|Drought in Bangladesh|
Drought is a shortage of precipitation that results in a water deficit for some activity. Droughts occur in both arid and humid regions.
One problem in analyzing and assessing the impacts of drought, as well as in delimiting drought areas, is simply defining “drought” itself. Conditions considered a drought by a farmer whose crops have withered during the summer may not be seen as a drought by a city planner.
There are many types of drought: agricultural, hydrological, economic, and meteorological. The Palmer Drought Severity Index is the best known of a number of indexes that attempt to standardize the measurement of drought magnitude. Nevertheless, there still is much confusion and uncertainty on what defines a drought.
Roger G. Barry and Richard J. Chorley, in Atmosphere, Weather, and Climate (1998), have noted that drought conditions tend to be associated with one or more of four factors: increases in extent and persistence of subtropical high-pressure cells; changes in the summer monsoonal circulation patterns that can cause a postponement or failure of the incursion of wet maritime tropical air onto the land; lower ocean surface temperatures resulting from changes in ocean currents or increased upwelling of cold waters; and displacement of mid-latitude storm tracks by drier air.
Effects of Drought
Drought can have wide-ranging impacts on the environment, communities, and farmers. Most plants and animals in arid regions are adapted to dealing with drought, either behaviorally or through specialized physical adaptations. Humans, however, are often unprepared or overwhelmed by the consequences of drought.
Farmers experience decreased incomes from crop failure. Low rainfall frequently increases a crop’s susceptibility to disease and pests. Drought can particularly hurt small rural communities, especially local business people who are dependent on purchases from farmers and ranchers.
Drought is a natural element of climate, and no region is immune to the drought hazard. Farmers in humid areas grow crops that are less drought-resistant than those grown in arid regions.
|Effects of Drought to drought sensitive (right) and drought resistance (left).|
In developing countries the effects of drought can include malnutrition and famine. A prolonged drought struck the Sahel zone of Africa from 1968 through 1974. Nearly 5 million cattle died during the drought, and more than 100,000 people died from malnutrition-related diseases during just one year of the drought.
Subsistence and traditional societies can be very resilient in the face of drought. American Indians either stored food for poor years or migrated to wetter areas. The !Kung Bushmen of southern Africa learned to change their diet, find alternate water sources, and generally adapt to the fluctuation of seasons and climate in the Kalahari Desert.
More than any other event, the Dust Bowl years of the 1930’s influenced Americans’ perceptions and knowledge of drought. Stories of dust storms that turned day into night, fences covered by drifting soil, and the migration of destitute farmers from the Great Plains to California captured public and government attention.
The enormous topsoil loss to wind erosion, continuous crop failures, and widespread bankruptcies suggested that the United States had in some way failed to adapt to the drought hazard.
Federal Drought Response in the United States
Beginning in the 1930’s, the federal government took an increasing role in drought management and relief. In 1933 the federal government created the Soil Erosion Service, known today as the Natural Resources Conservation Service. No other single federal program or organization has had a greater impact on farmers’ abilities to manage the drought hazard.
President Franklin D. Roosevelt’s Prairie States Forestry Project (1934-1942) planted more than 230,000 acres of shelter belts in the Plains states forwind erosion control. The federal government purchased nearly 1 million acres of marginal farmland for replanting with grass. Federal agencies constructed water resource and irrigation projects.
Post-Dust Bowl droughts still caused hardships, but the brunt of the environmental, economic, and social consequences of drought were considerably lessened. Fewer dust storms ravaged the Plains.
New crop varieties and better farming practices decreased crop losses during drought years. Government programs and better knowledge have enabled families and communities to cope better with drought.
Coping with Future Droughts
Numerous attempts have been made to predict droughts, especially in terms of cycles. However, attempts to predict droughts one or more years into the future have generally been unsuccessful. The shorter the prediction interval has been, the more accurate the prediction has been.
Nevertheless, progress has been made in estimating drought occurrence and timing. For example, the El Niño/Southern Oscillation may be a precursor of drought in some areas. Possibly with time, the physical mechanics of climate and drought will be understood adequately for long-term predictions to have value.
Perhaps of greater value is the current capacity to detect and monitor drought in its early stages (usually meaning within one to twelve months). Early recognition of potential drought conditions can give policymakers and resource managers the extra time needed to adjust their management strategies.
|Coping with Future Droughts|
Information on soil moisture conditions aids farmers with planting and crop selection, seeding, fertilization, irrigation rates, and harvest decisions. Communities that have a few months’ warning of impending drought can increase water storage, implement water conservation measures, and obtain outside sources of water.
Unfortunately, the progress made in the world’s developed countries has not always been available to the developing nations. Overpopulation and overuse of agricultural lands have resulted in regional problems of desertification and impeded the ability of developing nations to respond.
Monitoring equipment can be costly. Furthermore, drought adjustments used in the United States may not be applicable to other countries’ drought situations.