The Great Famine was a period of great starvation, disease and emigration in Ireland between 1845 and 1852 during which the islands population dropped by 20-25 percent. Approximately one million people died and a million more emigrated from Ireland. The proximate cause of famine was a potato disease commonly known as potato blight. Although blight ravaged potato crops throughout Europe during the 1840s the impact and human cost in Ireland where a third of the population was entirely dependent on the potato for food was exacerbated by a host of political, social, and economic factors which remain the subject of historical debate. The famine was a watershed in the history of Ireland. Its effects permanently changed the islands demographic, political and cultural landscape. For both the native Irish and those in the resulting diaspora, the famine entered folk memory and became a rallying point for various nationalist movements.