It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Wednesday, January 24, 2024
Risk of death during heatwaves in Brazil linked to socioeconomic factors
48,075 deaths in 2000-2018 could be attributed to the increasingly frequent heatwaves in Brazil
A new study suggests that heatwaves are exacerbating socioeconomic inequalities in Brazil, with people who are female, elderly, Black, Brown, or who have lower educational levels potentially facing greater risk of death during heatwaves. Djacinto Monteiro dos Santos of Universidade Federal do Rio de Janeiro, Brazil, and colleagues present these findings in the open-access journal PLOS ONE on January 24, 2024.
As climate change progresses, heatwaves are becoming hotter, longer, and more frequent in many regions worldwide, including in Brazil. Heatwaves can increase the risk of dying from a chronic condition, such as heart disease or pneumonia. Prior research has linked heatwaves in Brazil to higher risk of death. However, few studies have explored the role played by socioeconomic and demographic factors in heat-related deaths in Brazil.
To help clarify, Monteiro dos Santos and colleagues analyzed death rates during heatwaves between 2000 and 2018 in 14 major urban areas of Brazil, representing more than one third of the national population.
In line with prior research, they found that Brazil experienced three to 11 heatwaves per year in the 2010s, up from zero to three per year in the 1970s. Between 2000 and 2018, 48,075 deaths could be attributed to heatwaves, with the most frequent causes of death being circulatory diseases, respiratory diseases, and cancer.
Heatwave-related death rates varied between geographical regions within Brazil, which the researchers linked to known North-South inequalities pertaining to socioeconomic and health indicators, including life expectancy. Heatwave-related death rates were higher among people who were female, elderly, Black, Brown, or who had lower educational levels.
The researchers also found that a technique known as event-based surveillance analysis—which looks for emerging signals in social media rumors or other sources—would have been unsuccessful in providing early warning of high rates of heatwave-related deaths, suggesting that extreme heatwaves are neglected disasters in Brazil.
These findings could help inform efforts to reduce deaths during future heatwaves. Further research could address some of this study’s limitations by covering a longer time period, incorporating more socioeconomic indicators, and using data from more than one weather station for each urban area.
The authors add: “Heatwaves were responsible for more than 48,000 deaths in urban areas in Brazil. Women, black and brown people, the elderly and those with a lower level of education are the most affected, reinforcing how human-induced climate change has exacerbated the socioeconomic inequalities in the country.”
Citation: Monteiro dos Santos D, Libonati R, Garcia BN, Geirinhas JL, Salvi BB, Lima e Silva E, et al. (2024) Twenty-first-century demographic and social inequalities of heat-related deaths in Brazilian urban areas. PLoS ONE 19(1): e0295766. https://doi.org/10.1371/journal.pone.0295766
Author Countries: Brazil, Portugal
Funding: D.M.S. acknowledges the support of FIOCRUZ [grant VPPCB-003-FIO-19], FAPERJ [grant E-26/205.890/2022]. RL was supported by FAPERJ [grant E-26/200.329/2023 and E-26/210.078/2023] and CNPQ [grant 311487/2021-1]. A.R. and R.M.T. were supported by Fundação para a Ciência e a Tecnologia, I.P./ MCTES through national funds (PIDDAC)” –UIDB/50019/2020 and also by Project ROADMAP (JPIOCEANS/0001/2019). B.N.G. was supported by CNPQ [grant 161075/2021-5]. J.L.G. acknowledges the support of FCT (Fundação para a Ciência e Tecnologia) for the PhD Grant 2020.05198.BD. HG was supported by CNPQ [grant 317617/2021-4] and International Joint Laboratory “Sentinela” (Fiocruz, UnB, IRD) (grant IRD LMI-Sentinela). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
(A) LOCATION OF THE ORDOS PLATEAU; (B) AERIAL PHOTOGRAPH FROM THE SOUTHERN SIDE OF SHI-ER-LIAN-CHENG (AN ANCIENT CITY WHICH HAS BEEN OCCUPIED FOR THE LONGEST TIME IN THE ORDOS PLATEAU); (C) DE- TAILED SATELLITE IMAGE OF THE ORDOS PLATEAU (GOOGLE EARTH, 2010). THE PURPLE LINE MARKS THE LOCATION OF THE MING GREAT WALL, AND THE YELLOW STARS REPRESENT THE FOLLOWING ANCIENT CITIES: 1, TIEZHUQUAN; 2, ZHANGJIACHANG; 3, BAYANHURIHU; 4, TONGWAN CITY; 5, SHI-ER-LIAN-CHENG.
Recent research has unveiled the intricate patterns of human settlements on China's Ordos Plateau, stretching back to the Neolithic Age. This study analyzing the spatiotemporal distribution of these settlements, sheds new light on the dynamic interplay between humans and their environment through millennia.
The Ordos Plateau, a distinctive geomorphic entity in China, has been a cradle of human civilization since the late Paleolithic era. Its unique geographical and climatic conditions have fostered a rich tapestry of human history, reflected in the settlement patterns that have evolved over thousands of years.
On a new study (https://doi.org/10.1007/s11442-023-2179-6) published in the periodical Journal of Geographical Sciences, researchers from Lanzhou University meticulously analyzed the spatial and temporal characteristics of settlements on the Ordos Plateau since the Neolithic Age. They found that the settlements predominantly clustered in the southern and eastern parts of the plateau, areas less affected by the deserts. The settlement sizes varied, with most being small to medium, and a few larger ones. The spatial distribution displayed fractal characteristics, indicating an agglomerated pattern. This study also discovered that the frequency of these settlements underwent periodic fluctuations, influenced by various natural factors such as climate change, hydrology, and topography. Human factors, including socio-political dynamics, wars, and changes in subsistence strategies, also played a significant role.
The study concludes that the Ordos Plateau's human settlements were a product of complex interactions between natural environments and human activities. These settlements serve as a historical record, reflecting how humans have adapted to and influenced their surroundings. Professor Wang Nai’ang, the corresponding author of this article, states, "This research provides unprecedented insights into the resilience and adaptability of human societies in the face of environmental challenges. It underscores the profound impact of climate and socio-political forces in shaping human settlements over millennia."
This research not only contributes to our understanding of historical human-land relationships in the Ordos Plateau but also offers valuable lessons for modern society in terms of sustainable living and environmental management. The findings highlight the importance of a holistic approach that considers both natural and human factors in studying human settlements.
National Natural Science Foundation of China, No.41871021; Gansu Province Science and Technology Project, No.22JR5RA161; The Young Teachers’ Scientific Research Ability Improvement Program of Northwest Normal University, No.NWNU-SKQN2022-04
Journal of Geographical Sciences is an international and multidisciplinary peer-reviewed journal focusing on human-nature relationships. It publishes papers on physical geography, natural resources, environmental sciences, geographic information, remote sensing and cartography. Manuscripts come from different parts of the world.
ABOUT HALF OF EUROPE’S PLASTIC WASTE IS EXPORTED TO SEVERAL COUNTRIES IN THE GLOBAL SOUTH, INCLUDING VIETNAM. A UTRECHT UNIVERSITY RESEARCH TEAM VENTURED TO MINH KHAI CRAFT VILLAGE, THE LARGEST RECYCLING HUB IN VIETNAM, TO FOLLOW THE RECYCLING PATH. HERE A WOMAN IS PICTURED WALKING THROUGH THE VILLAGE'S STREETS.
Despite strict EU regulations on plastic recycling, there is little oversight on plastic waste shipped from the EU to Vietnam. A large percentage of the exported European plastic cannot be recycled and gets dumped in nature. That is what new research led by Utrecht University’s Kaustubh Thapa has found.
Following the recycling path
About half of Europe’s plastic waste is exported to a number of countries in the Global South, including Vietnam. A Dutch and Vietnamese research team ventured to Minh Khai Craft Village, the largest recycling hub in Vietnam, to follow the recycling path of European plastic.
Shifting responsibilities
“We observed people cooking, eating and living within the recycling facility, surrounded by the noxious fumes of melting plastic. Children play in this suffocating environment,” Kaustubh Thapa, lead researcher, recounts. According to the research, seven million litres of toxic wastewater is dumped into the waterways of the village daily. “Although such waste trade is profitable for some, shifting producer responsibility of waste management to villages like these causes harm to people, communities and the environment.”
Striking contrast
Currently, UN negotiations for an international plastics treaty are ongoing. Thapa’s new research shows the striking contrast between Vietnamese and European policies and the realities in recycling hubs in the Global South. “European consumers make an effort to separate recycling, yet we can clearly see that their efforts are, for a considerable percentage, in vain,” says Thapa. He adds, “focusing on increasing recycling rates in the EU without systematically tackling the associated human and environmental harm throughout the entire value chain is neither ethical, circular or sustainable.”
Tackling the problem
The researchers are not without hope: they believe that outsourcing plastic waste for recycling is possible in a sustainable way. “The European Green New Deal, its Circular Economy Actions Plan and the ongoing UN talks around a legally binding Global Plastics Treaty cannot ignore our findings. As we consume more and more, and thus generate more waste, waste trade for recycling must be tackled on a systematic level,” Thapa concludes.
Towards a Just Circular Economy Transition: the Case of European Plastic Waste Trade to Vietnam for Recycling
New tool predicts flood risk from hurricanes in a warming climate
Using New York as a test case, the model predicts flooding at the level experienced during Hurricane Sandy will occur roughly every 30 years by the end of this century.
Coastal cities and communities will face more frequent major hurricanes with climate change in the coming years. To help prepare coastal cities against future storms, MIT scientists have developed a method to predict how much flooding a coastal community is likely to experience as hurricanes evolve over the next decades.
When hurricanes make landfall, strong winds whip up salty ocean waters that generate storm surge in coastal regions. As the storms move over land, torrential rainfall can induce further flooding inland. When multiple flood sources such as storm surge and rainfall interact, they can compound a hurricane’s hazards, leading to significantly more flooding than would result from any one source alone. The new study introduces a physics-based method for predicting how the risk of such complex, compound flooding may evolve under a warming climate in coastal cities.
One example of compound flooding’s impact is the aftermath from Hurricane Sandy in 2012. The storm made landfall on the East Coast of the United States as heavy winds whipped up a towering storm surge that combined with rainfall-driven flooding in some areas to cause historic and devastating floods across New York and New Jersey.
In their study, the MIT team applied the new compound flood-modeling method to New York City to predict how climate change may influence the risk of compound flooding from Sandy-like hurricanes over the next decades.
They found that, in today’s climate, a Sandy-level compound flooding event will likely hit New York City every 150 years. By midcentury, a warmer climate will drive up the frequency of such flooding, to every 60 years. At the end of the century, destructive Sandy-like floods will deluge the city every 30 years — a fivefold increase compared to the present climate.
“Long-term average damages from weather hazards are usually dominated by the rare, intense events like Hurricane Sandy,” says study co-author Kerry Emanuel, professor emeritus of atmospheric science at MIT. “It is important to get these right.”
While these are sobering projections, the researchers hope the flood forecasts can help city planners prepare and protect against future disasters. “Our methodology equips coastal city authorities and policymakers with essential tools to conduct compound flooding risk assessments from hurricanes in coastal cities at a detailed, granular level, extending to each street or building, in both current and future decades,” says study author Ali Sarhadi, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences.
The team’s open-access study appears online today in the Bulletin of the American Meteorological Society. Co-authors include Raphaël Rousseau-Rizzi at MIT’s Lorenz Center, Kyle Mandli at Columbia University, Jeffrey Neal at the University of Bristol, Michael Wiper at the Charles III University of Madrid, and Monika Feldmann at the Swiss Federal Institute of Technology Lausanne.
The seeds of floods
To forecast a region’s flood risk, weather modelers typically look to the past. Historical records contain measurements of previous hurricanes’ wind speeds, rainfall, and spatial extent, which scientists use to predict where and how much flooding may occur with coming storms. But Sarhadi believes that the limitations and brevity of these historical records are insufficient for predicting future hurricanes’ risks.
“Even if we had lengthy historical records, they wouldn’t be a good guide for future risks because of climate change,” he says. “Climate change is changing the structural characteristics, frequency, intensity, and movement of hurricanes, and we cannot rely on the past.”
Sarhadi and his colleagues instead looked to predict a region’s risk of hurricane flooding in a changing climate using a physics-based risk assessment methodology. They first paired simulations of hurricane activity with coupled ocean and atmospheric models over time. With the hurricane simulations, developed originally by Emanuel, the researchers virtually scatter tens of thousands of “seeds” of hurricanes into a simulated climate. Most seeds dissipate, while a few grow into category-level storms, depending on the conditions of the ocean and atmosphere.
When the team drives these hurricane simulations with climate models of ocean and atmospheric conditions under certain global temperature projections, they can see how hurricanes change, for instance in terms of intensity, frequency, and size, under past, current, and future climate conditions.
The team then sought to precisely predict the level and degree of compound flooding from future hurricanes in coastal cities. The researchers first used rainfall models to simulate rain intensity for a large number of simulated hurricanes, then applied numerical models to hydraulically translate that rainfall intensity into flooding on the ground during landfalling of hurricanes, given information about a region such as its surface and topography characteristics. They also simulated the same hurricanes’ storm surges, using hydrodynamic models to translate hurricanes’ maximum wind speed and sea level pressure into surge height in coastal areas. The simulation further assessed the propagation of ocean waters into coastal areas, causing coastal flooding.
Then, the team developed a numerical hydrodynamic model to predict how two sources of hurricane-induced flooding, such as storm surge and rain-driven flooding, would simultaneously interact through time and space, as simulated hurricanes make landfall in coastal regions such as New York City, in both current and future climates.
“There’s a complex, nonlinear hydrodynamic interaction between saltwater surge-driven flooding and freshwater rainfall-driven flooding, that forms compound flooding that a lot of existing methods ignore,” Sarhadi says. “As a result, they underestimate the risk of compound flooding.”
Amplified risk
With their flood-forecasting method in place, the team applied it to a specific test case: New York City. They used the multipronged method to predict the city’s risk of compound flooding from hurricanes, and more specifically from Sandy-like hurricanes, in present and future climates. Their simulations showed that the city’s odds of experiencing Sandy-like flooding will increase significantly over the next decades as the climate warms, from once every 150 years in the current climate, to every 60 years by 2050, and every 30 years by 2099.
Interestingly, they found that much of this increase in risk has less to do with how hurricanes themselves will change with warming climates, but with how sea levels will increase around the world.
“In future decades, we will experience sea level rise in coastal areas, and we also incorporated that effect into our models to see how much that would increase the risk of compound flooding,” Sarhadi explains. “And in fact, we see sea level rise is playing a major role in amplifying the risk of compound flooding from hurricanes in New York City.”
The team’s methodology can be applied to any coastal city to assess the risk of compound flooding from hurricanes and extratropical storms. With this approach, Sarhadi hopes decision-makers can make informed decisions regarding the implementation of adaptive measures, such as reinforcing coastal defenses to enhance infrastructure and community resilience.
“Another aspect highlighting the urgency of our research is the projected 25 percent increase in coastal populations by midcentury, leading to heightened exposure to damaging storms,” Sarhadi says. “Additionally, we have trillions of dollars in assets situated in coastal flood-prone areas, necessitating proactive strategies to reduce damages from compound flooding from hurricanes under a warming climate.”
This research was supported, in part, by Homesite Insurance.
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Written by Jennifer Chu, MIT News
Paper: “Climate change contributions to increasing compound flooding risk in New York City”
“Climate change contributions to increasing compound flooding risk in New York City”
NEWS RELEASE
Paper provides a clearer picture of severe hydro hazards
Understanding the likelihood of a major rain event, or pluvial, following a drought and vice versa will aid in planning and preparation for ‘climate hazard flip.’
Over the last two decades an estimated three billion people have been affected by water-related natural disasters such as droughts and floods. Climate change is expected to increase the frequency of these hydro hazards, with some prognosticators estimating there will be upwards of $3.7 trillion in water-related damage over the next 30 years in the U.S. alone. Beyond damaging homes and infrastructure, severe wet and dry spells will also devastate crops and deplete water reservoirs.
An increasing area of interest to researchers is the frequency of compound drought and pluvial flooding (caused by quick, heavy rainfall or sustained rainfall beyond the norm), which is when both occur in succession in the same area within a year of each other. Historically, this level of coincidence has been under-examined.
Of similar interest is when the reverse happens: extreme rainfall followed by a meteorological drought. Meteorological drought is when dry weather patterns prevail, which can eventually trigger hydrological drought, leading to dry streams and plunging reservoir levels, such as what happened at Lake Mead in 2022.
A new study co-authored by researchers in the University of Arkansas Department of Geosciences, as well as colleagues in China, now provides a global examination of drought-pluvial volatility — or the tendency to shift from one extreme to another (from dry to wet or wet to dry) in a short period of time.
Yichan Li, a Ph.D. candidate at the U of A, was the first of four authors on the paper, “Observational Uncertainty for Global Drought-Pluvial Volatility,” published in Water Resources Research, while Linyin Cheng, an assistant professor of geosciences, was second author.
The study looks at extreme dry-to-wet and wet-to-dry transitions over the past seven decades through event coincidence analysis, a method of quantifying the number of consecutive extreme events that also considers instantaneous or lagged responses within an uncertain period between them. The study used three widely used climate data sets to provide evidence of increased drought-pluvial volatility on time scales of less than a year.
The team also evaluated the accuracy of these data sets, finding varying strengths and weaknesses of each due to observational uncertainties in data collection. For instance, the remoteness of a region may play a role in collecting accurate data.
Averaged out at the global scale, the team found that 15.46% of all meteorological droughts were succeeded by a pluvial the following season. The wet-to-dry transition percentage proved remarkably similar: 15.49%. However, prominent differences exist when looking at particular regions.
Toward that end, the study provides a map demonstrating how incidents of these two phenomena are distributed globally. Overall, the spatial pattern of extreme dry-to-wet and wet-to-dry events’ coincidence rates is largely in agreement among the three data sets, though there is prominent regional variability.
For instance, in Eurasia since the mid-20th century, there is a relatively low probability for meteorological droughts transitioning to pluvials, but a higher chance for the opposite scenario, rapid shifts from wet to dry events. A similar pattern also exists over western North America, which sees severe wet to dry transitions at a frequency greater than 17% on average. Conversely, South Asia and Australia are more prone to immediate transitions from meteorological droughts to pluvials.
The authors noted: “Our findings indicate that differences associated with drought-pluvial volatility among the considered observations are in many regions larger than that of their single events [droughts or pluvials alone], highlighting a need of to use multiple independent observation-based data sets for more robust examinations when studying such compound extreme events.”
Ultimately, the authors stress the need to use multiple independent observation-based data sets when analyzing extreme, compound dry-to-wet events. This will provide clearer guidelines for climate-related decision making, especially water resources planning, as well as ensure better accuracy when modeling future weather events.
Additional co-authors in the paper included Chiyun Miao, with Beijing Normal University and Zhiyong Liu, with Sun Yat-sen University.
LEFT TO RIGHT: HANG DU, JUN YAN, JUANWEI CHEN: “AS WE ADVANCE THE INTEGRATION OF RENEWABLE ENERGIES, IT IS IMPERATIVE TO RECOGNIZE THAT WE ARE VENTURING INTO UNCHARTED TERRITORY, WITH UNKNOWN VULNERABILITIES AND CYBER THREATS.”
The hurrying pace of societal electrification is encouraging from a climate perspective. But the transition away from fossil fuels toward renewable sources like wind presents new risks that are not yet fully understood.
Researchers from Concordia and Hydro-Quebec presented a new study on the topic in Glasgow, United Kingdom at the 2023 IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm). Their study explores the risks of cyberattacks faced by offshore wind farms. Specifically, the researchers considered wind farms that use voltage-source-converter high-voltage direct-current (VSC-HVDC) connections, which are rapidly becoming the most cost-effective solution to harvest offshore wind energy around the world.
“Offshore wind farms are connected to the main power grid using HVDC technologies. These farms may face new operational challenges,” Chen explains.
“Our focus is to investigate how these challenges could be intensified by cyber threats and to assess the broader impact these threats might have on our power grid.”
Concordia PhD student Hang Du, CIISE associate professor Jun Yan and Gina Cody School dean Mourad Debbabi, along with Rawad Zgheib from the Hydro-Quebec Research Institute (IREQ), also contributed to the study. This work is part of a broad research collaboration project involving the group of Prof. Debbabi and the IREQ cybersecurity research group led by Dr. Marthe Kassouf and involving a team of researchers including Dr. Zgheib.
Complex and vulnerable systems
Offshore wind farms require more cyber infrastructure than onshore wind farms, given that offshore farms are often dozens of kilometres from land and operated remotely. Offshore wind farms need to communicate with onshore systems via a wide area network. Meanwhile, the turbines also communicate with maintenance vessels and inspection drones, as well as with each other.
This complex, hybrid-communication architecture presents multiple access points for cyberattacks. If malicious actors were able to penetrate the local area network of the converter station on the wind farm side, these actors could tamper with the system’s sensors. This tampering could lead to the replacement of actual data with false information. As a result, electrical disturbances would affect the offshore wind farm at the points of common coupling.
In turn, these disturbances could trigger poorly dampened power oscillations from the offshore wind farms when all the offshore wind farms are generating their maximum output. If these cyber-induced electrical disturbances are repetitive and match the frequency of the poorly dampened power oscillations, the oscillations could be amplified. These amplified oscillations might then be transmitted through the HVDC system, potentially reaching and affecting the stability of the main power grid. While existing systems usually have redundancies built in to protect them against physical contingencies, such protection is rare against cyber security breaches.
“The system networks can handle events like router failures or signal decays. If there is an attacker in the middle who is trying to hijack the signals, then that becomes more concerning,” says Yan, the Concordia University Research Chair (Tier 2) in Artificial Intelligence in Cyber Security and Resilience.
Yan adds that considerable gaps exist in the industry, both among manufacturers and utilities. While many organizations are focusing on corporate issues such as data security and access controls, much is to be done to strengthen the security of operational technologies.
He notes that Concordia is leading the push for international standardization efforts but acknowledges the work is just beginning.
“There are regulatory standards for the US and Canada, but they often only state what is required without specifying how it should be done,” he says. “Researchers and operators are aware of the need to protect our energy security, but there remain many directions to pursue and open questions to answer.”
This research is supported by the Concordia/Hydro-Québec/Hitachi Partnership Research Chair, with additional support from NSERC and PROMPT.
CARL R. WOESE INSTITUTE FOR GENOMIC BIOLOGY, UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
IMAGE:
ESTHER NGUMBI, LEFT, AND ERINN DADY STUDIED THE EFFECT OF ARBUSCULAR MYCORRHIZAL FUNGI, CATERPILLARS, AND THE VARIETY OF TOMATO PLANTS ON PLANT CHEMISTRY.
Plants produce a range of chemicals known as volatile organic compounds that influence their interactions with the world around them. In a new study, researchers at the University of Illinois Urbana-Champaign investigated how the type and amount of these VOCs change based on different features of tomato plants.
The smell of cut grass is one of the defining fragrances of summer. Smells like that are one of the ways plants signal their injury. Because they cannot run away from danger, plants have evolved to communicate with each other using chemical signals. They use VOCs for a variety of reasons: to help prepare their own defenses, to warn each other of threats, to recruit beneficial soil microbes that can help plants grow, and to alert insect predators that there is a pest chewing on that plant’s leaves.
“When a caterpillar chews on a leaf, the plant sends out a signal that calls out to the caterpillar’s predators. It’s like a billboard that tells them where lunch is,” said Erinn Dady, a graduate student in the Ngumbi lab.
Studying the factors that influence VOC emissions, therefore, is key to understanding plant health. In the past, other studies have looked at how soil microbes like arbuscular mycorrhizal fungi or caterpillars or the variety of tomato plant can influence VOCs. In the current study, the researchers studied the collective influence of all these factors on plant chemistry using four tomato varieties—two heirlooms and two hybrids.
“Previous studies looked at tomato varieties that are grown conventionally at a massive scale for processing, and are not usually grown by small farmers, so we decided to ask Illinois farmers what they grow. Based on their feedback, we chose tomato varieties that are commonly grown in central Illinois,” Dady said. The hybrids used were Mountain Fresh and Valley Girl, and the organic heirlooms were Amish Paste and Cherokee Purple.
The researchers compared the responses of untreated plants to those that had been exposed to AMF, caterpillars, or both. They studied the VOCs by enclosing the eight-week-old tomato plants with an odor-blocking oven bag for an hour. They drew out the air around the plants and analyzed the different chemicals produced by each plant using gas chromatography-mass spectrophotometry.
The AMF and the caterpillars, separately, decreased the volatile emissions in all four varieties of tomato plants. Their effect when present together was minimal compared to the effects when either one was present.
Although it is unclear why the beneficial fungal associations decreased the VOCs, it is concerning that the plants were not as responsive to the caterpillars. Furthermore, the hybrid tomatoes emitted lower quantities of volatiles compared to the heirloom tomatoes. “Heirloom tomatoes—the big, juicy tomatoes we all love—are bred for flavor. Meanwhile, hybrids are grown for large scale conventional production, which comes at a cost to the plant,” said Esther Ngumbi (CIS/MMG), an assistant professor of integrative biology. “Our work suggests that we are compromising plant defenses through our breeding processes.”
The plants were also evaluated based on their growth both above the ground and in the soil. The researchers found that plants that had associations with the fungi had higher leaf biomass and more complex root structures.
“AMF form partnerships in over 80% of the land plants, setting up a trade where the fungi extract nutrients from the soil in exchange for carbon from plants,” Dady said. “We found that, especially in Cherokee Purple, AMF may confer additional benefits, including enhanced growth and greater emission of VOCs.”
Surprisingly, the plants that were treated with caterpillars had greater plant growth. “These plants had more biomass in both their roots and above the ground, which seems counterintuitive because they’ve actively been eaten. I would assume they would have less biomass,” Dady said. “It is possible that the caterpillars triggered a growth response, similar to how you prune a tree to make it produce new growth.”
The researchers are interested in further investigating the growth response to caterpillars. “It’s possible that the plants decided that the number of caterpillars we were using were not sufficient to be considered a threat and that’s why they kept growing. It is also possible that the caterpillars weren’t hungry enough to cause enough damage,” Ngumbi said.
“There’s a lot going on behind the scenes that we don’t yet understand. For example, we are barely scratching the surface in understanding the role of different microbes,” Dady said. “People tend to think that plants are not intelligent, but our studies have shown that they are actively responding to the environment around them using chemistry.”
“We are trying to spread the gospel of plant chemistry, it’s the language plants use to communicate and we are excited to learn more,” Ngumbi said.
The study “Plant Variety, Mycorrhization, and Herbivory Influence Induced Volatile Emissions and Plant Growth Characteristics in Tomato” was published in the Journal of Chemical Ecology and can be found at https://doi.org/10.1007/s10886-023-01455-w. The work was funded by the University of Illinois Urbana-Champaign.
