Analyzing ways to help golden eagle populations weather wind-energy growth

"We are taking basic information about golden eagle ecology in the Anthropocene and developing it into predictive frameworks for how to protect them," says Eric Lonsdorf, Emory assistant professor of environmental sciences.

By Carol Clark

Wind energy is a major component of the U.S. clean-energy goals. Already one of the fastest growing and lowest-cost sources of electricity in the country, it is poised for even more rapid growth, according to the U.S. Department of Energy. 

Wind power, however, does not come without tradeoffs, including some negative impacts on wildlife. Throughout the United States, for example, it’s been estimated that as many as three golden eagles per wind farm are killed each year by wind turbines. 

“Renewable energy sources, including wind energy, are critical for us to achieve a net-zero emissions future,” says Eric Lonsdorf, assistant professor of environmental sciences at Emory University. “We need to address conflicts between renewable energy and wildlife conservation so that we can combat climate change while also limiting damage to biodiversity.” 

Lonsdorf and colleagues are developing data-driven methods to determine how much effort is needed to save golden eagles in order to offset the impact of wind turbines on their populations. 

The Journal of Wildlife Management recently published their latest model for calculating the benefit of one mitigation strategy — removal of large, road-killed animals that can lead to golden eagles getting hit by cars. 

Quantifying the benefits of natural capital

Lonsdorf is an expert in natural capital, or the quantifiable benefits that nature provides humans. He translates ecological principles and data into computer models that enable industry leaders and policymakers to better manage natural resources. 

Co-authors of the current study include James Gerber and Deepak Ray, from the University of Minnesota; Steven Slater, from HawkWatch International; and Taber Allison, from the Renewable Energy Wildlife Institute. 

The U.S. Fish and Wildlife Service (FWS) monitors golden eagle populations, which are protected through the Bald and Golden Eagle Protection Act and the Migratory Bird Treaty Act. Threats to golden eagles include loss of habitat and prey. 

Additional threats that are directly linked to human activities include illegal shootings, electrocution at power poles, lead poisoning from consuming parts of bullets in the entrails of deer carcasses discarded at the site of hunters’ kills, collisions with cars at sites where the birds are scavenging roadkill and collisions with the blades of a wind turbine. 

Across the western United States, hundreds of wind turbines have gone up in sage-brush flats that are part of golden eagles’ core habitat, and many more turbines are planned. In order to meet the permit requirements of the FWS, wind-energy companies must agree to mitigate their impact on the animals by offsetting the predicted number of golden eagles that will fly into their turbines each year. 

Currently, the only offset strategy approved by the FWS for wind-energy companies is to retrofit power poles to prevent golden eagles from becoming electrocuted. 

Adding empirical data

For the past five years, Lonsdorf and his colleagues have combined their expertise to develop a range of potential offset strategies for golden eagle fatalities. 

Their current paper — an updated model for golden eagle mortality due to vehicle collisions based on data from Wyoming — considered myriad factors such as the population density for golden eagles in the region, the number and size of deer roadkill carcasses expected and the traffic volume on the roads. The model also incorporated observational evidence of eagle-carcass roadside interactions obtained by motion-triggered cameras, data that was lacking in a previous model the researchers created. 

The addition of this empirical data allowed the researchers to make estimates for how long a golden eagle typically spends at a carcass, how the decay rate of the carcass affects the number of visits from eagles and the effects of seasonality on the scavenging behavior of the eagles. 

The model results suggest that carcass relocation is a viable golden eagle mitigation strategy that could save up to seven golden eagles annually in some Wyoming counties. On average, the model indicates that the prompt removal of four roadside carcasses would save at least one golden eagle. 

The researchers can make a user-friendly version of the prediction framework available to the FWS and wind-energy companies if the FWS decides to approve carcass removal as an eagle mortality offset strategy. 

“We’re taking basic information about golden eagle ecology in the Anthropocene and developing it into predictive frameworks for how to protect them,” Lonsdorf says. “As wind energy continues to grow, more mitigation strategies will likely be needed. Our goal is to provide scientific evidence for a portfolio of methods to help accomplish a zero-net loss of golden eagles from wind-energy facilities.” 

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Natural compound found in plants inhibits deadly fungi

A 3D illustration of the newly emerged species of fungus Candida auris, which is often drug-resistant and has a high mortality rate. (Dr_Microbe, Getty Images)

By Carol Clark

A new study finds that a natural compound found in many plants inhibits the growth of drug-resistant Candida fungi — including its most virulent species, Candida auris, an emerging global health threat. The journal ACS Infectious Diseases published the discovery led by scientists at Emory University. 

Laboratory-dish experiments showed that the natural compound, a water-soluble tannin known as PGG, blocks 90% of the growth in four different species of Candida fungi. The researchers also discovered how PGG inhibits the growth: It grabs up iron molecules, essentially starving the fungi of an essential nutrient. By starving the fungi rather than attacking it, the PGG mechanism does not promote the development of further drug resistance, unlike existing antifungal medications. 

Laboratory-dish experiments also showed minimal toxicity of PGG to human cells. 

“Drug-resistant fungal infections are a growing healthcare problem but there are few new antifungals in the drug-development pipeline,” says Cassandra Quave, senior author of the study and associate professor in Emory School of Medicine’s Department of Dermatology and the Center for the Study of Human Health. “Our findings open a new potential approach to deal with these infections, including those caused by deadly Candida auris.” 

C. auris is often multidrug-resistant and has a high mortality rate, leading the Centers for Disease Control and Prevention (CDC) to label it a serious global health threat. 

“It’s a really bad bug,” says Lewis Marquez, first author of the study and a graduate student in Emory’s molecular systems and pharmacology program. “Between 30 to 60% of the people who get infected with C. auris end up dying.” 

An emerging threat 

Candida is a yeast often found on the skin and in the digestive tract of healthy people. Some species, such as Candida albicans, occasionally grow out of control and cause mild infections in people. In more serious cases, Candida can invade deep into the body and cause infections in the bloodstream or organs such as the kidney, heart or brain. 

Immunocompromised people, including many hospital patients, are most at risk for invasive Candida infections, which are rapidly evolving drug resistance. 

In 2007, the new Candida species, C. auris, emerged in a hospital patient in Japan. Since then, C. auris has caused health care-associated outbreaks in more than a dozen countries around the world with more than 3,000 clinical cases reported in the United States alone. 

A ‘natural’ approach to drug discovery 

Quave is an ethnobotanist, studying how traditional people have used plants for medicine to search for promising new candidates for modern-day drugs. Her lab curates the Quave Natural Product Library, which contains 2,500 botanical and fungal natural products extracted from 750 species collected at sites around the world. 

“We’re not taking a random approach to identify potential new antimicrobials,” Quave says. “Focusing on plants used in traditional medicines allows us to hone in quickly on bioactive molecules.” 

Previously, the Quave lab had found that the berries of the Brazilian peppertree, a plant used by traditional healers in the Amazon for centuries to treat skin infections and some other ailments, contains a flavone-rich compound that disarms drug-resistant staph bacteria. Screens by the Quave lab had also found that the leaves of the Brazilian peppertree contain PGG, a compound that has shown antibacterial, anticancer and antiviral activities in previous research. 

A 2020 study by the Quave lab, for instance, found that PGG inhibited growth of Carbapenem-resistant Acinetobacter baumannii, a bacterium that infects humans and is categorized as one of five urgent threats by the CDC. 

The Brazilian peppertree, an invasive weed in Florida, is a member of the poison ivy family. “PGG has popped up repeatedly in our laboratory screens of plant compounds from members of this plant family,” Quave says. “It makes sense that these plants, which thrive in really wet environments, would contain molecules to fight a range of pathogens.” 

Experimental results 

The Quave lab decided to test whether PGG would show antifungal activity against Candida. Laboratory-dish experiments demonstrated that PGG blocked around 90% of the growth in 12 strains from four species of Candida: C. albicans, multidrug-resistant C. auris and two other multidrug-resistant non-albicans Candida species. 

PGG is a large molecule known for its iron-binding properties. The researchers tested the role of this characteristic in the antifungal activity. 

“Each PGG molecule can bind up to five iron molecules,” Marquez explains. “When we added more iron to a dish, beyond the sequestering capacity of the PGG molecules, the fungi once again grew normally.” 

Dish experiments also showed that PGG was well-tolerated by human kidney, liver and epithelial cells. “Iron in human cells is generally not free iron,” Marquez says. “It is usually bound to a protein or is sequestered inside enzymes.” 

A potential topical treatment 

Previous animal studies on PGG have found that the molecule is metabolized quickly and removed from the body. Instead of an internal therapy, the researchers are investigating its potential efficacy as a topical antifungal. 

“If a Candida infection breaks out on the skin of a patient where a catheter or other medical instrument is implanted, a topical antifungal might prevent the infection from spreading and entering into the body,” Marquez says. 

As a next step, the researchers will test PGG as a topical treatment for fungal skin infections in mice. 

Meanwhile, Quave and Marquez have applied for a provisional patent for the use of PGG for the mitigation of fungal infections. 

“These are still early days in the research, but another idea that we’re interested in pursuing is the potential use of PGG as a broad-spectrum microbial,” Quave says. “Many infections from acute injuries, such as battlefield wounds, tend to be polymicrobial so PGG could perhaps make a useful topical treatment in these cases.” 

Scientists from the University of Toronto are co-authors of the paper, including Yunjin Lee, Dustin Duncan, Luke Whitesell and Leah Cowen. Whitesell and Cowen are co-founders and shareholders in Bright Angel Therapeutics, a platform company for development of antifungal therapeutics, and Cowen is a science advisor for Kapoose Creek, a company that harnesses the therapeutic potential of fungi. 

The work was supported by grants from the National Institutes of Health, National Center for Complementary and Integrative Health; the Jones Center at Ichauway, the CIHR Frederick Banting and Charles Best Canada Graduate Scholarship and the Canadian Institutes of Health Research Foundation. 

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NIH funds Emory center to advance cellular mechanics

"We are catalyzing the process of spreading our technology so that studying biomechanics becomes common and routine in biology," says Khalid Salaita, Emory professor of chemistry and director of the new Center for Molecular Mechanobiology.

By Carol Clark

The National Institutes of Health (NIH) awarded Emory University $5.6 million to establish a national center to advance pioneering technology for cellular mechanics. The center is directed by Khalid Salaita, Emory professor of chemistry, whose lab developed the first sensors for detecting cell-receptor forces at the molecular level. 

“We’ve been working on our molecular-force probes for more than a decade,” Salaita says. “We’ve demonstrated that these probes can be used to visualize, measure and map cellular forces down to the level of piconewtons. The center allows us to get this technology into the hands of end users — researchers in the biomedical sciences.” 

The Center for Molecular Mechanobiology encompasses labs from seven leading research institutions including: Children’s Hospital of Philadelphia, Dana-Farber Cancer Institute, Emory, Georgia Tech, Memorial Sloan Kettering, University of Utah and Vanderbilt University. 

The center members will use the molecular-force probes to investigate the biomechanics of processes such as the clotting of blood cells, the response of immune cells to an infection and the migration of cancer cells. Better understanding these processes may lead to the development of new treatments and therapies for a range of diseases and disorders. 

In addition to supplying the technology, the center will train researchers to use the molecular-force probes and help adapt the technology to answer specific biomedical research questions. 

“Working directly with the research community will help us to further refine and optimize the technology,” Salaita says. “We envision that measuring cellular forces will soon become part of the standard repertoire of biochemical techniques that scientists use to study living systems.” 

The center’s associate directors are Yonggan Ke (associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Emory and Georgia Tech) and Alexa Mattheyses (associate professor in the Department of Cell Developmental and Integrative Biology at the University of Alabama). 

The five-year award from the National Institute of General Medical Sciences is part of the NIH Biomedical Technology Optimization and Dissemination Centers program. The goal is to optimize and disseminate state-of-the-art, late-stage biomedical technologies. 

The first detailed view of mechanical forces

The Salaita lab works at the intersection of chemistry, biology and the physical sciences. It uses the building blocks of nature — nucleic acids — to create synthetic micro motors and probes for investigating fundamental questions of biology. 

The molecular-force probes, developed by the Salaita lab in 2011, provide the first detailed view of the mechanical forces on the surface of a cell. The technology can detect mechanical forces as fleeting as the blink of an eye and as faint as piconewtons — about one billionth the weight of a paperclip. 

The probes are made from strands of synthetic DNA tagged with fluorescence so that they function like molecular beacons, shining when they sense force. The technique is noninvasive, does not modify the cell and can be done with a standard fluorescence microscope. 

In 2014, the lab used the new method to demonstrate how adherent cells — the kind that form the architecture of all multicellular organisms — mechanically sense their environments, migrate and stick to things. 

In 2016, the molecular-force probes provided the first direct evidence for the mechanical forces of T cells, the security guards of the immune system. The lab’s experiments on T cells drawn from mice showed how they use a kind of mechanical “handshake” to test whether a cell they encounter is a friend or a foe. 

In 2017, the lab shined its molecular beacons on platelets, the cells in the blood whose job is to stop bleeding by sticking together to form clots and plug up a wound. That work revealed the key molecular forces on platelets that trigger the clotting process. 

In 2020, the lab and its collaborators combined advances in optical imaging with the molecular-force probes to capture forces at a resolution of 25 nanometers — far shorter than the length of a light wave. “That resolution is akin to being on the moon and seeing the ripples caused by raindrops hitting the surface of a lake on the Earth,” Salaita said at the time. 

Key technological goals 

The Center for Molecular Mechanobiology will build on this foundational work of the Salaita lab. It will focus on three key technological development goals:

• Optimizing the highest-resolution technique of the molecular-force probes so that it can be applied to a range of research questions. 

• Tagging cells based on their force level in order to use force as a marker to barcode cells and their receptors. The idea is to classify the mechanics of individual cells and then link these classifications to gene-expression levels to study the cause-and-effect relationships. 

• Amplifying the molecular-force signals to better understand the role of even the weakest forces involved in cellular mechanics, including those involved in the immune response. 

Researchers from throughout the country will come to the Center for Molecular Mechanobiology to receive hands-on training in the molecular-force probes and then return to their home labs to become ambassadors for the technology. 

“We’ll be adding a whole other layer of information for researchers working on everything from designing vaccines to cancer immunotherapy agents,” Salaita says. 

Decades ago, he points out, complicated techniques such as crystallography, PCR and mass spectrometry were not frequently used but have since become routine workhorses in the biomedical sciences. 

“We are catalyzing the process of spreading our technology so that studying biomechanics also becomes common and routine in biology,” Salaita says. “Molecular forces are a missing piece to understanding the way biology works.” 

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Buffalo slaughter left lasting impact on Indigenous peoples

"Bison were not just key to the economies of some Indigenous nations," says Emory economist Maggie Jones, co-author of the study. "The bison were also important cultural and spiritual symbols."

By Carol Clark

The mass slaughter of North American bison by settlers of European descent is a well-known ecological disaster. An estimated eight million bison roamed the United States in 1870, but just 20 years later fewer than 500 of the iconic animals remained. 

The mass slaughter provided a brief economic boon to some newly arriving settlers, hunters and traders of the Great Plains who sold the hides and bones for industrial uses. In contrast, Indigenous peoples whose lives depended on the bison suffered a devastating economic shock — one that still reverberates in these communities today, an economic study finds. 

The Review of Economic Studies published the findings by economists at Emory University, the University of Toronto and the University of Victoria. The researchers quantified both the immediate and long-term economic impacts of the loss of the bison on Indigenous peoples whose lives depended on the animals. 

 

Changes in the average height of bison-related people is one striking example of the fallout. Adult height across a population is one proxy of wealth and health given that it can be impacted by nutrition and disease, particularly early in development. 

Bison-reliant Indigenous men stood around six feet tall on average, or about an inch taller than Indigenous men who were not bison-reliant. 

“They were among the tallest people in the world in the mid-19th century,” says Maggie Jones, assistant professor of economics at Emory University and a co-author of the paper. “But after the rapid near-extinction of the bison, the height of the people born after the slaughter also rapidly declined.” 

Within one generation, the average height of Indigenous peoples most impacted by the slaughter dropped by more than an inch. 

“That’s a major drop, but given the magnitude of the economic shock it’s not necessarily surprising,” Jones says. 

By the early 20th century, the paper shows, the child-mortality rate of bison-dependent Indigenous nations was 16 percentage points higher and the probability of a working-age male reporting an occupation was 19 percentage points lower compared with Indigenous nations that were never reliant on bison. 

And income per capita remained 25% lower, on average, for bison-reliant nations compared to other nations through the latter half of the 20th century to today. The persistent gap could not be explained by differences in factors such as agricultural productivity, self-governance or application of the Dawes Act of 1887, which authorized the breakup of reservation land into small allotments parceled out for individual ownership. 

The researchers find that limited access to credit was one factor that curtailed the ability of some bison-reliant nations to adjust economically following the near-extinction of the bison. 

“One role of economists is to provide quantitative evidence that people can turn to when trying to design more effective policies,” Jones says. “By providing data that benchmarks disparities among bison-reliant people and the sources and evolution of these disparities, we hope to support efforts to improve the situation.” 

The paper’s other co-authors are economists Donn Feir (University of Victoria) and Rob Gillezeau (University of Toronto). 

Jones’ economic research focus includes history, labor and education. She uses quantitative tools from these areas to better understand the persistence of socioeconomic inequalities between groups in North America. 

The economic effects of the bison slaughter are an overlooked piece of the history of Indigenous peoples that she and her co-authors decided to investigate. 

For more than 10,000 years, bison served as the primary source of the livelihood for many Native Americans in regions of the Great Plains, the Northwest and the Rocky Mountains. Along with nutrition, the animals provided hides for clothing, lodging and blankets as well as bones for tools and implements. Nearly every part of the animal was used, including the brains to obtain grease for tanning hides and the stomach for creating bags and water containers. 

Evidence suggests that bison-reliant Indigenous societies enjoyed living standards comparable to, or in some cases better than, their European contemporaries. 

A gradual decline of the bison population started with the introduction of the horse and the arrival of Europeans. By 1870, however, mass slaughter of the animals began. Factors that drove the kill-off included the completion of the transcontinental railroad, improvements in European tanning technology that made bison hides more desirable and encouragement by the U.S. Army to eliminate the animals to help in their efforts to force Indigenous peoples onto reservations. 

In some regions, the bison was eliminated in a little more than a decade. Jones and her co-authors describe the slaughter as one of the largest and most rapid losses of a critical industry in North American history. 

“Centuries of human capital were built around the use of the bison, and within 10 to 20 years this economic underpinning disappeared,” Jones says. “And many channels of economic adjustment were cut off for Indigenous populations.” 

Indigenous people were forced onto reservations, their movements were restricted and they were not allowed to become citizens of the United States until 1924, the authors note. 

Among the sources Jones and her colleagues drew on to quantify the impacts of the bison slaughter are data collected by anthropologists and published in the 15-volume Smithsonian Handbook on Native American Populations. 

The economists defined nearly 24 Indigenous nations as “exposed to the slaughter,” based on geographic location and whether bison served as their primary food source. 

In their quantitative analysis of bison-reliant nations with Indigenous nations that were not bison-reliant, they controlled for factors such as differences in self-governance status of communities, differences in forms of agricultural productivity and the suitability of the land for agricultural production, the effects of the Dust Bowl and differential application of the Dawes Act. 

To measure the persistent effects of the bison’s decline on economic outcomes, the researchers drew from several sources: the Bureau of Indian Affairs (beginning in 1945), the U.S. Census (1980, 1990, 2000) and American Community Surveys (2007-2012 and 2015-2019). 

The data showed that the income of formerly bison-reliant nations remained 25% lower than those of other Indigenous nations through 2019. 

The researchers find relatively more favorable trajectories for bison-reliant communities that were located nearer to financial institutions in 1870 when the mass slaughter of the bison began. 

“Proximity to a bank and access to credit appeared to be one important factor to help alleviate some of the financial hardship generated by the bison’s decline,” Jones says. “Many Indigenous communities are still located in banking deserts. That makes it more difficult to adjust to any kind of hardship that comes your way.” 

The researchers are now exploring the potential role of psychological trauma on the economic outcomes of bison-reliant nations. 

“Bison were not just key to the economies of some Indigenous nations,” Jones says. “The bison were also important cultural and spiritual symbols. You would expect a psychological impact when they were ripped away. That’s an important part of the story that this paper didn’t get to tell.”

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Biologist gets the scoop on squash bug poop

The tell-tale gut: Tagging different strains of bacteria in different fluorescent colors allows the researchers to determine what strain an insect carries in its gut. (Jason Chen)

By Carol Clark

The squash bug carries a gut bacterium that is essential for the bug’s development into an adult. But when they hatch from their eggs, squash bug nymphs do not have the bacteria in their systems. That left scientists who study the interplay between insects and their internal microbes wondering: How do the nymphs acquire these essential microbes? 

Jason Chen, an Emory University graduate student in the Department of Biology, stumbled upon a clue one evening in the lab. 

He had finished up experiments on some adult squash bugs whose Caballeronia bacteria he had tagged with a red fluorescent protein. The bugs were housed in a plastic box with pieces of paper towel inside as bedding. He tossed some nymphs inside the container just as a place to hold them while he cleaned up for the day. 

“When I came back to turn the lights out, I noticed that all the nymphs had flocked around one of the poop spots left on a paper towel by the adults,” Chen says. “Normally nymphs wander around a lot but they had all stopped around this poop. They were transfixed by it. I wondered what that behavior meant.” 

He eventually checked the nymphs under a microscope and saw that their guts lit up with the same red fluorescence as the adults. More experiments confirmed the finding — nymph squash bugs eat the feces of adults to acquire the bacteria they need to grow. 

Current Biology published the discovery, which may offer insights for improved methods to control the squash bug, a significant agricultural pest. 

Read more about the discovery here.

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