western and southwestern drought will continue, but he said, "With ongoing climate change, this is a glimpse of things to come. It's a preview of our future."

Ault said that the West and Southwest must look for mitigation strategies to cope with looming long-drought scenarios. "This will be worse than anything seen during the last 2,000 years and would pose unprecedented challenges to water resources in the region," he said.

In computer models, while California, Arizona and New Mexico will likely face drought, the researchers show the chances for drought in parts of Washington, Montana and Idaho may decrease.

link.

Demographics of the Baby Boom of Anasazi America

Long and spatially variable Neolithic Demographic Transition in the North American Southwest

Authors:

Kohler et al

Abstract:

In many places of the world, a Neolithic Demographic Transition (NDT) is visible as a several-hundred-year period of increased birth rates coupled with stable mortality rates, resulting in dramatic population growth that is eventually curtailed by increased mortality. Similar processes can be reconstructed in particular detail for the North American Southwest, revealing an anomalously long and spatially variable NDT. Irrigation-dependent societies experienced relatively low birth rates but were quick to achieve a high degree of sociopolitical complexity, whereas societies dependent on dry or rainfed farming experienced higher birth rates but less initial sociopolitical complexity. Low birth rates after A.D. 1200 mark the beginning of the decline of the Hohokam. Overall in the Southwest, birth rates increased slowly from 1100 B.C. to A.D. 500, and remained at high levels with some fluctuation until decreasing rapidly beginning A.D. 1300. Life expectancy at 15 increased slowly from 900 B.C. to A.D. 700, and then increased rapidly for 200 y before fluctuating and then declining after A.D. 1400. Life expectancy at birth, on the other hand, generally declined from 1100 B.C. to A.D. 1100/1200, before rebounding. Farmers took two millennia (∼1100 B.C. to ∼A.D. 1000) to reach the carrying capacity of the agricultural niche in the Southwest.

Super Drought Research Suggests Stronger Monsoon in the Southwest US With Global Warming?

Multidecadal to multicentury scale collapses of Northern Hemisphere monsoons over the past millennium

Authors:

1. Yemane Asmerom (a)
2. Victor J. Polyak (a)
3. Jessica B. T. Rasmussen (b)
4. Stephen J. Burns (c)
5. Matthew Lachniet (d)

Affiliations:

a. Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131;

b. Leander Independent School District, Leander, TX 78646;

c. Department of Geosciences, University of Massachusetts, Amherst, MA 01003; and

d. Department of Geoscience, University of Nevada, Las Vegas, NV 89154

Abstract:

Late Holocene climate in western North America was punctuated by periods of extended aridity called megadroughts. These droughts have been linked to cool eastern tropical Pacific sea surface temperatures (SSTs). Here, we show both short-term and long-term climate variability over the last 1,500 y from annual band thickness and stable isotope speleothem data. Several megadroughts are evident, including a multicentury one, AD 1350–1650, herein referred to as Super Drought, which corresponds to the coldest period of the Little Ice Age. Synchronicity between southwestern North American, Chinese, and West African monsoon precipitation suggests the megadroughts were hemispheric in scale. Northern Hemisphere monsoon strength over the last millennium is positively correlated with Northern Hemisphere temperature and North Atlantic SST. The megadroughts are associated with cooler than average SST and Northern Hemisphere temperatures. Furthermore, the megadroughts, including the Super Drought, coincide with solar insolation minima, suggesting that solar forcing of sea surface and atmospheric temperatures may generate variations in the strength of Northern Hemisphere monsoons. Our findings seem to suggest stronger (wetter) Northern Hemisphere monsoons with increased warming.

That's interesting when combined with the projection of the monsoon being delayed under global warming. A stronger, but later monsoon could be...not so good.  Oh my green chiles!

Changes to Trade and Social Connectivity in the Pre Hispanic American Southwest

Transformation of social networks in the late pre-Hispanic US Southwest

Authors:

1. Barbara J. Mills (a)
2. Jeffery J. Clark (b)
3. Matthew A. Peeples (b)
4. W. R. Haas, Jr. (a)
5. John M. Roberts, Jr. (c)
6. J. Brett Hill (b,d)
7. Deborah L. Huntley (b)
8. Lewis Borck (a)
9. Ronald L. Breiger (e)
10. Aaron Clauset (f,g)
11. M. Steven Shackley (h)

Affiliations:

a. School of Anthropology, University of Arizona, Tucson, AZ 85721

b. Archaeology Southwest, Tucson, AZ 85701

c. Department of Sociology, University of Wisconsin, Milwaukee, WI 53201

d. Department of Sociology and Anthropology, Hendrix College, Conway, AR 72032

e. Department of Sociology, University of Arizona, Tucson, AZ 85721

f. Department of Computer Science and BioFrontiers Institute, University of Colorado, Boulder, CO 80309

g. Santa Fe Institute, Santa Fe, NM 87501

h. Archaeological XRF Laboratory, Albuquerque, NM 87113

Abstract:

The late pre-Hispanic period in the US Southwest (A.D. 1200–1450) was characterized by large-scale demographic changes, including long-distance migration and population aggregation. To reconstruct how these processes reshaped social networks, we compiled a comprehensive artifact database from major sites dating to this interval in the western Southwest. We combine social network analysis with geographic information systems approaches to reconstruct network dynamics over 250 y. We show how social networks were transformed across the region at previously undocumented spatial, temporal, and social scales. Using well-dated decorated ceramics, we track changes in network topology at 50-y intervals to show a dramatic shift in network density and settlement centrality from the northern to the southern Southwest after A.D. 1300. Both obsidian sourcing and ceramic data demonstrate that long-distance network relationships also shifted from north to south after migration. Surprisingly, social distance does not always correlate with spatial distance because of the presence of network relationships spanning long geographic distances. Our research shows how a large network in the southern Southwest grew and then collapsed, whereas networks became more fragmented in the northern Southwest but persisted. The study also illustrates how formal social network analysis may be applied to large-scale databases of material culture to illustrate multigenerational changes in network structure.