The complexity of drought
Most of us in the United States would define drought as a period of unusually dry weather. That’s because, for many of us, that’s all that drought is. We might pay a little more for some groceries. If things get really bad, we might be faced with restrictions on how much we can water our lawns or when we can wash our cars.
Because so few of us work in agriculture, most Americans don’t appreciate the subtle cues in the natural world that tell us something isn’t quite right. We don’t notice if crops aren’t growing as high as they should. We don’t notice when storms don’t come or when reservoirs aren’t as full as they should be. We don’t notice when topsoil slowly dries out. The great majority of us don’t grow food or live in close proximity to where our food is grown, so we don’t notice when droughts start to take hold.
We don’t know there’s a drought until someone tells us, and by then it’s usually reached crisis level. Once the rain returns, most of us assume things are back to normal.
But drought is far more complex than that. A lack of precipitation does more than dry out fields and reduce the amount of water available for human consumption. Even when droughts seem not to last very long, they have consequences that resonate for a very long time.
Drought is a series of events
It is more accurate to think of drought as a series of events triggered by an initial lack of precipitation.
1. No precipitation. Drought can come slowly or quickly, but it always begins the same way: snows don’t come in winter and rains don’t come in spring.
California state capitol, Sacramento, displaying a sign promoting water conservation over lawn care, July 2014. Photo Credit: Kevin Cortopassi (Used under Creative Commons license).
2. Pests. Drought dries up crops and kills farm animals, but that’s often only the most obvious effect drought has on plants and animals. More fundamentally, drought throws nature’s natural checks-and-balances system out of whack, creating the conditions in which pest populations explode. Also, just as drought displaces people, it displaces animals, too, and swarms of insects and rodents sometimes move out of drought areas and cause disasters elsewhere.
Potato psyllid nymphs. Photo Credit: Center for Invasive Species Research (Used under Creative Commons license).
3. Flooding. When precipitation returns after a drought, it often falls on land that is too dry to hold it. Droughts don’t end sooner when rain falls fast—heavy rains pile huge amounts of water on top of hardened soil that cannot absorb it. Soil needs time to recover after a drought, but the gentle, soaking rains that do the most good for drought recovery aren’t usually the rains that first arrive. Droughts are frequently broken by floods, not relief.
Flooding in Cedar Rapids, Iowa, June 2008. Photo Credit: Don Becker, U.S. Geological Survey (Used under Creative Commons license).
4. Disease. Both droughts and floods can create conditions favorable to the spread of disease among plants, animals and people. Droughts weaken the ability of crops and animals to resist disease—any living creature suffering from thirst and hunger is extremely vulnerable to disease. Conversely, floods are a perfect medium to spread viral and bacterial diseases. Floodwaters contain a wide array of contaminants from petroleum to human waste, making floods a highly efficient method of contaminating both soil and drinking water.
Floods pollute water sources near an evacuation center in Madagascar, creating an urgent need for safe drinking water. Photo Credit: European Commission Humanitarian Aid and Civil Protection (Used under Creative Commons license).