The causes of migration may be numerous and these may range from natural calamities, climatic change, epidemics, and draught to social, economic, cultural and political. The over population 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 level of technology and economic opportunities also cause large scale migration. (a) Technology
People with more sophisticated technology may evade and conquer new areas. Contrary to this, less advanced groups may be attracted to the greater opportunities provided by 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. 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 20thcentury and the main reason was to colonise the under developed countries and to exploit their resources. (b) Economic causes
One of the prime motives of emigration seems to be economic. Man’s need to have a virgin land to till has inspired him to migrate to distant areas. It was because of this reason that the slaves (AfricanNegros) were transported to the plantations in tropical America. These Negros subsequently settled in the United States of America, Latin America and West Indies. Heavy pressure on the land resources in the mother land also forced the people to outmigrate and to settle in areas where economic benefits may be achieved. Non availability of proper jobs and unemployment are also the economic reasons which compel the youth to leave their homes for places, areas, regions and countries where employment may be found. The agricultural laburers if unemployed, also leave their native places in every age, the labours emigrate to neighboring or distant fertile tracts. At present, laburers from Bihar, Uttar Pradesh and Rajasthan are migrating to Haryana, Punjab and Hmachal Pradesh. Thus the economic poverty, unemployment and attraction for better economic opportunities always motivated and forced the people to emigrate from their native places. For example, poverty of agricultural labourers in West Bengal, Orissa and Bihar resulted into the emigration waves towards the metropolitan cities and the productive plains and agricultural developed parts of countries. 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. (c) Overpopulation
Throughout the human history, migration took place because of the overpopulation in the 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 LatinAmerica. The people of these countries are emigrating to Saudi Arabia, Kuwait, U.A.E., Canada, France, Greece, 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 3lakh skilled and semi skilled people outmigrate. (d) Social and Religious causes
The human desire to stay, work and enjoy life with the people of his ethnic, social and religious groups is also in important cause of migration. In every period of human history social factors led to large scale emigration. The feeling of insecurity is compelling many of the Kashmiri Pandits and Punjabi Hindus to outmigrate from Jammu and Kashmir and Punjab respectively, while the Muslims prefer to migrate from the Hindu dominated areas to Muslimslocalities and vice versa, irrespectictive of the social amenities. Health, climate, education and other social amenities are also responsible for migration at the regional, national and international levels. (e) Political causes
One of the important causes of migration, especially after the Second World War, is the political one. A political refugee is a worldwide phenomenon. One can list numerous examples of political migration. This included, Turkish, Armenians and white Russians early in the 20thcentaury; European Jews after the second world war, Palestinians, Chinese, Hungarian( freedom fighters), Cubans, Indians, Pakistanis, Bangladeshis, Kashmiris, Tamils, Vietnamese, Afghans, Iranians,Somalians, Kurds, Siberians,Bosnians, kosovos and Albanians. All these are the example of forced migrations induced by political factors. Another form of involuntary migration is the expulsion or exchange of minority by nation. The Muslims and Hindus exchanged when India and Pakistan created by the partition of sub continent in 1947. (f) Demographic causes
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. 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.
(g) Diffusion of information
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, conservatisms, traditions and customs and strong communal ties are less mobile than those which are socially more awaken, progressive and have more contacts and exposure with 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. (h) General rise in the level of aspiration
With the advancement in science and technology, new items of comfort and luxuryappear in the market and the level of aspiration of the educated and uneducated goes up. Every body is tempted to enjoy a better standard of living. India and Pakistan as well as all developing countries, the young men who were better off than their fathers were nonetheless dissatisfied, and many sought to better themselves overseas. It mainly because of these reasons the Indian engineers and doctors are emigrating to USA, Canada and in large number of skilled and semi skilled labourers in migrating towards Saudi Arabia and Gulf countries. (i) Wars
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 to 1919 A.D.) involved a displacement of about 6 million people, and the second world war ( 1939 to 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. Million were moved in the forced transference of ethnic minorities, million more in evacuation and flight from the battle fronts. Forced labour movements and deportation accounted to several millions and subsequent resettlement involved still further movement. (j) Government policy
The government policy of a particular country also favourably or adversely affected the pattern of population migration. The British, French, German, Russian, American, New Zealand, Canadian and South African governments have specific population policy and most of them discourage immigrants.
Human Geography culture, society and space sixth edition by H.J. de Blij And Alexander B. Murphy