The phenomenon of drought has to be understood in its various displays. The Inter-governmental Panel on Climate Change (IPCC) refers to four types of drought: meteorological, that is an extended period of abnormally low rainfall; agricultural, when soil moisture is low; hydrological, or an abnormal decrease of surface and groundwater; and environmental drought, a combination of the others.
In the future, IPCC estimates lands affected by extreme drought will increase by a factor of 10 to 30, from today’s 1-3% to 30% by the 2090s. The main driver is the change of the water cycle due to global warming: even if episodes of both extremely high and low rainfall are predicted to increase, in average the drying trend will prevail.
The impacts of drought on the human society are numerous. Since 1900, drought-related deaths amount to more than 11 million, and more than 2 billion people have been affected by its consequences. Reduced access to clean water is the primary or concomitant cause of most diseases and deaths. As reported by OCHA, one of the most impacted areas is the Horn of Africa: the people displaced for drought-related issues now amount to 3.7 million, while 14.3 million live in conditions of severe food insecurity.