. in
South Australia was abandoned. Drought is one of the most complex and major
natural hazards, and it has devastating impacts on the environment, economy, water resources, agriculture, and society worldwide. One can divide the impacts of droughts and water shortages into three groups: environmental, economic and social (including health).
Environmental and economic impacts Environmental effects of droughts include: lower surface and subterranean water-levels, lower flow-levels (with a decrease below the minimum leading to direct danger for amphibian life), increased
pollution of surface water, the drying out of
wetlands, more and larger
wildfires, higher deflation intensity,
loss of biodiversity, worse health of trees and the appearance of pests and dendroid diseases. Drought-induced mortality of trees lacks in most
climate models in their representation of forests as
land carbon sink. Economic losses as a result of droughts include lower agricultural, forests, game and fishing output, higher food-production costs, lower energy-production levels in hydro plants, losses caused by depleted water tourism and transport revenue, problems with water supply for the
energy sector and for technological processes in metallurgy, mining, the chemical, paper, wood, foodstuff industries etc., disruption of
water supplies for municipal economies. It has been calculated by the
Food and Agriculture Organization of the United Nations that droughts had caused USD 278 billion of damage between 1991 to 2023. Further examples of common environmental and economic consequences of drought include: • Alteration of
diversity of plant communities, which can have an impact on net
primary production and other
ecosystem services. •
Wildfires, such as
Australian bushfires and
wildfires in the United States, become more common during times of drought and may cause human deaths. •
Dust Bowls, themselves a sign of
erosion, which further erode the
landscape •
Dust storms, when drought hits an area suffering from desertification and
erosion •
Habitat damage, affecting both
terrestrial and
aquatic wildlife •
Snake migration, which results in snake-bites • Reduced
electricity production due to reduced water-flow through
hydroelectric dams • Shortages of water for
industrial users
Agricultural impacts on soil moisture at 2 °C of global warming. A reduction of one
standard deviation means that average soil moisture will approximate the ninth driest year between 1850 and 1900. Droughts can cause land degradation and loss of soil moisture, resulting in the destruction of cropland productivity. This can result in diminished
crop growth or yield productions and
carrying capacity for
livestock. Drought in combination with high levels of grazing pressure can function as the tipping point for an ecosystem, causing
woody encroachment. Water stress affects plant development and quality in a variety of ways: firstly drought can cause poor germination and impaired seedling development. At the same time plant growth relies on cellular division, cell enlargement, and differentiation. Drought stress impairs
mitosis and cell elongation via loss of
turgor pressure which results in poor growth. Development of leaves is also dependent upon turgor pressure, concentration of nutrients, and carbon assimilates all of which are reduced by drought conditions, thus drought stress lead to a decrease in leaf size and number. This explains why droughts and water scarcity operate as a factor which increases the gap between
developed and
developing countries. Effects vary according to vulnerability. For example, subsistence farmers are more likely to migrate during drought because they do not have alternative food-sources. Areas with populations that depend on water sources as a major food-source are more vulnerable to famine. arriving at a camp in
Dolo Ado, Ethiopia, 2011 Further examples of social and health consequences include: •
Water scarcity,
crop failure,
famine and
hunger – drought provides too little water to support food crops;
malnutrition,
dehydration and related diseases •
Mass migration, resulting in
internal displacement and international
refugees • Social
unrest •
War over natural resources, including water and food •
Cyanotoxin accumulation within food chains and water supply (some of which are among the most potent toxins known to science) can cause cancer with low exposure over the long term. High levels of
microcystin appeared in
San Francisco Bay Area salt-water shellfish and fresh-water supplies throughout the state of California in 2016. Severe drought has been noted to cause unrest and precede in some cases periods of political upheaval.
Loss of fertile soils Wind erosion is much more severe in arid areas and during times of drought. For example, in the
Great Plains, it is estimated that soil loss due to wind erosion can be as much as 6100 times greater in drought years than in wet years.
Loess is a homogeneous, typically nonstratified, porous,
friable, slightly coherent, often calcareous, fine-grained,
silty, pale yellow or buff, windblown (
Aeolian)
sediment. It generally occurs as a widespread blanket deposit that covers areas of hundreds of square kilometers and tens of meters thick. Loess often stands in either steep or vertical faces. Loess tends to develop into highly rich soils. Under appropriate climatic conditions, areas with loess are among the most agriculturally productive in the world. Loess deposits are geologically unstable by nature, and will erode very readily. Therefore, windbreaks (such as big trees and bushes) are often planted by farmers to reduce the wind erosion of loess. == Regions particularly affected ==