The Great Famine, also known as the Great Hunger, the Famine and the Irish Potato Famine, was a period of starvation and disease in Ireland lasting from 1845 to 1852 that constituted a historical social crisis and subsequently had a major impact on Irish society and history as a whole. The most severely affected areas were in the western and southern parts of Ireland—where the Irish language was dominant—and hence the period was contemporaneously known in Irish as an Drochshaol, which literally translates to "the bad life" and loosely translates to "the hard times". The worst year of the famine was 1847, which became known as "Black '47". During the Great Hunger, roughly 1 million people died and more than 1 million more fled the country, causing the country's population to fall by 20–25% between 1841 and 1871. Between 1845 and 1855, at least 2.1 million people left Ireland, primarily on packet ships but also on steamboats and barques—one of the greatest exoduses from a single island in history.

In agriculture, monoculture is the practice of growing one crop species in a field at a time. Monoculture is widely used in intensive farming and in organic farming: both a 1,000-hectare cornfield and a 10-ha field of organic kale are monocultures. Monoculture of crops has allowed farmers to increase efficiency in planting, managing, and harvesting, mainly by facilitating the use of machinery in these operations, but monocultures can also increase the risk of diseases or pest outbreaks. This practice is particularly common in industrialized nations worldwide. Diversity can be added both in time, as with a crop rotation or sequence, or in space, with a polyculture or intercropping.