Impact of drought on human health

Temporal and Spatial Effects of Extreme Drought Events on Human Epidemics over Ancient China in 1784-1787 CE

Extreme drought events can impact human health, notably triggering epidemics that impose significant global health and economic burdens. Understanding these effects and developing response strategies is crucial. However, there is limited epidemiological evidence on how climate change influenced ancient epidemics before large-scale urbanization and frequent population movements. In this study, we utilized the Reconstructed East Asian Climate Historical Encoded Series (REACHES) climate database and the self-constructed ancient Chinese epidemics database to examine extreme drought events in ancient China from 1784-1787 CE. We analyzed factors like grain prices, population density, and socioeconomic conditions to explore the temporal and spatial mechanism and influence the degree of extreme drought events on epidemics outbreaks. The results show that there is a clear positive link between drought and the spread of epidemics, with a notable one-year lag effect of drought. Drought impacts epidemics directly and indirectly through locust plague, famine, crop failure, and social turmoil, with famine being the most crucial factor. Official disaster management can mitigate epidemics. This study intuitively shows the relationship between extreme drought events and epidemics in ancient China and offering insights into the climate change-epidemic relationship. Placing the conclusions of this paper in a broader context has global implications, providing historical experience for polycrisis and modern challenges.

Health effects of climate change in Africa: A call for an improved implementation of prevention measures

The world's climate, particularly in Africa, has changed substantially during the past few decades, contributed by several human activities. Africa is one of the continents that is most vulnerable to climate change globally. Since the beginning of 2022, extreme weather events in Africa have affected about 19 million people and killed at least 4,000 individuals. Cyclones, floods, heatwaves, wildfires, droughts, and famine were among the severe weather occurrences. Natural disasters and extreme weather events brought on by climate change may compromise access to clean water, sanitation systems, and healthcare facilities, making people more vulnerable to a number of illnesses. Floods and drought can lead to both communicable and non-communicable diseases. The African population is more likely to experience more mental health disorders than before because of natural disasters, which result in the loss of property and sometimes loss of lives more frequently. We, therefore, call for an improved implementation of strategies to prevent the health effects of climate change so that the health of the people in Africa can be maintained.

Determining and forecasting drought susceptibility in southwestern Iran using multi-criteria decision-making (MCDM) coupled with CA-Markov model

Forecasting drought and determining relevant data to predict drought are an important topic for decision-makers and planners. It is critical to predicting drought in the south of Fars province, an important agricultural center in Iran located in arid and semi-arid climates. The purpose of this study was to generate a drought map in 2019 using 12 parameters: altitude, aridity index, erosion, groundwater depth, land use, PET (Potential evapotranspiration), precipitation days, precipitation, slope, soil texture, soil salinity, and distance to river, and predict drought maps in 2030 and 2040 using the cellular automata (CA)-Markov model spatially. The fuzzy method was first used to homogenize the data. Next, by evaluating each parameter, the weight of each parameter was calculated using the analytic hierarchy process (AHP), and a map of drought-prone areas was generated. The results of the fuzzy-AHP method showed that the eastern and southeastern regions of the study area were prone to drought. The four most predictive parameters in causing drought, i.e., aridity index, PET, precipitation, and soil texture, were selected using the Best search method and were then chosen as the input to determine drought mapping using the fuzzy and AHP methods. Finally, the CA-Markov model was used to predict future drought maps, and the results showed that in 2030 and 2040 the drought situation in the east and south of the study area would intensify.

Drought effects on specific-cause mortality in Lisbon from 1983 to 2016: Risks assessment by gender and age groups

Portugal (Southwestern Europe) experiences a high incidence of dry hazards such as drought, a phenomenon that entails a notable burden of morbidity and mortality worldwide. For the first time in the Lisbon district, a time-series study was conducted to evaluate the impact of drought measured by the Standardised Precipitation Index (SPI) and Standardised Precipitation-Evapotranspiration Index (SPEI) on the daily natural, circulatory, and respiratory mortality from 1983 to 2016. An assessment by gender and adult age population groups (45-64, 65-74, ≥75 years old) was included. To estimate the relative risks and attributable risks, generalised linear models with a Poisson link were used. Additionally, the influence of heatwaves and atmospheric pollution for the period from 2007 to 2016 (available period for pollution data) was considered. The main findings indicate statistically significant associations between drought conditions and all analysed causes of mortality. Moreover, SPEI shows an improved capability to reflect the different risks. People in the 45-64 year-old group did not indicate any significant influence in any of the cases, whereas the oldest groups had the highest risk. The drought effects on mortality among the population varied across the different study periods, and in general, the men population was affected more than the women population (except for the SPEI and circulatory mortality during the long study period). The short-term influence of droughts on mortality could be explained primarily by the effect of heatwaves and pollution; however, when both gender and age were considered in the Poisson models, the effect of drought also remained statistically significant when all climatic phenomena were included for specific groups of the total population and men. This type of study facilitates a better understanding of the population at risk and allows the development of more effective measures to mitigate the drought effects on the population.

Short-term effects of drought on daily mortality in Spain from 2000 to 2009

Spain is a country of southern Europe that is prone to drought, and it is likely that this type of hydrological extreme will become substantially more frequent and intense in the 21st century, which could lead to greater health risks if adequate adaptive measures are not taken. For the first time, we calculated the relative risks (RRs) of daily natural (ICD10: A00-R99), circulatory (ICD10: I00-I99), and respiratory (ICD: J00-J99) mortality associated with drought events in each province of Spain from 2000 to 2009. For this purpose, we compared the performance of the Standardized Precipitation Index (SPI) and Standardized Precipitation- Evapotranspiration Index (SPEI) obtained at 1 month of accumulation (denoted as SPI-1/SPEI-1) to estimate the short-term risks of droughts on daily mortality using generalised linear models. Attributable risks were calculated from the RR data. The main findings of this study revealed statistically significant associations between the different causes of daily mortality and drought events for the different provinces of Spain, and clear spatial heterogeneity was observed across the country. Western Spain (northwest to southwest) was the region most affected, in contrast to northern and eastern Spain, and daily respiratory mortality was the group most strongly linked to the incidence of drought conditions. Moreover, for a considerable number of provinces, the effect of SPI-1 and SPEI-1 largely reflected the impact of atmospheric pollution and/or heatwaves; however, for other regions, the effect of drought conditions on daily mortality remained when these different climatic events were controlled in Poisson models. When the performances of the SPEI and SPI were compared to identify and estimate the risks of drought on daily mortality, the results were very similar, although there were slight differences in the specific causes of daily mortality.

Effects of droughts on health: Diagnosis, repercussion, and adaptation in vulnerable regions under climate change. Challenges for future research

There is little doubt about the effects of drought events on human health in the present climate. Projections of climate change indicate an increase in the occurrence and severity of droughts in the 21st century in a number of regions, thus it is likely that these types of hydrological extremes could have more of an impact if appropriate adaptation measures are not taken. The majority of studies on the effects of drought are focused on meteorological, agricultural, or hydrological contexts, but there are rather fewer assessments of the impacts of droughts on health. In particular, there have been hardly any attempts to compare different drought indices in order to identify and quantify the impacts of drought on health systems. In addition, rather better knowledge is needed on the mechanisms of vulnerability involved. In this paper, we attempt to describe the complexity of drought phenomena and the difficulty involved in quantifying the health risks linked to their occurrence. From an international perspective, we provide a brief review of the harmful effects of droughts on health in the context of climate change, as well as the vulnerability factors related to droughts. We make an assessment of aspects that have not yet been investigated, or which require further attention to be devoted to this topic. The principal aim of this paper is therefore to draw attention to the need to consider closely the relationship between drought indices and human health, in order to achieve a more fundamental understanding, and to propose specific courses or lines of action for future years, which could eventually be of use to healthcare providers and services.

Assessing land surface drying and wetting trends with a normalized soil water index on the Loess Plateau in 2001-2016

Long-term drought may cause severe damage to ecosystems. To assess drought intensity, we introduced a normalized soil water index (NSWI) of land surface, on the basis of rainfall and actual evapotranspiration. Areas undergoing land surface drying on the Loess Plateau in 2001-2016 were assessed on the basis of the values of NSWI combined with rainfall and land surface water storage (LSWS). The extent of soil drying and wetting at depths of 0-0.01 m, 0-0.1 m and 0-2 m was also quantified. Results showed that up to 7.16% of the Loess Plateau was subjected to decreasing LSWS. On an inter-annual time scale, land surface drying intensified starting in 2003, and this pattern was chiefly evident at the soil depth of 2 m. The approach proposed in this study could also be used to identify temporary dry soil layers (DSLs) in arid ecosystems.