The main causes of famine include both environmental and political factors. While the vast majority of famines throughout history have been caused by unexpected environmental difficulties, many have been caused by political mismanagement. In more recent history, famines have commonly been caused by regional strife and misallocation of resources by totalitarian governments.
Some of the most notorious famines of the 20th century were caused by overtly political actions. According to Slate, the Great Chinese Famine of 1958 to 1961 was a direct result of leader Mao Zedong's disastrous "Great Leap Forward" campaign, an attempt to rapidly transition the country from an agrarian to industrial society. Similarly, the Ukrainian "Holodomor" of 1932 to 1933, which killed between 2.4 and 7.5 million Ukrainians, is widely perceived as a deliberate genocide attempt by Joseph Stalin. Even the Irish Potato Famine of 1845 to 1852, ostensibly caused by the crop disease potato blight, was greatly aggravated by the governmental policies of the British, Ireland's colonial rulers. Recent famines in many African countries are also examples of a confluence of political and environmental factors whereby droughts were often exacerbated by political discord and poor government policy.
Political factors aside, many famines have been caused mainly by environmental factors. From droughts to overly long rainy seasons and plant diseases, most historical famines were caused by factors that were difficult, if not impossible, to prevent.