Agricultural impact of flooding

I can barely hear Esther Ngumbi over the roar of greenhouse fans as she shows me around her rooftop laboratory in Morrill Hall. The benches are full of tomato plants, and the tomatoes don't look good. Half of the plants are submerged in bins of water. Their leaves are yellow and withering. Some of the dying tomatoes have flowered. I see one or two baby tomatoes on a couple of spindly plants.

This isn't the only torture inflicted on the tomatoes. Someone has tied little baggies to their stems. Inside the bags, fat green caterpillars are chowing down on the tomato leaves.

Entomology professor Ngumbi has questions -- lots of them -- and this is how she's set out to answer some of them. She is purposely flooding the tomatoes to see how they might respond to flooded conditions in farmers' fields -- a scenario that is becoming more common as a result of climate change.

"In nature, there are many stressors on plants during flooding," Ngumbi says. "Once the tomatoes get flooded, they're already weak, so most likely they will be attracting insects, which like to eat weaker plants. We're investigating how the plants deal with the combined stress of flooding and herbivory."

This explains the caterpillars. They are the larval form of Manduca sexta, the tobacco hornworm. They are feasting on one of the two heirloom tomato varieties Ngumbi is using in the experiment: Cherokee purple and striped German.

Half of the tomato plants in the greenhouse are not flooded, allowing the team to compare the stressed plants with those grown in more common conditions. But there are more investigations going on here.

"Also, within this experiment, we're looking at the microbes," Ngumbi says. "We want to understand how the microbial community changes in flooded conditions."

One of Ngumbi's key focuses is how soil microbes influence plant health and productivity. She's fascinated by mycorrhizal fungi, which form intimate associations with plant roots, offering essential elements like nitrogen to the plants in exchange for glucose supplied by the roots.

The tomato plants are all growing in soil from an Illinois farm, but half were also inoculated with mulch from a local farmer who has developed his own recipe for nurturing mycorrhizal fungi in the soil. Ngumbi wants to see if this inoculation makes any difference to the plants' ability to defend themselves from the fat caterpillars.

To measure plant defenses, Ngumbi's team collects samples of gases emitted by the plants and screens them for volatile organic compounds, the chemicals plants use to ward off bugs that would eat them.

Two years later, Ngumbi publishes the results of these and other laboratory experiments. She found that the two tomato varieties differed in gene expression and in the volatile compounds they emitted -- before any intervention. And when flooded, both varieties of tomatoes had very different chemical emission profiles than when grown in normal conditions. Herbivory influenced the production of these volatile compounds, but not as much as flooding did.

Today, the experiments continue, and Ngumbi's interest in the effects of flooding has only intensified. In a new review published in the journal Trends in Plant Research, she spells out the many changes that occur when plants are inundated with water for days or weeks at a time.

"Flooding is different from other climate-related stressors because it deprives plants of oxygen, an essential and indispensable element and substrate for plant growth and development," Ngumbi writes. Flooding disrupts plant metabolism and energy generation. It interferes with photosynthesis. Flooding kills beneficial bacteria and promotes pathogenic microbes in the soil. It also can compromise plants' ability to defend themselves from disease and harmful insects like the tobacco hornworm.

Ngumbi also warns that increased flooding can undermine decades of research aimed at making plants more resilient to climate change. Flooding may thwart efforts to build soil quality and microbial health to make crops more resilient to stressors such as heat and drought. Flooding also may eliminate gains derived from genetic engineering or plant breeding.

With flooding intensity and frequency predicted to increase by roughly 7% for every 1° C increase in global average temperatures, Ngumbi writes, scientists must consider the impacts of floods to "protect the monumental gains made in building climate-resilient crops."

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Agriculture: Less productive yet more stable pastures

Climate change will have a considerable influence on the biodiversity and productivity of meadows and pastures. However, according to the results of the large-scale climate and land use experiment, GCEF, which has been conducted at the Helmholtz Centre for Environmental Research (UFZ) for 10 years, the extent of these changes depends on the land use. Grassland optimised for high yield responds much more sensitively to periods of drought than less intensively used meadows and pastures. According to an article recently published in Global Change Biology, this can certainly have economic consequences for the farmers affected.

Grassland is one of the most important and most widespread ecosystems on earth. Such open landscapes with grasses and herbs not only cover more than one quarter of the entire land surface but also store at least one third of the terrestrial carbon, are crucial for food production, and can be extremely species-rich in a relatively small area. But what is the future of these habitats? The study provides new insights into this question.

It has long been clear that two environmental changes are threatening the world's grasslands. Particularly in Europe, grasslands are now fertilised much more heavily, mowed more frequently, and grazed more intensively. In addition, farmers often sow only a handful of grass varieties that promise a particularly high yield. This intensification of land use is fundamentally changing the species composition and functionality of meadows and pastures. The same applies to climate change. For Germany, climate change will result in a shift in the seasonal distribution of precipitation as well as an increase in hydrological extremes (e.g. heavy rainfall and droughts), among other things. It is considered the second largest threat for these ecosystems.

When both changes come together, they can reinforce each other. However, nobody yet knows exactly what will happen. Most experiments on this topic have so far focussed on either the climate or land use. "What makes our study unique is that we investigated the interaction of both factors," explains Dr Lotte Korell, biologist at the UFZ and first author of the publication.

This was made possible by the large-scale and long-term experiment of the UFZ in Bad Lauchstädt near Halle, the Global Change Experimental Facility (GCEF). It consists of 50 plots, each measuring 16 × 24 m; these are used with varying degrees of land use intensity. Temperatures and precipitation levels can also be manipulated with the help of mobile roof systems. For example, some plots receive 10% more precipitation in spring and autumn and 20% less in summer than the untreated control plots. This roughly corresponds to the conditions that climate models project for central Germany.

An eight-year data series from this experiment has now been compiled for the new study. The researchers analysed the biodiversity and productivity of the plants on the differently used plots between 2015 and 2022. "This period includes three of the driest years this region has experienced since beginning of records," recalls Korell. These droughts apparently had a much stronger effect on the plants than the experimentally simulated climate change.

However, in both cases, the trend pointed in the same direction: species-rich grassland that is only rarely mown or sparsely grazed withstood the heat and drought much better than the intensively used high-performance meadows. "Among other factors, this is probably related to the diversity of species," says Korell. This varied greatly depending on the land use of the grasslands.

A diverse mixture of more than 50 native grasses and herbs grew on the less intensively used meadows and pastures of the GCEF. However, on the intensively used grassland, the UFZ team had sown only the five grass varieties recommended to farmers by the Saxony-Anhalt State Institute for Agriculture and Horticulture for drier sites at the start of the experiment. These included varieties of meadow grass (Dactylis glomerata) and perennial ryegrass (Lolium perenne).

Because such grasses are bred for maximum yield and were also heavily fertilised -- as is common in agricultural practice -- the intensive meadows were initially much more productive than the more diverse grasslands. However, they were able to make use of this advantage only in favourable climatic conditions and were not able to withstand the drought as well as the plants in the low-intensity meadows and pastures. In times of drought, the grasses in the intensively used meadows increasingly died back and were replaced by other species such as chickweed (Stellaria media), shepherd's purse (Capsella bursa-pastoris), dandelion (Taraxacum officinale), and small-flowered cranesbill (Geranium pusillum). "These are mostly short-lived species that survive as seeds," explains Dr Harald Auge, also a biologist at the UFZ and senior author of the study. When the more competitive plants succumb to drought, these species take the opportunity to invade their habitats: they either migrate from the low-intensity grassland or germinate from the seed stock in the soil.

This shift in species composition is not particularly welcomed by farmers, especially because most of the new arrivals have a lower fodder quality than the grasses originally sown. The common ragwort (Senecio vulgaris), which was frequently represented among the immigrating species in the experiment, is in fact poisonous. All of this reduces the productivity of the land.

Farmers have long been aware of this kind of degradation of high-performance grassland by immigrating species. They therefore expect to have to plough up and reseed their land every few years. "However, climate change may accelerate this need and lead to additional costs," says Korell. Perhaps everything will go well for a few years and it will rain enough. However, it is also possible that several dry summers will follow one another. Climate change is making conditions even more unpredictable.

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Sustainable plastics from agricultural waste

In our rapidly industrialized world, the quest for sustainable materials has never been more urgent. Plastics, ubiquitous in daily life, pose significant environmental challenges, primarily due to their fossil fuel origins and problematic disposal.

Now, a study led by Jeremy Luterbacher's team at EPFL unveils a pioneering approach to producing high-performance plastics from renewable resources.

The research, published in Nature Sustainability, introduces a novel method for creating polyamides -- a class of plastics known for their strength and durability, the most famous of which are nylons -- using a sugar core derived from agricultural waste.

The new method leverages a renewable resource, and also achieves this transformation efficiently and with minimal environmental impact.

"Typical, fossil-based plastics need aromatic groups to give rigidity to their plastics -- this gives them performance properties like hardness, strength and high temperature resistance," says Luterbacher.

"Here, we get similar results but use a sugar structure, which is ubiquitous in nature and generally completely non-toxic, to provide rigidity and performance properties."

Lorenz Manker, the study's lead-author, and his colleagues developed a catalyst-free process to convert dimethyl glyoxylate xylose, a stabilized carbohydrate made directly from biomass such as wood or corn cobs, into high-quality polyamides.

The process achieves an impressive atom efficiency of 97%, meaning almost all the starting material is used in the final product, which drastically reduces waste.

The bio-based polyamides exhibit properties that can compete with their fossil counterparts, offering a promising alternative for various applications.

What's more, the materials demonstrated significant resilience through multiple cycles of mechanical recycling, maintaining their integrity and performance, which is a crucial factor for managing the lifecycle of sustainable materials.

The potential applications for these innovative polyamides are vast, ranging from automotive parts to consumer goods, all with a significantly reduced carbon footprint.

The team's techno-economic analysis and life-cycle assessment suggest these materials could be competitively priced against traditional polyamides including nylons (e.g. nylon 66), with a global warming potential reduction of up to 75%.

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New study is first step in predicting carbon emissions in agriculture

For the first time, researchers at the University of Minnesota Twin Cities (UMN) and the University of Illinois Urbana-Champaign (UIUC) have demonstrated that it is possible to provide accurate, high-resolution predictions of carbon cycles in agroecosystems, which could help mitigate the impacts of climate change.

The study by scholars from the UMN-led National Artificial Intelligence Institute for Climate-Land Interactions, Mitigation, Adaptation, Tradeoffs and Economy (AI-CLIMATE) and UIUC-led Agroecosystem Sustainability Center was recently published in Nature Communications, a peer-reviewed, open access, scientific journal.

The study's findings are a critical first step in developing a credible Measurement, Monitoring, Reporting, and Verification (MMRV) of agricultural emissions that can be used to incentivize the implementation of climate smart practices while boosting rural economies. This follows the national strategy, set by the White House, highlighting the need to quantify greenhouse gas emission across sectors with a goal of net-zero emissions by no later than 2050.

Accurate, scalable, and cost-effective monitoring and reporting of greenhouse gas emissions are needed to verify what are called "carbon credits" or permits that offset greenhouse gas emissions. Farmers can be reimbursed for practices that reduce greenhouse gas emissions. Agriculture accounts for about 25 percent of greenhouse gas emissions, but large corporations can be hesitant about purchasing these credits without knowing how much carbon is being stored.

Right now, to accurately gather carbon data, a farmer would need to hire someone to come to their farm, take what is called a soil core (vertical profile of the soil), and send that back to the lab for analysis.

"To gather the amount of data needed at each individual farm, it could cost the farmers time and money that they may not be willing to give," said Licheng Liu, the lead author and a research scientist in the University of Minnesota Department of Bioproducts and Biosystems Engineering.

The emerging field of Knowledge-Guided Machine Learning (KGML), pioneered by researchers at the University of Minnesota, combines the strength of artificial intelligence (AI) and process-based models from physical sciences. With observations in the United States Corn Belt, the KGML-ag framework significantly surpasses both process-based and pure machine learning models in accuracy, especially with limited data. Remarkably, KGML-ag operates over 10,000 times faster than traditional process-based models, delivering high-resolution and high-frequency predictions cost-effectively.

"These knowledge-guided machine learning (KGML) techniques are fundamentally more powerful than standard machine learning approaches and traditional models used by the scientific community to address environmental problems," said Vipin Kumar, a University of Minnesota Regents Professor and William Norris Endowed Chair in the Department of Computer Science and Engineering and a researcher in the AI-CLIMATE Institute, whose group has pioneered the development of the KGML framework.

Instead of taking soil cores at every farm, with KGML-ag, researchers can use the power of satellite remote sensing, computational models, and AI to provide an estimate of carbon in each individual field. This allows for compensation to individual farmers that are fair and accurate. The researchers say this is key to fostering trust in carbon markets and supporting the adoption of sustainable practices.

"KGML-ag combines the most advanced understanding of mechanisms in agriculture with the state-of-the-art AI techniques and thus offers a new powerful lens to monitor and manage our agricultural ecosystems," said Zhenong Jin, the corresponding author for this study and assistant professor in the University of Minnesota Department of Bioproducts and Biosystems Engineering, who co-leads the KGML special interest group in the AI-CLIMATE.

Now, AI-CLIMATE researchers are investigating the potential of the KGML framework for forestry, leveraging its capabilities to address the pressing challenges in sustainable forestry management and the capturing and storing of carbon. The team is also exploring a KGML-based data assimilation approach to make use of the rapidly growing different kinds of satellite data flexibly.

"The KGML is one of the key research topics of the AI-CLIMATE," said Shashi Shekhar, a University of Minnesota ADC Chair and Distinguished McKnight University Professor in the Department of Computer Science and Engineering and the lead researcher of the AI-CLIMATE Institute. "These initial results demonstrate the immense potential of AI for developing more accurate and cheaper methods for estimating emissions from agriculture. This may lubricate carbon markets and incentivize adoption of climate-smart practices."

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Scammed! Animals 'led by the nose' to leave plants alone

University of Sydney researchers have shown it is possible to shield plants from the hungry maws of herbivorous mammals by fooling them with the smell of a variety they typically avoid.

Findings from the study published in Nature Ecology & Evolution show tree seedlings planted next to the decoy smell solution were 20 times less likely to be eaten by animals.

"This is equivalent to the seedlings being surrounded by actual plants that are unpalatable to the herbivore. In most cases it does trick the animals into leaving the plants alone," said PhD student Patrick Finnerty, the study's lead author from the School of Life and Environmental Sciences Behavioural Ecology and Conservation Lab.

"Herbivores cause significant damage to valuable plants in ecological and economically sensitive areas worldwide, but killing the animals to protect the plants can be unethical," he said.

"So, we created artificial odours that mimicked the smell of plant species they naturally avoid, and this gently nudged problematic herbivores away from areas we didn't want them to be.

"Given that many herbivores use plant odour as their primary sense to forage, this method provides a new approach that could be used to help protect valued plants globally, either in conservation work or protecting agricultural crops."

The experiment, conducted in Ku-ring-gai Chase National Park in Sydney, used the swamp wallaby as model herbivore.

The researchers selected an unpalatable shrub in the citrus family, Boronia pinnata, and a palatable canopy species, Eucalyptus punctata, to test the concept.

The study compared using B. pinnata solution and the real plant and found both were equally successful at protecting eucalyptseedlings from being eaten by wallabies.

As part of his doctoral research, Mr Finnerty has also tested the method successfully with African elephants, but that fieldwork does not form part of this research paper.

Previous attempts to use repellent substances, such as chilli oil or motor oil, to control animal consumption of plants have inherent limitations, Mr Finnerty said.

"Animals tend to habituate to these unnatural cues and so deterrent effects are only temporary," he said.

"By contrast, by mimicking the smell of plants herbivore naturally encounter, and avoid in day-to-day foraging, our approach works with the natural motivators of these animals, with herbivores less likely to habituate to these smells."

Researchers took this idea and used solutions that produce these undesired aromas.

"As a management tool to protect palatable plants, our technique offers many advantages over real plants as a repellent," Mr Finnerty said.

"Our approach should be transferable to any mammalian, or potentially invertebrate, herbivore that relies primarily on plant odour information to forage and could protect valued plants globally, such as threatened species."

Current solutions to herbivore-related problems often involve costly and environmentally impactful measures such as lethal control or fencing.

The new research introduces an alternative low-cost, humane strategy based on understanding herbivores' foraging cues, motivations and decisions.

"Plant browsing damage caused by mammalian herbivore populations like deer, elephants and wallabies is a growing global concern," said senior study author Professor Clare McArthur.

"This damage is one of the greatest limiting factors in areas of post-fire recovery and revegetation, destroying more than half the seedlings in these areas. It also threatens endangered plants and causes billions of dollars of damage in forestry and agriculture globally.

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Scaling up urban agriculture: Research team outlines roadmap

Urban agriculture has the potential to decentralize food supplies, provide environmental benefits like wildlife habitat, and mitigate environmental footprints, but researchers have identified knowledge gaps regarding both the benefits and risks of urban agriculture and the social processes of growing more food in urban areas.

In a new paper published in Nature Food, an interdisciplinary group of experts, including a researcher from the University of Illinois Urbana-Champaign, survey existing international studies on the benefits and downsides of urban agriculture and propose a framework for scaling it up.

Study co-author Chloe Wardropper, assistant professor in the Department of Natural Resources and Environmental Sciences in the College of Agricultural, Consumer and Environmental Sciences (ACES) at U. of I., says more than two-thirds of the global population is expected to live in urban areas by 2050, and the resilience of these areas may be compromised by their heavy reliance on imported food.

Increasing urban agriculture could reinforce the sustainability and resilience of urban regions in the future, but Wardropper says there are open questions about how best to scale up and what environmental, health, and equity concerns would need to be addressed.

"We propose a framework of three interconnected phases to better understand and shape urban agriculture growth in the future," Wardropper said.

"The first phase of growth would include expanding individuals' interest in, knowledge of, and access to resources to undertake agriculture in urban regions. This phase should be followed by institutionalization, or the transformation of rules and organizational support for urban agriculture. Third, economic and market growth would increasingly support and diversify urban food."

She notes that urban agriculture is not a panacea; urban-rural connections will remain important for global food security and consumption.

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Coastal river deltas threatened by more than climate change

Worldwide, coastal river deltas are home to more than half a billion people, supporting fisheries, agriculture, cities, and fertile ecosystems. In a unique study covering 49 deltas globally, researchers from Lund University and Utrecht University have identified the most critical risks to deltas in the future. The research shows that deltas face multiple risks, and that population growth and poor environmental governance might pose bigger threats than climate change to the sustainability of Asian and African deltas, in particular.

"We can clearly show that many risks are not linked to climate. While climate change is a global problem, other important risk factors like land subsidence, population density and ineffective governance are local problems. Risks to deltas will only increase over time, so now is the time for governments to take action," says Murray Scown, associate senior lecturer, Lund University Centre for Sustainability Studies, and lead author.

Collapse of delta environments could have huge consequences for global sustainable development.

In the worst-case scenario, deltas could be lost to the sea; other consequences are flooding, salinization of water, which affects agriculture, coastal squeeze, and loss of ecosystems.

The study, published in Global Environmental Change, looked at five different IPCC scenarios for global development in 49 deltas all over the world, including famous deltas such as the Nile, Mekong, and Mississippi, but also more understudied deltas such as the Volta, Zambezi and Irrawaddy deltas.

The research identifies possible risks to deltas stretching 80 years into the future.

The researchers based their analysis on 13 well-known factors affecting risk in deltas and drew upon unique models to identify which of these risks are most likely to endanger different deltas in the future.

Risk factors include increasing population density, urban development, irrigated agriculture, changes to river discharge, land subsidence and relative sea-level rise, limited economic capacity, poor government effectiveness, and low adaptation readiness.

Population density, land subsidence and ineffective governance are high risk factors

The analysis shows that there are some risks that are more critical to deltas than others -- in all of the five future scenarios.

These include land subsidence and relative sea-level rise, population density, ineffective governance, economic capacity, and crop land use.

For some deltas, physical risks are especially pronounced. Land subsidence is, for example, the highest risk factor for the Mekong delta in Vietnam.

Extreme sea levels are among the most concerning risk factors for deltas in China, on the Korean peninsula, and in the Colorado (Mexico) and Rhine (Netherlands) deltas.

In the Nile (Egypt), Niger (Nigeria), and the Ganges (Bangladesh) deltas, it is increasing population density that is of most concern under certain scenarios.

For other deltas, it is the lack of economic capacity and government effectiveness to manage risks, for example in the Irrawaddy (Myanmar) and Congo (Angola and Democratic Republic of the Congo) deltas.

"Analysed all together, we can see that the Asian mega-deltas are at greatest risk, with potentially devastating consequences for millions of people, and for the environment. They are under pressure from population growth, intense agricultural land use, relative sea-level rise, and lagging adaptation readiness," says Murray Scown.

Local and global approaches and a mixture of hard and soft adaptation can mitigate risks

"Instead of sitting back, governments need to think long-term, and put plans in place to reduce or mitigate risks. In the Mekong delta, for example, the Vietnamese government are making strong efforts to restrict future groundwater extraction in the delta to reduce land subsidence and salinization," says Philip Minderhoud, assistant professor at Wageningen University and Research.

The researchers highlight that a mixture of hard ("grey") and soft ("green") adaptation approaches will be required to manage and mitigate delta risks.

They include both hard infrastructures, like sea walls to stop the sea inundating the delta, and soft approaches using nature-based solutions.

One example is the Dutch experience of creating room for the river in the Rhine delta, by lowering floodplains, relocating levees, and using spaces that are allowed to flood for grazing.

Initiatives to build up delta surfaces by allowing rivers to flood and deposit sediment on the delta to maintain elevation above sea level are also promising, notes Frances Dunn, assistant professor at Utrecht University.

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Wildfires and farming activities may be top sources of air pollution linked to increased risk, cases of dementia

No amount of air pollution is good for the brain, but wildfires and the emissions resulting from agriculture and farming in particular may pose especially toxic threats to cognitive health, according to new research from the University of Michigan.

Increasingly, evidence shows exposure to air pollution makes the brain susceptible to dementia. And now the findings of Boya Zhang and Sara Adar, environmental epidemiology researchers in U-M's School of Public Health, point to a strong likelihood that agriculture and wildfires, with their release of a range of harmful emissions at high concentrations, need to be more closely studied and monitored for their risks to public health, specifically dementia.

"We saw in our research that all airborne particles increased the risk of dementia but those generated by agricultural settings and wildfires seemed to be especially toxic for the brain," said Adar, associate chair of the Department of Epidemiology in the School of Public Health. She currently leads several large cohort studies on the impacts of exposures on cognitive aging and dementia.

"Our findings indicate that lowering levels of particulate matter air pollution, even in a relatively clean country like the United States, may reduce the number of people developing dementia in late life," Adar said.

Adar and Zhang's paper, "Comparison of Particulate Air Pollution From Different Emission Sources and Incident Dementia in the U.S.," appears today in the Journal of the American Medical Association's Internal Medicine.

Zhang, a research fellow who focuses on the effects of air pollution on cardiopulmonary disease and cognitive aging, said: "This work suggests that particulate matter air pollution from agriculture and wildfires might be more neurotoxic compared with other sources. However, more research is needed to confirm these effects, especially for these two sources which have received less attention in prior research."

"Given that the development of dementia could take a long time, this study mainly aimed to provide evidence for policymakers to reduce exposures to these sources of emissions," Zhang said.

The findings come as unusually poor air quality is regularly triggering alerts in the U.S. The alerts are aimed at protecting the public from the unseen, swirling mix of microscopic toxins in air pollution, specifically fine particulate matter or PM2.5. It is one of the most concerning elements of air pollution. At less than 2.5 microns in size, PM2.5 is less than the width of a human hair. Because it's so small, it can enter the brain through the nose directly or cross the blood-brain barrier in other ways. PM2.5 is also known to affect the lungs, heart, and in emerging research, the brain and cognitive function.

"These findings are quite timely given the increasing frequency of wildfire smoke in our

communities," Adar said. "Our data suggest that in addition to some of the more obvious health impacts of wildfire smoke like irritation to our throats and eyes along with breathing difficulties, high smoke days might also be taking a toll on our brains."

The record number of air quality alerts in the U.S. this year are due in large part to smoke from wildfires burning in Canada since May. The effect of wildfire is not new in the U.S., especially given the fires in the western part of the country.

Adar, a long-time environmental epidemiologist, said that wildfire smoke is becoming a more widespread stressor with many cities experiencing 30-plus days each year impacted by smoke. Given the extremely high levels of exposure to the public, wildfires are thought to contribute up to 25% of fine particulate matter exposures over a year across the U.S. and as much as 50% in some western regions of the country, Adar said.

"While individual wildfires may be short-lived, these events are becoming more frequent in our communities due to warmer temperatures, drier conditions, and longer fire seasons. As we've seen, wildfire smoke can also travel very far distances," Adar said.

Their findings are based on research into the development of dementia among nearly 30,000 adults from across the U.S. over an 18-year period. The data comes from the Health and Retirement Study, a nationally-representative collection of cohorts of older adults who have been followed since 1992. Pollution estimates in Adar and Zhang's study were based on home addresses of participants. Participants have been interviewed biennially about their cognition, overall health, and health behaviors until death or loss of contact for the survey.

They observed that higher levels of particulate matter air pollution, especially from agriculture and wildfires, were associated with greater risks of dementia. The findings could not be explained by other factors such as individual, neighborhood, socioeconomic status, occupation, or hometown or region of the country.

"With the knowledge of which sources are more toxic than others, it may be possible to design interventions for specific sources as a more effective way to decrease the burden of dementia," Zhang said.

Dementia is currently the seventh leading cause of death and one of the major causes of disability and dependency for older people, according to the World Health Organization.

The research specifically sought to test the hypothesis that a variation in emission sources could explain which are most toxic, but measuring the emissions with their distinct physical and chemical characteristics is challenging.

Past studies analyzing exposures to source specific fine particulate matter meant researchers mainly investigated relationships with the total mass of fine particulate matter in the air.

"In our study, we used a sophisticated prediction model that includes information about the chemical transformations and dispersion of pollution from different sources to estimate the levels of source-specific particulate matter air pollution at participants' residential addresses," Zhang said. "This approach is beneficial because it not only accounts for pollution directly emitted by a source but also pollution generated through reactions with other chemicals in the air."

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Abundance of urban honeybees adversely impacts wild bee populations

Who hasn't received a pot of homegrown honey from a friend or relative who decided to take up urban beekeeping? The sentiment behind the gift is sweet, but their newfound interest in urban agriculture may be adversely affecting local biodiversity.

In a new paper in the journal PeerJ, a team led by Concordia researchers argue that the rapid growth in urban honeybee-keeping over the past decade may be negatively impacting nearby wild bee populations. Small bees with limited foraging ranges may be especially at risk, they write.

The researchers compared bee population data collected from sites around the island of Montreal in 2013 to data they collected at the same sites in the summer of 2020.

"We found that the sites with the largest increase in honeybee populations across sites and years also had the fewest wild bee species," says Gail MacInnis, a former Concordia postdoctoral researcher and the study's lead author. Etienne Normandin from the Université de Montréal and Carly Ziter, an assistant professor in the Department of Biology, are co-authors.

According to Quebec's Ministère de l'Agriculture, des Pêcheries et de l'Alimentation (Ministry of Agriculture, Fisheries and Food), the number of honeybee colonies on the island of Montreal has increased over twelvefold. In 2013, there were under 250 colonies. That number has ballooned to almost 3,000 in 2020.

Honeybees are not native to the region, the researchers note. This type of bee is therefore in competition with almost 180 other species for resources like pollen and nectar, as identified in the 2013 study.

Invasive and hungry

The researchers visited 15 sites across the island of Montreal that were known to attract pollinators. Sites included community gardens, cemeteries and large urban parks. The researchers used a standardized system of pan trap triplets -- multicoloured bowls designed to attract bees -- and nets to collect their samples. Each site was sampled five times between late June and early September 2020, with a total sample size of 6,200 bees. The researchers also measured other important factors that influence wild bee populations, like habitat and floral resource availability.

Nearly 4,000 samples turned out to be wild bees belonging to 120 species. Roughly 2,200 were honeybees. By contrast, in 2013, approximately 5,200 bees were collected at similar locations. Nearly all of these samples were wild bees belonging to 163 species.

Statistical analyses were performed across sites in 2020 on wild bee diversity; bee traits and honeybee abundance; wild bee community composition; and pollen depletion. Similar analyses compared the bee communities of 2013 and 2020.

The study found that wild bee species richness declined significantly. Honeybee abundance increased but remained similar to 2013 levels in areas where the honeybee population was comparatively lower. Honeybee abundance was also associated with pollen depletion in white clover flowers.

Not a risk-free hobby

MacInnis points out that a lack of registry or regulations makes studying bee populations difficult. Understanding honeybee colony density is crucial, she says, as just one honeybee colony can support up to 50,000 individuals.

"We need to provide food if we want to support large bee populations. But we also need to be careful about population density, especially for commercially managed bees, because they are prone to many diseases," she says. "This issue can become especially bad when there are many new beekeepers in the area. They may not be as knowledgeable about controlling for things like mites, viruses and other pathogens."

"Beekeeping provides an agricultural product that is valuable to people in the form of honey. My concern is that urban beekeeping is often falsely marketed as a solution to biodiversity loss," Ziter adds. "Just as we wouldn't advocate keeping backyard chickens to save the birds, we shouldn't look to beekeeping to save the bees. It's important that our actions match our goals or motivations."

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Humans need Earth-like ecosystem for deep-space living

Can humans endure long-term living in deep space? The answer is a lukewarm maybe, according to a new theory describing the complexity of maintaining gravity and oxygen, obtaining water, developing agriculture and handling waste far from Earth.

Dubbed the Pancosmorio theory -- a word coined to mean "all world limit" -- it was described in a paper published in Frontiers in Astronomy and Space Sciences.

"For humans to sustain themselves and all of their technology, infrastructure and society in space, they need a self-restoring, Earth-like, natural ecosystem to back them up," said co-author Morgan Irons, a doctoral student conducting research with Johannes Lehmann, professor in the School of Integrative Plant Science at Cornell University. Her work focuses on soil organic carbon persistence under Earth's gravity and varying gravity conditions. "Without these kinds of systems, the mission fails."

The first key is gravity, which Earth life needs to function properly, said co-author Lee Irons, Morgan Irons' father and executive director of the Norfolk Institute, a group that aims to solve problems of human resilience on Earth and in space.

"Gravity induces a gradient in the fluid pressure within the body of the living thing to which the autonomic functions of the life form are attuned," he said. "An example of gravity imbalance would be the negative affect on the eyesight of humans in Earth orbit, where they don't experience the weight necessary to induce the pressure gradient."

Morgan Irons said that it would be unwise to spend billions of dollars to set up a space settlement only to see it fail, because even with all other systems in place, you need gravity.

Humans and all Earth life have evolved within the context of 1G of gravity. "Our bodies, our natural ecosystems, all the energy movement and the way we utilize energy is all fundamentally based upon 1G of gravity being present," she said. "There is just no other place in space where there is 1G of gravity; that just doesn't exist anywhere else in our solar system. That's one of the first problems we must solve."

Oxygen is another key factor. Earth's ecosystem generates oxygen for humans and other life forms. If a technologically advanced primary and a back-up system failed to provide oxygen for the moon base, for example, it would mean instant doom for the astronauts. "A reserve exists everywhere in Earth's nature," Lee Irons said. "Think of the hundreds of thousands of species of plants that generate oxygen. That's the kind of system reserve we need to replicate to be truly sustainable."

Such an ecological system of an outpost would need an enormous amount energy from the sun. The more distant planets and moons from the sun in our own solar system get decreased amounts of energy.

Read more at Science Daily

Evolution of wheat spikes since the Neolithic revolution

Around 12,000 years ago, the Neolithic revolution radically changed the economy, diet and structure of the first human societies in the Fertile Crescent of the Near East. With the beginning of the cultivation of cereals -- such as wheat and barley -- and the domestication of animals, the first cities emerged in a new social context marked by a productive economy. Now, a study published in the journal Trends in Plant Science and co-led by the University of Barcelona, the Agrotecnio centre and the University of Lleida, analyses the evolution of wheat spikes since its cultivation began by the inhabitants of ancient Mesopotamia -- the cradle of agriculture in the world -- between the Tigris and the Euphrates.

The authors of the study are Rut Sánchez-Bragado and Josep Lluís Araus-Ortega, from the UB Faculty of Biology and Agrotecnio-UdL; Gustavo A. Slafer, ICREA researcher at the UdL School of Agrifood and Forestry Science and Engineering, and Gemma Molero, from the International Maize and Wheat Improvement Center in Mexico, currently a researcher at KWS Seeds Inc.

A cereal that changed human history

The cultivation of wheat -- a grass that became basic food -- represented a turning point in the progress of human civilisation. Today it is the world's most important crop in terms of food security, but EU data warn that the impact of climate change could significantly increase its price and modify its production process in certain areas of the world.

Throughout the domestication process of wheat, the plant phenotype has undergone both rapid (within a few hundred years) and slow (thousands of years) changes, such as the weakening of the rachis, the increase in seed size, and the reduction or disappearance of the awns. In particular, awned and awnless wheat varieties are found all over the world, although the latter tend to be abundant in regions with arid climates, especially during the final stages of cultivation in late spring, a condition typical of Mediterranean environments.

"It is important to conduct studies that show which wheat varieties are best adapted to different environmental growing conditions, especially in a context of climate change. Studying the past retrospectively can give us an idea of the evolution of wheat cultivation over the millennia since agriculture appeared in ancient Mesopotamia," says Rut Sánchez-Bragado, first author of the study, who got a PhD at the UB.

"Awns are organs of the spike that have traditionally been associated with the plant's adaptations to drought conditions," says Josep Lluís Araus, professor at the Department of Evolutionary Biology, Ecology and Environmental Sciences of the Faculty of Biology.

"However, archaeological and historical records show that the wheat spike has existed predominantly with awns for more than ten millennia after the domestication of wheat. It is not until the last millennium that evidence shows in many cases the absence of awns, indicating a selection by farmers -- probably in an undirected way -- against this organ," stresses Araus, one of the most cited authors in the world according to Clarivate Analytics' Highly Cited Researchers (2022).

"The role of wheat awns in their performance remains controversial despite decades of studies," says researcher Gustavo A. Slafer, corresponding author of the study.

Spike awns: beneficial for the plant?

Is the presence of awns on the spike beneficial for the plant and the crops? Although there is no scientific consensus, "everything suggests that in conditions where the plant does not suffer from water stress, the extra photosynthetic capacity of the awns does not compensate for other potential negative effects (reduced susceptibility to fungal diseases, limitation in the total number of large ones that an ear supports, etc.)," says Araus.

"However, in wetter climates the awns accumulate moisture and can promote the spread of diseases," says Rut Sánchez-Bragado. "So, as the world's population is continuously growing, it is necessary to investigate the role of the awned spikes in the changing conditions of our climate in order to meet the world's demand for a primary food commodity such as wheat."

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Agriculture linked to changes in age-independent mortality in North America

The transition to agriculture from hunting and gathering in pre-colonial North America led to changes in age-independent mortality, or mortality caused by factors that are not associated with age, according to a new study by a Penn State-led research team. The team found that the intensification of crop use occurred in two phases, the first of which led to a decline in human age-independent mortality, while the second is associated with a rise in it. The study is the first to tie patterns of age-independent mortality to food production.

"This study tells the story of our shared human experience," said George Milner, distinguished professor of anthropology at Penn State and lead author. "We have several examples around the world where we see a move toward crop domestication as an independent event -- eastern North America, particularly the midcontinent, being one of them, but so too the Fertile Crescent in the Middle East. Also, there are demographic changes happening. This paper addresses the relationship between the move toward agriculture and demographic change."

The researchers examined previously published data to identify general trends in archaeobotanical samples, or the remains of plants in the archaeological record, and skeletal samples from sites across eight states stretching from Illinois to northern Alabama. They wanted to study the relationship between the domestication of crops and an index that uses skeletal data to capture the frequency of juveniles aged five to 19 years old relative to all individuals aged five or more. Anthropologists normally use the index to measure fertility rates and population growth, but the new work shows it is more responsive to age-independent mortality.

Mortality models, including those for pre-industrial societies, contain three components: juvenile mortality, which declines as children get older; adult mortality, where the probability of dying increases with advancing age; and age-independent mortality, an equal probability of dying for members of all age groups, which might occur in extreme events like food shortages, epidemics or warfare.

The researchers studied the archaeobotanical data to identify where the record showed an increase in the consumption of domesticated crops compared to foraged foods like nuts. They also examined skeletal data to identify decreases or increases in the indicator of age-independent mortality. The index focuses on individuals between five and 19 years old because in human populations that age range is characterized by low mortality relative to other age groups. Increases in mortality for this age group would indicate the occurrence of events like famines or conflict.

The researchers identified a strong correlation between crop domestication and changing age-independent mortality rates. Crop domestication happened in two stages in pre-colonial North America, with a decrease in age-independent mortality noted during the first stage of crop domestication and a rise during the second stage. The researchers reported their findings in the Proceedings of the National Academy of Sciences.

"What we've found is the index that has traditionally been interpreted as a fertility and population growth indicator is more tightly correlated to age-independent mortality, which reflects the number of deaths in the part of the age distribution where very few people die," said Milner. "This means that the pattern of first adoption of agriculture, seen elsewhere in the world and observed in eastern North America as well, coincides with lower age-independent mortality. Basically, it's good times, and that's what we see culturally."

The first stage of agricultural intensification in North America, which includes the cultivation of plants such as squash, sunflower and other native plants, occurred approximately 2,000 years ago during the Middle Woodland period up to about A.D. 500, said Milner. Indigenous societies flourished during this time. They established long-distance exchange networks, had an incredibly rich ceremonial life, and constructed big mounds and earthwork complexes.

The archaeological record shows that in the centuries just before A.D. 1000, and from that time onward, there was an increase in warfare. During this time Indigenous societies began cultivating maize and beans, and a number of new cultural changes occurred, including the initial development of powerful chiefdom societies. Age-independent mortality increased during this period, presumably due to conflict and the spread of diseases from higher numbers of individuals living near one another.

"The overall pattern seen in the demographic picture of North American pre-European contact is similar to other datasets from around the world," Milner said. "The entire story makes perfect sense in terms of agricultural productivity, demographic change and cultural developments, including change over time in conflict and sociopolitical systems."

The study links, for the first time, a worldwide pattern to age-independent mortality and agricultural developments, according to Milner.

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How intensive agriculture turned a wild plant into a pervasive weed

New research in Science is showing how the rise of modern agriculture has turned a North American native plant, common waterhemp, into a problematic agricultural weed.

An international team led by researchers at the University of British Columbia (UBC) compared 187 waterhemp samples from modern farms and neighbouring wetlands with more than 100 historical samples dating as far back as 1820 that had been stored in museums across North America. Much like the sequencing of ancient human and neanderthal remains has resolved key mysteries about human history, studying the plant's genetic makeup over the last two centuries allowed the researchers to watch evolution in action across changing environments.

"The genetic variants that help the plant do well in modern agricultural settings have risen to high frequencies remarkably quickly since agricultural intensification in the 1960s," said first author Dr. Julia Kreiner, a postdoctoral researcher in UBC's Department of Botany.

The researchers discovered hundreds of genes across the weed's genome that aid its success on farms, with mutations in genes related to drought tolerance, rapid growth and resistance to herbicides appearing frequently. "The types of changes we're imposing in agricultural environments are so strong that they have consequences in neighbouring habitats that we'd usually think were natural," said Dr. Kreiner.

The findings could inform conservation efforts to preserve natural areas in landscapes dominated by agriculture. Reducing gene flow out of agricultural sites and choosing more isolated natural populations for protection could help limit the evolutionary influence of farms.

Common waterhemp is native to North America and was not always a problematic plant. Yet in recent years, the weed has become nearly impossible to eradicate from farms thanks to genetic adaptations including herbicide resistance.

"While waterhemp typically grows near lakes and streams, the genetic shifts that we're seeing allow the plant to survive on drier land and to grow quickly to outcompete crops," said co-author Dr. Sarah Otto, Killam University Professor at the University of British Columbia. "Waterhemp has basically evolved to become more of a weed given how strongly it's been selected to thrive alongside human agricultural activities."

Notably, five out of seven herbicide-resistant mutations found in current samples were absent from the historical samples. "Modern farms impose a strong filter determining which plant species and mutations can persist through time," said Dr. Kreiner. "Sequencing the plant's genes, herbicides stood out as one of the strongest agricultural filter determining which plants survive and which die."

Waterhemp carrying any of the seven herbicide resistant mutations have produced an average of 1.2 times as many surviving offspring per year since 1960 compared to plants that don't have the mutations.

Herbicide resistant mutations were also discovered in natural habitats, albeit at a lower frequency, which raises questions about the costs of these adaptations for plant life in non-agricultural settings. "In the absence of herbicide applications, being resistant can actually be costly to a plant, so the changes happening on the farms are impacting the fitness of the plant in the wild," said Dr. Kreiner.

Agricultural practices have also reshaped where particular genetic variants are found across the landscape. Over the last 60 years, a weedy southwestern variety has made an increasing progression eastward across North America, spreading their genes into local populations as a result of their competitive edge in agricultural contexts.

"These results highlight the enormous potential of studying historical genomes to understand plant adaptation on short timescales," says Dr. Stephen Wright, co-author and Professor in Ecology and Evolutionary Biology at the University of Toronto. "Expanding this research across scales and species will broaden our understanding of how farming and climate change are driving rapid plant evolution."

Read more at Science Daily

New analysis of obsidian blades reveals dynamic Neolithic social networks

An analysis of obsidian artifacts excavated during the 1960s at two prominent archaeological sites in southwestern Iran suggests that the networks Neolithic people formed in the region as they developed agriculture are larger and more complex than previously believed, according to a new study by Yale researchers.

The study, published Oct. 17 in the journal Proceedings of the National Academy of Sciences, is the first to apply state-of-the-art analytical tools to a collection of 2,100 obsidian artifacts housed at the Yale Peabody Museum. The artifacts were unearthed more than 50 years ago at Ali Kosh and Chagha Sefid, sites on Iran's Deh Luran Plain that yielded important archaeological discoveries from the Neolithic Era -- the period beginning about 12,000 years ago when people began farming, domesticating animals, and establishing permanent settlements.

Original analyses performed shortly after the artifacts were discovered had suggested people first acquired the obsidian -- volcanic glass -- from Nemrut Dağ, a now dormant volcano in Eastern Turkey, and then relied on an unknown second source for the material. This new elemental analysis showed the obsidian came from seven distinct sources, including Nemrut Dağ, in present-day Turkey and Armenia, which is as far as about 1,000 miles on foot from the excavation sites.

"It wasn't a simple pattern of people obtaining obsidian from one source and then shifting to the next," said Ellery Frahm, an archaeological scientist in the Department of Anthropology in Yale's Faculty of Arts and Sciences, and the study's lead author. "Rather, our analysis shows that they were acquiring obsidian from an increasingly diverse number of geological sources over time -- a trend that was impossible to detect with the technology and methods available 50 years ago."

The new analysis, combined with computer modeling, indicates that there were intensifying connections among Neolithic people, suggesting the presence of a greater number of settlements between the source volcanoes and the two sites where the artifacts were unearthed thousands of years later, Frahm said.

The artifacts were collected in the 1960s during multiple excavations of the two sites led by Frank Hole, the C.J. MacCurdy Professor Emeritus of Anthropology at Yale. The initial analyses were based largely on the artifacts' appearance, specifically their color when held up to sunlight. A subset of 28 artifacts were then subjected to an elemental analysis method common at the time that involved grinding them into powder.

Frahm and coauthor Christina M. Carolus, a doctoral student in the Department of Anthropology, are the first researchers to study the elemental composition of the obsidian artifacts since these early analyses. They used state-of-the-art portable X-ray fluorescence instruments, which allowed them to examine the entire collection without damaging the artifacts.

"Every aspect of the discoveries made at these sites had been revisited since the 1960s except the elemental composition and sourcing of the obsidian artifacts," Carolus said. "A lot more is known about the source volcanoes today than 50 years ago, and we know that sorting obsidian by color will miss a lot of nuances. Fortunately, we have instruments the size of cordless drills that, in a matter of seconds and without destroying material, give us a more accurate elemental signature than anything that was possible in the past."

Scientists widely believed that humanity's transition from the hunter-gatherer lifestyle to agriculture produced a period of rapid population growth due to the increased birth rates made possible by enhanced food supplies and permanent settlements. Finding evidence of this demographic shift often requires excavating locations that include burial sites, which can indicate a given settlement's population and provide a clearer picture of how agriculture allowed people to disperse across a landscape, Frahm said.

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Longhorned tick discovered in northern Missouri

The Longhorned tick causes the loss of millions of dollars in agricultural revenue to cattle producers worldwide, and it is now in northern Missouri.

Originally found in eastern Russia and the Australasian region, this tick was first found in the United States in 2017 in New Jersey. It has since reached the Mid-Atlantic, New England and Midwestern regions of the U.S., and now has been discovered in northern Missouri for the first time by researchers at the University of Missouri.

Last year, the Longhorned tick was found in the southern part of the state. This latest discovery indicates an additional economic burden to cattle producers due to ticks; as the Longhorned tick infestation could lead to significant loss in weight gain for cattle, similar to an already widely prevalent disease called anaplasmosis; but so far, the threat from this species of tick to cattle -- and people and their pets -- in Missouri remains low. However, researchers emphasize that the discovery of the Longhorned tick in the state increases the need for more vigilance towards ticks in general.

While most ticks reproduce traditionally, female Longhorned ticks can lay thousands of eggs without the help of a male, which makes it easier for them to quickly establish in new areas. Infestation of the Longhorned tick can lead to possible transmission of bovine theileriosis, a disease that kills red blood cells in cattle.

While there have currently not been any confirmed cases of bovine theileriosis in Missouri cattle, this discovery further heightens the need for Missouri cattle ranchers to make informed decisions regarding quarantining protocols when introducing new cattle into their herds in an effort to protect the health of their livestock, which has significant economic implications.

"Studying the prevalence of invasive ticks in different geographical regions can help veterinarians and farmers take proactive, preventative steps that may ultimately protect the health of livestock, which has huge economic implications," said Rosalie Ierardi, an anatomic pathologist at the MU College of Veterinary Medicine who recently discovered two Longhorned ticks in Linn County, Missouri, while conducting anaplasmosis surveillance research.

Ierardi collaborated on the project with Ram Raghavan, a professor in the MU College of Veterinary Medicine and MU School of Health Professions. Raghavan, who has been tracking the spread of various species of ticks in the U.S. for 15 years, predicted the potential geographic distribution of the Longhorned tick back in 2019. So far, the tick appears to be establishing in the areas that he had predicted in that study. He said there not only appears to be an increase in the abundance of all ticks in the Midwest in the past decade, but also an increase in the pathogens and diseases they transmit to cattle, humans and pets.

"Warmer temperatures in the Midwest seem to be creating perfect conditions for ticks and the pathogens they carry to thrive, and this problem may get worse going forward as the planet continues to warm, which is concerning," Raghavan said. "We must be vigilant and devote resources toward trying to prevent these ticks from spreading diseases that harm the health of cattle, humans and their pets. The discovery of Longhorned ticks in northern Missouri greatly increases the need for more vigilance towards ticks in general and the need for routine monitoring of the pathogens they transmit."

Ierardi encourages cattle ranchers who notice weakness, jaundice and pregnancy loss in their cattle to contact their local veterinarian and the MU Veterinary Medical Diagnostic Laboratory for assistance with tracking down the causes for such signs.

Read more at Science Daily

Agriculture emissions pose risks to health and climate

Agricultural pollution comes from the prairie, but its economic impact on humans is a problem for cities.

A study led by environmental scientists at Rice University's George R. Brown School of Engineering puts numbers to the toll of reactive nitrogen species produced in America's croplands.

The study led by Daniel Cohan, an associate professor of civil and environmental engineering, and graduate student Lina Luo quantifies emissions of nitrogen oxides, ammonia and nitrous oxide from fertilized soils over three years (2011, 2012 and 2017) and compares their impacts by region on air quality, health and climate.

While seasonal and regional impacts differ across types of emission, the study found total annual damages from ammonia were much larger overall -- at $72 billion -- than those from nitrogen oxides ($12 billion) and nitrous oxide ($13 billion).

Air pollution damages are measured by increased mortality and morbidity and the value of statistical life, while monetized damages from climate change include the threats to crops, property, ecosystem services and human health.

On that basis, the researchers found the health impact of air pollution from ammonia and nitrogen oxides, which react to form particulate matter and ozone, substantially outweighed climate impact from nitrous oxide in all regions and years.

The highest social costs arose from agriculture-heavy regions of California, Florida and the Midwest, where ammonia and nitrogen oxides form air pollution upwind of population centers. For both pollutants, emissions peak in the spring after fertilizers are applied.

The study in the American Chemical Society journal Environmental Science & Technology concludes air pollution, health and climate should all be considered in future assessments of how farming practices affect reactive nitrogen emissions.

"We always talk about how carbon dioxide and methane contribute to greenhouse gases, but nitrous oxide is about 300 times more potent than carbon dioxide for its global warming potential," Luo said.

She noted farming strategies that reduce greenhouse gases can increase air pollutants and vice versa. "We need to see if they can reduce all three nitrogen species -- or make some tradeoffs -- and still not decrease crop yield," Luo said.

Nitrogen is essential for crop growth, Cohan added, but the study shows the importance of controlling agricultural emissions has been largely neglected by air quality management and climate policy, even as the Environmental Protection Agency considers tightening air quality standards and the Biden administration seeks to slash greenhouse gas emissions.

He said federal agencies have focused on controlling transportation and industrial emissions, leaving agriculture as the largest source of damaging nitrogen pollutants in the United States, a problem exacerbated by climate change and increased crop production.

"Our group had been studying nitrogen oxide emissions for a number of years and began to realize that we can't just focus on that," Cohan said. "We needed to consider the range of emissions that come from soils, and we became curious about the relative impacts of different air pollutants and greenhouse gases the emanate from agricultural soils.

"A big part of our motivation was realizing that choices in farming practices might cause some emissions to go up and other emissions to go down," he said. For instance, switching from surface broadcast to deep injection of fertilizers would lower ammonia but raise nitrogen oxide emissions. That would benefit nearby cities sensitive to particulate matter levels, but harm regions where ozone is of more concern.

Cohan said when all the emissions are quantified on a monetary basis, ammonia and nitrogen oxides that form air-polluting particulate matter and ozone and contribute to global warming have the greatest impact.

"Those of us who study these pollutants for a living know how potent ammonia is, but the message hasn't gotten through to most regulators and policymakers," Cohan said. "In fact, ammonia is one of the most potent sources of particulate matter because of how it binds with other pollutants to have a multiplying effect.

"That's an important message: We need to take more steps to control ammonia," he said.

If there's a silver lining, Cohan said, it's that pollution from other sources has dropped enough to make agriculture's impact prevalent.

"What's crucial is to take steps that have more of the nitrogen go to the crops, and less of it be released to the air and water," he said. That could involve adding biochar or other amendments to soil, a topic of ongoing study at Rice.

"Before we can do that, we needed to establish a baseline of emissions coming from the soil," Cohan said. "This paper lays that out."

Read more at Science Daily

The genetic origins of the world's first farmers clarified

The genetic origins of the first agriculturalists in the Neolithic period long seemed to lie in the Near East. A new study published in the journal Cell shows that the first farmers actually represented a mixture of Ice Age hunter-gatherer groups, spread from the Near East all the way to south-eastern Europe. Researchers from the University of Bern and the SIB Swiss Institute of Bioinformatics as well as from the Johannes Gutenberg University Mainz and the University of Fribourg were involved in the study. The method they developed could help reveal other human evolution patterns with unmatched resolution.

The first signs of agriculture and a sedentary lifestyle are found in the so-called 'Fertile Crescent', a region in the Near East where people began to settle down and domesticate animals and plants about 11,000 years ago. The question of the origin of agriculture and sedentism has occupied researchers for over 100 years: did farming spread from the Near East through cultural diffusion or through migration? Genetic analyses of prehistoric skeletons so far supported the idea that Europe's first farmers were descended from hunter-gatherer populations in Anatolia. While that may well be the case, this new study shows that the Neolithic genetic origins cannot clearly be attributed to a single region. Unexpected and complex population dynamics occurred at the end of the Ice Age, and led to the ancestral genetic makeup of the populations who invented agriculture and a sedentary life-style i.e. the first Neolithic farmers.

First farmers emerged from a mixing process starting 14,000 years ago

Previous analyses had suggested that the first Neolithic people were genetically different from other human groups from that time. Little was known about their origins. Nina Marchi, one of the study's first authors from the Institute of Ecology and Evolution at the University of Bern and SIB says: "We now find that the first farmers of Anatolia and Europe emerged from a population admixed between hunter-gatherers from Europe and the Near East." According to the authors, the mixing process started around 14,000 years ago, which was followed by a period of extreme genetic differentiation lasting several thousand years.

A novel approach to model population history from prehistoric skeletons

This research was made possible by combining two techniques: the production of high-quality ancient genomes from prehistoric skeletons, coupled with demographic modeling on the resulting data. The research team coined the term "demogenomic modeling" for this purpose. "It is necessary to have genome data of the best possible quality so that the latest statistical genomic methods can reconstruct the subtle demographic processes of the last 30 thousand years at high resolution," says Laurent Excoffier, one of the senior authors of the study. Laurent Excoffier is a professor at the Institute of Ecology and Evolution at the University of Bern and group leader at SIB. He initiated the project together with Joachim Burger of the Johannes Gutenberg University in Mainz and Daniel Wegmann of the University of Fribourg. Nina Marchi adds: "Simply comparing the similarity of different ancient genomes is not enough to understand how they evolved. We had to reconstruct the actual histories of the populations studied as accurately as possible. This is only possible with complex population genetic statistics."

Interdisciplinarity key to solve such ancient puzzles

Joachim Burger of the University of Mainz and second senior author emphasizes the necessity of interdisciplinarity: "It took close to ten years to gather and analyze the skeletons suitable for such a study. This was only possible by collaborating with numerous archaeologists and anthropologists, who helped us to anchor our models historically." The historical contextualisation was coordinated by Maxime Brami, who works with Burger at Johannes Gutenberg University. The young prehistorian was surprised by some of the study's findings: "Europe's first farmers seem to be descended from hunter-gatherer populations that lived all the way from the Near East to the Balkans. This was not foreseeable archaeologically."

Towards a general model of human population evolution

Genetic data from fossils (skeletons) are badly damaged and must be processed accordingly using bioinformatics, as Daniel Wegmann from the University of Fribourg and group leader at SIB explains: "The high-resolution reconstruction of the prehistory of the Europeans was only possible thanks to methods that we specifically developed to analyse ancient fossil genomes." Joachim Burger adds: "With these approaches, we have not only elucidated the origins of the world's first Neolithic populations, but we have established a general model of the evolution of human populations in Southwest Asia and Europe."

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Study sheds new light on the origin of civilization

New research from the University of Warwick, the Hebrew University of Jerusalem, Reichman University, Universitat Pompeu Fabra and the Barcelona School of Economics challenges the conventional theory that the transition from foraging to farming drove the development of complex, hierarchical societies by creating agricultural surplus in areas of fertile land.

In The Origin of the State: Land Productivity or Appropriability?, published in the April issue of the Journal of Political Economy, Professors Joram Mayshar, Omer Moav and Luigi Pascali show that high land productivity on its own does not lead to the development of tax-levying states.

It is the adoption of cereal crops that is the key factor for the emergence of hierarchy.

The authors theorise that this is because the nature of cereals require that they be harvested and stored in accessible locations, making them easier to appropriate as tax than root crops which remain in the ground, and are less storable.

The researchers demonstrate a causal effect of cereal cultivation on the emergence of hierarchy using empirical evidence drawn from multiple data sets spanning several millennia, and find no similar effect for land productivity.

Professor Mayshar said: "A theory linking land productivity and surplus to the emergence of hierarchy has developed over a few centuries and became conventional in thousands of books and articles. We show, both theoretically and empirically, that this theory is flawed."

Underpinning the study, Mayshar, Moav and Pascali developed and examined a large number of data sets including the level of hierarchical complexity in society; the geographic distribution of wild relatives of domesticated plants; and land suitability for various crops to explore why in some regions, despite thousands of years of successful farming, well-functioning states did not emerge, while states that could tax and provide protection to lives and property emerged elsewhere.

Professor Pascali said: "Using these novel data, we were able to show that complex hierarchies, like complex chiefdoms and states, arose in areas in which cereal crops, which are easy to tax and to expropriate, were de-facto the only available crops. Paradoxically, the most productive lands, those in which not only cereals but also roots and tubers were available and productive, did not experience the same political developments."

They also employed the natural experiment of the Columbian Exchange, the interchange of crops between the New World and the Old World in the late 15th century which radically changed land productivity and the productivity advantage of cereals over roots and tubers in most countries in the world.

Professor Pascali said "Constructing these new data sets, investigating case studies, and developing the theory and empirical strategy took us nearly a decade of hard work. We are very pleased to see that the paper is finally printed in a journal with the standing of the JPE."

Professor Moav said: "Following the transition from foraging to farming, hierarchical societies and, eventually, tax-levying states have emerged. These states played a crucial role in economic development by providing protection, law and order, which eventually enabled industrialization and the unprecedented welfare enjoyed today in many countries."

"The conventional theory is that this disparity is due to differences in land productivity. The conventional argument is that food surplus must be produced before a state can tax farmers' crops, and therefore that high land productivity plays the key role.

Professor Mayshar added: "We challenge the conventional productivity theory, contending that it was not an increase in food production that led to complex hierarchies and states, but rather the transition to reliance on appropriable cereal grains that facilitate taxation by the emerging elite. When it became possible to appropriate crops, a taxing elite emerged, and this led to the state.

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Agricultural expansion a major cause to doubling of annual tropical carbon loss over past two decades

Using multiple high-resolution satellite datasets, researchers from the Department of Civil Engineering at the University of Hong Kong (HKU) and Southern University of Science and Technology (SUSTech) found that tropical carbon loss has doubled over the past two decades due to excessive forest removal in the tropics.

The tropics are an important ecosystem as they store massive amounts of carbon in their woody vegetation and soil -- but they have suffered from extensive forest clearance since 2001. The researchers analysed the gross forest carbon loss associated with forest removal in the tropics (between 23.5° N and 23.5 S but excluding northern Australia) during the 21st century. They revealed a two-fold increase in gross tropical forest carbon loss worldwide from 0.97 gigatons of carbon per year in 2001-2005 to 1.99 gigatons of carbon per year in 2015-2019 due to rapid forest loss.

The study has been published in the academic journal Nature Sustainability in an article entitled "Doubling of annual forest carbon loss over the tropics during the early twenty-first century."

Given the key role of the tropics in the carbon cycle, the study poses serious implications. "The findings are critical because they suggest that existing strategies to reduce forest loss are questionable; this failure underscores the importance of monitoring deforestation trends following one of the new pledges made -- to halt and reverse deforestation -- by UN climate summit-the twenty-sixth Conference of the Parties (COP26) in Glasgow in November 2021," said Professor Ji CHEN from HKU's Department of Civil Engineering.

Tropical forests are the largest terrestrial component of the global carbon cycle, storing about 250 gigatons of biomass carbon in its woody vegetation and absorbing about 70 gigatons of atmospheric carbon per year through photosynthesis. The rapid and steady loss of forests could be devastating because it leads to the loss of stored carbon in biomass and soil. Deforestation also obstructs carbon sequestration or the process of capturing and retaining carbon dioxide.

"The doubling and acceleration in the loss of forest carbon, including biomass and soil organic carbon, is primarily driven by agricultural expansion which differs from current estimates of land-use change emissions in the assessments of the global carbon budget that shows a flat or decreasing trend. In addition to carbon, conversion of forests to agricultural lands also induces other environmental consequences, like biodiversity extinction and land degradation," said Yu FENG, a PhD candidate of the HKU and SUSTech joint programme.

Most of the tropical forest carbon loss (82%) was set off by agricultural expansion, for example shifting cultivation, particularly in Africa.

"While some agricultural lands may reappear as forested due to abandonment or policies, we still observed about 70% of former forest lands converted to agriculture in 2001-2019 remained so in 2020, confirming a dominant role of agriculture in long-term pan-tropical carbon reductions on formerly forested landscapes," said research team member Dr Zhenzhong Zeng, Associate Professor at SUSTech.

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Co-occurring droughts could threaten global food security

Droughts occurring at the same time across different regions of the planet could place an unprecedented strain on the global agricultural system and threaten the water security of millions of people, according to a new study in Nature Climate Change.

A Washington State University-led research team analyzed climate, agricultural and population growth data to show continuing fossil fuel dependence will increase the probability of co-occurring droughts 40% by the mid-21st century and 60% by the late 21st century, relative to the late-20th century. That comes out to an approximately ninefold increase in agricultural and human population exposure to severe co-occurring droughts unless steps are taken to lower carbon emissions.

"There could be around 120 million people across the globe simultaneously exposed to severe compound droughts each year by the end of the century," said lead author Jitendra Singh, a former postdoctoral researcher at the WSU School of the Environment now at ETH Zurich, Switzerland. "Many of the regions our analysis shows will be most affected are already vulnerable and so the potential for droughts to become disasters is high."

The elevated risk of compound droughts estimated by Singh and colleagues is a result of a warming climate coupled with a projected 22% increase in the frequency of El Niño and La Niña events, the two opposite phases of the El Niño Southern Oscillation (ENSO).

The researchers' projections show that nearly 75% of compound droughts in the future will coincide with these irregular but recurring periods of climatic variation in the world's oceans, which have played a large role in some of the greatest environmental disasters in world history.

For example, El Nino-fueled droughts that concurrently occurred across Asia, Brazil and Africa during 1876-1878 led to synchronous crop failures, followed by famines that killed more than 50 million people.

"While technology and other circumstances today are a lot different than they were in the late 19th century, crop failures in multiple breadbasket regions still have the potential to affect global food availability," said study coauthor Deepti Singh, an assistant professor in the WSU School of the Environment. "This could in turn increase volatility in global food prices, affecting food access and exacerbating food insecurity, particularly in regions that are already vulnerable to environmental shocks such as droughts."

The researchers' analysis specifically focused on ten regions of the planet that receive most of their rainfall during June-September, have high variability in monthly summer precipitation and are affected by ENSO variations, factors that lead to an increased potential for co-occurring drought. Several of the regions analyzed include important agricultural regions and countries that are currently facing food and water insecurity.

Their results indicate areas of North and South America are more likely to experience compound droughts in a future, warmer climate than regions of Asia, where much of the agricultural land is projected to become wetter.

Food produced in the Americas could therefore be more susceptible to climatic hazards. For instance, the United States is a major exporter of staple grains and currently ships maize to countries across the globe. Even a modest increase in the risk of compound droughts in the future climate could lead to regional supply shortfalls that could in turn cascade into the global market, affecting global prices and amplifying food insecurity.

"The potential for a food security crisis increases even if these droughts aren't affecting major food producing regions but rather many regions that are already vulnerable to food insecurity," said coauthor Weston Anderson, an assistant research scientist at the Earth System Science Interdisciplinary Center at the University of Maryland. "Simultaneous droughts in food insecure regions could in turn amplify stresses on international agencies responsible for disaster relief by requiring the provision of humanitarian aid to a greater number of people simultaneously."

There is some good news, Anderson said. The researchers' work is based on a high fossil fuel emissions scenario, and in recent years, the global community has made progress toward lowering carbon emissions which would greatly mitigate the frequency and intensity of co-occurring droughts by the end of the 21st century.

Also, the occurrence of nearly 75% of compound droughts alongside ENSO events in the future climate highlights the potential to predict where these droughts may occur with a lead time of up to nine months.

"This means that co-occurring droughts during ENSO events will likely affect the same geographical regions they do today albeit with greater severity," said Deepti Singh. "Being able to predict where these droughts will occur and their potential impacts can help society develop plans and efforts to minimize economic losses and reduce human suffering from such climate-driven disasters."

Moving forward the researchers plan to take a closer look at how co-occurring droughts will affect various aspects of the global food network, how vulnerable communities are affected by and adapting to such climate extremes, as well as how society can be better prepared to manage the risk of increasing simultaneous disasters.

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