Drought Intensity Research Articles

Code 1583 - preliminary steps for studies to assess the safety of an earth dam in terms of use and lowering the reservoir level for public supply during the water crisis

The spring 2021 climate forecast report from the National Institute of Meteorology (INMET) and the National Institute for Space Research (INPE) indicated an increased possibility of below-average rainfall in almost the entire region of the state of Paraná, which is consistent with the historical trend of decreasing rainfall in the Paraná River basin since the 1990s, with an intensification in the 2000s. This led to a water emergency situation in Paraná, which was decreed by the state government in 2020 and 2021. The Curitiba region depends on the Curitiba and Metropolitan Region Integrated Supply System (SAIC). Due to the intense drought in 2020 and 2021, SAIC's reservoirs suffered a significant reduction in stored water levels and volumes, reaching 28% of their total capacity in August 2020. This was the biggest water crisis in the last 90 years in the history of the state of Paraná, with several reservoirs reaching levels close to historic lows, but maintaining constant discharges in order to maintain power generation or public supply. In these cases, with the reservoirs at lower levels and with a smaller volume, the variation in the water level on the upstream slope of the earth dam varies differently from the levels when the dam and reservoir are in normal operation or outside of a water crisis. In view of the atypical behavior of reservoir levels, and based on good dam engineering practice, when the operating regime changes or the reservoir water level drops, the safety aspects of these structures should be reassessed through geotechnical analyses for conditions of rapid lowering, in order to learn how these structures behave under these conditions. This article sheds light on the important stages of this thorough technical investigation of the extensive documentation of a project like this, data on instrumentation and performance, how they were built and behaved during the construction and filling of the reservoir, knowledge of geotechnical parameters of the materials of the dam massif and foundation, recorded field observations made at the time of preliminary investigation during the design, project and construction phase; obtaining hydro-meteorological data from the region, in order to obtain the "as-built" geometry of the structure, with the aim of modeling the typical section reliably to the structure in the field in order to infer this numerical model and vice versa, and obtain results on its performance during this atypical period.

The human health burden of climate change: Non-economic losses and ethical considerations towards achieving planetary health

Climate change presents an urgent and growing threat to the health and well-being of people and the planet. More frequent and intense heatwaves, droughts and floods are breaching critical ecosystem boundaries, causing cascading impacts that are increasingly complex to govern. Unsustainable development pathways and economic choices that are fueling the climate crisis are also directly engendering global health issues. Furthermore, the global response to climate change has been uneven and the lack of a conceptual framework for loss and damage has allowed developed countries the latitude to adopt differing takes on its framing, undermining the urgency and progression of the loss and damage mechanism to the detriment of developing countries. Current research on the governance of climate ethics posits that while economic and legal considerations largely influence climate policies, decision-making processes in climate adjacent sectors such as health need to be further grounded on ethically sound principles. Framing the health impacts of climate change as a moral issue can therefore be viewed as an effort to reshape the current political discourse with a humanistic lens and move the international community and state-level actors to action. The framing of this issue is particularly important as it recenters the focus on human health as an imperative for effective climate policies rather than as a contributor to the cache of peripheral co-benefits. It also underscores climate change as an ethical issue, in which failure to respond to the climate impacts can worsen health inequities, especially for socially and economically marginalized communities and vulnerable groups.

Quantification Assessment of Winter Wheat Sensitivity under Different Drought Scenarios during Growth

To effectively reveal the disaster-causing mechanism between water stress and yield loss under different drought combinations during multiple growth periods of winter wheat, based on biennial wheat drought experiments, a crop growth analysis method was used to quantitatively identify and assess wheat yield loss sensitivity. The results showed that there was a significant negative correlation between the total dry matter relative growth rate (RGR) of wheat and the daily average degree of drought stress. The average determination coefficients of logarithmic fitting for 2017 and 2018 were 0.7935 and 0.7683, respectively. Wheat dry matter accumulation differed under the different drought combination scenarios. The yield loss sensitivity response relationship between the decrease in the RGR of wheat dry matter (relative to no drought stress) and the daily average degree of drought stress could be quantitatively identified by an S-shaped curve, and the 2017 and 2018 average coefficients of determination R2 were 0.859 and 0.849, respectively. Mild drought stress at the tillering stage stimulates adaptability and has little effect on yield. The soil water content (SWC) can be controlled to 65–75% of the field water holding capacity; the SWC at the jointing and booting stage can be controlled to be higher than the field water holding capacity of 55%. The SWC was maintained at a level higher than 75% of the field water holding capacity during the heading and flowering stages and the grain-filling and milky stages to achieve a harmonization of yields and water savings. In addition, during the production process, continuous severe drought during the jointing and booting stage and the heading and flowering stage should be avoided. This study elucidates the response relationship between drought intensity and drought-induced losses from the perspective of physical genesis, provides effective irrigation guidance for regional wheat planting, lays the foundation for the construction of quantitative agricultural drought loss risk curves, and provides technical support for predicting the trend of yield losses in wheat under different drought stresses.

A Spatio-Temporal Analysis of the Frequency of Droughts in Mexico’s Forest Ecosystems

Droughts can affect forest ecosystems and lead to soil degradation, biodiversity loss, and desertification. Not all regions of Mexico are affected in the same way, as some areas are naturally more prone to drought due to their geographical location. Therefore, the objective of this work was to carry out a spatio-temporal analysis of the occurrence of droughts (severe and extreme) in Mexican forest systems, covering the period 2000–2021, and to study the area covered by these events in Mexican forest systems. This analysis was divided into three stages: the classification of land use and vegetation, spatial mapping and the classification of drought intensity, and an analysis of drought frequency and probability in forest systems. The results show that more than 46% of Mexico’s forest area experienced severe and extreme droughts during the 21-year period studied. Broadleaved forests were most affected by severe and extreme droughts, with a frequency of 6 years. The increasing frequency of droughts poses a major challenge to the resilience of forest ecosystems in Mexico, highlighting the need to implement climate change adaptation and forest management measures to protect the country’s biodiversity and natural resources.

Impacts of multiple temporal and spatial scale drought on grassland vegetation dynamics in the Tibetan Plateau region of China, 1982–2015

The Tibetan Plateau is a sensitive area to global climate change, and the special natural environmental conditions have nurtured extremely fragile vegetation and its ecosystems, making it one of the ideal regions to study the response of vegetation to climate change. In this study, we used the drought index (SPEI) and the vegetation index (NDVI) as drought and green indicators, respectively. The spatial and temporal variation patterns of vegetation greenness on the Tibetan Plateau from 1982 to 2015 were analysed, and the response of vegetation greenness to dry and wet changes was investigated. The results showed that the grassland vegetation improved overall (slope = 0.00015, P < 0.05) and degraded locally during 34 years. The NDVI of grassland vegetation showed an increasing trend from 1982 to 2008 (slope = 0.00005, P = 0.86), and a significant decreasing trend from 2009 to 2015 (slope = −0.002, P < 0.05). The degraded areas of grassland NDVI were mainly distributed in wet areas. Meanwhile, the Tibetan Plateau as a whole showed a non-significant trend of increasing drought, with a mitigating trend of drought in dry areas and an increasing trend of drought in wet areas. The probability of vegetation growth loss was higher with increasing drought. The vulnerability of grassland vegetation to drought events was significantly higher in the humid region than in the arid region. Under the current drought intensification, the risk of loss of grassland vegetation to drought in the humid zone will increase. This suggests that we need to pay more attention to the stability of vegetation in the humid region and drought trends.

Effects of Drought at Anthesis on Flag Leaf Physiology and Gene Expression in Diverse Wheat (Triticum aestivum L.) Genotypes

The current study aimed to quantify the effects of two drought intensities achieved by deprivation of watering for 45 and 65% of the volumetric soil moisture content (VSMC) for 14 days after wheat anthesis to identify physio-biochemical and molecular changes associated with drought tolerance in six genotypes with different drought tolerance. Drought at 65% of VSMC induced a significant decrease in the chlorophyll a content in the drought-sensitive genotype, which indicated a strong loss of photosynthetic reaction centres. Further, in the drought-tolerant genotype, the content of carotenoids, which could play a vital role in resisting water shortage stress, tended to increase. The increased production of malondialdehyde showed that the antioxidant system in the drought-sensitive genotypes was not properly activated. A significant decrease in catalase (CAT; EC 1.11.1.6) was observed at a 45% reduction in VSMC, compared to the control, in the drought-sensitive genotype, and at a reduction in VSMC of 65%, in all medium sensitive genotypes. Further, the drought-tolerant and -medium tolerant genotypes responded to drought with a decline in total glutathione concentrations with the intention to reinforce their defence system. Thereby, dehydroascorbate reductase (DHAR; EC 1.8.5.1), monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and glutathione reductase (GR; EC 1.6.4.2) were critical enzymes involved in the ascorbate–glutathione cycle together with CAT, showing their main role in the detoxification of ROS produced with the reduction in VSMC by 65%. The results of gene expression analysis showed that severe drought increased the levels of the DHN5 and WZY2 genes (that were significantly positively correlated) in the drought-tolerant genotype, whose grain weight, area, and length did not change in maturity. Also, it was seen that DHN5 expression showed a significant positive correlation with grain length and proline content at a 45% reduction in VSMC. The identification of different mechanisms under drought can contribute to the selection of drought-tolerant genotypes.

Evaluation of the performance of meteorological drought indices in Morocco: A case study of different climatic zones

AbstractUnderstanding drought occurrence and evolution is important in minimizing the impacts associated with it. This work assesses the performance of 10 commonly used meteorological indices to measure drought in Morocco. The studied indices are Deciles Index (DI), Percent of Normal Index (PNI), Z‐Score Index (ZSI), China‐Z Index (CZI), Rainfall Anomaly Index (RAI), Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Palmer Drought Severity Index (PDSI), its self‐calibrated variant (scPDSI) and Palmer Z Index (PZI). Rainfall and temperature gridded data is sourced from PERSIANN‐CDR and ERA5, respectively, for the period 1983–2021. The study area exhibits three main climatic regimes; subhumid, semi‐arid and arid, with a drying and warming climate, as depicted by the rainfall and temperature trends analysis. Results show that most rainfall‐based indices perform relatively poorly in drought monitoring in the study area. DI and PNI appear to be inconsistent and abnormally responsive to rainfall. RAI reports droughts 56.5% more frequently and slightly underestimate drought intensity compared to other indices. Similarly, ZSI and CZI largely underestimate drought intensity. PDSI and scPDSI are computationally demanding, often underestimate drought intensity and overestimate drought duration by at least 115% compared to SPI and SPEI. Conversely, PZI can be used for drought onset detection as it reported droughts early compared to the other indices. SPI and SPEI perform overall better regarding their consistent drought identification and severity assessment. However, SPEI is found to be more suitable than SPI in the arid and semi‐arid regions and performed better considering the warming climate of the country.

Transcriptomic and Metabolomic Insights into ABA-Related Genes in Cerasus humilis under Drought Stress.

Cerasus humilis, a small shrub of the Cerasus genus within the Rosaceae family, is native to China and renowned for its highly nutritious and medicinal fruits, robust root system, and remarkable drought resistance. This study primarily employed association transcriptome and metabolome analyses to assess changes in abscisic acid (ABA) levels and identify key regulatory genes in C. humilis subjected to varying degrees of drought stress. Notably, we observed distinct alterations in transcription factors across different drought intensities. Specifically, our transcriptome data indicated noteworthy shifts in GATA, MYB, MYC, WRKY, C2H2, and bHLH transcription factor families. Furthermore, combined transcriptomic and metabolomic investigations demonstrated significant enrichment of metabolic pathways, such as 'Carbon metabolism', 'Biosynthesis of amino acids', 'Biosynthesis of cofactors', 'Phenylpropanoid biosynthesis', 'Starch and sucrose metabolism', and 'Plant hormone signal transduction' under moderate (Mod) or severe (Sev) drought conditions. A total of 11 candidate genes involved in ABA biosynthesis and signaling pathways were identified. The down-regulated genes included secoisolariciresinol dehydrogenase-like and PYL2. Conversely, genes including FAD-dependent urate hydroxylase-like, cytochrome P450 97B2, carotenoid cleavage dioxygenase 4 (CCD4), SnRK2.2, ABI 5-like protein 5, PP2C 51, and SnRK2.3, were up-regulated under Mod or Sev drought stress. This study lays the genetic foundation for ABA biosynthesis to enhance drought tolerance and provides genetic resources for plant genetic engineering and breeding efforts.

Trends and Directions in Oats Research under Drought and Salt Stresses: A Bibliometric Analysis (1993-2023).

With global climate change leading to increasing intensity and frequency of droughts, as well as the growing problem of soil salinization, these factors significantly affect crop growth, yield, and resilience to adversity. Oats are a cereal widely grown in temperate regions and are rich in nutritive value; however, the scientific literature on the response of oat to drought and salt stress has not yet been analyzed in detail. This study comprehensively analyzed the response of oat to drought stress and salt stress using data from the Web of Science core database and bibliometric methods with R (version4.3.1), VOSviewer (version 1.6.19), and Citespace (version6.3.1.0) software. The number of publications shows an increasing trend in drought stress and salt stress in oat over the past 30 years. In the field of drought-stress research, China, the United States, and Canada lead in terms of literature publication, with the most academic achievements being from China Agricultural University and Canadian Agricultural Food University. The journal with the highest number of published papers is Field Crops Research. Oat research primarily focuses on growth, yield, physiological and biochemical responses, and strategies for improving drought resistance. Screening of drought-tolerant genotypes and transformation of drought-tolerant genes may be key directions for future oat drought research. In the field of salt-stress research, contributions from China, the United States, and India stand out, with the Chinese Academy of Agricultural Sciences and Inner Mongolia Agricultural University producing the most significant research results. The largest number of published articles has been found in the Physiologia Plantarum journal. Current oat salt-stress research primarily covers growth, physiological and biochemical responses, and salt-tolerance mechanisms. It is expected that future oat salt research will focus more on physiological and biochemical responses, as well as gene-editing techniques. Despite achievements under single-stress conditions, combined drought and salt-stress effects on oat remain understudied, necessitating future research on their interaction at various biological levels. The purpose of this study is to provide potential theoretical directions for oat research on drought and salt stress.

Archetypes of climate change adaptation among large-scale arable farmers in southern Romania

Effects of climate change and especially the associated climate variability require farmers to adjust to increasing frequencies of extreme events. In the agriculturally highly productive Romanian Plain, the frequency, intensity, and duration of heatwaves and drought have increased over the past 20 years. Although recent surveys revealed farmers’ awareness of climate change and enumerated a number of farm adaptation measures in the Romanian context, a systems approach to adaptation that allows conclusions on farm vulnerability and adaptive capacity is missing. Here, we use archetypal analysis to elucidate and characterize for the first time the types of adaptation responses of arable farmers in southern Romania. We conducted semi-structured interviews with 30 farmers managing 51,500 ha located across the southern lowlands of Romania, selected for their diversity of management approaches. Farmers were asked about experienced climatic disturbances, crop production losses during the most extreme events over the past 5–10 years, and the adaptation measures they implemented over that period of time. In addition, structural characteristics of the farm were recorded. The adaptation measures were classified and mapped on the efficiency, substitution, and redesign gradient used to classify sustainability stages. Results revealed three archetypes of adaptation, consisting of measures at field and farm level ranging from predominantly efficiency-enhancing ones (e.g., crop choice and management and risk insurance) to complete farm redesign involving agrotechnical and financial management changes. Structural farm characteristics did not explain differences between farms in their association with one of the archetypes. Our approach and results show for the first time both the need for strengthening farmer-level support in one of Europe’s key food production areas and the lessons that can be drawn from the outlier adaptation examples. Current European and national policies offer opportunities for farmer organizations in Romania to make these conclusions actionable.

Drought and nitrogen deposition regulate plant nutrient resorption in a typical steppe

The impending rise in drought events in grasslands of northern China over the next few decades, coupled with escalating nitrogen (N) deposition, will have an important impact on nutrient resorption. Previous research has mostly focused on examining the individual effect of specific drought scenario or N enrichment on nutrient resorption. Nonetheless, the impacts of different drought regimes on the resorption of nutrients have rarely been distinguished, especially under the scenario of N enrichment in temperate typical steppe in Inner Mongolia, we studied how intense drought (excluding 100 % rainfall in June), chronic drought (excluding 50 % rainfall during June-August), reduced rainfall frequency (reducing half rainfall events without changing rainfall amount in June-August), and N deposition (0 and 10 g N m−2 yr−1) affected the efficiency of plants in reabsorbing N and phosphorus (P). Both intense and chronic drought significantly reduced N (by 9.41 % and 9.53 %, respectively) and P resorption efficiency (by 6.71 % and 6.62 %, respectively) in plant communities (defined as the proportion of N and P nutrient resorption from senescing leaves), however reducing rainfall frequency had less effects on plant community N and P resorption efficiency. Nitrogen deposition had no effects on N and P resorption efficiency. Drought and N addition interacted to affect plant community P resorption efficiency. Structural equation modeling (SEM) showed that drought reduced N and P resorption efficiencies in plant communities by directly decreasing soil moisture, suppressing nutrient concentrations in green leaves, and enhancing soil nutrient content. Nitrogen deposition reduced P resorption efficiency by reducing P concentration in green leaves, but this effect was offset by the reduction of soil P availability. These results imply that rainfall amount is more important than rainfall frequency in determining the nutrient resorption efficiency of plant communities in the typical steppe. This study highlights the importance of soil water and N availabilities as well as nutrient concentrations in green leaves in modulating the responses of plant nutrient resorption to global change in the typical steppe.

Drought intensity and duration effects on morphological root traits vary across trait type and plant functional groups: a meta-analysis

The increasing severity and frequency of drought pose serious threats to plant species worldwide. Yet, we lack a general understanding of how various intensities of droughts affect plant traits, in particular root traits. Here, using a meta-analysis of drought experiments (997 effect sizes from 76 papers), we investigate the effects of various intensities of droughts on some of the key morphological root traits. Our results show that root length, root mean diameter, and root area decline when drought is of severe or extreme intensity, whereas severe drought increases root tissue density. These patterns are most pronounced in trees compared to other plant functional groups. Moreover, the long duration of severe drought decreases root length in grasses and root mean diameter in legumes. The decline in root length and root diameter due to severe drought in trees was independent of drought duration. Our results suggest that morphological root traits respond strongly to increasing intensity of drought, which further depends on drought duration and may vary among plant functional groups. Our meta-analysis highlights the need for future studies to consider the interactive effects of drought intensity and drought duration for a better understanding of variable plant responses to drought.

Projection of Changes in Rainfall and Drought Based on CMIP6 Scenarios on the Ca River Basin, Vietnam

In this study, future precipitation and drought in the Ca river basin, Vietnam, were projected based on an ensemble of 27 CMIP6 models for four climate change scenarios. The impact of climate change on precipitation and drought was investigated. Monthly precipitation observation data were adjusted using the bias correction method. To detect drought events, the Standard Precipitation Index (SPI) was employed. Changes in drought were assessed using SPI3, SPI6, and SPI12. Although the amount of annual total precipitation slightly increased, the drought events may become more severe. There is a high likelihood of increased drought intensity and severity in Vietnam due to climate change. The frequency of droughts is likely to change depending on the location and climate change scenario. We found that the frequency and severity of droughts may be altered depending on the window size of SPI. The short-term drought events will be more frequent and severe, and long-term drought events will become more severe in the Ca river basin.

Sap Flow Density of the Prevailing Tree Species in a Hemiboreal Forest under Contrasting Meteorological and Growing Conditions

This study aimed to assess the adaptive capacity of the dominant tree species in Lithuania, namely Scots pine, Norway spruce, and silver birch, to current climate conditions based on their changes in transpiration expressed through the tree sap flow intensity. The species-specific responses were investigated at two typical edaphically different forest sites with water-limited and water-saturated soils. Contrasting events like overflow in 2017 and drought in 2019 provided an opportunity to detect the adaptative capacity of the monitored tree species to these meteorological extremes. Norway spruce trees, due to having both the most intense sap flow at the beginning of the growing season and the longest period of active transpiration, demonstrated the highest annual transpiration rate, regardless of the hydrological regime of the site. Their decreased resilience to subsequent biogenic damage caused by pests due to a significant decrease in sap flow density during intense and prolonged droughts may reduce their importance in Lithuanian forestry. Silver birch trees, which demonstrated a reduction in sap flow after a drought following the untimely drop of their leaves and the end of active vegetation, even at the end of a prolonged warm period, can be seen to not have appropriate adaptations to current climate conditions. Scots pine trees are the best adapted to mitigating the recent threats of climate change.

How much rainwater contributes to a spring discharge in the Guarani Aquifer System: insights from stable isotopes and a mass balance model

ABSTRACT Outcrops play an important role in groundwater recharge. Understanding groundwater origins, dynamics and its correlation with different water sources is essential for effective water resources management and planning in terms of quantity and quality. In the case of the Guarani Aquifer System (GAS) outcrop areas are particularly vulnerable to groundwater pollution due to direct recharge processes. This study focuses on the Alto Jacaré-Pepira sub-basin, a watershed near Brotas, a city in the central region of the state of São Paulo, Brazil, where groundwater is vital for supporting tourism, agriculture, urban water supply, creeks, river and wetlands. The area has a humid tropical climate with periods of both intense rainfall and drought, and the rivers remain perennial throughout the year. Therefore, the aim of this study is to investigate the interconnections between a spring and its potential sources of contribution, namely rain and groundwater, in order to elucidate the relationships between the different water sources. To achieve this, on-site monitoring of groundwater depth, rainfall amount, and stable isotope ratios (deuterium (2H) and oxygen-18 (18O)) from rain, spring discharge, and a monitoring well was carried out from 2013 to 2021. The results indicate that the mean and standard deviations for δ18O in rainwater exhibit higher variability, resulting in −4.49 ± 3.18 ‰ VSMOW, while δ18O values from the well show minor variations, similar to those of the spring, recording −7.25 ± 0.32 ‰ and −6.94 ± 0.28 ‰ VSMOW, respectively. The mixing model’s outcomes reveal seasonal variations in water sources contribution and indicate that groundwater accounts for approximately 80 % of spring discharge throughout the year. Incorporating stable isotopes into hydrological monitoring provides valuable data for complementing watershed analysis. The values obtained support the significance of the aquifer as a primary source, thereby offering critical insights into stream dynamics of the region.

Assessment the impact of drought on vegetation carbon source/sink at a spatial scale and identify the dominant factors in the Middle Reaches of the Yellow River Basin, China

Drought poses a severe threat to terrestrial ecosystems’ carbon sequestration function, which in turn affects regional sustainable development. Understanding its impact on carbon source/sink dynamics is crucial for addressing extreme climate change challenges. This study, based on the Carnegie-Ames-Stanford approach (CASA) model and soil heterotrophic respiration equation, the Net Ecosystem Productivity (NEP) of the middle reaches of the Yellow River Basin (MRYRB) from 2001 to 2019 were estimated and utilized to characterize the vegetation carbon source/sink. Additionally, four factors, namely, average surface temperature (AST), root-zone soil moisture (RM), drought frequency (DF), and drought intensity (DI), were selected and a multiscale geographically weighted regression (MGWR) model was applied to assess the dominant factors influencing vegetation carbon source/sink dynamics at the spatial scale. The results indicated that: (1) MRYRB vegetation acted as a carbon sink, showing an increasing trend. Carbon sink was primarily located in Shaanxi’s central region, while carbon source was primarily located in Inner Mongolia and Shaanxi’s northern part. (2) Both the extent and severity of drought in the MRYRB showed a mitigating trend, presenting a spatial distribution of high-intensity low-frequency and low-intensity high-frequency. (3) AST, RM, DF, and DI had larger effects on carbon source than carbon sink. AST dominated mainly in northern Shanxi and Shaanxi, RM in central Shaanxi and Gansu, while DI and DF were concentrated in central Shaanxi and northern Shanxi.

Mountain Peatlands and Drought: Carbon Cycling in the Pyrenees Amidst Global Climate Change

AbstractThis study provides a multi‐year (2017–2022) Net Ecosystem Carbon Balance (NECB) of a Pyrenean mountainous peatland through the integration of field data, satellite imagery, and statistical modeling. Fluvial organic carbon export was measured at 30 min frequency, while gaseous (CO2 and CH4) exchanges were measured monthly using closed chambers. These measurements were combined with Sentinel‐2 derived chlorophyll index and in situ high frequency (1 hr) measurements of key environmental variables such as air temperature, photosynthetically active radiation, and water table level, to develop hourly gaseous carbon flux models (R2 = 0.69 for GPP, R2 = 0.84 for ER, R2 = 0.59 for CH4). Over the 2017–2022 period, modeled average GPP (610 ± 39 gC.m−2.year−1) and ER (641 ± 59 gC.m−2.year−1) showed that the peatland acted as a weak source of CO2 to the atmosphere, releasing 31 ± 73 gC.m−2.year−1. Considering fluvial carbon export and CH4 exchanges, the loss of carbon from the peatland increased to 55 ± 73 gC.m−2.year−1. Dissolved organic carbon constituted 8%–106% of the NECB. The estimated long‐term organic accumulation rate indicated a steady carbon accumulation rate of 16.4 gC.m−2.year−1, contrasting with the contemporary NECB, suggesting a recent shift in ecosystem functioning from a carbon sink to a source. The study underscores the role of water availability and air temperature through a drought index (DI), in shaping the NECB. The DI correlated significantly with annual carbon gaseous fluxes, except for 2022, marked by an intense drought. During this year the peatland became a large source of carbon (189 gC.m−2.year−1) to the atmosphere.

Cyanide in cassava: Understanding the drivers, impacts of climate variability, and strategies for food security

AbstractThe consumption of cassava, a vital staple food for more than 1 billion people worldwide, holds particular significance in sub‐Saharan Africa (SSA). Expansion in cassava production in SSA is driven by increasing market demand, local consumption, and adaptability to diverse environments. However, cyanide concentration in cassava tubers and products across SSA ranges from 9 to 1148 ppm – most exceed the World Health Organisation's recommended safe level of 10 ppm. Such variation and high cyanide concentrations in cassava products are expected to be exacerbated by climate‐induced increases in the frequency, intensity and occurrence of drought, heat waves and biotic stresses, further jeopardising regional food security. Thus, it is essential to examine cassava production and cyanide toxicity under climate change and their implications for food security in SSA. In this review, we look at the drivers of cassava production and spatial variation in cyanide concentrations across SSA, impacts of climate variability and biotic stresses on cassava cyanide concentrations in SSA, and crop management practices for reducing cyanogenic glucosides in cassava tubers. We surmise that urgent actions are required to adopt improved cassava varieties and management strategies that reduce cassava cyanide toxicity amid climate‐induced challenges in SSA.

Internal erosion in granular soils with different microstructures under cyclically increased hydraulic gradients

Internal erosion is one of the leading causes of failures and accidents of embankment dams, dikes, and slopes. The hydraulic loading acts as the driving force to detach the soil particles, while the initial soil microstructure determines the susceptibility of particle loss. In engineering practices, the soil may be subjected to cyclic hydraulic loadings due to water level fluctuations by extreme weather of intensive rainfall and drought. Under such conditions, the soil internal erosion process will be different from that under the steady unidirectional seepage, which has not been fully studied and needs urgent investigation. Thus, in this study, the internal erosion process and hydraulic characteristics of soils with different microstructures were investigated by both laboratory seepage tests and the discrete element method (DEM) simulation. The results indicate that the soil with a higher fine content was more structurally stable, and required a larger hydraulic gradient for erosion initiation. Once the internal erosion occurred, the particle loss and the soil hydraulic conductivity increased with increasing fine content. Additionally, when the applied hydraulic gradient was essentially the same, the soil experienced a server erosion under the cyclically than monotonically increased hydraulic gradients, and the amount of eroded soils increased with the increasing gradient amplitude. The results of this study will expand our understanding of the physical mechanism and hydraulic behaviors of soils subjected to cyclically increased hydraulic gradients and with different microstrures.

Clash of Drought Narratives: A Study on the Role of Small Reservoirs in the Emergence of Drought Impacts

AbstractIn regions characterized by a high concentration of small reservoirs, there is often public debate about the effectiveness of these structures in locally adapting to and mitigating drought impacts, bearing in mind their potential to modify or induce drought events in downstream areas. In this study, we investigated the influence of a Dense Network of Small Reservoirs (DNR) on the emergence and intensification of drought impacts at catchment scale, as well as their local social benefits. This analysis was based on the Socio‐Hydrological‐Agricultural‐Reservoir (SHARE) model, specially developed for this purpose, with a medium‐sized catchment in the semi‐arid region of Brazil as a case study. We identified that, while a DNR can prolong the effects of a hydrological drought on storage in a large strategic reservoir at the catchment outlet by obstructing surface‐runoff connectivity, it plays a crucial role in mitigating drought impacts at a local level. Specifically, the presence of small reservoirs has the potential to boost local agricultural production by up to 5 times compared to scenarios without these structures. In addition, our simulation results suggest there is a notable reduction in the need for emergency water distribution by water trucks in the presence of a DNR. This study highlights the need for a balanced approach to implementing public policies, weighing the local benefits of small reservoirs against the possible downstream impacts on large reservoirs.