Short-term drought occurred in many places in the world during the 20th century. western Europe, including England, experienced years of drought on a number of occasions, as did parts of the United States. South America, Africa, and Asia have also known years in which drought conditions occurred. In the 1960s, drought appeared in the northeastern United States. Winter snows failed in the western United States 1975-77. In 1976, western Europe suffered a summertime drought. In the late 1960s and in the early 2000s, parts of Africa suffered from drought.
There are regions of the world where drought is normal. Some areas, such as the northeastern area of Brazil or other semi-arid regions, have regularly re-occurring patterns of drought. Drought in some areas of the Amazon basin, in 2005, was recorded as a 100-year drought. Some Brazilian scientists argued that it was due to deforestation that was pushing the Amazon rainforest to a tipping point where it would never recover as a rainforest.
In areas of the Mediterranean, or where a Mediterranean climate occurs (California, Central Chile, South Africa, and south and southwestern Austra-
lia) drought in the summertime is normal because there is less than 4 in. (2.54 cm.) of rain that falls during the summer months. The winters in areas with a Mediterranean climate are cooler and wetter than the summers. The rains of the non-summer months cause plants to grow profusely. However, the long dry summers expose the plants to fire hazard. Southern California is well known for brush fires that destroy the vegetation in many thousands of acres. People who have built homes in fire-prone areas may lose them to these wildfires. Plants in such regions are adapted to drought and to depend upon periodic fires for renewals. Fires that occur in drought conditions can be so severe that great expanses of timber and grassland are destroyed. With the cover crops and vegetation removed by fire, hot, dry winds can pick up soil and further damage soil productivity.
During the 1930s, a period of drought (1931-38), afflicted the states of the Great Plains. The 1920s had been a wetter time. It had also been a time in which farmers used the plowing techniques of the eastern United States. The deeper soil in the east was improved by plowing deep to bring up minerals from under the soil. However, in the drier conditions of the Great Plains, plowing deep broke the water table's contact with surface plants. The conditions were created for the terrible dust storms that occurred in the famous Dust Bowl.
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