Wednesday, April 01, 2020

Researcher offers recommendations on using remote sensing to quantify forest health

by University of Delaware

University of Delaware assistant professor Pinki Mondal recently had a paper published in the Remote Sensing of Environment Journal that shows the importance of using finer scale satellite data in protected areas to ensure they are maintaining their health and are being reported on accurately. Credit: University of Delaware

While using large swaths of coarse satellite data can be an effective tool for evaluating forests on a national scale, the resolution of that data is not always well suited to indicate whether or not those forests are growing or degrading.

A new study led by the University of Delaware's Pinki Mondal recommends that in addition to using this broad scale approach, it is important for countries to prioritize areas such as national parks and wildlife refuges and use finer scale data in those protected areas to make sure that they are maintaining their health and are being reported on accurately.

To help create an easy-to-implement reporting framework for six Southeast Asian forest ecosystems—in Bangladesh, Bhutan, India, Nepal, Pakistan, and Sri Lanka—Mondal led a study that first looked at those countries using a broad brush approach and then used higher resolution data to focus on two specific protected areas to show how the coarse satellite data can sometimes overlook or misinterpret temporal changes in forest cover.

Sustainable Development Goals

The work was conducted to develop a reporting framework that can help the countries with their Sustainable Development Goal (SDG) reporting to the United Nations.

In 2015, the United Nations General Assembly set forth 17 SDGs to serve as a blueprint to achieve a better and more sustainable future for all, with the hope to achieve these goals by the year 2030. Among these, goal No. 15—Life on Land—is to protect the world's forests to strengthen natural resource management and increase land productivity. To help with reporting SDG 15, Mondal and her research group have been using remote sensing to look at forests around the world.

Mondal, an assistant professor in the Department of Geography and Spatial Sciences in UD's College of Earth, Ocean and Environment, recently had a paper published in the Remote Sensing of Environment Journal looking at SDG 15.

Coarse Satellite Data

Most countries, especially the ones with limited access to computing resources and finer scale remote sensing data, use freely available remote sensing assets such as those from coarse-scale satellite sensors.

"Depending on the scale of a study, people tend to use coarser resolution data because generally, those satellite images have a larger footprint," said Mondal. "Only a few satellite images can cover an entire country and it's easier to use or analyze that kind of data."

The researchers used a broad-brush approach with coarser resolution satellite data to calculate vegetation trends in response to rainfall changes in the six countries.

At the country-level since 2001, the vegetation trends fluctuated and the researchers found instances of localized greening in Pakistan, India, and Nepal, and browning in Bangladesh and Sri Lanka, with Bhutan showing almost no trend. The greening found in India and Nepal was more localized and the forests showed localized browning in the northeastern states of India, and parts of Nepal and Sri Lanka.

While the coarse-resolution data could indicate an overall greening trend for an area, when they looked at two specific protected areas using finer scale data, they found that there was a lot more going on.

Protected Areas

Using finer-resolution satellite data, the researchers looked at intact versus non-intact forests that were located in two protected areas, the Sanjay National Park in India and the Ruhuna National Park in Sri Lanka. Since both test cases are national parks, they are expected to host mostly intact, or undisturbed forests that would not be impacted by human populations.

"Protected areas are supposed to host and maintain quality forest. But by using this finer scale data, we were able to see non-intact forests that could be a result of factors such as fire, disease, or human activities. If we cannot maintain a healthy forest even within protected areas, then that's a problem," said Mondal.

When using a broad-brush approach, the Sanjay National Park showed an overall greening trend but when using the more in-depth data, they found almost one-third of the Sanjay National Park to have non-intact forest. In addition, they were also able to identify spots in the national parks that had no forests at all. Maintaining the balance between healthy forests and other ecosystems such as grasslands within these protected areas and minimizing degradation should be high priority for land managers moving forward.

This finer scale data allowed the researchers to generate maps of 87 percent and 91 percent overall accuracy for the Indian and Sri Lankan protected areas.

Challenges in reporting

Mondal said one of the challenges facing researchers has been developing a broad definition for a forest, as depending on a country's ecosystem, their forests can be very different.

"If you work in a country like India, it's so diverse that by definition, you can't have one uniform forest," said Mondal. "In the land change science community, we have been debating the definition for a forest, but an acceptable measure is the one with 10 percent canopy cover."

This indicator of a forest can be tracked with satellites, and researchers use satellite images over time to measure how much of a particular mapping unit is covered by forest canopy.

"If you're working in a country with a diverse landscape, the status of forest cover might change pretty rapidly over time. But you cannot capture that change with this coarse-level, broad-brush input approach, which is what most of the national level studies use," said Mondal.

Overall, Mondal said that the goal of the paper was to encourage people to realize that there is not a one-size-fits-all approach to monitoring and reporting progress toward SDG.

"Our goal is to encourage landscape managers to think more deeply about the methods they are using in terms of reporting these SDGs because depending on what data you're using, your result might look completely different than what you're reporting at the U.N. level," said Mondal.

Explore further

Identifying forests for protection in Borneo

More information: Pinki Mondal et al. A reporting framework for Sustainable Development Goal 15: Multi-scale monitoring of forest degradation using MODIS, Landsat and Sentinel data, Remote Sensing of Environment (2019). DOI: 10.1016/j.rse.2019.111592

Provided by University of Delaware

Overcoming carbon loss from farming in peatlands

by Kaine Korzekwa, American Society of Agronomy

In many regions of the world, farming must be done on areas of soil categorized as histosols. Histosols have a thick layer of rich organic matter, called peat.

Scientists are concerned, because farming can cause these soils to lose valuable carbon.

That's where Jacynthe Dessureault-Rompré and her team at Laval University in Canada come in. She is trying to show that histosols can be sustainably used for farming.

To do this, the research team performed a two-step experiment that involved adding different kinds of plant material to the soil. Their work is similar to how a backyard gardener may add compost to soil to add nutrients that have been lost.

"The first objective was to get a better understanding of plant material decomposition," Dessureault-Rompré says. "We looked at decomposition qualities of specific plant materials and how these affected long-term carbon stores in the soil. The second objective was to determine which plant performed best based on simulations of the long-term soil carbon storage."

Carbon in these soils is lost by erosion, tillage and a natural process called mineralization. The carbon is released from the soil as carbon dioxide, a harmful greenhouse gas, into the atmosphere.

For their first experiment, the team used three common biomass crops: sorghum, miscanthus, and willow. They put plant material from these crops inside permeable bags and placed the bags directly in the soil.

Then, they analyzed which plant materials had the best decomposition characteristics. The ones that broke down slowly are the best for storing carbon in the soil longer.

"The field decomposition study gave us data on what happened to the three different plant materials over a period of 17 months," Dessureault-Rompré says. "A good candidate is a crop that will last longer in the soil because the buildup of the carbon stock will be more efficient, therefore you need less biomass applied each year. The stability characteristics of the plant material are very important."

Next, researchers used decomposition data to simulate how much each plant would help the soil over a long period of time. They found that miscanthus and willow performed much better than sorghum. They also calculated amounts of the plants that would help the soils be the most sustainable.

"If you have a crop such as miscanthus that decomposes less than sorghum, the buildup over the years is much more efficient," she explains. "The simulation part added a new perspective because we were then able to see that carbon equilibrium is something that can be achieved. It was fantastic to see that adding plant material year after year allows farmers to overcome the carbon lost during farming in histosols."

She adds that it is hard to estimate when these farmers could adopt this practice. However, it's possible that within the next 10 years, this new soil conservation practice could be used by farmers.

While many scientists don't think histosols should be used for farming, many of the farmers have no choice. For the agricultural community, processing facilities and distribution services to make a living, farmers must grow crops on the land available to them.

The findings from Dessureault-Rompré and her team are important for easing concerns. This research demonstrates that it is possible to farm these soils sustainably.

"I was afraid this research would be criticized because it is a very new way of looking at crop production on these very special soils," she says. "Many scientists believe that cultivated histosols should be brought back to their natural state or that the degradation process of these soil is irreversible. But this project really aims to develop a sustainable way of growing high value crops on these soils.

Are sinking soils in the Everglades related to climate change?

More information: Jacynthe Dessureault‐Rompré et al. Biomass crops as a soil amendment in cultivated histosols: can we reach carbon equilibrium?, Soil Science Society of America Journal (2020). DOI: 10.1002/saj2.20051

Journal information: Soil Science Society of America Journal

]Provided by American Society of Agronomy

Scary red or icky green? We can't say what color coronavirus is and dressing it up might feed fears

by Simon Weaving, The Conversation

Credit: Shutterstock

Images of the latest coronavirus have become instantly recognizable, often vibrantly colored and floating in an opaque background. In most representations, the shape of the virus is the same—a spherical particle with spikes, resembling an alien invader.

But there's little consensus about the color: images of the virus come in red, orange, blue, yellow, steely or soft green, white with red spikes, red with blue spikes and many colors in between.

In their depictions of the virus, designers, illustrators and communicators are making some highly creative and evocative decisions.

Color, light and fear

For some, the lack of consensus about the appearance of viruses confirms fears and increases anxiety. On March 8 2020, the director-general of the World Health Organisation warned of the "infodemic" of misinformation about the coronavirus, urging communicators to use "facts not fear" to battle the flood of rumors and myths.

The confusion about the color of coronavirus starts with the failure to understand the nature of color in the sub-microscopic world.

Our perception of color is dependent on the presence of light. White light from the sun is a combination of all the wavelengths of visible light—from violet at one end of the spectrum to red at the other.

When white light hits an object, we see its color thanks to the light that is reflected by that object towards our eyes. Raspberries and rubies appear red because they absorb most light but reflect the red wavelength.

An artist’s impression of the pandemic virus. Credit:

Fusion Medical Animation/Unsplash, CC BY

But as objects become smaller, light is no longer an effective tool for seeing. Viruses are so small that, until the 1930s, one of their scientifically recognized properties was their invisibility. Looking for them with a microscope using light is like trying to find an ant in a football stadium at night using a large searchlight: the scale difference between object and tool is too great.

It wasn't until the development of the electron microscope in the 1930s that researchers could "see" a virus. By using electrons, which are vastly smaller than light particles, it became possible to identify the shapes, structures and textures of viruses. But as no light is involved in this form of seeing, there is no color. Images of viruses reveal a monochrome world of gray. Like electrons, atoms and quarks, viruses exist in a realm where color has no meaning.

Vivid imagery

Grey images of unfamiliar blobs don't make for persuasive or emotive media content.

A colorised scanning electron micrograph image of a VERO E6 cell (blue) heavily infected with SARS-COV-2 virus particles (orange), isolated from a patient sample. Credit: NIAID/Flickr, CC BY

Research into the representation of the Ebola virus outbreak in 1995 revealed the image of choice was not the worm-like virus but teams of Western medical experts working in African villages in hermetically sealed suits. The early visual representation of the AIDS virus focused on the emaciated bodies of those with the resulting disease, often younger men.

With symptoms similar to the common cold and initial death rates highest amongst the elderly, the coronavirus pandemic provides no such dramatic visual material. To fill this void, the vivid range of colorful images of the coronavirus have strong appeal.

Many images come from stock photo suppliers, typically photorealistic artists' impressions rather than images from electron microscopes.

The Public Health Library of the US government's Centre for Disease Control (CDC) provides one such illustration, created to reveal the morphology of the coronavirus. It's an off-white sphere with yellow protein particles attached and red spikes emerging from the surface, creating the distinctive "corona" or crown. All of these color choices are creative decisions.

The CDC illustration reveals ‘ultrastructural morphology’ exhibited by coronaviruses.

Credit: CDC/Alissa Eckert, MS; Dan Higgins/MAMS

Biologist David Goodsell takes artistic interpretation a step further, using watercolor painting to depict viruses at the cellular level.

One of the complicating challenges for virus visualisation is the emergence of so-called "color" images from electron microscopes. Using a methodology that was originally described as "painting," scientists are able to add color to structures in the grey-scale world of imaging to help distinguish the details of cellular micro-architecture. Yet even here, the choice of color is arbitrary, as shown in a number of colored images of the coronavirus made available on Flickr by the National Institute of Allergy and Infectious Diseases (NIAID). In these, the virus has been variously colored yellow, orange, magenta and blue.

A composite of images created by NIAID. Colours have been attributed by scientists but these are arbitrary. Credit: NIAID/Flickr, CC BY

Embracing grey

Whilst these images look aesthetically striking, the arbitrary nature of their coloring does little to solve WHO's concerns about the insecurity that comes with unclear facts about viruses and disease.

Some artists’ impressions include blood platelet images. Credit: Shutterstock

One solution would be to embrace the colorless sub-microscopic world that viruses inhabit and accept their greyness.

This has some distinct advantages: firstly, it fits the science that color can't be attributed where light doesn't reach. Secondly, it renders images of the virus less threatening: without their red spikes or green bodies they seem less like hostile invaders from a science fiction fantasy. And the idea of greyness also fits the scientific notion that viruses are suspended somewhere between the dead and the living.

Stripping the coronavirus of the distracting vibrancy of vivid color—and seeing it consistently as an inert grey particle—could help reduce community fear and better allow us to continue the enormous collective task of managing its biological and social impact

Provided by The Conversation This article is republished from The Conversation under a Creative Commons license. Read the original article.

When warblers warn of cowbirds, blackbirds get the message

by University of Illinois at Urbana-Champaign

This is the story of three bird species and how they interact. The brown-headed cowbird plays the role of outlaw: It lays its eggs in other birds' nests and lets them raise its young—often at the expense of the host's nestlings. To combat this threat, yellow warblers have developed a special "seet" call that means, "Look out! Cowbird!"

In a new study, researchers at the University of Illinois at Urbana-Champaign report that red-winged blackbirds respond to the seet call as if they know what it means.

"Does this mean red-winged blackbirds understand that the call is specific to cowbirds or are they just responding to a general alarm?" said graduate student Shelby Lawson, who led the study with Mark Hauber, a professor of evolution, ecology and behavior at the U. of I. The researchers sought to answer that question by playing back the calls of several bird species in warbler and blackbird territories to see how the birds reacted.

They report their findings in the journal Communications Biology.

"We know that eavesdropping on the calls of other species is common across the animal kingdom," Lawson said. "Birds do it. Mammals do it. There are studies of different primates that do it—and even birds that listen in when they do."

In the rainforests of Ivory Coast, for example, tropical birds known as hornbills have deciphered some of the calls of the Diana monkey. The hornbills ignore the monkeys' alarm calls for ground predators, which are no threat to the birds, but heed the monkeys' calls for hawks, which are predators of hornbills.

"Chickadees have very general alarm calls that we now know signal the size of different predators," Lawson said. "A lot of birds will listen to these calls and respond based on the danger posed to them. There's also a study of nuthatches listening to chickadee calls."

But all these studies look at alarm calls directed at predators that can kill adult animals, Lawson said.

"Yellow warblers are the only bird we know about that has developed a specific call for a brood parasite," she said. "When they see a brown-headed cowbird, yellow warblers will make the seet call and then females that hear the call will go back to their nest and sit on it tightly to protect their eggs. They only do this with cowbirds. They don't seet at predators or anything else."

In an earlier study, Lawson and her colleagues were playing audio of seet calls to study warbler behavior when they noticed that red-winged blackbirds were also responding aggressively to the calls. This prompted the new study.

To learn what the red-winged blackbirds understood about the calls, the researchers played a variety of bird calls in red-wing and yellow warbler territories and watched how the birds responded. They found that the red-winged blackbirds responded identically to the seet calls, the sound of cowbird chatter and blue jay calls—all of which signal a threat to their nests.

"They responded very aggressively to these calls, more so than they did to the warbler 'chip' call, which is just a general antipredator call," Lawson said. When red-wings heard the warblers seeting, they flew close to the loudspeaker and looked around for the threat, she said.

When red-winged blackbirds see any kind of predator in their territory, they swoop at it and dive bomb it. Male red-wings have so many mates in so many nests that they must defend a wide territory from interlopers and threats, Lawson said. This is why red-winged blackbirds are known as the "knights of the prairie."

In defending their own nests from predators, they end up helping out other bird species—in particular, yellow warblers. Previous research shows that yellow warblers that nest near red-winged blackbirds suffer less from cowbirds laying their eggs in their nests.

The warblers also appear to help the blackbirds by warning of nest predators, the researchers said.

"We found that the red-winged blackbirds that nest really close to the warblers respond more strongly to the seet calls than those that nest far away," Lawson said.

The researchers have more work to do to determine whether the blackbirds understand that the seet call means "cowbird," specifically, or if it is just interpreted as a general danger to the nest. In a future study, the researchers will play the seet call to re-wings at the end of the nesting season to see if the blackbirds respond as aggressively to the sound after their eggs have hatched. Yellow warblers stop making the seet call when their nestlings are secure and too old to be bothered by cowbirds.

"This is the first report of a bird eavesdropping on another species' warning of a brood parasite," Hauber said. "We don't yet know if the red-winged blackbirds understand that the warning is specific to cowbirds, but it's obvious they understand that the call represents a threat to the nest—and that benefits them."Red-winged blackbird nestlings go silent when predators are near

More information: "Heterospecific eavesdropping on an anti-parasitic referential alarm call" Communications Biology (2020). DOI: 10.1038/s42003-020-0875-7

Journal information: Communications Biology

Provided by University of Illinois at Urbana-Champaign

Soy scaffolds: Breakthrough in cultivated meat production

by American Technion Society

Researchers from the Technion-Israel Institute of Technology and Aleph Farms have achieved a breakthrough in the production of cultivated meat grown outside an animal's body. In findings published today in Nature Food, soy protein, which is readily available and economically efficient, can be used as scaffolds for growing bovine tissue.

The innovative technology, whereby cultured meat is grown on scaffolds made of soy protein, was spearheaded by Professor Shulamit Levenberg, dean of Technion's Faculty of Biomedical Engineering, over the past few decades. The technology was originally intended for medical applications, in particular for tissue engineering for transplants in humans.

There are several incentives for developing cultured meat. These include environmental damage caused by the meat-production industry, increased use of antibiotics that accelerates the growth of drug-resistant bacteria, ethical reservations about the suffering of animals during the meat production process, and the industry's detrimental ecological impact due to the intensive use of natural resources.

Aleph Farms is the first company to successfully grow slaughter-free steaks, using original technology developed by Prof. Levenberg and her team. Prof. Levenberg is the company's founding partner and chief scientist, and the current research was supervised by doctoral student Tom Ben-Arye and Dr. Yulia Shandalov.

The article in Nature Food presents an innovative process for growing cultured meat tissue in only three-to-four weeks that resembles the texture and taste of beef. The process is inspired by nature, meaning that the cells grow in a controlled setting similar to the way they would grow inside a cow's body.

The cells grow on a scaffold that replaces the extracellular matrix (ECM) found in animals. Since this is a food product, the scaffold must be edible, and therefore only edible alternatives were considered. Soy protein was selected as the scaffold on which the cells adhere and proliferate with the help of myogenesis-related growth factors, similarly to the tissue engineering technology developed by Prof. Levenberg.

Soy protein, an inexpensive byproduct obtained during the production of soy oil, is readily available and rich in protein. It is a porous material, and its structure promotes cell and tissue growth. Soy protein's tiny holes are suitable for cell adherence, division, and proliferation. It also has larger holes that transmit oxygen and nutrients essential for building muscle tissue. Furthermore, soy protein scaffolds for growing cultured meat can be produced in different sizes and shapes, as required.

The cultured meat in this research underwent testing that confirmed its resemblance to slaughtered steak in texture and taste. According to Prof. Levenberg, "We expect that in the future it will be possible to also use other vegetable proteins to build the scaffolds. However, the current research using soy protein is important in proving the feasibility of producing meat from several types of cells on plant-based platforms, which increases its similarity to conventional bovine meat."

Scientists enhance color and texture of cultured meat

More information: Tom Ben-Arye et al. Textured soy protein scaffolds enable the generation of three-dimensional bovine skeletal muscle tissue for cell-based meat, Nature Food (2020). DOI: 10.1038/s43016-020-0046-5

Mystery solved: The origin of the colors in the first color photographs
by CNRS

Edmond Becquerel, Solar spectra, 1848, photochromatic images, Musée Nicéphore Niépce, Chalon-sur-Saône.

A palette of colors on a silver plate: That is what the world's first color photograph looks like.

It was taken by French physicist Edmond Becquerel in 1848. His process was empirical, never explained, and quickly abandoned.

Now, a team at the Centre de recherche sur la conservation (CNRS/Muséum National d'Histoire Naturelle/Ministère de la Culture), in collaboration with the SOLEIL synchrotron and the Laboratoire de Physique des Solides (CNRS/Université Paris-Saclay), reports that the colors obtained by Edmond Becquerel were due to the presence of metallic silver nanoparticles.

Their study was published on 30 March 2020 in Angewandte Chemie International Edition.
In 1848, in the Muséum d'Histoire Naturelle in Paris, Edmond Becquerel managed to produce a color photograph of the solar spectrum. These photographs, which he called "photochromatic images," are considered to be the world's first color photographs. Few of these have survived because they are light-sensitive and because very few were produced in the first place. It took the introduction of other processes for color photography to become popular in society.

For more than 170 years, the nature of these colors has been debated in the scientific community, without resolution. Now we know the answer, thanks to a team at the Centre de recherche sur la conservation (CNRS/Muséum National d'Histoire Naturelle/Ministère de la Culture) in collaboration with the SOLEIL synchrotron and the Laboratoire de Physique des Solides (CNRS/Université Paris-Saclay).

After having reproduced Edmond Becquerel's process to make samples of different colors, the team started by re-examining 19th-century hypotheses using 21st century tools. If the colors were due to pigments formed during the reaction with light, there should have been variations in chemical composition from one color to another, which no spectroscopy method has shown. If they were the result of interference, like the shades of some butterflies, the colored surface should have shown regular microstructures about the size of the wavelength of the color in question. Yet no periodic structure was observed using electron microscopy.

However, when the colored plates were examined, metallic silver nanoparticles were revealed in the matrix made of silver chloride grains—and the distributions of sizes and locations of these nanoparticles vary according to color.

The scientists assume that according to the light's color (and therefore its energy), the nanoparticles present in the sensitized plate reorganize: Some fragment and others coalesce. The new configuration gives the material the ability to absorb all colors of light, with the exception of the color that caused it, thereby producing the color that we see.

Nanoparticles having properties related to color are known as surface plasmons, electron vibrations (here, those of the metallic silver nanoparticles) that propagate in the material. A spectrometer in an electron microscope measured the energies of these vibrations to confirm this hypothesis.

Explore further
Speedy and precise multicolor imaging of biomolecules now possible

More information: Victor de Seauve et al, Spectroscopies and electron microscopies unravel the origin of the first colour photographs, Angewandte Chemie (2020). DOI: 10.1002/ange.202001241

Replication and study of the colouration of Edmond Becquerel's photochromatic images, Victor de Seauve, Marie-Angélique Languille, Saskia Vanpeene, Christine Andraud, Chantal Garnier, Bertrand Lavédrine, Journal of Cultural Heritage, 2020 (in press). arxiv.org/abs/2001.05250

Journal information: Angewandte Chemie International Edition , Angewandte Chemie

Mesoamerican copper smelting technology aided colonial weaponry

by David L. Chandler, Massachusetts Institute of Technology

When Spanish invaders arrived in the Americas, they were generally able to subjugate the local peoples thanks, in part, to their superior weaponry and technology. But archeological evidence indicates that, in at least one crucial respect, the Spaniards were quite dependent on an older Indigenous technology in parts of Mesoamerica (today's Mexico, Guatemala, Belize, and Honduras).

The invaders needed copper for their artillery, as well as for coins, kettles, and pans, but they lacked the knowledge and skills to produce the metal. Even Spain at that time had not produced the metal domestically for centuries, relying on imports from central Europe. In Mesoamerica they had to depend on local smelters, furnace builders, and miners to produce the essential material. Those skilled workers, in turn, were able to bargain for exemption from the taxes levied on the other Indigenous people.

This dependence continued for at least a century, and perhaps as long as two centuries or more, according to new findings published in the journal Latin American Antiquity, in a paper by Dorothy Hosler, professor of archeology and ancient technology at MIT, and Johan Garcia Zaidua, a researcher at the University of Porto, in Portugal.

The research, at the site of El Manchón, in Mexico, made use of information gleaned from more than four centuries worth of archeological features and artifacts excavated by Hosler and her crew over multiple years of fieldwork, as well as from lab work and historical archives in Portugal, Spain, and Mexico analyzed by Garcia.

El Manchón, a large and remote settlement, initially displayed no evidence of Spanish presence. The site consisted of three steep sectors, two of which displayed long house foundations, some with interior rooms and religious sanctuaries, patios, and a configuration that was conceptually Mesoamerican but unrelated to any known ethnic groups such as the Aztec. In between the two was an area that contained mounds of slag (the nonmetallic material that separates out during smelting from the pure metal, which floats to the surface).

The Spanish invaders urgently needed enormous quantities of copper and tin to make the bronze for their cannons and other armaments, Hosler says, and this is documented in the historical and archival records. But "they didn't know how to smelt," she says, whereas archaeological data suggest the Indigenous people had already been smelting copper at this settlement for several hundred years, mostly to make ritual or ceremonial materials such as bells and amulets. These artisans were highly skilled, and in Guerrero and elsewhere had been producing complex alloys including copper-silver, copper-arsenic, and copper-tin for hundreds of years, working on a small scale using blowpipes and crucibles to smelt the copper and other ores.

But the Spanish desperately required large quantities of copper and tin, and in consultation with Indigenous smelters introduced some European technology into the process. Hosler and her colleagues excavated an enigmatic feature that consisted of two parallel courses of stones leading toward a large cake of slag in the smelting area. They identified this as the remains of a thus-far-undocumented hybrid type of closed furnace design, powered by a modified hand-held European bellows. A small regional museum in highland Guerrero illustrates just such a hybrid furnace design, including the modified European-introduced bellows system, capable of producing large volumes of copper. But no actual remains of such furnaces had previously been found.

The period when this site was occupied spanned from about 1240 to 1680, Hosler says, and may have extended to both earlier and later times.

The Guerrero site, which Hosler excavated over four field seasons before work had to be suspended because of local drug cartel activity, contains large heaps of copper slag, built up over centuries of intensive use. But it took a combination of the physical evidence, analysis of the ore and slags, the archaeological feature in the the smelting area, the archival work, and reconstruction drawing to enable identification of the centuries of interdependence of the two populations in this remote outpost.

Earlier studies of the composition of the slag at the site, by Hosler and some of her students, revealed that it had formed at a temperature of 1150 degrees Celsius, which could not have been achieved with just the blowpipe system and would have required bellows. That helps to confirm the continued operation of the site long into the colonial period, Hosler says.

Years of work went into trying to find ways to date the different deposits of slag at the site. The team also tried archaeomagnetic data but found that the method was not effective for the materials in that particular region of Mexico. But the written historical record proved key to making sense of the wide range of dates, which reflected centuries of use of the site.

Documents sent back to Spain in the early colonial period described the availability of the locally produced copper, and the colonists' successful tests of using it to cast bronze artillery pieces. Documents also described the bargains made by the Indigenous producers to gain economic privileges for their people, based on their specialized metallurgical knowledge.

"We know from documents that the Europeans figured out that the only way they could smelt copper was to collaborate with the Indigenous people who were already doing it," Hosler says. "They had to cut deals with the Indigenous smelters."

Hosler says that "what's so interesting to me is that we were able to use traditional archeological methods and data from materials analysis as well as ethnographic data" from the furnace in a museum in the area, "and historical and archival material from 16th century archives in Portugal, Spain, and Mexico, then to put all the data from these distinct disciplines together into an explanation that is absolutely solid."Maize, not metal, key to native settlements' history in NY

More information: Johan García Zaldúa et al. Copper Smelting at the Archaeological Site of El Manchón, Guerrero: From Indigenous Practice to Colonial-Scale Production, Latin American Antiquity (2020). DOI: 10.1017/laq.2019.105

Provided by Massachusetts Institute of Technology

How the layouts, or textures, of cities influence extreme weather events

by Andrew Logan, Massachusetts Institute of Technology

Researchers at the MIT Concrete Sustainability Hub are studying the connections between urban layouts and hazard losses. Credit: NASA

If you've ever turned down a city street only to be blasted with air, you've stepped into what is known as an urban canyon.

Much like their geological counterparts, urban canyons are gaps between two tall surfaces—in this case, buildings. The gusts they channel, however, have real implications. They can magnify a hurricane's winds or increase a city's air temperature depending on their arrangement—an arrangement known as city texture. The problem is, according to researchers at the MIT Concrete Sustainability Hub (CSHub), that current hazard mitigation practices don't consider city texture. Consequently, they frequently underestimate damages, in some cases by as much as a factor of three.

Reconsidering current practices

To understand the potential impact of city texture, CSHub researchers first investigated the current construction practices. One of the practices they examined were building codes.

According to the Federal Emergency Management Agency, "Building codes are sets of regulations governing the design, construction, alteration, and maintenance of structures." One of their purposes is to protect the inhabitants of a building from natural disasters by specifying the strength of that building.

To keep buildings safe from wind hazards, codes stipulate how a building must interact with the wind, a value known as a drag coefficient. The drag coefficient of a building determines the amount of air resistance it will experience when exposed to the wind. As a building's drag coefficient increases, so does its likelihood of damage.

"Design codes assume that buildings have fixed drag coefficients. And in a way, that makes sense—the shape of a building doesn't change much," says Jake Roxon, a researcher at CSHub. "However, we've found that it's not just the shape of the building that affects its drag coefficient, but also the local configuration of adjacent buildings, which we refer to as urban texture."

Urban texture measures the probability of finding a neighboring building at a certain distance away from a given building. Roxon calculates it by drawing rings of a certain diameter around each building in a city. Then he counts the number of buildings in each ring.

The more buildings in each ring, the greater the probability is of finding a building at that distance. And the higher the probability, the more ordered and regular the local texture is, while the lower the probability, the more disordered and unpredictable. To capture a whole city's texture, Roxon averages together the texture of each of its buildings.

"On average, we have found that areas with disordered textures have more resilience," says Roxon. "If you are unable to predict which angle the wind will come from, it will offer the greatest level of protection. On the other hand, for an ordered city with the same density of buildings, you would expect to see more damage during an extreme hazard event."

The reason behind the resilience of disordered streets is how they distribute wind. By distributing wind more randomly, disordered cities like Boston or Paris experience less of the magnification that occurs as the wind travels the corridors of ordered cities, such as New York. In some cases, cities with more ordered textures can magnify hurricane winds from a Category 3 to a Category 4, Roxon has found.

The impact of city texture on drag coefficients and wind loads appeared prominently during Hurricane Irma in 2017, which passed through West Florida.

"An example of the texture effect is Sarasota and Lee counties in Florida during Irma," explains Ipek Bensu Manav, a CSHub researcher collaborating with Roxon. "Those counties are situated close to each other geographically, so they experience a similar hurricane risk. And when you look at the building stocks, they are also similar—mostly single and two-floor single-family houses."

However, the two counties differed in terms of texture.

"Sarasota County has a less-ordered texture, falling less onto a typical grid, and Lee County has a more orderly texture," says Manav. "When looking at Lee County we saw more structural damage—some buildings collapsed completely. There were more flooding and overturning of vegetation as well. So, Irma caused a lot more damage in the county that had a higher texture effect."

It turns out, too, that ordered textures have a similar effect on heat.

"We have found this to be the case with temperature as well—specifically, the urban heat island effect," says Roxon. "Ordered cities experience the greatest temperature difference between them and their rural surroundings at night."

Code cracking

So, then, if layouts of streets greatly influence hazard damage, why don't building codes account for them?
Credit: Massachusetts Institute of Technology

Simply put, it's currently too difficult to incorporate them.

Right now, the standard tool for investigating the drag coefficients of a building is computational fluid dynamics (CFD). CFD simulations measure the drag coefficient of a building and its hazard risk by modeling the flow of heat and wind. Though highly accurate, CFD simulations demand prohibitively intense time and computing requirements at scale.

"Using current resources, CFD simulations simply don't work on the scale of cities," says Roxon. "New York City, for example, has over 1 million buildings. Running a simulation would take a long time. And if you make just one small adjustment to the arrangement of buildings or the direction of the wind, you have to rerun the simulation."

Despite their imperfections, CFD simulations remain an important tool for understanding wind flow. But Roxon believes his city texture model can compensate for CFD's limitations and, in the process, make cities more resilient.

"We have found that there are certain variables derived from city texture that allow us, with relative accuracy, to estimate the drag coefficients for buildings and identify areas vulnerable to risks of damage. Then we can run CFD simulations to determine precisely where that damage will occur."

Essentially, city texture serves as a first-line tool for stakeholders, allowing them to assess risk and then use their resources, including CFD, more efficiently to identify vulnerable buildings for retrofit and, in turn, save lives.

The complete picture

In addition to the loss of life, natural disasters inflict an immense financial toll. According to the National Oceanographic and Atmospheric Administration, 258 natural disasters have caused more than $1.75 trillion of damage in the United States since 1980.

While numerous practices can predict and mitigate these costs, Manav has found that they still leave a lot on the table—namely, city texture.

By collaborating with Roxon, she has discovered that by discounting community characteristics like city texture, current models underestimate losses, often dramatically.

To apply texture to hurricane losses, Manav looked once again to Florida's Sarasota and Lee counties. She conducted a conventional loss estimation and a city texture-adjusted loss estimation for each county based on the 95th percentile of annual expected hazard events—equivalent to some of the strongest hurricanes, like Irma. She found that the expected losses increased when she incorporated city texture into her estimations. The increase was particularly acute in Lee County, whose ordered texture would likely magnify wind loads.

"In Sarasota County, we saw an increase in the expected loss from 1 percent to 6 percent of average home's value when incorporating city texture," says Manav. "But doing the same for Lee County, we saw an appreciably higher amount of damage, equivalent to approximately 9 percent of an average home's value."

Without incorporating city texture, then, these conventional estimations dramatically underestimate damages. This makes residents unaware of their hazard risk, and consequentially leaves them vulnerable.

The incentives for resilience

As sobering as these loss estimations are, Manav hopes they may yet help communities become more hazard-resilient.

Currently, she notes, hazard resilience has not become broadly implemented because most remain unaware of its cost benefits.

"One reason hazard-mitigation practices are not being implemented is that their benefits are not being communicated thoroughly," she says. "Obviously, there is the cost of constructing to better standards. But to balance out these costs there are the benefits of reduced repair costs following hazard events."

These reduced damage costs are significant.

Actions as simple as choosing hardier shingles, improving roof-to-wall connections, and adding shutters and impact-rated windows can mitigate hazard damages enough to pay back in as little as two years in hazard-prone areas like coastal Florida.

By using city texture to calculate hazard costs, Manav and Roxon hope homeowners, developers, and policymakers will choose to implement these relatively simple practices. The only key is making their incentives widely known.

Explore furtherAn atomic-scale erector set
More information: Role of City Texture in Urban Heat Islands at Nighttime. hdl.handle.net/1721.1/114808

Provided by Massachusetts Institute of Technology

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.

Sophisticatedly engineered 'watercourts' stored live fish, fueling Florida's Calusa kingdom

by Natalie Van Hoose, Florida Museum of Natural History

The Calusa kingdom ranks among the most politically complex groups of hunter-gatherers of the historic world. Unusually, it was powered by fishing, not farming. Massive enclosures enabled the Calusa to store enough fish to sustain population growth and fuel large-scale construction projects. Credit: Merald Clark/Florida Museum

The mighty Calusa ruled South Florida for centuries, wielding military power, trading and collecting tribute along routes that sprawled hundreds of miles, creating shell islands, erecting enormous buildings and dredging canals wider than some highways. Unlike the Aztecs, Maya and Inca, who built their empires with the help of agriculture, the Calusa kingdom was founded on fishing.

But like other expansive cultures, the Calusa would have needed a surplus of food to underwrite their large-scale construction projects. This presented an archaeological puzzle: How could this coastal kingdom keep fish from spoiling in the subtropics?

A new study points to massive structures known as watercourts as the answer. Built on a foundation of oyster shells, these roughly rectangular enclosures walled off portions of estuary and likely served as short-term holding pens for fish before they were eaten, smoked or dried. The largest of these structures is about 36,000 square feet—more than seven times bigger than an NBA basketball court—with a berm of shell and sediment about 3 feet high. Engineering the courts required an intimate understanding of daily and seasonal tides, hydrology and the biology of various species of fish, researchers said.

The watercourts help explain how the Calusa could rely primarily on the sea.

"What makes the Calusa different is that most other societies that achieve this level of complexity and power are principally farming cultures," said William Marquardt, curator emeritus of South Florida Archaeology and Ethnography at the Florida Museum of Natural History. "For a long time, societies that relied on fishing, hunting and gathering were assumed to be less advanced. But our work over the past 35 years has shown the Calusa developed a politically complex society with sophisticated architecture, religion, a military, specialists, long-distance trade and social ranking—all without being farmers."

The "West Court" marked in this LiDAR map of Mound Key, the capital of the Calusa kingdom, is more than 36,000 square feet, more than seven times the size of an NBA basketball court. These courts were engineered with knowledge of tides and fish biology. Credit: Victor Thompson et al.

The fact that the Calusa were fishers, not farmers, created tension between them and the Spaniards, who arrived in Florida during the 16th century when the Calusa kingdom was at its zenith, said study lead author Victor Thompson, director of the University of Georgia's Laboratory of Archaeology.

"The Spanish soldiers, priests and officers were used to dealing with agriculturalists, such as the people they colonized in the Caribbean who grew maize surpluses for them," Thompson said. "This would not have been possible with the Calusa. In fact, in a late 1600s mission attempt by the Franciscans, hoes were unloaded off the ship, and when the Calusa saw this, they remarked, 'Why didn't they also bring slaves to till the ground?'"

Thompson, Marquardt and colleagues analyzed two watercourts along the southwest shore of Mound Key, an island in Estero Bay off Florida's Gulf Coast and the seat of Calusa power for about 500 years.

These courts, still visible today, flank the grand canal, a marine highway nearly 2,000 feet long and averaging 100 feet wide, which bisects the key. Both have yards-long openings in the berms along the canal, possibly to allow Calusa to drive fish into the enclosures, which could then be closed with a gate or net.

The team studied the watercourts and surrounding areas using remote sensors, cores of sediment and shell and excavations. The bisected key features two large shell mounds, one on either side of the island. Remote sensing showed slopes leading from the watercourts to the top of the mounds, which may have been causeways for transporting food. On the shoreline, researchers found evidence of burning and small post molds, possibly for racks used to smoke and dry fish.

The fish surplus stored in watercourts likely enabled the Calusa to complete large-scale construction projects. The largest watercourt was built during a key construction phase of the king's manor on Mound Key. The Spanish recorded the manor as capable of holding 2,000 people. Credit: Merald Clark/Florida Museum

Radiocarbon dating suggests the watercourts were built between A.D. 1300 and 1400—around the end of a second phase in the construction of a king's manor, an impressive structure that would eventually hold 2,000 people, according to Spanish documents.

A.D. 1250 also corresponds to a drop in sea level, which "may have impacted fish populations enough to help inspire some engineering innovation," said Karen Walker, Florida Museum collection manager of South Florida Archaeology and Ethnography.

Fish bones and scales found in the western watercourt show the Calusa were capturing mullet and likely pinfish and herring, all schooling species. Florida Gulf Coast University geologist Michael Savarese's analysis of watercourt core samples revealed dark gray sediment that was rich in organic material, suggesting poor circulation. High tide would have refreshed the water to some extent, Marquardt said.

"We can't know exactly how the courts worked, but our gut feeling is that storage would have been short-term—on the order of hours to a few days, not for months at a time," he said.

While researchers previously hypothesized watercourts were designed to hold fish, this is the first attempt to study the structures systematically, including when they were built and how that timing correlates with other Calusa construction projects, Marquardt said.

Archaeological specimens of mullet (Mugil sp.) fish scales recovered from a live-storage area at Mound Key, the capital of the Calusa Kingdom in Southwest Florida. Credit: Zachary S. Randall (Florida Museum of Natural History, Gainesville, FL).

The Calusa dramatically shaped their natural environment, but the reverse was also true, Thompson said.

"The fact that the Calusa obtained much of their food from the estuaries structured almost every aspect of their lives," he said. "Even today, people who live along coasts are a little different, and their lives continue to be influenced by the water—be it in the food they eat or the storms that roll in on summer afternoons in Southwest Florida."

The study will publish this week in the Proceedings of the National Academy of Sciences.

Explore further

Building on shells: Interdisciplinary study starts unraveling mysteries of Calusa kingdom
More information: Victor D. Thompson et al, Ancient engineering of fish capture and storage in southwest Florida, Proceedings of the National Academy of Sciences (2020). DOI: 10.1073/pnas.1921708117

Journal information: Proceedings of the National Academy of Sciences

Provided by Florida Museum of Natural History

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