A drought occurs when a region becomes deficient in its natural water supply whether on the surface or underground. Droughts can last for months and even years. In general, droughts occur when a region receives less than the average rainfall in an annual year. Droughts can have a substantial impact on the ecosystem, agriculture, and society of the affected region. Contrary to popular opinion, short intense droughts can cause significant damage insomuch as dry periods that last for several years. Due to its impact on agricultural production, droughts can severely harm the economy.
Some global regions have withstood extended droughts that literally transformed the terrain and life forms that inhabited it. For instance, the succulent plant species have adaptations that enhance their ability to tolerate drought. Others may survive extreme dry periods in the ground as buried seeds. Arid ecosystems with semi-permanent droughts may be referred to as deserts or grasslands. Droughts have triggered mass migration in the past, which played in the role of forming crises in the Horn of Africa, the Sahel, and other regions similar to them.
The consequences of extended droughts have had a significant impact on the agricultural, economic, environmental, and social aspects of entire civilizations. The severity of the consequences vary according to the region's vulnerability. In other words, a region will not feel the worst of a severe drought if alternatives exist for the inhabitants that reside there. However, if a region depends on natural rainfall for agricultural production, then the area becomes more drought-prone. Droughts drastically reduce the water quality of a region, because the lower water flow does not dilute the pollutants already within it, thus increasing the overall concentration of contaminants. The most common consequences of drought include a steady decrease of crop growth and raising livestock, dust bowels, dust storms, famine, ecosystem damage, dehydration, malnutrition, mass migration, reduced electricity output and industrial production, snake migration, wildfires, social unrest, and even war.
Droughts have impacted society since the dawn of civilization. In fact, the earliest recorded documents have outlined its effects on the terrain, people, and wildlife of a particular region. For instance, the Epic of Gilgamesh and the biblical stories of the Hebrew exodus from Ancient Egypt detail the harsh effects of drought on the most prominent civilizations in the history of mankind. Other events mark the mass migration of hunter-gatherer communities out of Africa and into the rest of the world around 9,500 B.C.E. Modern societies have developed irrigation and agricultural technologies that can mitigate the effects of drought on their land. Drought mitigation technologies help preserve human habitation in an era heavily dominated by densely populated regions.
Regions impacted by recurring droughts have developed into deserts in the Horn of Africa, which have led to catastrophic events for the people and wildlife that inhabit the land. In fact, it prompted food shortages all across the region, ultimately leading to widespread famine in neighboring countries. For instance, the Darfur and Sudanese conflict was fueled through decades of recurring droughts. Drought may impact regions in different ways. For instance, India, Pakistan, Myanmar, Nepal, China, and Pakistan may experience intense flooding followed by extended droughts in the next couple of decades, because of the drainage basin connected to the Himalayan rivers. The Amazon basin had previously dried out in 2005; however, the worst modern drought has spawned and currently affects East Africa. According to the United Nation's World Food Program, over four million Kenyans have become affected by the drought-spawned famine.
People define droughts in one of three ways, including meteorological, agricultural, and hydrological. A meteorological drought occurs when a region experiences an extended dry period that measures less than the average rainfall per annual year. Agricultural drought primarily affects crop production. Agricultural drought usually occurs when a region experiences a change in rainfall levels, so much so that the soil conditions begin to erode. Hydrological drought occurs when the available water reserves, such as reservoirs, lakes, and aquifers, start to dry below the previously recorded levels. Each of these types of droughts can affect all aspects of societies within a given region. Therefore, modern and future societies need to incorporate several strategies to mitigate the potential losses caused by extended drought, including the construction of dams, desalination of ocean water, drought monitoring, crop rotation, rainwater harvesting, recycling water, transvasement, water restriction enforcement, and cloud seeding.
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