The book “The Grapes of Wrath” by John Steinbeck tells the story of a farming family in Oklahoma who are forced to abandon their land due to the drought. This work, made into a film by John Ford and starring Henry Fonda, is based on real events that occurred in the 1930s, when the Great Plains of the United States, known as the breadbasket of the world, suffered several years of extreme drought that dried out the soil so much that huge dust storms were unleashed.
In the summer of 2012, a similar situation occurred in the same region where the story of the book and movie takes place. Farmers in the area were expecting a big harvest, but days after planting corn in May, a sudden drought emerged and in a matter of weeks destroyed their crops. According to official sources, losses exceeded US$30 billion, and 76% of crops were affected. This event exceeded in terms of water deficit the one described in Steinbeck’s book.
The concept of flash droughts, also known as flash floods, was first raised 10 years ago, but these phenomena have always existed. What differentiates them from conventional hydrological droughts is their speed and intensity. Slow droughts occur after months or years of below-average precipitation, while flash droughts emerge and reach their maximum intensity in a matter of weeks or even days. Moreover, these droughts are the result of a complex process that goes beyond a shortage of rainfall.
Under normal conditions, rain waters the soil and plants, providing hydration to the air through evaporation from the soil and transpiration from the leaves (evapotranspiration). But if it does not rain, the atmosphere still needs a water supply that is stolen from the surface and vegetation. If a heat wave or dry winds occur in a place where it has not rained for a long time, a sudden drought is triggered.
A group of Chinese and US researchers have analyzed data available since 1951 to detect the evolution and distribution of sudden droughts. Their work, published in the scientific journal Science, shows an upward trend of these events, both in territory and in time. Sudden droughts are occurring more frequently in humid regions of the planet, from Canada to Siberia, via the Gulf of Guinea, the Amazon rainforest, the jungles of Southeast Asia, and the large islands of Indonesia and Papua New Guinea. In these parts of the world, the frequency of sudden droughts is up to three times higher than in the rest of the world.
The problem of flash droughts is global and worsening. The frequency of these droughts has increased over 74% of the Earth’s surface, excluding the poles.