Wednesday, January 29, 2025

Remote sensing tools yield insights into abandoned pre-Columbian Mexican city


Awareness of the Zapotecs’ level of political and social organization stands to shed light on their level of agency in negotiating with the Spanish


McGill University

Serpent sculpture 

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Serpent sculpture from the serpent plaza found by an earlier archaeological expedition and now in the Oaxacan hall in the National Museum of Anthropology in Mexico City.

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Credit: Pedro Guillermo Ramón Celis





A McGill University researcher has discovered that Guiengola, a 15th century Zapotec site in southern Oaxaca, Mexico, which had been thought to be simply a fortress where soldiers were garrisoned, was in fact a sprawling, fortified city. It covered 360 hectares, with over 1,100 buildings, four kilometres of walls, a network of internal roads and a clearly organized urban layout with temples and communal spaces such as ballcourts, and the elites and commoners lived in separate neighbourhoods.

According to Pedro Guillermo Ramón Celis, a Banting postdoctoral researcher in McGill’s Department of Anthropology and the author of a recent article in Ancient Mesoamerica, the evidence strongly suggests the city was abandoned just before the Spanish arrived, and that its people moved just 20 kilometres away to Tehuantepec, a small city where their descendants still live today.

Ramón Celis said investigating how the Mesoamerican city was organized on the eve of the Spanish conquest is just the first step. He said he is convinced that as work on Guiengola advances, it will give researchers a better sense of the Zapotecs’ level of political and social organization, and thus a greater understanding of their level of agency in negotiating with the Spanish.

The finding was made by using a remote sensing tool known as lidar (light detection and ranging). Lidar relies on pulsing laser beams, in a process akin to sonar, to provide precise, detailed, three-dimensional topographic information about what is on the earth’s surface, below the dense forest canopy.

“My mother’s family is from the region of Tehuantepec which is about 15 km from the site, and I remember them talking about it when I was a child. It was one of the reasons that I chose to go into archaeology,” Ramón Celis said. “Although you could reach the site using a footpath, it was covered by a canopy of trees. Until very recently, there would have been no way for anyone to discover the full extent of the site without spending years on the ground walking and searching. We were able to do it within two hours by using remote sensing equipment and scanning from a plane.”

By analyzing the data generated by the scans and using the Geo Analytic laboratory at McGill, Ramón Celis has been able to map the size and the layouts of the remaining built structures and infer their use based on the artifacts found at the locations.

To explore how power was distributed in the city, he has calculated how much building space was given over to elite areas such as the temples and ballcourts, for example, compared to what was built in the areas used by commoners. Ballcourts were built in Mesoamerica for the purpose of practicing a ritual ballgame, and represent both the underworld and fertility, since they are a way of connecting with the ancestors and seeds grow below the soil, where the underworld is found.

Ramón Celis added, “Because the city is only between 500 and 600 years old, it is amazingly well preserved, so you can walk there in the jungle, and you find that houses are still standing… you can see the doors… the hallways… the fences that split it from other houses. So, it is easy to identify a residential lot. It's like a city frozen in time, before any of the deep cultural transformations brough by the Spanish arrival had taken place.”

 

The research: “Airborne lidar at Guiengola, Oacaxa: Mapping a Late Postclassic Zapotec city” by Pedro Guillermo Ramón Celis was published in Ancient Mesoamerica

DOI: https://doi.org/10.1017/S0956536124000166

The funding: Wenner-Gren Foundation, Indiana University College of Arts and Sciences and now the Canadian Social Sciences and Humanities Research Council.


Public and Private spaces in Guiengola 

View of Guiengola’s North Plaza from above, the only area not covered by the tree canopy

Credit

Pedro Guillermo Ramón Celis

Lidar scan showing the Civic and Ceremonial Center (left) and the commoner areas (right), split by a defensive wall (centre)

Credit

Pedro Guillermo Ramón Celis

 

Turning farm waste into sustainable roads



Xianming Shi, civil and architectural engineering department chair at the University of Miami, was awarded a grant from the U.S. Department of Agriculture to research how to turn farming byproducts into sustainable asphalt.



University of Miami





A typical road is made of rocks and sand held together by petroleum to create the smooth surfaces we drive on every day. But some of these materials come at a cost: during the production and installation of asphalt, harmful emissions are released, posing health risks to workers and communities.

Now, researchers led by Xianming Shi, chair of the civil and architectural engineering department at the University of Miami College of Engineering, are exploring a cleaner, greener alternative. With a $1 million grant from the U.S. Department of Agriculture, the team is studying how agricultural waste can be converted into biochar to build roadways. The three-year project aims to revolutionize the transportation industry by reducing reliance on petroleum-based materials and providing a carbon-neutral alternative for infrastructure development.

“This is an exciting opportunity, as this is likely the very first solution to truly move asphalt pavement toward net-zero — that is, carbon neutrality,” Shi said. “In addition, we can clearly observe fewer toxic fumes being emitted from asphalt pavement during production.”

At the heart of the project is biochar, a CO2-negative material produced by heating organic waste, such as orchard trimmings, wheat straw, and poultry litter, in a low-oxygen environment through a process known as pyrolysis. The approach not only repurposes millions of tons of agricultural byproducts and waste generated annually on farms across the country but also turns them into a material that can sequester carbon in asphalt pavement while potentially extending the lifespan of roads.

Millions of tons of organic waste at farms are often discarded or left to decompose, releasing methane and other harmful gases into the atmosphere. By converting this waste into biochar (and bio-oil) and using high doses of reclaimed asphalt pavement, Shi and his team aim to sequester large amounts of carbon in the asphalt pavement itself. The project could also create economic opportunities for farmers and poultry producers by diverting farm waste toward better uses.

Turning Waste Into a Revenue Stream

The research team is multidisciplinary, including three economists to analyze how the technology can help local communities.

“This project goes beyond engineers working together to decarbonize asphalt,” Shi said. “This is a bold approach that will essentially create a new market and green jobs; that is why we also consider the socioeconomic dimensions of this innovation.”

Shi, along with researchers from California State University-Chico, Washington State University, and the University of Georgia, also plans to partner with two tribal communities to test the biochar-enhanced asphalt on local paving projects, showcasing the material’s real-world potential.

A Vision for Climate-Driven Engineering

Shi’s leadership has brought a renewed focus on environmental sustainability, with infrastructure decarbonization and coastal resilience at the core of the department’s mission.

“We are transforming into a climate infrastructure engineering department,” Shi said. “We have faculty doing exciting research on the decarbonization of the built environment—whether it’s roads, bridges, tunnels, ports, or buildings—especially looking at how we can reduce their carbon footprint. Being in Miami, it makes sense to also focus on coastal resilience, with internationally known innovations like the SEAHIVE for coastal defense.”


 

Most mental health crisis services did not increase following 988 crisis hotline launch



Strategies needed to boost availability of crisis services at mental health treatment facilities



RAND Corporation





The launch of the nation’s 988 mental health hotline did not coincide with significant and equitable growth in the availability of most crisis services, except for a small increase in peer support services, according to a new RAND study.

Examining reports from thousands of mental health treatment facilities about the types of crisis services offered before and after the July 2022 rollout of the 988 hotline, researchers found that there was an increase in peer support services, a significant decrease in psychiatric walk-in services, and small declines in mobile crisis response and suicide prevention services.

Significant variation across states was observed in service availability trends before and after 988. The findings are published in the journal JAMA Psychiatry.

“The lack of meaningful growth in most crisis services may limit the long-run success of 988, in particular if callers feel that reaching out to 988 fails to result in access to appropriate sources of care,” said Jonathan Cantor, lead author of the study and a policy researcher at RAND, a nonprofit research organization. 

“Mental health officials and policymakers should consider strategies to boost the financing and availability of crisis services at mental health treatment facilities to meet increased demand generated by the 988 Suicide and Crisis Lifeline,” Cantor said. 

The 988 Suicide and Crisis Lifeline provides an easy-to-remember phone number to access trained crisis counselors and emergency mental health services. It replaced the National Suicide Prevention Lifeline, which had been reachable via an 800 phone number and was narrowly focused on suicide as opposed to mental health crises more broadly. 

The 988 crisis line is intended to complement other forms of mental health emergency response services and connect callers with a variety of mental health services on the crisis care continuum.

However, mental health emergency response systems may not be amenable to rapid change despite increases in demand prompted by 988. In particular, the U.S. continues to contend with a shortage of psychiatric beds in many regions, as well as a limited and unevenly distributed mental health care workforce.

RAND researchers evaluated the availability of crisis services offered by mental health treatment facilities throughout the U.S. from November 2021 through June 2023.

Information came from details reported by licensed mental health treatment facilities to the Substance Abuse and Mental Health Services Administration. RAND has aggregated that data over time to create the longitudinal Mental health and Addiction Treatment Tracking Repository. The study included information from a large sample of reports from more than 15,000 mental health treatment facilities nationally.

The largest changes were observed for peer support services, which increased from being available at 39% of facilities prior to 988 to 42% afterward, and for availability of emergency psychiatric walk-in services, which declined from 32% to 29%.

The availability of other service types at mental health treatment facilities also declined at the national level. Mobile crisis response dropped from being provided by 22% of facilities before the rollout of 988 to being offered by 21% afterward. The availability of suicide prevention services dropped from 69% to 68% over the period.

There were also significant differences observed in crisis service availability based on facility characteristics. For example, public facilities had the highest odds of offering each of the four crisis services, followed by not-for-profit facilities. For-profit facilities, which comprised about one-quarter of the sample, consistently had the most-limited services.

State-level rates of suicide prevention services remained the same for most states over the study period. The largest increase in the availability of suicide prevention services was seen in Montana (11.5% increase), and the largest decline in availability was in Rhode Island (11.4% decrease). 

In contrast, most states experienced an increase in the number of facilities offering peer support services. The largest gain in offering of peer support services was in Kansas (19.6% increase) and the largest decline in peer support services was found in Georgia (3.2% decrease).  

Support for the study came from the National Institute of Mental Health. Other authors of the study are Megan S. Schuler, Rose Kerber and Ryan K. McBain, all of RAND, and Jonathan Purtle of New York University. 

RAND Health Care promotes healthier societies by improving health care systems in the United States and other countries.

 

Discovery of a unique drainage and irrigation system that gave way to the “Neolithic Revolution” in the Amazon




Universitat Autonoma de Barcelona
Ponds 

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Ponds in the studied area.

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Credit: Author: Umberto Lombardo ICTA-UAB




A pre-Columbian society in the Amazon developed a sophisticated agricultural engineering system that allowed them to produce maize throughout the year, according to a recent discovery by a team of researchers from the Institute of Environmental Science and Technology (ICTA-UAB) and the Department of Prehistory at the Universitat Autònoma de Barcelona, (Spain); the Universities of Exeter, Nottingham, Oxford, Reading and Southampton (UK); the University of São Paulo (Brazil) and Bolivian collaborators. This finding contradicts previous theories that dismissed the possibility of intensive monoculture agriculture in the region.

The study, published today in the journal Nature, describes how the pre-Hispanic Casarabe society of the Llanos de Moxos in Bolivia designed and implemented an innovative landscape engineering system, including the construction of extensive drainage canals and farm ponds. This advancement allowed the transformation of flooded tropical savannahs into highly productive fields, thereby driving the development of the “Neolithic Revolution” in the Amazon, understood as the process towards an economy based on grain production.

This region, inhabited by the Casarabe people between 500 and 1400 A.D., is a tropical lowland savannah marked by intense rainy seasons and flooding, as well as very dry seasons. The discovery, led by Umberto Lombardo, an environmental archaeologist at the UAB, has identified a unique agricultural infrastructure previously undocumented anywhere else in the world.. This system enabled them to drain excess water from flooded fields during the rainy season, facilitating agricultural productivity. In addition to the drainage canals, the Casarabe people constructed clusters of farm ponds that served as water reservoirs. These ponds enabled pot-irrigation, allowing maize cultivation to continue throughout the dry season.

This dual water management system enabled at least two harvests of maize per year, ensuring a stable food supply year-round, which was essential for sustaining a relatively large population. "This intensive agricultural strategy indicates that maize was not only cultivated but was likely the staple crop of the Casarabe culture," explains Lombardo.

This agricultural model did not rely on traditional slash-and-burn techniques used to create fertile fields. Instead, the Casarabe people preserved nearby forests for other purposes, such as obtaining firewood and medicinal plants, while implementing practices that maximized the efficient use of water and soil in the seasonally flooded savannas.

These conclusions were made possible through meticulous fieldwork combining techniques such as microbotanical analysis, remote sensing, and environmental archaeology. The analysis of 178 phytolith (plant microfossils) and pollen samples from a farm pond confirmed the presence of maize in the fields and the crucial role of maize monoculture in the diet of this pre-Columbian society. "The data shows the absence of other types of crops," Lombardo adds.

"We can document that this is the first grain-based agrarian economy in the Amazon, where until now it was believed that agriculture was based on agroforestry polyculture and not on large-scale monocultures. Now we know that this was not the case in Llanos de Moxos", says Lombardo, who asserts that this innovative piece of engineering allowed for the transformation of a challenging environment into a productive system that ensured food stability and supported the development of a growing population.

The research not only sheds light on the technological capabilities of pre-Columbian civilizations but also offers valuable lessons for modern agricultural sustainability. This discovery is a testament to the ingenuity and adaptability of the Casarabe people, who thrived due to their ability to design long-term sustainable agricultural solutions in an adverse environment.

Photo of Umberto Lombardo in the field. 

Credit

Author Sergio Quezada, free to use.


Artwork of the ponds described in the paper. From the Extended data which are open access.

Credit

Author Julian Puig Guevara

 

Research contrasts drought sensitivity of Eurasian and North American grasslands



Findings have broad implications for land management practices on both continents



Colorado State University

Test site in China 

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A test site in China

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Credit: Credit Colorado State University College of Natural Scie





Grasslands in Asia and North America differ in their responses to drought, according to a new paper in the journal Nature led by faculty at Colorado State University. The findings show that differences in the dominant grasses and lower species diversity in the Eurasian Steppe grasslands may make it more vulnerable to drought than the North American Great Plains.

The findings have broad implications for land management practices on both continents and provide a valuable comparison point that was not previously available when addressing climate change.

The work at CSU was led by Professors Melinda Smith and University Distinguished Professor Alan Knapp in the Department of Biology. Smith said the multi-year project was built through ongoing collaboration with researchers in China, including first author and Smith’s former postdoctoral researcher at CSU, Qiang Yu. Together, the team established six sites on each continent and imposed extreme drought conditions over a four-year period. They found the Eurasian grasslands saw a 43% reduction in annual productivity – plant growth each year – compared to just a 25% reduction in North America under the same conditions.

Smith said the findings also show that the negative effects of drought in Eurasia increased over time. Meanwhile, the North American system was able to stabilize in the second year of the experiment. The paper explores that difference, specifically considering how plant diversity impacted each region’s ability to cope with prolonged extreme droughts.

Smith said the research shows the difference may be linked to the overall number of uncommon, subordinate plant species in each region. These species make up the bulk of plant diversity there and contribute to overall productivity – even as primary species struggle to do so in drought conditions. The findings show these key subordinate species declined in Eurasian grasslands during drought conditions but increased in North America – potentially stabilizing production losses there over time. 

“Particularly in North America, we show that subordinate species seem to be minimizing losses and picking up the slack in a way that is not happening in Eurasia where there is less species richness,” she said. “These species’ ability to step up – possibly, due to drought tolerance developed over time – provides a unique perspective on these two vast grassland regions and how they function in these conditions.”

The two regions also support different types of dominant grass species. The Eurasian grasslands are primarily suited to supporting C3 grasses, like wheat, that prefer cooler and wetter conditions, while C4 grasses, like corn, flourish in the warmer American Midwest. That allows for interesting comparisons related to agriculture and management practices under drought conditions, said Knapp.

“In general, C4 plants have more efficient photosynthetic pathways and are more productive with less water than C3 plants. Such differences may be especially important when trying to understand how productivity will change with increasingly more severe droughts,” Knapp said.

Plant productivity is a fundamental component of the global carbon cycle. That is because plant photosynthesis is the primary way that atmospheric carbon, as carbon dioxide, enters ecosystems and is made available for consumption by animals and storage as biomass. Because grasslands cover 40% of the Earth’s surface, they play a large role in balancing and facilitating carbon uptake and sequestration globally.

Smith said understanding how these similar, yet differing biomes contribute to that process has proven difficult in the past. That is because researchers around the globe struggled to standardize experiments in a way that allowed for clear comparisons. This work directly addresses that need by developing a large-scale, coordinated, multi-year experiment at multiple sites. The 12 total test sites for the project are collectively known as the Extreme Drought Grasslands Experiment (EDGE) and were chosen because they represent a variety of grasslands located along precipitation gradients. 

Smith said the work shows how vulnerable regions with lower species diversity can be to prolonged droughts. It also shows the need for management strategies that increase and maintain plant diversity to enhance resistance to extreme drought events under future climate change scenarios.

“Dryer grassland tends to be where a lot of cattle grazing happens and where many people live globally. They are also important when we consider how carbon is stored related to climate change,” she said. “So, there is a real need to develop management strategies in these areas, as climate change is expected to increasingly impact them with extreme, prolonged droughts.”