Anthropogenic Drought Research Articles

Socio-hydrological lock-in; an emergent phenomenon in the face of anthropogenic drought

This study investigates the drought of three major terminal lakes: Great Salt Lake, Salton Sea, and Lake Urmia, driven by socio-hydrological lock-in—a phenomenon characterized by feedback loops between human activities and environmental processes. Previous research has linked this drying to socio-hydrological lock-in, where rational actions by individuals collectively lead to suboptimal outcomes, exacerbating water scarcity and ecological degradation. Despite existing studies, a critical knowledge gap remains in understanding how these feedback mechanisms operate across different socio-economic and ecological contexts. This research seeks to address this gap through an integrative analysis of historical data and case studies, highlighting the interplay between increased water demand for agriculture, population growth, and governance challenges. The resultant shrinkage of these lakes exposes saline playas, generating salt-rich dust with severe ecological and health impacts, including soil salinization and respiratory illnesses. By comparing the socio-hydrological lock-in across diverse regions, this study provides insights into preventing and mitigating these cycles. It emphasizes the necessity for holistic water management strategies that integrate both supply and demand-side measures. The key contribution of this research lies in its systematic exploration of the feedback mechanisms driving socio-hydrological lock-ins, offering a foundation for developing sustainable water resource management policies globally. This work aims to influence policy and practice by highlighting the need for integrated, long-term strategies that balance economic pursuits with environmental sustainability, ensuring resilience in water management amidst mounting environmental challenges.

Anthropogenic drought monitoring using socio-hydrological modeling for surface water deficit: Lessons from Northern Taiwan

To illustrate anthropogenic drought, the comprehensive dual-system concept, which formalizes pathways and socio-hydrological interactions, was introduced. To quantify this concept, a modified water accounting and vulnerability evaluation plus (WAVE + ) model that integrates factors such as return water from precipitation, local water stress robustness, and the risk of freshwater deprivation threshold (RFD threshold) derived from historical data was proposed. This process-based model provides regional cross-comparable scarcity and seasonal socio-hydrological water vulnerability patterns. The RFD and conditional water depletion index (CWDI) were derived from the modified WAVE + model to describe anthropogenic-hydrological drivers. By leveraging the dual-system concept and the modified WAVE + model, the proposed RFD–CWDI method effectively identified and evaluated the duration, intensity, and severity of anthropogenic drought events. The performance of the RFD–CWDI method matches or surpasses that of the improved multivariate standardized reliability and resilience index, a powerful product-based index used for the characterization of anthropogenic and socioeconomic drought. Moreover, the RFD–CWDI method simplifies the analysis of anthropogenic drought event cycles by combining the degree of water deficiency with dual-system vulnerability, distinguishing it from meteorological-hydrological and hydrological-socioeconomic cycles. The dual-system and modified WAVE + model define dynamics and socio-hydrological interactions, and they provide a widely applicable process-based method, the RFD–CWDI method, for assessing anthropogenic drought events.

Modern anthropogenic drought in Central Brazil unprecedented during last 700 years

A better understanding of the relative roles of internal climate variability and external contributions, from both natural (solar, volcanic) and anthropogenic greenhouse gas forcing, is important to better project future hydrologic changes. Changes in the evaporative demand play a central role in this context, particularly in tropical areas characterized by high precipitation seasonality, such as the tropical savannah and semi-desertic biomes. Here we present a set of geochemical proxies in speleothems from a well-ventilated cave located in central-eastern Brazil which shows that the evaporative demand is no longer being met by precipitation, leading to a hydrological deficit. A marked change in the hydrologic balance in central-eastern Brazil, caused by a severe warming trend, can be identified, starting in the 1970s. Our findings show that the current aridity has no analog over the last 720 years. A detection and attribution study indicates that this trend is mostly driven by anthropogenic forcing and cannot be explained by natural factors alone. These results reinforce the premise of a severe long-term drought in the subtropics of eastern South America that will likely be further exacerbated in the future given its apparent connection to increased greenhouse gas emissions.

Uncovering the Depletion Patterns of Inland Water Bodies via Remote Sensing, Data Mining, and Statistical Analysis

Addressing the issue of shrinking saline lakes around the globe has turned into one of the most pressing issues for sustainable water resource management. While it has been established that natural climate variability, human interference, climate change, or a combination of these factors can lead to the depletion of saline lakes, it is crucial to investigate each case and diagnose the potential causes of this devastating phenomenon. On that note, this study aims to promote a comprehensive analytical framework that can reveal any significant depletion patterns in lakes while analyzing the potential reasons behind these observed changes. The methodology used in this study is based on statistical analysis, data mining techniques, and remote sensing-based datasets. To achieve the objective of this study, Maharlou Lake has been selected to demonstrate the application of the proposed framework. The results revealed two types of depletion patterns in the lake’s surface area: a sharp breaking point in 2007/2008 and a gradual negative trend, which was more pronounced in dry seasons and less prominent in wet seasons. Furthermore, the analysis of hydro-climatic variables has indicated the presence of abrupt and gradual changes in these variables’ time series, which could be interpreted as a signal that climate change and anthropogenic drought are changing the basin’s status quo. Lastly, analyzing the statistically significant correlation between hydro-climatic variables and the lake’s surface area showed the potential connection between the observed changing patterns. The results obtained from data mining models suggest that Maharlou Lake has undergone a morphological transformation and is currently adopting these new conditions. If preventive measures are not taken to revive Maharlou Lake, the tipping point might have been reached, and reviving the lake could be improbable, if not impossible.

Anthropogenic drought in the Yellow River basin: Multifaceted and weakening connections between meteorological and hydrological droughts

Connections between meteorological and hydrological droughts (CMHDs) have changed due to increasingly intensified human activities. Understanding such changes from an anthropogenic perspective is, therefore, of critical importance for drought monitoring, early warning, and adaptation. As the second-longest river system in China, the Yellow River basin (YRB) has been seriously impacted by humans and has a high risk of drought due to its dry climate, dense population and massive water demand. However, the effects of human activities on CMHDs in the YRB are still unclear. We thus used the standardized precipitation evapotranspiration index (SPEI) and the standardized streamflow index (SSI) to indicate meteorological drought (MD) and hydrological drought (HD), respectively, and analysed CMHDs with multiple indicators including trends, correlation, difference, and drought propagation characteristics. Our results highlighted the heterogeneity of CMHDs in terms of subregions and indicators and showed that this heterogeneity was impacted by humans by quantifying the effects of human activities (mainly referring to water abstraction and regulation) on CMHDs in each subregion. We found that 1) human activities aggravated the disconnections between MD and HD by sharpening the downward trend in the SSI and weakening the correlation (amplifying the difference) between the SPEI and SSI, and 2) human activities reduced the drought propagation rate from MD to HD, manifested by a decreased number of HD but a lengthening of the HD duration. In addition to the abovementioned effects that were consistent for most of the YRB, there were also some effects, for example, on HD intensity and drought propagation time, that differed among subregions, and these kinds of diverse responses of CMHDs might be related to the various human activities in terms of intensities, types, and regions. By analysing human effects on CMHDs, this study may be helpful in understanding drought and drought propagation in the Anthropocene, which is beneficial to watershed management.

Interrelations of vegetation growth and water scarcity in Iran revealed by satellite time series

Iran has experienced a drastic increase in water scarcity in the last decades. The main driver has been the substantial unsustainable water consumption of the agricultural sector. This study quantifies the spatiotemporal dynamics of Iran’s hydrometeorological water availability, land cover, and vegetation growth and evaluates their interrelations with a special focus on agricultural vegetation developments. It analyzes globally available reanalysis climate data and satellite time series data and products, allowing a country-wide investigation of recent 20+ years at detailed spatial and temporal scales. The results reveal a wide-spread agricultural expansion (27,000 km^2) and a significant cultivation intensification (48,000 km^2). At the same time, we observe a substantial decline in total water storage that is not represented by a decrease of meteorological water input, confirming an unsustainable use of groundwater mainly for agricultural irrigation. As consequence of water scarcity, we identify agricultural areas with a loss or reduction of vegetation growth (10,000 km^2), especially in irrigated agricultural areas under (hyper-)arid conditions. In Iran’s natural biomes, the results show declining trends in vegetation growth and land cover degradation from sparse vegetation to barren land in 40,000 km^2, mainly along the western plains and foothills of the Zagros Mountains, and at the same time wide-spread greening trends, particularly in regions of higher altitudes. Overall, the findings provide detailed insights in vegetation-related causes and consequences of Iran’s anthropogenic drought and can support sustainable management plans for Iran or other semi-arid regions worldwide, often facing similar conditions.

Drought monitoring using the long-term CHIRPS precipitation over Southeastern Iran

Climate change and global warming are often considered the main reason for water scarcity in Iran. However, there is little evidence showing that the arid/wet regions get drier/wetter due to climate change. Some researchers believe that parts of water challenges in Iran arise from bad governance and mismanagement of water resources. To address the role of climate change on the water scarcity, this study aims to detect the drought trends in the southeast of Iran to investigate drought characteristics changes during 1981–2020. The nonparametric Mann–Kendall test was used for this purpose. CHIRPS product was collected as an alternative source of ground data for trend analysis of drought characteristics. The evaluation metrics show that the CHIRPS product performs better at monthly and annual scales (correlation higher than 0.8) than daily (correlation less than 0.4). The results also illustrate that the duration and severity of short-term droughts (3, 6, and 9 months) have decreased, while their intensity has increased. Conversely, duration, severity, and intensity changes for long-term droughts (12, 18, and 24 months) are insignificant. The trend in the Standardized Precipitation Index (SPI) showed that, in general, the southeast of Iran has not been getting drier during the last four decades. One may conclude that the change in precipitation is not the only reason for water challenges in this area, and both natural and anthropogenic drought might cause water scarcity. Accordingly, it is suggested that the effects of human activities and governmental plans should be considered as well.

Reconstructing butterfly-pollen interaction networks through periods of anthropogenic drought in the Great Basin (USA) over the past century

Interactions between plants and insects dominate terrestrial biomes and are altered in response to global human-environmental change. Documenting such changes in complex interactions is challenging, however, because traditional methods for describing plant-insect interactions at community scales are often based on relatively short sampling periods. This paper investigates quantitative networks of pollen-insect interactions gleaned from adult Lepidoptera from long-term museum collections that helped to overcome the challenge of limited temporal resolution. The paper reports how richness and frequency of butterfly-pollen associations have changed over a 100-year time series (1910–2020) in the Great Basin of Nevada and California, USA. First, we examined changes in pollen richness for 19 butterfly species over five consecutive 20-year time periods. We pooled interaction networks associated with specimens captured before and after the onset of drought in 2000. In doing so, we estimated variation in pollen-pollinator interactions under anthropogenic drought periods in the Great Basin in the last two decades. Overall, pollen richness associated with butterflies declined slightly over the study period. The details depend on the species, however, where a few species experienced moderate declines in richness and two species exhibited small increases in pollen richness. Butterfly-pollen networks indicated specialization in most pollen-butterfly species interactions. They are apparently more reticulate than observational networks. Interaction networks associated with specimens captured before and after the year 2000 revealed that, compared to previous decades, butterfly-pollen networks over the past 20 years had higher connectivity and diversity of interactions. • Plant-pollinator interactions contribute substantially to biodiversity. • Moderately generalized networks are likely to provide ecosystem stability in the face of anthropogenic global change. • Pollen-butterfly interactions are changing in response to global change, especially more generalized interactions. • Most pollen-butterfly interaction networks are specialized, which could make them more susceptible to anthropogenic change. • Pollen diversity on Great Basin butterflies has declined over the past 100 years, concurrent with drought in the region.

Drought and society: Scientific progress, blind spots, and future prospects

Human activities have increasingly intensified the severity, frequency, and negative impacts of droughts in several regions across the world. This trend has led to broader scientific conceptualizations of drought risk that account for human actions and their interplays with natural systems. This review focuses on physical and engineering sciences to examine the way and extent to which these disciplines account for social processes in relation to the production and distribution of drought risk. We conclude that this research has significantly progressed in terms of recognizing the role of humans in reshaping drought risk and its socioenvironmental impacts. We note an increasing engagement with and contribution to understanding vulnerability, resilience, and adaptation patterns. Moreover, by advancing (socio)hydrological models, developing numerical indexes, and enhancing data processing, physical and engineering scientists have determined the extent of human influences in the propagation of drought hazard. However, these studies do not fully capture the complexities of anthropogenic transformations. Very often, they portray society as homogeneous, and decision‐making processes as apolitical, thereby concealing the power relations underlying the production of drought and the uneven distribution of its impacts. The resistance in engaging explicitly with politics and social power—despite their major role in producing anthropogenic drought—can be attributed to the strong influence of positivist epistemologies in engineering and physical sciences. We suggest that an active engagement with critical social sciences can further theorizations of drought risk by shedding light on the structural and historical systems of power that engender every socioenvironmental transformation.This article is categorized under:Climate, History, Society, Culture > Disciplinary Perspectives

Interconnected governance and social barriers impeding the restoration process of Lake Urmia

Lake Urmia in Iran has undergone catastrophic desiccation due to increasing anthropogenic development, especially in the agricultural sector. A paramount national goal is to restore the lake to its former healthy condition, but corresponding water governance and restoration efforts have encountered various, mostly human-related, challenges. We argue here that these challenges stem from lack of awareness and insufficient consideration of the local social conditions and the subtleties of human-water interactions, which we collectively refer to as socio-hydrological barriers. Ignorance of such socio-hydrological barriers can lead to policy efforts that are mismatched with local realities and, thus, ineffective lake restoration efforts. This study, therefore, focuses on identifying and teasing out how various socio-hydrological factors influence the anthropogenic drought and water governance efforts using the case of Lake Urmia. To this end, a series of interviews with farmers in the lake basin and with specialist staffs in Urmia Lake Restoration Program were conducted and analyzed. In addition, broader strategies for improving the region’s water governance are identified and suggested based on the lessons learned. Although the current study is placed-based, the insights generated here can be relevant for similar cases in the Middle East and beyond that are vulnerable to anthropogenic droughts.

How Anthropogenic Drought Plays Out

Drought should be considered and modeled as a process, including human–nature interactions, and not merely a product of water deficit.

Anthropogenic drought dominates groundwater depletion in Iran

Using publicly-available average monthly groundwater level data in 478 sub-basins and 30 basins in Iran, we quantify country-wide groundwater depletion in Iran. Natural and anthropogenic elements affecting the dynamics of groundwater storage are taken into account and quantified during the period of 2002–2015. We estimate that the total groundwater depletion in Iran to be ~ 74 km3 during this period with highly localized and variable rates of change at basin and sub-basin scales. The impact of depletion in Iran’s groundwater reserves is already manifested by extreme overdrafts in ~ 77% of Iran’s land area, a growing soil salinity across the entire country, and increasing frequency and extent of land subsidence in Iran’s planes. While meteorological/hydrological droughts act as triggers and intensify the rate of depletion in country-wide groundwater storage, basin-scale groundwater depletions in Iran are mainly caused by extensive human water withdrawals. We warn that continuation of unsustainable groundwater management in Iran can lead to potentially irreversible impacts on land and environment, threatening country’s water, food, socio-economic security.

Anthropogenic Drought: Definition, Challenges, and Opportunities

AbstractTraditional, mainstream definitions of drought describe it as deficit in water‐related variables or water‐dependent activities (e.g., precipitation, soil moisture, surface and groundwater storage, and irrigation) due to natural variabilities that are out of the control of local decision‐makers. Here, we argue that within coupled human‐water systems, drought must be defined and understood as a process as opposed to a product to help better frame and describe the complex and interrelated dynamics of both natural and human‐induced changes that define anthropogenic drought as a compound multidimensional and multiscale phenomenon, governed by the combination of natural water variability, climate change, human decisions and activities, and altered micro‐climate conditions due to changes in land and water management. This definition considers the full spectrum of dynamic feedbacks and processes (e.g., land‐atmosphere interactions and water and energy balance) within human‐nature systems that drive the development of anthropogenic drought. This process magnifies the water supply demand gap and can lead to water bankruptcy, which will become more rampant around the globe in the coming decades due to continuously growing water demands under compounding effects of climate change and global environmental degradation. This challenge has de facto implications for both short‐term and long‐term water resources planning and management, water governance, and policymaking. Herein, after a brief overview of the anthropogenic drought concept and its examples, we discuss existing research gaps and opportunities for better understanding, modeling, and management of this phenomenon.

Using GRACE satellite observations for separating meteorological variability from anthropogenic impacts on water availability

Gravity Recovery and Climate Experiment (GRACE) observations provide information on Total Water Storage Anomaly (TWSA) which is a key variable for drought monitoring and assessment. The so-called Total Water Storage Deficit Index (TWSDI) based on GRACE data has been widely used for characterizing drought events. Here we show that the commonly used TWSDI approach often exhibits significant inconsistencies with meteorological conditions, primarily upon presence of a trend in observations due to anthropogenic water use. In this study, we propose a modified version of TWSDI (termed, MTWSDI) that decomposes the anthropogenic and climatic-driven components of GRACE observations. We applied our approach for drought monitoring over the Ganges–Brahmaputra in India and Markazi basins in Iran. Results show that the newly developed MTWSDI exhibits consistency with meteorological drought indices in both basins. We also propose a deficit-based method for drought monitoring and recovery assessment using GRACE observations, providing useful information about volume of deficit, and minimum and average time for drought recovery. According to the deficit thresholds, water deficits caused by anthropogenic impacts every year in the Ganges–Brahmaputra basin and Markazi basins is almost equal to an abnormally dry condition and a moderate drought condition, receptively. It indicates that unsustainable human water use have led to a form of perpetual and accelerated anthropogenic drought in these basins. Continuation of this trend would deplete the basin and cause significant socio-economic challenges.

An evidential reasoning-based leader-follower game for hierarchical multi-agent decision making under uncertainty

In multi-agent decision making, agents’ decisions are coherently interdependent, and the objectives of agents are possibly inconsistent. In this type of decision-making, agents need to reason and act strategically. Therefore, game theory can be used to study the strategic interactions among decision-makers. This paper presents a new hierarchical decision-making methodology, which uses the advantages of both game theory (i.e. Stackelberg leadership model) and Evidential Reasoning (ER). ER, as a multi-attribute decision-making method, considers both qualitative and quantitative attributes, and incorporates existing uncertainties in evaluating alternatives. The backward induction method and Monte-Carlo theory are used to solve the deterministic and stochastic forms of the proposed leader–follower game. The methodology is applied to choose the best restoration scenario for Urmia Lake, which is the biggest saltwater lake in the Middle East. In the past decade, the lake’s surface area has dramatically decreased due to climate change and an anthropogenic drought. In this paper, 19 lake restoration scenarios have been evaluated, and a scenario, which is corresponding to a 40% reduction in agricultural water consumption and water release from Nezam Abad dam, is found to be the equilibrium solution for both types of the game.

Plasticity in life history traits of a cyprinid fish in an intermittent river

The extreme seasonal environmental variation of intermittent rivers has a profound effect on freshwater fish communities. Yet, few studies have examined the consequences of the seasonal cycles of flooding and drying to fish condition and reproduction in these ecosystems. In this study, we compared the body condition, reproduction and diet of two chub populations from two adjacent sites (a perennial and an intermittent site) on the main stem of a Mediterranean river (Evrotas River, S. Greece). The study was conducted in spring 2017, three months after flow resumption and before the onset of chub reproductive period. Condition (net weight adjusted for length) of fish did not differ significantly between the two sites, despite lower aquatic macroinvertebrate availability at the intermittent site. Fish at the intermittent site compensated for the lower aquatic prey availability by increasing their feeding intensity and by shifting to higher terrestrial prey consumption. In addition, chub liver weight (adjusted for length) and gonadal weight (adjusted for length) were significantly higher at the intermittent site, indicating higher somatic and reproductive investment. These results highlight the resilience of fish populations inhabiting streams with extreme variation in flow, due to natural and/or anthropogenic drought.

Climate-informed environmental inflows to revive a drying lake facing meteorological and anthropogenic droughts

The rapid shrinkage of Lake Urmia, one of the world’s largest saline lakes located in northwestern Iran, is a tragic wake-up call to revisit the principles of water resources management based on the socio-economic and environmental dimensions of sustainable development. The overarching goal of this paper is to set a framework for deriving dynamic, climate-informed environmental inflows for drying lakes considering both meteorological/climatic and anthropogenic conditions. We report on the compounding effects of meteorological drought and unsustainable water resource management that contributed to Lake Urmia’s contemporary environmental catastrophe. Using rich datasets of hydrologic attributes, water demands and withdrawals, as well as water management infrastructure (i.e. reservoir capacity and operating policies), we provide a quantitative assessment of the basin’s water resources, demonstrating that Lake Urmia reached a tipping point in the early 2000s. The lake level failed to rebound to its designated ecological threshold (1274 m above sea level) during a relatively normal hydro-period immediately after the drought of record (1998–2002). The collapse was caused by a marked overshoot of the basin’s hydrologic capacity due to growing anthropogenic drought in the face of extreme climatological stressors. We offer a dynamic environmental inflow plan for different climate conditions (dry, wet and near normal), combined with three representative water withdrawal scenarios. Assuming effective implementation of the proposed 40% reduction in the current water withdrawals, the required environmental inflows range from 2900 million cubic meters per year (mcm yr−1) during dry conditions to 5400 mcm yr−1 during wet periods with the average being 4100 mcm yr−1. Finally, for different environmental inflow scenarios, we estimate the expected recovery time for re-establishing the ecological level of Lake Urmia.

Sociohydrological Impacts of Water Conservation Under Anthropogenic Drought in Austin, TX (USA)

AbstractMunicipal water providers increasingly respond to drought by implementing outdoor water use restrictions to reduce urban water withdrawals and maintain water availability. However, restricting urban outdoor water use to support watershed‐scale drought resilience may generate unanticipated cross‐scale interactions, for example, by altering drought response and recovery in urban vegetation or urban streamflow. Despite this, urban water conservation is rarely conceptualized or modeled as endogenous to the water cycle. Here we investigate cross‐scale interactions among urban water conservation and water availability, water use, and sociohydrological response in Austin, TX (USA) during a recent anthropogenic (human‐influenced) drought. Multiscalar statistical analyses demonstrated that outdoor water conservation for reservoir management at the municipal scale produced responses that can cascade both “upward” from the city to the watershed (e.g., decoupling streamflow patterns upstream and downstream of Austin at the watershed scale) and “downward” to exert heterogeneous effects within the city (e.g., redistributing water along a socioeconomic gradient at submunicipal scales, with effects on terrestrial and aquatic ecosystems). We suggest that adapting to anthropogenic drought through irrigation curtailment requires sustained engagement between hydrology and social sciences to integrate socioeconomic status and political feedbacks within and among irrigator groups into the water cycle. Findings from this cross‐disciplinary study highlight the importance of a multiscalar and spatially explicit perspectives in urban sociohydrology research to uncover how water conservation as adaptation to anthropogenic drought links hydrological processes with issues of socioeconomic inequality and spatiotemporal scale in the Anthropocene.

Forest health. Forest health in a changing world. Introduction.

![Figure][1] Mountain pine beetle infections are becoming more intense as weather warms in coniferous forests, like this one in central British Columbia. Infected trees die slowly, resulting in a forest full of various levels of colorful dieback. PHOTO: TOM NEVESELY/ALL CANADA PHOTOS/CORBIS Forests and woodlands cover about 20% of Earth's land surface, spanning all but the highest latitudes. In the millennia since humans dispersed across all forested continents, we have transformed large areas of natural forest. Historically, our greatest impacts were made in temperate regions, but they now extend to forests in the tropics and the boreal zone. Only a fraction of the forests present centuries ago have escaped human influence; in many regions the forest is gone, has regrown as secondary forest, or consists of managed and plantation forests. Humans have also introduced new species, including pests and pathogens of trees. Other influences—such as climate warming that causes tree species to shift geographically and anthropogenic drought that causes forest dieback—take effect more slowly and may occur far from their source. Even though modern forests are generally much altered from their natural state, their “health” still matters. It will dictate whether forests persist and function into the future, sustaining wildlife, producing timber, sequestering carbon, and performing other services. Yet forest health is difficult to define. Forests experience plenty of natural disturbances: fire, weather variations, competition between plant species, and attacks by insect pests and pathogens. They also experience longer-term successional change. When we speak of threats to forest health, we tend to imply the impacts of humans. However, it may not always be obvious whether human activity or a forest's natural dynamics are at play in, for example, the dieback of a stand or the outbreak of an insect herbivore. Recognizing the signs of ill forest health and teasing apart the causes are important both for sustaining the services that humans rely on and for the effective conservation of forest biomes. Understanding how we influence forest health and function is a key challenge for the future, as we increasingly realize the importance of forests to the maintenance of a healthy planet. [1]: pending:yes

Water and climate: Recognize anthropogenic drought

California's current extreme drought must be a lesson for managing water in a warmer, more densely populated world, say Amir AghaKouchak and colleagues.