The causes of migration may be numerous and these may range from natural calamities, climatic change, epidemics, and drought to social, economic, cultural and political.
The overpopulation and heavy pressure on resources may be the cause of permanent or temporary, and long distance or short distance migration. Many a time the differences between groups in levels of technology and economic opportunities also cause large-scale migration.
People with more sophisticated technology may invade and conquer new areas. Contrary to this, less advanced groups may be attracted to the greater opportunities provided by a more developed society.
For example, ancient Romans conquered vast areas in Europe, North Africa and South-West Asia. During this period, many people migrated to Rome which provided better economic and employment opportunities.
During the medieval period, the Arabs were quite advanced in education and technology. With this, they conquered large territories in Central Asia, Northern Africa, Iberian Peninsula (Spain and Portugal) and eastern parts of Europe.
In the 14th and 15th centuries, the Europeans had better navigation ships and they discovered America, Australia and numerous unknown islands of the Arctic, Atlantic, Indian and Pacific Oceans. They colonized and exploited more populated territories of Asia and Africa.
After the Industrial Revolution in 1779, the Europeans emigrated to North America, Australia, New Zealand, South Africa and South America.
The large-scale emigration from European countries continued up to the first part of the 20th century and the main reason was to colonize the underdeveloped countries and to exploit their resources.
One of the prime motives of emigration seems to be economic. Man’s need to have virgin land to till has inspired him to migrate to distant areas.
It was because of this reason that the slaves (African Negroes) were transported to the plantations in tropical America.
These Negroes subsequently got settled in the United States of America, Latin America and the West Indies. Lust for virgin land also motivated the Europeans to emigrate from UK, Ireland, France, Germany, Italy, Spain, Portugal, Holland, Belgium and Denmark and to settle into the Praries of USA and Canada.
In the 17th and 18th centuries, about 20 to 40 hectares of land 152 Migration was used to be given free of cost to the emigrants in USA who owned nothing in their homeland. The temptation to have land became a great magnetic force for the Europeans to settle in America.
Heavy pressure on the land resources in the motherland also forced the people to out migrate and to settle in areas where economic benefits may be achieved.
The pastoral people and nomads of Central Asia invaded the territories of the sedentary people. The Mongols, Tatars, Uzbeks, Yakuts and Kurds migrated in the medieval period and got settled in the fertile valleys of Farghana, Panjsheer (Afghanistan), Volga, Armenia and Caucasus mountains.
Non-availability of proper jobs and unemployment are also the economic reasons which compel the youths to leave their home for the places, areas, regions and countries where employment may be found.
It was the main cause of the migration of the Scotch-Irish in the 17th and 18th centuries after the decline of the woolen industry and the slump in linen in consequence of the rise of cotton textile industry in Britain.
The invention of spinning machine and the establishment of large-scale cotton factories made many of the weavers of the subcontinent of India (India, Pakistan and Bangladesh) unemployed. In 1930, the slump and economic depression resulted into an exodus of British workers to Canada and USA in spite of efforts to stop them.
The agricultural labourers, if unemployed, also leave their native places. In every age, the labourers immigrated to neighbouring or distant fertile tracts.
For example, in about 2000 B.C., Abraham migrated from Ur (Mesopotamia) to Cannan the Greeks migrated to Scythia, the Jews migrated to Nile Valley and Mesopotamia, and the Bihar, Odisha and Rajasthan labourers migrated to West Indies and South-East Asia.
At present, labourers from Bihar, Uttar Pradesh, Odisha, Madhya Pradesh and Rajasthan are migrating to Haryana, Punjab and Himachal Pradesh.
Thus, the economic poverty, unemployment and attraction for better economic opportunities always motivated and forced the peoples to emigrate from their native places.
For example, poverty of agricultural labourers in West Bengal, Odisha and Bihar resulted into the emigration waves towards the metropolitan cities and the productive plains and agriculturally developed parts of the country.
The regions and districts of marginal farmers and small farmers also emigrate with the agricultural labourers, as the tiny size of their holdings is unable to provide them adequate sustenance.
An excess of population in an area in relation to resources and available technology is known as overpopulation.
Overpopulation may exist at local, regional and national levels. At present, it is most frequently seen in underdeveloped rural areas where the outstripping of resources by population growth may be evident in undernourishment or underemployment.
Throughout the human history, migration took place because of the overpopulation in a community or region. In such a case, emigration may affect all social classes.
At present, overpopulation is the most important cause of emigration in the developing countries of Asia, Africa and Latin America.
The people of these countries are emigrating to Saudi Arabia, Kuwait, Oman, Yemen, UAE, Canada, Greece, France, Germany, Australia and New Zealand.
The emigrants include domestic servants, agricultural labourers, unskilled workers, technicians, engineers, doctors and academicians. Each year, from India alone, about 3 lakh skilled and semi-skilled people out migrate.
The human desire to stay, work and enjoy life with the people of his ethnic, social and religious groups is also an important cause of migration.
In every period of human history social factors led to large-scale emigration. In the middle ages, there was the emigration of Balkan peoples owing to the dominance of Muslim Turks.
In the 20th century, there has been expulsion of Jews from Germany, Spain and Russia (erstwhile USSR). There is large-scale outmigration of Muslims from Bosnia and Serbia (erstwhile Yugoslavia). Muslims are moving out from Myanmar (Burma) to Bangladesh.
The feeling of insecurity is compelling many of the Kashmiri Pandits and Punjabi Hindus to out migrate from Jammu & Kashmir and Punjab respectively, while the Muslims prefer to migrate from the Hindu dominated areas to Muslim localities and vice versa, irrespective of the social amenities.
Many of the well-off Muslims are moving towards the Muslim slum localities in Delhi, Mumbai, Ahmadabad, Meerut, Allahabad, Agra, Kanpur, Lucknow, etc., because of social and religious persecutions and same is the case of Hindus as they are out migrating from the Muslim dominated areas to Hindu dominated areas. Health, climate, education and other social amenities are also responsible for migration at the regional, national and international levels.
One of the important causes of migration, especially after the Second World War, is the political one. A political refugee is a worldwide phenomenon today. One can list numerous examples of political migration.
These included, Turkish, Armenians, and white Russians early in the 20th century; European Jews after the Second World War, Palestinians, Chinese, Hungarian (freedom fighters), Cubans, Indians, Pakistanis, Bangladeshis,
Kashmir’s, Tamils, Vietnamese, Afghans, Iranians, Somalians, Kurds, Serbians, Bosnians, Kosovos and Albanians all these are the examples of forced migrations induced by political factors.
Another form of involuntary migration is the expulsion or exchange of minorities by nations. For example, the Sudeten Germans repatriated from Czechoslovakia after the Second World War, and the Muslims and Hindus exchanged when India and Pakistan were created by the partition of the subcontinent in 1947.
The forced and compulsory migration is always bound up with tragic highlights in human history. During the medieval period, Negroes used to be sold in the urban markets of Portugal, Spain, France and Italy.
These slaves (Negroes) were exported to USA from the western coast of Africa, from the Senegal to the Gold Coast and Congo. The settling of the New World (after 1492) opened up new markets, but it was Spain which needed them in the Americas.
A number of demographic factors also play a vital role in the migration Pattern. For example, age has been recognized as one of the important demographic factors controlling the degree of desire to move among the Potential migrants. It is not surprising that adults are more migratory than other age groups.
It is the rate of growth of population that determines the extent of population pressure in an area. The great historic movement of the Europeans across the Atlantic Ocean was an expression of increasing pressure of population on the resource base of Europe.
Similarly, in India, the large-scale outmigration from the densely populated parts of Orissa, West Bengal, Kerala, Bihar and Uttar Pradesh is largely due to a poor population-resource ratio in these areas.
The availability of information through education, cultural contacts and spatial interaction also increase the chances of population migration.
The communities that are ruled by orthodoxy, conservatives’, traditions, customs and strong communal ties are less mobile than those which are socially more awakened, progressive and have more contacts and exposure with the outside world.
The information network and cultural contact increase the horizons of job opportunities. Thus, migration generates more migration, which signifies the role of information network in the stimulation of migration. In India, the Sikhs are the most adventurous and well-informed people, who migrate even to the less developed and less attractive areas like Bolivia, Columbia, Ecuador, Honduras, Nicaragua, Central African Republic, Chad, Sudan, Ethiopia, Yemen, etc.
With the advancement in science and technology, new items of comfort and luxury appear in the market and the level of aspiration of the educated and uneducated people goes up. Everybody is tempted to enjoy a better standard of living.
In India and Pakistan as well as in all the developing countries, the young men who were better-off than their fathers were nonetheless dissatisfied, and many sought to better themselves overseas.
It is mainly because of this reasons that Indian engineers and doctors are emigrating to USA, Canada and in large number unskilled and semi-skilled labour in migrating towards Saudi Arabia and the Gulf countries.
Wars have been one of the important causes of human migration. Wars have always involved upheavals, particularly in the regions where these have been fought.
The First World War (1914-1919 A.D.) involved the displacement of about 6 million people, and the Second World War (1939-1945 A.D.) involved the involuntary displacement of about 60 million people.
Some people were forced to move to avoid political and religious persecution even long before the war. Millions were moved in the forced transference of ethnic minorities, millions more in evacuation and flight from the battle fronts.
Forced labour movements and deportation accounted for several millions, and subsequent resettlement involved still further movement.
Nearly a million Poles and Jews were deported “by Germany during the war, another million by Russia, who also moved a large number of Germans from the Volga to the far eastern parts of Siberia.
The population of Europe was in constant flux during the war, from the Volga to Paris, and the end of the war led to the movement of refugees. All these migrations resulted into the changes of human resources, in land use, customs, traditions and human values.
After the Turko-Greek war of 1921, about 0.35 million Turks were moved to Turkey from Greece and about 1.2 million Greeks went to their own country from Turkey.
As stated above, transfer on a much greater scale followed the partition of India, where approximately six million Hindus left Pakistan and an equal number of Muslims left India for Pakistan, though large minorities remained in both countries.
In the summer of 1999, millions of Muslims from Kosovo were forced to migrate to Albania and Macedonia. After the attack of USA on Afghanistan in October 2001, and Iraq in 2004, millions of refugees migrated to Iran, Pakistan, Syria, Tajakistan and Uzbekistan.
The government policy of a particular country also favourably or adversely affected the pattern of population migration.
The British, French, German, Russian, USA, New Zealand, Canadian, UK and South African governments have specific population policies and most of them discourage immigrants. In the early fifties, a large number of people moved out from the countryside to the urban areas as a result of collectivization of farms.
Similarly, the political totalitarianism in Russia resulted in the migration of people from their homeland at the time of Bolshevik Revolution, also known as the Great October Revolution, 1917.