Monday, February 28, 2022

Data-driven study digs into the state of U.S. farm livelihoods

"Farmers are fundamental to our survival, their work is risky and difficult, and ensuring their quality of life is necessary for U.S. agriculture to persist," says Emily Burchfield, Emory assistant professor of environmental sciences and lead author of the study.

By Carol Clark

U.S. agricultural systems are world leaders in the production of food, fuel and fiber. This high level of production enables U.S. consumers to spend an average of only 8.6 percent of their disposable income on food, a percentage that has been trending downward since 1960. Growing evidence, however, shows that many hidden costs of cheap food may be passed on through factors such as reduced nutritional content, environmental degradation and the diminishing livelihoods of U.S. farm operators. 

A major new study led by Emory University digs deeper into the question of why, despite the extraordinary productivity of U.S. agriculture, U.S. farm operators are systematically losing money. The journal Frontiers of Sustainable Food Systems published the analysis, which drew from publicly available data from the U.S. Department of Agriculture, the U.S. Bureau of Economic Analysis and other sources. 

“It’s not that agriculture as a sector is not profitable,” says Emily Burchfield, assistant professor in Emory’s Department of Environmental Sciences and lead author of the study. “It’s that, despite hard work and significant financial risk, many of the people who operate U.S. farms are not able to make a decent living at it.” 

Rising input costs, shrinking production values, commodity specialization and challenges to land access all appear to be connected to declining farm operator livelihoods, the study concludes. 

“We’ve shown in a quantitative, systematic way the extent to which these trends are happening and, in many cases, how they appear to be worsening,” Burchfield says. 

An online data repository

“People who work in the agricultural space already know that it is difficult to make a living as a farmer,” she adds. “In this paper, we’ve cleaned and merged tremendous amounts of data from multiple sources to bring key information together into one place. This allows us to tell a more complete and clear story about how and why this is happening at a national scale.” 

The researchers deposited the cleaned and merged data into a free, online repository ( so that other agricultural stakeholders can easily access it. They hope that their “one-stop,” centralized data hub on farmer livelihoods will serve as an educational tool and inspire more research into the topic. 

The USDA reported in 2020 that the average funds generated by farm operators to meet living expenses and debt obligations, after accounting for production expenses, have been negative for nine out of the last 10 years. In 2017, for instance, median net-cash farm income was $1,035 in the red per farm household in the country. 

Paying to farm

In many regions of the United States, the authors write, farm operators actually have to pay to engage in the labor- and time-intensive act of operating a farm. 

“What we were really surprised to find in the data is that the low, or negative, median farm operator income applies even when you factor in government subsidies,” Burchfield says. “Given that the federal government is subsidizing farming with billions of dollars annually, it raises the question of how we might do so more effectively. How are we going to convince folks to continue growing our food if they are locked into a system where they can’t make money?” 

Burchfield’s research combines spatial-temporal, social and environmental data to understand the future of food security in the United States, including the consequences of a changing climate. 

Co-authors of the current paper include: Britta Schumacher, a former Emory research assistant in Burchfield’s lab; Andrea Rissing, an Emory post-doctoral fellow in the lab; and Kaitlyn Spangler, a post-doctoral fellow at Penn State. 

Relying on off-farm income

Understanding how much income individual farms are losing on average is complicated by farm households often having a family member bringing in income through a non-farm occupation, Burchfield notes. In 2019, the USDA reported that on-farm production contributes to less than 25 percent of farm household income, on average, with the remaining 75 percent earned off-farm. This suggests that many farmers rely on off-farm income to stay afloat. 

“Farming is one of the hardest jobs on the planet,” Burchfield says, “and it’s going to get even harder due to climate change. The combination of more gradual shifts in average climate conditions, and the increased prevalence of extreme weather events, presents a serious challenge to farmers.” 

These ongoing challenges, the authors argue, require an urgent rethinking of how federal subsidies can play a role in encouraging and supporting new, adaptive approaches to agriculture. 

U.S. farm operations currently cover approximately 900 million cultivated acres, more than half of the nation’s land area. And three crops — corn, soy and wheat — are cultivated exclusively on more than two thirds of agricultural acres. 

“A lack of crop diversification can make farming increasingly brittle and less adaptable,” Burchfield says. “Climate change, meanwhile, makes the need for innovation and adaptation more crucial and inevitable.” 

The paper also highlights the lack of diversification among farm operators. Statistically, the “average” U.S. farmer is a 58-year-old white male. Those not identifying as white currently operate about 7 percent of farmland representing just 5 percent of operations. Only 1.4 percent of operators identify as Black, and these operators are heavily concentrated in the Southeast. And, on average, white operators receive twice as much from federal subsidy programs ($14,000 per farm) as Black operators ($6,400 per farm). 

A call for diversity of people, plants and practices

“We need better data to track the persistent inequities at the intersection of race, class and livelihoods in the agriculture space,” Burchfield says. 

She recommends finding ways to support the diversity of people, plants and practices in the national farm landscape to help address the growing issues of agricultural sustainability and climate change. “Small-scale experimentation and the emergence of grassroots alternatives along with technical innovations are all needed in order to better weather the challenges,” she says. 

Burchfield also cites the need for the availability of more fine-scale data on the livelihoods of farmers that goes beyond yields and acreage to cover issues such as access to health insurance. “Farmers are fundamental to our survival, their work is risky and difficult, and ensuring their quality of life is necessary for U.S. agriculture to persist,” she says. 

As Burchfield and her co-authors conclude: “Measuring and monitoring agricultural progress using only metrics of production, efficiency and revenue masks the lived realities of the humans operating our farms.” 

The research was supported in part by the U.S. Department of Agriculture and the National Science Foundation.


Diverse landcover boosts yields for major U.S. crops, study finds

Wednesday, February 23, 2022

Snail competition leads to fewer parasites that cause schistosomiasis

Field research was conducted in the Mwanza region of Tanzania where schistosomiasis is endemic. Running water is often not accessible in the area and many people use surface water ponds and hand-dug open wells that dot the clay-soil landscape. (Civitello Lab)

By Carol Clark

Schistosomiasis is a debilitating disease caused by a parasitic worm that develops in freshwater snails before infecting people. Knocking back snail populations with pesticides is one method to control the spread of the disease, also known as “snail fever.” 

A new study led by Emory University, however, shows that schistosome transmission can actually be highest when freshwater snail populations are low. The Proceedings of the National Academy of Sciences published the study, the first to demonstrate how the size of a freshwater snail population relates to its parasitic infection rate. 

“We’ve shown that the more snails you have in a freshwater source, the less dangerous each individual snail is, in terms of the number of parasites they’re releasing,” says David Civitello, an Emory assistant professor of biology and lead author of the study. “The incredible strength of our finding is that we’ve demonstrated the effect both in the field, using natural transmission sites, and in an experimental context, through outdoor laboratory experiments.” 

The research carries important implications for policies aimed at reducing the transmission of schistosomiasis. Considered one of the most significant of the neglected tropical diseases, the parasites that cause schistosomiasis currently infect more than 200 million people. 

“Our results suggest that if you apply a heavy dose of pesticides to reduce a snail population, the infectivity of the remaining snails might actually skyrocket,” Civitello says. “It’s basically impossible to kill every snail and so you set the stage for a rebound in infection risk. As the snail population begins to recover, our data tells us that this is a time with extremely high potential for transmission of the parasites to humans.” 

Click on the image for a detailed view of the transmission cycle of schistosomiasis. (CDC)

Previous laboratory experiments had found that when an individual freshwater snail infected with the parasite is well fed, it can generate as many as thousands more parasites per day compared to an underfed snail. In fact, an underfed infected snail may generate as few as a single parasite per day. 

“In general, when an animal needs to fight off an infection of some kind, it helps to have good nutrition to support the immune system,” Civitello says. “It appears to be the opposite case in these freshwater snails. When the snails are full of energy, it provides more nutrients for the parasites to steal from them and to reproduce.” 

Chronic infections of schistosomiasis cause considerable morbidity in sub-Saharan Africa and parts of the Middle East, South America and Southeast Asia. The disease cycles between humans and freshwater snails that live in water sources where people may bathe, wash their clothes and dishes and collect water for household use. Children, who like to play in water, are at especially high risk for infection. 

When eggs of the parasitic worms hatch in water, the larvae burrow into snails. Once the larvae develop into free-swimming worms, they burrow back out of their snail hosts and return to the water. These swimming worms can then burrow into the skin of people who come into contact with the water. 

Inside their human hosts, the worms enter blood vessels where they eat red blood cells for fuel as they mature into adults, pair up and mate. The female lays hundreds of thousands of eggs per day. Many of the eggs are excreted through feces and urine that re-enters water sources, continuing the cycle of infection. Some of the eggs, however, become lodged in the tissues and organs of their human hosts, leading to immune reactions and progressive damage to organs, such as the liver, the bladder, kidneys and the urogenital tract. One of the classic symptoms of a chronic infection is blood in the urine. 

"It's important to unite the ecology of a pathogen with human disease interventions and control measures," says David Civitello (center), shown in the field in Tanzania.

The prescription medication Praziquantel treats schistosomiasis but has limitations. “One problem is that the drug kills the mature adult schistosomes in humans, but not schistosomes that are only five or six weeks old and still maturing,” Civitello says. 

And a follow-up drug treatment does not eliminate the infection in the environment. 

“There is growing recognition in recent years that effective control of freshwater snails is needed, along with treatment of people, in order to disrupt transmission of schistosomiasis,” Civitello says. “In many cases, however, snail control policies have not been updated for decades.” 

For the PNAS paper, the researchers wanted to test whether the effect of food intake seen on the infection rate of individual freshwater snails in a laboratory would scale up to a population in the wild. Their hypothesis was that the larger the snail population, the more the snails would have to compete for food resources, lowering their energy levels along with their infectivity rate. 

They conducted field research in the Mwanza region of Tanzania where schistosomiasis is endemic, in collaboration with Tanzania’s National Institute for Medical Research Mwanza Center. Running water is not accessible in villages in the area and many people use surface water ponds and hand-dug open wells that dot the clay-soil landscape. 

The researchers found that snails collected from these water sources where the snail populations were dense were poorly infectious. In contrast, in the water sources where the snail population was low, their parasitic infection rate was high. 

The outdoor laboratory experiments, conducted in collaboration with the University of South Florida, further showed how the growth of a snail population from low to high density creates a burst of infectivity among the population before competition once again forces the infectivity to subside. 

“Our results suggest that, if you treat water bodies infrequently with a pesticide to control snails, you are likely to soon get a rebound of the snail population with a higher infectivity rate, potentially creating a surge of transmission to people,” Civitello. “It may be better either to not apply a pesticide at all, or else to apply the pesticide more frequently to prevent the snails rebounding.” 

The Civitello Lab plans to continue to collaborate with colleagues in Tanzania to gather more detailed data to help develop the most effective methods of freshwater snail control, for use in combination with other preventative methods for schistosomiasis. 

“It’s important to unite the ecology of a pathogen with human disease interventions and control measures,” Civitello says. 

Co-authors of the PNAS include: Safair Kinung’hi, Teckla Angelo, Moses Mahalila and Jenitha Charles (National Institute for Medical Research Mwanza Center); Jason Rohr (University of Notre Dame); Karena Nguyen, Rachel Hartman, Naima Starkloff and Lynda Bradley (Emory Department of Biology); Andres Manrique (University of Florida); Bryan Delius (Duquesne University); and Roger Nisbet (University of California, Santa Barbara). 

The work was supported by the U.S. National Institute of Allergy and Infectious Diseases, the National Science Foundation, the National Institutes of Health, and the Indiana Clinical and Translational Sciences Institute.


Water temperature key to schistosomiasis risk and prevention strategies

Thursday, February 17, 2022

Antibiotic used on food crops affects bumblebee behavior, lab study finds

A wild bumblebee visits a blossom. The current study involved lab experiments on a different species of bumblebee as a first step to understanding the potential effects of the agricultural use of streptomycin on pollinators.

By Carol Clark

An antibiotic sprayed on orchard crops to combat bacterial diseases slows the cognition of bumblebees and reduces their foraging efficiency, a laboratory study finds. Proceedings of the Royal Society B published the findings by scientists at Emory University and the University of Washington. 

The research focused on streptomycin, an antibiotic used increasingly in U.S. agriculture during the past decade. 

“No one has examined the potential impacts on pollinators of broadcast spraying of antibiotics in agriculture, despite their widespread use,” says Laura Avila, first author of the paper and a post-doctoral fellow in Emory’s Department of Biology. 

The current study was based on laboratory experiments using an upper-limit dietary exposure of streptomycin to bumblebees. It is not known whether wild bumblebees are affected by agricultural spraying of streptomycin, or whether they are exposed to the tested concentration in the field. 

“This paper is a first step towards understanding whether the use of streptomycin on food crops may be taking a toll on pollinators that benefit agriculture,” says Berry Brosi, senior author of the paper. Brosi began the work as a faculty member in Emory’s Department of Environmental Sciences and is currently with the University of Washington. 

Funded by a U.S. Department of Agricultural grant, the researchers will now conduct field studies where streptomycin is sprayed on fruit orchards. If a detrimental impact is found on bumblebees, the researchers hope to provide evidence to support recommendations for methods and policies that may better serve farmers. 

“Production of our food, farmer livelihoods and the health of pollinators are all tied together,” Brosi says. “It’s critically important to find ways to maintain agricultural production while also conserving the ecosystem services — including pollination — that a biodiverse ecosystem provides.” 

"I decided to become a bee biologist because I wanted to understand how the natural environment can influence agriculture and vice versa," says Laura Avila, above. Her work spans experiments in both the lab and field.

Based on established evidence, the researchers hypothesize that the negative impact of streptomycin on bumblebees seen in the lab experiments may be due to the disruption of the insects’ microbiome. 

“We know that antibiotics can deplete beneficial microbes, along with pathogens,” Avila says. “That’s true whether the consumers of the antibiotics are people, other animals or insects.” 

Avila is a member of the lab of Nicole Gerardo, Emory professor of biology and an entomologist who studies the co-evolution of insect-microbe systems. 

During the past decade, the spraying of antibiotics on U.S. crops has increased exponentially as farmers battle a rise in plant bacterial infections. “Fire blight” can turn the blossoms and shoots of apple and pear trees black, making them appear scorched by fire, and can also kill entire trees. “Citrus greening,” also known as “yellow dragon disease,” turns citrus fruits green, bitter and unusable and has devasted millions of acres of crops throughout the United States and abroad. 

“I’ve seen the struggle of making a living by producing crops, how expensive and difficult it can be to control diseases and pests,” says Avila, who grew up in a coffee-producing region of Costa Rica. 

Largely untouched forests bordered her family farm. “The diversity all around us fascinated me,” Avila says. “I decided to become a bee biologist because I wanted to understand how the natural environment can influence agricultural production and vice versa.” 

Seventy-five percent of the world’s food crops depend on pollination by at least one of more than 100,000 species of pollinators, including 20,000 species of bees, as well as other insects and vertebrates like birds and bats. And yet, many of the insect pollinator species, particularly bees, face risks of extinction. 

Previous studies have shown that the antibiotic tetracycline, used to treat pathogens in managed honeybee hives, can alter the gut microbiome of the insects and indirectly increase susceptibility to pathogens and mortality. Exposure to high oxytetracycline concentrations has also been found to have a similar effect on the bumblebee gut microbiome, decreasing their immunity to pathogens. And exposure to high doses of tetracycline have been found to affect honeybee learning, while oxytetracycline slows the onset of foraging in managed colonies. 

For the current paper, the researchers conducted lab experiments with managed bumblebees, Bombus impatiens, to test the effects of an upper-limit dietary exposure to streptomycin. Half of the bees were fed on plain sucrose, or sugar water, to simulate nectar. The remaining bees were fed on sucrose dosed with streptomycin. 

After two days on this diet, the bees were presented different-colored cardboard strips — one yellow and the other blue. One color was saturated with plain water and the other was saturated with sucrose. In a series of training trials, each bee was presented a single, colored strip until it touched it with its antennae or proboscis. 

The researchers measured the number of trials it took for a bee to show a preference for the color strips saturated with sucrose. The bees fed streptomycin often required roughly three times as many trials to make the association, relative to the other bees. The antibiotic-treated bees were also more likely to display avoidance behavior towards either of the stimuli. 

Those bees that passed a training threshold were given a short-term memory test five minutes later. Each bee was presented with both of cardboard strips simultaneously and allowed to select one. The rate at which the bees dosed with streptomycin selected the sucrose reward was around 55 percent, while the untreated bees selected the sucrose at a rate of nearly 87 percent. 

To assess foraging ability, trials were conducted in a foraging chamber containing an experimental array of artificial flowers that dispensed sucrose or plain water. The flowers were either blue or yellow but were identical in size and shape. Each bee was outfitted with a tiny, ultra-lightweight radio frequency identifier “backpack” to monitor its movements among the artificial flowers, which were each equipped with a short-range antenna and tracking system. 

The computer-analyzed results showed that the antibiotic-exposed bees visited far fewer sucrose-rewarding flowers relative to the control bees. 

In the spring, Avila and Brosi will launch field studies to determine if broadcast spraying of streptomycin affects bumblebees in pear orchards. 

“I was surprised at how strong an effect we found of streptomycin on bumblebees in the laboratory experiments,” Brosi says. “That makes it imperative to learn if we see similar effects in an agricultural setting.” 

The timing of antibiotic application, the amount applied and possible alternatives to the use of an antibiotic may be potential mitigation methods should the field research identify harmful impacts on bumblebees of agricultural spraying of streptomycin, the researchers note. 

Co-authors of the current study include Elizabeth Dunne, who did the work as an Emory environmental sciences major and has since graduated; and David Hofmann, a former post-doctoral fellow in Emory’s Department of Physics.


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