The Great Irish Potato Famine occurred during a period of mass famine, disease and emigration between 1845 and 1850. According to the magazine “The Context of Migration: The Example of Ireland in the Nineteenth Century” by James H. Johnson, this caused the Irish population to decline by 20-25% and did not stabilize again until the 1930s. Although there was a potato crop failure in Europe in 1840, a third of the Irish population depended on this crop. This was inevitable due to the Irish people's exclusive dependence on home-grown potatoes and the population nearly doubling from 1800 to 1840. The journal "Spaces for Famine: A Comparative Analysis in Ireland and the Highlands in the 1840's" by Liz Young states that “if the harvest was poor or failed, families could not cope and, for comparison, 50,000 people died when crops failed in 1817-1819.” The Irish could not sustain their potato-based diet because they did not have the means to purchase more seed or, indeed, purchase the land on which to grow enough potatoes to feed their rapidly multiplying families for a year. As families increased in size, excess production, which would previously have provided them with the means to purchase livestock, etc., was consumed. There were many factors that were involved in this catastrophe. The main causes were environmental conditions, agricultural practices and climatic conditions, economic defects, and social and political trends. Social unrest and Ireland's history of poverty were the direct cause of the Irish potato famine and sole dependence on the potato crop which inevitably led to starvation. It is mentioned in the magazine "The Demographic Factor in Ireland's Movement into Partition" (1607 -1921)” ...... middle of paper ......b. 2012. http://www.jstor.org.>• Young, Liz. “Spaces for Famine: A Comparative Geographical Analysis of Famine in Ireland and the Highlands in the 1840s.” Transactions of the Institute of British Geographers 4th ser. 21 (1996): 666-80. JSTOR. Network. 25 February 2012. .• Johnson, James H. “The Context of Migration: The Example of Ireland in the Nineteenth Century.” Transactions of the Institute of British Geographers 3rd ser. 15 (1990): 259-76. JSTOR. Network. February 26, 2012. http://www.jstor.org.>• “Irish Potato Famine.” Encyclopedia Britannica. Encyclopedia Britannica Online academic edition. Enciclopedia Britannica Inc., 2012. Web. 25 February 2012. .• Fernandez-Armesto, Felipe. “Muscle Replacement: The Energy Revolutions.” World history. Boston: Pearson Prentice Hall, 2010. 5. Prin