The population of the world's cities has doubled in the last thirty years and will double again in the next twenty. An increasing percentage of the world's population is living in transitional settlements—shanty towns where non-integrated population groups crowd into makeshift, insanitary shelters which lack water, drainage, gas and electricity; and where the lack of protection against the hazards of fire and flood breeds a sense of insecurity. In the Third World, the result has been skyscrapers of steel and glass surrounded by slums of mud and wood. In both developed and developing countries the last decade in particular saw the rapid growth of unconventional urban settlements—squatter areas, slums, and, of less importance, mobile home parks. These represent the inability of human settlements to house population growth in terms of permanent accommodation at reasonable standards.
Uncontrolled urban growth and internal migration from countryside to the town are the major causes of urban slums. Migrants often arrive at a faster pace than the cities are able to absorb them. The development of infrastructures cannot keep pace, and the new arrivals pile up in settlements made of the flimsiest materials, sometimes without any form of municipal administration or public services. Living conditions in slum settlements are often materially worse than in the villages from which the migrants came. Overcrowding of premises in slums and shanty-type construction are typical. There is enormous pressure on water supplies and the arrangements for waste disposal. Malnutrition and diseases add to the burden on medical services. Schools are over crowded and anti-social behaviour is common. This concentration of unassimilated migrants tends to encourage juvenile delinquency, adult crime, vice, alcoholism, gambling, mental disorders, and political instability. Children of the slums are both materially and emotionally disadvantaged and underprivileged. Other social problems linked with urban environmental factors are the unbalanced distribution of population by age group in urban and suburban areas, non-adaptation of rural migrants, dissatisfaction due to instability of employment opportunities, and difficulty in integrating youth. Sickness and disease, along with high mortality rates, are commonplace.
In addition to degrading their own environment, the presence of urban slums is increasingly determining the physical environment of the entire urban area. Streams are polluted, land is laid waste and hillsides are eroded through overcrowding and the lack of even the most rudimentary public services. Rats and vermin spread. Trees and vegetation are all but eliminated by the cutting for use and sale of all available timber.
The fabric of urban life and contemporary society in many developing countries is threatened when these populations occupy 30 to 50% or more of urban areas, as in some cities of Latin America and elsewhere. In most developing countries it has not been possible to provide in advance a rational arrangement of space for living, transportation and recreation, or to provide rapidly enough for housing, water, sewage disposal, education, or the other amenities of urban life.
In developing countries, the urbanization process is accelerating. The annual average growth rate of the urban population between 1960 and 1970 was 4.1% in South Asia, 3.3% in East Asia, 4.8% in Africa and 4.3% in Latin America; the projections for 1970-75 indicated, respectively, 4.3%, 4.0%, 4.9% and 3.9%. These figures mean that in twenty years the urban population of these regions doubled or even tripled. Back in 1970 there were 11 cities in developing countries with more than 5 million inhabitants; by the year 2000 their number is likely to increase to 335.
When discussing "the Roma problem", most references focus on the part of the Romany population living in very poor rural and urban conditions. The number of Roma living in unbearable conditions in rural communities and devastated central city zones is agglomerating and represents a potentially very serious societal, social and economic problem. In former Czechoslovakia, housing is one of the most immediate problems of the Gypsies. Besides appalling conditions they live in, the occupied grounds belong either to the adjacent town or to private owners. That was not an issue for the totalitarian regime, when the communists occupied all private property, but now owners claim back the grounds where Gypsies had built their shacks or houses without any permission. Consequently, there is usually no proper water, sewage, gas and electricity supply, because nobody would finance a connection to an illegal site. This situation has naturally also further consequences in poor health condition of the Gypsies, low life expectancy, bad conditions for children and their education, etc. Environmental issues are important, too. Some of the camps, such as the one near Rudnany in Eastern Slovakia, were built on dumping grounds or other areas containing materials such as mercury and arsenic.
At least 600 million urban dwellers in Africa, Asia and Latin America live in squatter settlements and shanty towns, in housing of such poor quality and with such inadequate provision for water, sanitation, drainage and garbage removal that their lives and health are under continuous threat (UNCHS 1996). The number of people living in such conditions is likely to expand very rapidly; while large cities in some developing countries have been growing at rates of up to 10 per cent per annum, slums and squatter settlements in some of them are growing twice as fast. An increasing number of the urban poor, probably more than 100 million, are homeless, a serious problem in developed as well as in developing countries (UNCHS 1996).