Extreme Exposure Research Articles

Generalizability of Heat-related Health Risk Associations Observed in a Large Healthcare Claims Database of Patients with Commercial Health Insurance.

Extreme ambient heat is unambiguously associated with a higher risk of illness and death. The Optum Labs Data Warehouse (OLDW), a database of medical claims from US-based patients with commercial or Medicare Advantage health insurance, has been used to quantify heat-related health impacts. Whether results for the insured subpopulation are generalizable to the broader population has, to our knowledge, not been documented. We sought to address this question, for the US population in California from 2012 to 2019. We examined changes in daily rates of emergency department encounters and in-patient hospitalization encounters for all-causes, heat-related outcomes, renal disease, mental/behavioral disorders, cardiovascular disease, and respiratory disease. OLDW was the source of health data for insured individuals in California, and health data for the broader population were gathered from the California Department of Health Care Access and Information. We defined extreme heat exposure as any day in a group of 2 or more days with maximum temperatures exceeding the county-specific 97.5th percentile and used a space-time-stratified case-crossover design to assess and compare the impacts of heat on health. Average incidence rates of medical encounters differed by dataset. However, rate ratios for emergency department encounters were similar across datasets for all causes [ratio of incidence rate ratios (rIRR) = 0.989; 95% confidence interval (CI) = 0.969, 1.009], heat-related causes (rIRR = 1.080; 95% CI = 0.999, 1.168), renal disease (rIRR = 0.963; 95% CI = 0.718, 1.292), and mental health disorders (rIRR = 1.098; 95% CI = 1.004, 1.201). Rate ratios for inpatient encounters were also similar. This work presents evidence that OLDW can continue to be a resource for estimating the health impacts of extreme heat.

Associations between exposure to extreme ambient heat and neural tube defects in Georgia, USA: A population-based case-control study

IntroductionThe association between extreme ambient heat exposures during pregnancy and neural tube defects (NTDs) in offspring remains unclear. This study sought to estimate the association between exposure to extreme ambient heat during periconception and NTDs. MethodsThis population-based case-control study in Georgia, USA (1994–2017) included 825 isolated NTD cases (473 anencephaly, 352 spina bifida) and 3,300 controls matched 1:4 on county of residence and time period of delivery. Daily ambient temperature data were linked to fetal death and birth records by county of residence. Extreme ambient heat exposure was defined as the number of consecutive days the daily apparent temperature exceeded the county-specific 95th percentile (derived over 1980–2010) during an eight-week periconception period. We calculated adjusted odds ratios (aORs) and 95% confidence intervals (CI) using conditional logistic regression models adjusted for maternal age, education, and ethnicity and month and year of last menstrual period. ResultsThe aORs for NTDs were 1.09 (95% CI 1.01, 1.17), 1.18 (95% CI 1.03, 1.36), and 1.29 (95% CI 1.04, 1.58) for exposure to 1–2, 3–5, and 6 or more consecutive days with apparent ambient temperatures exceeding the county-specific 95th percentile during periconception, respectively, compared to no days of extreme ambient heat exposure. Weekly analysis of extreme heat exposure indicated consistently elevated odds of offspring NTDs during periconception. These results were largely driven by spina bifida cases. ConclusionsOur results highlight potential health threats posed by increasing global average temperatures for pregnant people with implications for increased risk of neural tube defects in their offspring.

Lactating striped hamsters (Cricetulus barabensis) do not decrease the thermogenic capacity to cope with extreme cold temperature

For small non-hibernating mammals, a high thermogenic capacity is important to increase activity levels in the cold. It has been previously reported that lactating females decrease their thermogenic activity of brown adipose tissue (BAT), whereas their capacity to cope with extreme cold remains uncertain. In this study we examined food intake, body temperature and locomotor behavior, resting metabolic rate, non-shivering thermogenesis, and cytochrome c oxidase activity, and the rate of state 4 respiration of liver, skeletal muscle, and BAT in striped hamsters (Cricetulus barabensis) at peak lactation and non- breeding hamsters (controls). The lactating hamsters and non- breeding controls were acutely exposed to −15°C, and several markers indicative of thermogenic capacity were examined. In comparison to non-breeding females, lactating hamsters significantly increased food intake and body temperature, but decreased locomotor behavior, and the BAT mass, indicative of decreased BAT thermogenesis at peak lactation. Unexpectedly, lactating hamsters showed similar body temperature, resting metabolic rate, non-shivering thermogenesis with non-breeding females after acute exposure to −15°C. Furthermore, cytochrome c oxidase activity of liver, skeletal muscle and BAT, and serum thyroid hormone concentration, and BAT uncoupling protein 1 expression, in lactating hamsters were similar with that in non-breeding hamsters after acute extreme cold exposure. This suggests that lactating females have the same thermogenic capacity to survive cold temperatures compared to non-breeding animals. This is particularly important for females in the field to cope with cold environments during the period of reproduction. Our findings indicate that the females during lactation, one of the highest energy requirement periods, do not impair their thermogenic capacity in response to acute cold exposure.

Extreme weather exposure and corporate carbon emissions management: Evidence from forty countries

Utilizing survey data for firms from 40 countries, we explore the impact of extreme weather exposure on corporate carbon emissions management. Our findings indicate that firms manage their carbon emissions better if they have suffered losses due to extreme weather events. These results persist after considering endogeneity concerns, including placebo tests, the Heckman two-stage method, propensity score matching, the instrumental variables approach, and other robustness tests. Cross-sectional analyses reveal that this impact is more pronounced for firms located in developed countries and in countries with superior climate protection and lower levels of carbon emissions. Furthermore, the effect of extreme weather exposure is more significant for firms with foreign ownership and political connections and those subject to an energy tax. Finally, improved management of carbon emissions accompanied by extreme weather exposure can lead to increased corporate capacity utilization and reduced production costs.

Increasing concurrent exposure of global breadbaskets to reproductive heat extremes

Abstract In recent years, circumglobal heatwaves are becoming increasingly frequent, motivating concerns about the concurrent exposure of global breadbaskets to heat extremes during crop reproductive periods. Here we project the likelihood of concurrent exposure of global breadbaskets of staple crops to widespread reproductive heat extremes. We find that circumglobal reproductive extreme heat exposure would be an agriculturally relevant climate feature in the coming decades. By 2028‒2057 (with approximately 2 oC warming above preindustrial levels), the probability of major breadbaskets of the world concurrently enduring at least 5 days of reproductive extreme heat over more than half of their croplands in a typical year is projected to rise from virtually unlikely to 0.43 for maize, 0.27 for wheat, 0.33 for rice and soybean. While as of 2050‒2079 (with approximately 3 oC warming above preindustrial levels), these probabilities would grow rapidly to 0.91, 0.83, 0.87, and 0.80, respectively. Should such dramatic increases in circumglobal reproductive extreme heat exposure occur, they could pose substantial stress on food production and agricultural adaptation, particularly when coinciding with agricultural droughts.

CRISPR-Cas9 mediated understanding of plants' abiotic stress-responsive genes to combat changing climatic patterns.

Multiple abiotic stresses like extreme temperatures, water shortage, flooding, salinity, and exposure to heavy metals are confronted by crop plants with changing climatic patterns. Prolonged exposure to these adverse environmental conditions leads to stunted plant growth and development with significant yield loss in crops. CRISPR-Cas9 genome editing tool is being frequently employed to understand abiotic stress-responsive genes. Noteworthy improvements in CRISPR-Cas technology have been made over the years, including upgradation of Cas proteins fidelity and efficiency, optimization of transformation protocols for different crop species, base and prime editing, multiplex gene-targeting, transgene-free editing, and graft-based heritable CRISPR-Cas9 approaches. These developments helped to improve the knowledge of abiotic stress tolerance in crops that could potentially be utilized to develop knock-out varieties and over-expressed lines to tackle the adverse effects of altered climatic patterns. This review summarizes the mechanistic understanding of heat, drought, salinity, and metal stress-responsive genes characterized so far using CRISPR-Cas9 and provides data on potential candidate genes that can be exploited by modern-day biotechnological tools to develop transgene-free genome-edited crops with better climate adaptability. Furthermore, the importance of early-maturing crop varieties to withstand abiotic stresses is also discussed in this review.

Who is ‘stuck’ in the past? The impact of the 1998 great flood on the adoption of agricultural technology in China

ABSTRACT This study estimates the impact of the 1998 Great Flood on the adoption of agricultural technology in China and its mechanism using a cross-sectional dataset collected from the ERA5-Land, the China Labor Force Dynamic Survey, the China Rural Statistical Yearbook, and the China Population Census. The analysis reveals an inverted U-shaped correlation between farmers’ exposure to the flood event and their propensity to embrace technological advancements in agriculture. Farmers who experienced medium flood exposure tend to be risk lovers and exhibit a 4.9% higher likelihood of adopting agricultural technology compared to their counterparts who did not experience the flood. On the contrary, farmers who faced extreme flood exposure tend to be risk averse and exhibit an 11.9% diminished likelihood of adopting agricultural technology compared to those who remained unscathed by the flood.

Unveiling community adaptations to extreme heat events using mobile phone location data

The escalating frequency, duration, and intensity of extreme heat events have posed a significant threat to human society in recent decades. Understanding the dynamic patterns of human mobility under extreme heat will contribute to accurately assessing the risk of extreme heat exposure. This study leverages an emerging geospatial data source, anonymous cell phone location data, to investigate how people in different communities adapt travel behaviors responding to extreme heat events. Taking the Greater Houston Metropolitan Area as an example, we develop two indices, the Mobility Disruption Index (MDI) and the Activity Time Shift Index (ATSI), to quantify diurnal mobility changes and activity time shift patterns at the city and intra-urban scales. The results reveal that human mobility decreases significantly in the daytime of extreme heat events in Houston while the proportion of activity after 8 p.m. is increased, accompanied with a delay in travel time in the evening. Moreover, these mobility-decreasing and activity-delaying effects exhibited substantial spatial heterogeneity across census block groups. Causality analysis using the Geographical Convergent Cross Mapping (GCCM) model combined with correlation analyses indicates that people in areas with a high proportion of minorities and poverty are less able to adopt heat adaptation strategies to avoid the risk of heat exposure. These findings highlight the fact that besides the physical aspect of environmental justice on heat exposure, the inequity lies in the population's capacity and knowledge to adapt to extreme heat. This research is the first of the kind that quantifies multi-level mobility for extreme heat responses, and sheds light on a new facade to plan and implement heat mitigations and adaptation strategies beyond the traditional approaches.

Climate change extreme events and exposure of local communities to water scarcity: a case study of QwaQwa in South Africa

ABSTRACT The exposure of local communities to multiple climate change-related events is on the rise across the globe. Despite extensive disaster research on climate change, exposure and vulnerability, few studies have focused on the exposure of local communities to multiple climate change-related events. For over a decade QwaQwa, in South Africa, has experienced persistent water crises which have been attributed to climate change and socio-economic drivers. However, there is a lack of understanding of the risk drivers to provide a solid basis for disaster risk reduction and resilience-building. This paper; therefore, aims to conduct analyses of hazards and exposure as part of risk analysis of climate change-related events; notably drought, flooding, wildfires, and water scarcity in QwaQwa. Quantitative and qualitative data sources included key informant interviews, household surveys, and field observations. The study employed the indicator method to analyse both the hazard and exposure. Qualitative data were anlysed using thematic analysis. On a five-point scale, the findings showed high indices of multiple hazards (3.6) and exposure (3.2). Analysis results were validated at a stakeholders’ workshop. The study recommends efficiency in implementing risk-sensitive land use plans, improving early warning systems, and the use of unmanned aerial vehicles to mitigate disaster risks.

The cost of climate change: A generalized cost function approach for incorporating extreme weather exposure into public transit accessibility

Public transit offers urban populations physical accessibility to resources and opportunities. However, at the same time, transit trips often expose users to extreme environmental conditions, such as extreme heat and cold since transit journeys usually include out-of-vehicle trip segments including walking and waiting. Such exposure can be considered as environmental health costs because exposure to weather extremes can lead to adverse health outcomes. Even worse, climate change is increasing the intensity and frequency of extreme weather events. In this context, how can we make public transit accessibility measures ready for climate change? This paper attempts to answer this question by developing a generalized cost function approach combining travel time and environmental health costs into an integrated measure of dual accessibility: a measure of the travel costs of accessing a fixed number of destinations. We synthesize transport science, environmental health, remote sensing, and urban climatology to empower the proposed framework. To demonstrate the utility of the proposed method, we carry out an example study that incorporates transit passengers' extreme cold exposure into accessibility measures in the city of Winnipeg, Manitoba, Canada. Further, we perform a social equity analysis to investigate whether the increase in total integrated costs (i.e., decrease in accessibility) due to the inclusion of environmental health costs disproportionately affects socially disadvantaged population groups. The proposed method enables a more realistic and practical measurement of public transit accessibility under climate change; thereby, improving the readiness and resilience of our society and transport systems for future challenges.

Extreme Temperatures, Birth Outcomes, and Social Inequalities: Evidence from South China

Abstract The impacts of climate change on health are a critical public health issue, but the association between extreme temperatures and birth outcomes remains poorly understood. This paper links over 1 million birth records from Dongguan, China, between 2004 and 2013, to meteorological data. We investigate the relationship between extreme temperatures and birth outcomes and explore the heterogeneity among different demographic and socioeconomic factors, including maternal migrant status, education level, and mode of delivery. We find that one percentage increase in the number of days exposed to extreme heat during pregnancy is associated with a reduction in birth weight of 2.31 g and a 2% increase in odds of low birth weight (LBW), while exposure to extreme cold temperatures is associated with a reduction in birth weight (0.66 g) and an increase in the risk of LBW (1%). The association between extreme high temperatures and adverse birth outcomes is stronger for groups with disadvantaged social status. Specifically, the migrant group (for extreme heat exposure, local residents, −0.37 g; intraprovincial migrants, −2.75 g; out-of-province migrants, −2.49 g), the less-educated group (for extreme heat exposure, middle school or below, −2.47 g; high school or above, −1.66 g), and the group with vaginal birth [for extreme heat exposure, cesarean sections (C-sections), −1.56 g; vaginal birth, −2.62 g] are more sensitive to extreme weather conditions. Our study provides further evidence about the association of extreme temperatures with birth outcomes and for vulnerable groups of pregnant women.

Durability of externally strengthened concrete prisms with CFRP laminates and galvanized steel mesh attached with epoxy adhesives and mortar

The long-term bond degradation and strength retention of flexural bond prisms strengthened with carbon fiber-reinforced polymer (CFRP) composite and galvanized steel mesh (GSM) systems, bonded to concrete using epoxy adhesives and cement-based mortar under aggressive conditioning regimes are compared in this paper. Notched prisms strengthened using low-cord density steel mesh (LSM) with epoxy (SME-strengthened) and cement mortar (SMM-strengthened), and CFRP-epoxy systems were weathered under saline water and direct sunlight for a period of 28 and 540 days. The results of the study were analyzed based on experimentally obtained ultimate load (Pu) values and empirically calculated average bond shear stress (τavg) and prism strength retention (Rp) values. The bond strength degraded by 39 and 34 % in CFRP strengthened, 2.9 and 33 % in SME strengthened, and 2.8 and 10.8 % in SMM-strengthened specimens following the 540-day exposure to saline water and direct sunlight, respectively. The average prism retention ratio was calculated to be 0.61 and 0.66 for CFRP-strengthened, 0.97 and 0.67 for SME-strengthened, and 0.97 and 0.89 for SMM-strengthened specimens after 540 days of saline water and direct sunlight exposure. Flexural prism environment strength reduction factors (CE) were proposed as 0.60, 0.95, and 0.95 for CFRP, SME, and SMM-strengthened specimens under saline water exposures and 0.65, 0.65, and 0.85 for CFRP, SME, and SMM strengthened specimens under direct sunlight exposures. Saline water exposure was observed to be most critical to all strengthening systems. Although CFRP-strengthened specimens showed minimum degradation in load-carrying capacity under both conditioning regimes, they showed maximum bond strength reduction in contrast to SMM-strengthened specimens. It was observed that the choice of bonding agent significantly influenced the extent of bond strength degradation under extreme exposure regimes, like those that prevail in the UAE and the Persian Gulf.

Association between baseline blood pressure variability and left heart function following short-term extreme cold exposure.

Extreme cold exposure has been widely considered as a cardiac stress and may result in cardiac function decompensation. This study was to examine the risk factors that contribute to changes in cardiovascular indicators of cardiac function following extreme cold exposure and to provide valuable insights into the preservation of cardiac function and the cardiac adaptation that occur in real-world cold environment. Seventy subjects were exposed to cold outside (Mohe, mean temperature -17 to -34°C) for one day, and were monitored by a 24-h ambulatory blood pressure device and underwent echocardiography examination before and after extreme cold exposure. After exposure to extreme cold, 41 subjects exhibited an increase in ejection fraction (EF), while 29 subjects experienced a decrease. Subjects with elevated EF had lower baseline coefficients of variation (CV) in blood pressure compared to those in the EF decrease group. Additionally, the average real variability (ARV) of blood pressure was also significantly lower in the EF increase group. Multivariate regression analysis indicated that both baseline CV and ARV of blood pressure were independent risk factors for EF decrease, and both indicators proved effective for prognostic evaluation. Correlation analysis revealed a correlation between baseline blood pressure CV and ARV, as well as EF variation after exposure to extreme cold environment. Our research clearly indicated that baseline cardiovascular indicators were closely associated with the changes in EF after extreme cold exposure. Furthermore, baseline blood pressure variability could effectively predict alterations in left cardiac functions when individuals were exposed to extreme cold environment.

Kidney Function Biomarkers During Extreme Heat Exposure in Young and Older Adults

This study investigates the effects of extreme heat exposure on kidney function using plasma-based biomarkers in young and older adults.

Physiological responses of the nickel hyperaccumulator Bornmuellera emarginata under varying nickel dose levels and pH in hydroponics

Abstract Background and aims The nickel hyperaccumulator Bornmuellera emarginata (Brassicaceae) is a species adapted to thrive on naturally nickel-enriched ultramafic soils in the Balkans and a promising candidate for use in nickel agromining. The main aim of this study was to provide insight into the physiological mechanisms of nickel hyperaccumulation in B. emarginata. Methods Bornmuellera emarginata was cultivated under various nickel exposure concentrations (control, 1, 10, and 100 µM nickel in solution), and different pH levels of the hydroponic solution for four weeks. During this period, the plants underwent assessment for various physiological parameters, including photosynthetic pigments, leaf relative water content, tolerance index, and metal accumulation in plant tissues. Results The results show that the translocation factors and bioconcentration factors were > 1 even at 1 µM nickel in solution. This confirms the ability of B. emarginata to hyperaccumulate nickel (up to 6600 mg kg−1) over a wide range of nickel concentrations in hydroponics. Nickel at 100 µM (a concentration that is an order of magnitude higher than the highest soil solution nickel concentration found in ultramafic soils) induced only mild physiological stress symptoms (e.g. a minor proline response). Alterations in the solution pH did not cause any significant effect on nickel accumulation in the plants. Conclusions Bornmuellera emarginata is a highly adapted nickel-tolerant and nickel hyperaccumulating species that shows very little stress responses even to extreme nickel exposure concentrations in hydroponics. This species shows interesting trade-off responses between nickel and other metals, including non-competitive uptake of zinc. The potential for this species to accumulate zinc should therefore be further explored.

Therapeutic characteristics of alveolar-like macrophages in mouse models of hyperoxia and LPS-induced lung inflammation.

Acute respiratory distress syndrome (ARDS) is a severe lung disease of high mortality (30-50%). Patients require lifesaving supplemental oxygen therapy; however, hyperoxia can induce pulmonary inflammation and cellular damage. Although alveolar macrophages (AMs) are essential for lung immune homeostasis, they become compromised during inflammatory lung injury. To combat this, stem cell-derived alveolar-like macrophages (ALMs) are a prospective therapeutic for lung diseases like ARDS. Using in vitro and in vivo approaches, we investigated the impact of hyperoxia on murine ALMs during acute inflammation. In vitro, ALMs retained their viability, growth, and antimicrobial abilities when cultured at 60% O2, whereas they die at 90% O2. In contrast, ALMs instilled in mouse lungs remained viable during exposure of mice to 90% O2. The ability of the delivered ALMs to phagocytose Pseudomonas aeruginosa was not impaired by exposure to 60 or 90% O2. Furthermore, ALMs remained immunologically stable in a murine model of LPS-induced lung inflammation when exposed to 60 and 90% O2 and effectively attenuated the accumulation of CD11b+ inflammatory cells in the airways. These results support the potential use of ALMs in patients with ARDS receiving supplemental oxygen therapy.NEW & NOTEWORTHY The current findings support the prospective use of stem cell-derived alveolar-like macrophages (ALMs) as a therapeutic for inflammatory lung disease such as acute respiratory distress syndrome (ARDS) during supplemental oxygen therapy where lungs are exposed to high levels of oxygen. Alveolar-like macrophages directly delivered to mouse lungs were found to remain viable, immunologically stable, phagocytic toward live Pseudomonas aeruginosa, and effective in reducing CD11b+ inflammatory cell numbers in LPS-challenged lungs during moderate and extreme hyperoxic exposure.

Plasma epinephrine and norepinephrine responses to extreme heat exposures in young and older adults.

Hyperthermia is known as a hyperadrenergic state, yet there is a lack of data on the sympathetic responses to ambient heat stress in humans. Therefore, we investigated the plasma epinephrine and norepinephrine concentrations of healthy young and older adults exposed to 3 h of very hot and dry, as well as hot and humid, heat, both with accompanying activities of daily living. We hypothesized that older adults, compared with young adults, would have augmented increases in epinephrine and norepinephrine concentrations secondary to increased thermal strain. Young (n = 20) and older (n = 18) participants underwent two 3-h heat exposures on different days: very hot and dry [47°C and 15% relative humidity (RH)] and hot and humid (41°C and 40% RH). To mimic heat generation comparable to activities of daily living, participants performed seven 5-min bouts of light cycling (approximately 3 METS) dispersed throughout the heat exposure. We measured plasma concentrations of epinephrine and norepinephrine at baseline, end, and 2-h postheat exposure. There was a group-wide increase in epinephrine from baseline to the end of the heat exposure (Δ19 ± 27 pg/mL; P < 0.001) in the hot and humid condition, but not in the very hot and dry condition (Δ6 ± 19 pg/mL; P = 0.10). There were group-wide decreases in norepinephrine concentrations from baseline to the end of the heat exposure in both the very hot and dry (Δ-131 ± 169 pg/mL; P < 0.001) and the hot and humid (Δ-138 ± 157 pg/mL; P < 0.001) conditions, with both returning to near baseline at 2-h postexposure. These data suggest that ambient heating with accompanying bouts of light intermittent exercise may lead to decreases in circulating concentrations of norepinephrine.NEW & NOTEWORTHY Herein we present plasma epinephrine and norepinephrine concentrations to 3 h of very hot and dry, as well as hot and humid, heat exposures with accompanying activities of daily living in young and older participants. We found 1) increased plasma concentrations of epinephrine in young and older adults following the hot and humid, but not the very hot and dry exposures and 2) decreased concentrations of norepinephrine in both groups following exposure to both conditions.

Extreme Humid-Heat Exposure and Mortality Among Patients Receiving Dialysis

Rationale & ObjectiveExposure to extreme heat events has been linked to increased morbidity and mortality in the general population. Patients receiving maintenance dialysis may be vulnerable to greater risks from these events, but this is not well understood. We sought to characterize the association of extreme heat events and the risk of death among patients receiving dialysis in the United States. Study DesignRetrospective cohort study. Setting & ParticipantsData from the United States Renal Data System were used to identify adults living in US urban settlements prone to extreme heat who initiated maintenance dialysis between 1997 and 2016. ExposureAn extreme heat event was defined as a time-updated heat index (a humid-heat metric) exceeding 40.6°C for ≥2 days or 46.1°C for ≥1 day. OutcomeDeath. Analytical ApproachCox proportional hazards regression to estimate the elevation in risk of death during a humid-heat event adjusted for age, sex, year of dialysis initiation, dialysis modality, poverty level, and climate region. Interactions between humid-heat and these same factors were explored. ResultsAmong 945,251 adults in 245 urban settlements, the mean age was 63 years and 44% were female. During a median follow-up of 3.6 years, 498,049 adults were exposed to at least one of 7,154 extreme humid-heat events, and 500,025 deaths occurred. In adjusted models, there was an increased risk of death (hazard ratio 1.18; 95% confidence interval 1.15-1.20) during extreme humid-heat exposure. Relative mortality risk was higher among patients living in the Southeast (P<0.001) compared with the Southwest. LimitationsPossibility of exposure misclassification, did not account for land use and air pollution co-exposures. ConclusionsThis study suggests that patients receiving dialysis face an increased risk of death during extreme humid-heat exposure.

Secretory structures in Baccharis platypoda DC. inflorescences (Asteraceae) and characterization of the chemical composition of its secretion.

Rocky outcrop environments at high altitudes have nutrient-poor soil, where species are exposed to water scarcity and high solar radiation. Baccharis platypoda DC. occurs in such an environment and has a rigid and transparent secretion that covers the entire inflorescence. We analysed and compared the secretory structures and their chemical composition in female and male inflorescences of B. platypoda, a dioecious species, to explore chemodiversity within this species and assess potential differences between individuals. Our investigation also aims to understand the occurrence of these substances in the genus Baccharis L. Chemical compounds and secretory structures were similar in female and male inflorescences. There are glandular trichomes on the epidermis of the abaxial surface of bracts, and secretory ducts in the axis of the inflorescence, as well as in sepals, petals, and bracts. Histochemical tests were positive for phenolic compounds, flavonoids, proteins, pectin, and lipids, but not for mucilage. Flavonoid content varied between 6.24% and 9.81%, being higher in female inflorescences. Chromatography revealed the presence of several phenolic compounds, some terpenes, and other less frequent classes in both female and male inflorescences. We highlight that trichomes found on these surfaces produce abundant phenolic compounds. These act as natural defence agents, absorbing UV radiation and minimizing oxidative stress to plant cells. The chemical composition of the secretion covering the inflorescences may reflect adaptation and survival mechanisms of these organisms under extreme sun exposure.

The U.S. Midwest and High Plains Aquifer-fed croplands are previously unrealized hotspots of extreme evaporative demand exposure

Total evaporative demand or atmospheric thirst is a primary determinant of agroecosystems’ water use and an indispensable input to scientifically based irrigation design and management. However, despite its extensive use to represent agricultural environments, it has not been assessed for its extreme behavior. Prolonged exposure to extreme evaporative demand conditions a.k.a thirstwaves can be especially stressful for agricultural output, water use, and management, but remain uninvestigated owing to lack of meaningful metrics for quantifying and reporting ‘extreme thirst exposure’. In this letter, I present spatial (county-level) and temporal (1981–2021) changes in exposure to extreme thirst during the agricultural growing season across the conterminous U.S. (CONUS). Using a fully physical metric of evaporative demand, i.e., standardized short crop reference evapotranspiration (ETo), I define two novel measures: cumulative extreme thirst exposure (thirstcum) and average extreme thirst anomaly (thirstanom) to represent the seasonal-level severity of thirstwaves. Both metrics showed significant spatiotemporal variation with long-term averages of 12 mm (thirstcum) and 0.66 mm d−1 (thirstanom) for CONUS. Distinct spatial patterns were revealed for extreme thirst exposure that had little in common with those observed for total ETo. Spatially, hotspots of high extreme thirst exposure were co-located with the Midwest and High Plains aquifer regions, that account for 64% of total acreage and 28% of irrigated acreage nationally, respectively. Critical for food and water security, these regions have experienced the highest extreme thirst exposure nationally, hence necessitating reevaluation of regional disparities in water stress. While thirstcum and thirstanom have increased by 5.6 mm and 0.21 mm d−1 on an average in CONUS, worsening of extreme thirst exposure is especially concerning for the High Plains aquifer region (12.6 mm and 0.54 mm d−1, respectively). The emergence of previously unrealized hotspots in regions critical for water security uncover potential pitfalls for planning and adaptation that may result from overlooking extreme measures of evaporative demand.