Droughts are widely considered the most destructive and economically challenging of all the climate hazards. Droughts affect several million people every year and growing evidence suggests that health is vulnerable to drought, causing morbidity and early mortality worldwide.
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The impact of droughts across diverse geographies
Droughts account for 15% of natural disasters globally, and 59% of the total deaths caused by extreme weather events account for the mortality related to droughts. They are slow-onset phenomena that develop over an extended period, and their effects can be geographically vast.
There are disparities in the magnitude and repercussions of drought impacts between continents. Drought-related morbidity and mortality are higher in resource-poor developing nations; in contrast, resource-rich developed nations predominantly experience an economic impact.
Heath consequence: Pathogenic disease
Several systematic reviews of the effects of drought on health have been conducted in several different contexts. A paper in 2013 highlighted that there is a significant impact of a reduction in water supply, with increases in diseases such as diarrhea, conjunctivitis, and scabies. This effect is particularly pronounced in developing nations.
The mechanisms of spread are complex; however, diseases are observed to spread predominantly due to lack of and reduced quantities, of water for hand-washing and personal hygiene.
Low water levels provide optimized conditions for concentrations of pathogens such as E Coli and cholera; this effect is pronounced in areas of the world such as Africa, however pathogenic illnesses are also seen in developed nations; leptospirosis was observed in the USA in 1993.
Drought also catalyzes the spread of harmful chemicals which are attributed to sewage, surface runoff, and animal feces. These accumulate in rivers, reservoirs, lakes, and groundwater sources combat, and their concentrations increase as volumes of water decrease.
This reduced water quality has been observed in outbreaks of water-borne diseases such as cholera and diarrhea, alongside blisters, vomiting, skin rashes, and headaches, predominantly in developing countries.
Agricultural shortages of drought lead to malnutrition
Agriculture is historically well-adapted to environmental shocks; however, food security and nutrition can be adversely affected in the case of drought. The mechanisms underlying this effect are complex and I dependant on several variables. These include socioeconomic status, alongside the adaptive capacity of the agricultural sector in the country; both are considered risk factors during drought.
The nutrition-related health impacts of droughts as well as other natural disasters are more pronounced in developing countries. The most notable of these is malnutrition, micronutrient deficiencies such as vitamin A deficiency on the consumption of “anti-nutrient” such as aflatoxins, produced by toxigenic strains of fungus which grow on carbohydrate-rich foods.
Respiratory effects of drought
Under conditions of drought, air and dust-related diseases are another negative health consequence. Most notably in the 1930s, the central United States “Dust Bowl” caused the death of thousands in the population because of dust-borne pneumonia in the Great Plains.
The Dust Bowl refers to a period of severe dust storms which swept from Texas to Nebraska during the 1930s. It serves to illustrate the implications of droughts on air quality and health in individuals with pre-existing respiratory conditions who are consequently considered most at risk to the health effects of dust.
Alongside this risk group, other at-risk groups include the elderly, who have a poor functioning immune system and suffered deterioration in general health as a result of age. In addition, very young people, who do not have a fully mature respiratory and cardiovascular system, are also at risk.
In the USA, reports of worsened respiratory conditions such as asthma with increased dust during drought periods have been recorded. It should be noted that further research is needed to determine the effect on other long-term conditions. In addition, in the USA there is an overall decreased risk of respiratory admission among older adults, although severe drought has been found to increase the risk of mortality.
Impact of drought on vector-borne diseases
Droughts also exert negative health consequences via vector-borne diseases. This problem is of notable concern in developing countries, where diseases such as malaria, chikungunya, and dengue are relatively prevalent.
In Europe, the spread of vector-borne diseases because of climate change is becoming a topic of increasing concern. This is particularly true of mosquito- and zoonotic-borne diseases.
The reason for this exacerbated effect of drought on vector-borne diseases can be attributed to the effect of precipitation on the reproduction, development, behavior, and population dynamics of vectors. The most susceptible vectors to these variables are termed arthropod vectors. These include mosquitoes, text, flies, lice, midges, ticks, and several other arthropods that carry and transmit pathogenic organisms.
Evidence for this concern stems from historical case studies; in 2016 outbreaks of necrotizing fasciitis in Austria on the West Nile virus through Africa and Europe in 2015 were observed. Both diseases were strongly associated with water deficit and heat brought on by summer drought. Other reported impacts of drought such as injuries incurred by wildfire and damaged infrastructure due to heatwaves have been reported.
Metal health consequences of drought
Alongside the physical effects of drought are mental health effects. Mental health effects have been a focus of significant research in developed countries compared to developing countries. The focus on mental health is foundational for the well-being and effective functioning of individuals and communities at large. Mental health and illnesses are complex and determined by several interconnected psychological, biological, and social factors.
Mental health impacts associated with drought are most severe for farmers and their families, an effect caused by the loss of livelihoods from reduced agricultural activity. The loss of livelihood is considered a risk factor for the development of anxiety and depression and with this a potential increase in domestic violence, abuse, and suicide.
Such negative mental health outcomes are prevalent in rural communities relative to urban environments. Alongside the loss of livelihood, environmental degradation due to drought has also been linked to depression and anxiety.
Overall, there is a worldwide disparity in the extent of ill- health due to drought. In developed countries, the effect is limited, predominantly due to improved infrastructure, access to aid, and availability of resources. Other additional variables such as potentially lower exposure to underlying risk factors because of infrequent droughts, robust policy, and legislative framework are also hypothesized to be causes of this ameliorated effect.
Developing countries, which experience droughts more frequently, are also likely to experience worsening of existing challenges following a period of drought. Consequently, drought-related morbidity and mortality are more reported in developing countries
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