Forced displacement has accompanied persecution, as well as war, throughout human history but has only become a topic of serious study and discussion relatively recently. This increased attention is the result of greater ease of travel, allowing displaced persons to flee to nations far removed from their homes, the creation of an international legal structure of human rights, and the realizations that the destabilizing effects of forced immigration, especially in parts of Africa, the Middle East, south and central Asia, ripple out well beyond the immediate region.
The concept of forced displacement envelopes demographic movements like flight, evacuation, displacement, and resettlement. The International Organization for Migration defines a forced migrant as any person who migrates to "escape persecution, conflict, repression, natural and human-made disasters, ecological degradation, or other situations that endanger their lives, freedom or livelihood".
The International Association for the Study of Forced Migration (IASFM) defines it as "a general term that refers to the movements of refugees and internally displaced people (those displaced by conflicts) as well as people displaced by natural or environmental disasters, chemical or nuclear disasters, famine, or development projects."
According to Alden Speare, "in the strictest sense migration can be considered to be involuntary only when a person is physically transported from a country and has no opportunity to escape from those transporting him." Movement under threat, even the immediate threat to life, contains a voluntary element, as long as there is an option to escape to another part of the country, go into hiding or to remain and hope to avoid persecution." However this thought has been questioned, especially by Marxians, who argue that in most cases migrants have little or no choice.
Causes for forced displacement can include: