Why Are We Concerned About
Drought is a natural hazard that cumulatively has affected more people in North America than any other natural hazard (Riebsame et al. 1991). The cost of losses due to drought in the United States averages $6-8 billion every year, but range as high as $39 billion for the three year drought of 1987-1989, which was the most costly natural disaster documented in U.S. history. Continuing uncertainty in drought prediction contributes to crop insurance payouts of over $175 million per year in western Canada.
Beyond the monetary costs, the impacts of drought on society, the economy, and the natural environment are tremendous. Although measures such as development of irrigation systems, financial aid programs and interbasin water transfers have been undertaken to mitigate the impacts of drought in recent decades, some regions of the U.S. are becoming more vulnerable to the impacts of drought.
Although irrigation has made it possible to grow crops on land that was once considered barren, this practice has led to a reliance on ground water and surface storage in reservoirs. Increasing demands on water have resulted in the depletion of ground water reserves in many areas, which can make the removal of additional water uneconomical if not impossible, especially during a drought. In many urban areas of the semi-arid and arid western U.S., population growth, expansion into marginal areas, and the subsequent development is overtaxing water supplies and heightening vulnerability to drought. Along with this increased vulnerability, concern exists because some research suggests that drought in the future may be amplified in certain areas due to changes in climate variability and extremes resulting from global warming.
Scientists have much to learn about the characteristics of drought and the conditions that lead to the persistence of drought. Although some progress has been made, (for instance, droughts that are related to El Niño and the Southern Oscillation (ENSO) are now more predictable on a seasonal scale), scientists still cannot predict longer, multi-year droughts.
The two major droughts of the 20th century, the 1930s Dust Bowl drought and the 1950s drought, lasted five to seven years and covered large areas of the continental U.S. Complete scientific understanding of how and why these two drought episodes occurred remains elusive. From a societal perspective, the important question is, how unusual are these events? Most instrumental records (from thermometers and rain gauges) are only about 100 years long, so they are too short to answer this question. However, paleoclimatic proxy data are a valuable tool to investigate this question by providing a longer context within which to evaluate the reoccurrence of these major droughts over hundreds to thousands of years.
For more complete information on the impacts of drought in North America, see the National Drought Commission report titled "Preparing for Drought in the 21st Century"
On to... 20th Century Drought