BY the year 2010, half the world's people will live in cities, many of which will find it difficult to cope with the fast influx of population from rural areas, particularly in developing nations. That is the prediction in ``Cities, Life in the World's 100 Largest Metropolitan Areas,'' the study just issued by the Population Crisis Committee, a Washington-based public policy group concerned with international family planning and population issues.
This urbanization trend is ``a real crisis,'' says Joseph Speidel, president of the committee. ``When we looked at 57 metropolitan areas in developing countries, and 53 of the 57 scored `fair' or `poor,' that means the average citizen living in those areas is experiencing a standard of living which we would consider intolerable.''
The study, which took two years to complete, provides a detailed breakdown of living conditions in 100 cities, ranging from the largest - Tokyo-Yokohama, with 28,700,000 people - down to the smallest, Pune, India, with 2,350,000 inhabitants. Large cities in developing countries are growing much faster than cities in the industrialized world.
For instance, it took London 130 years to expand from 1 million in 1860 to 8 million today. By contrast, Mexico City's population was 1 million just 50 years ago, and today has swollen to 20 million.
``By the end of this century, the urban population of the developing world will be almost double the size of that of the industrialized world,'' the study says. By the year 2025, it will be four times larger. Africa's population alone will be three times that of North America's.
Equally dramatic is the rapid spread of slums and shantytowns in the developing world. These areas, largely devoid of minimal sanitary facilities, municipal water, sewerage, energy, communications, and transportation, are growing at twice the rate of the cities as a whole, the study finds.
Arcot Ramachandran, under-secretary of the United Nations and executive director of HABITAT, the UN agency that seeks to carry out the world body's program, Global Strategy for Shelter in the Year 2000, says prospects for jobs in the cities and a shortage of arable land are behind the dramatic movement of families from the country to the towns.
``Immense populations now live in shantytowns and squatter settlements,'' Dr. Ramachandran notes. ``The first necessity is for urban local authorities to strengthen their management capacity and to involve the people from the very beginning, so that any facilities provided are properly maintained. Our whole settlement strategy for the year 2000 is based on this enabling concept - involving the community in the planning management and the development of their settlements.''
The urgency of the situation in many of the large cities is underscored by the extent of slums and squatter settlements. ``In some cases the bulk of the city's population lives in slums,'' the study finds, citing 1987 figures: 70 percent for Casablanca, Morocco; 67 percent for Calcutta; 60 percent for Bogot'a, Colombia, and Kinshasa, Zaire; and 42 percent for Mexico City.
According to the Population Crisis Committee, 58 of the world's 100 largest metropolitan areas are in the developing countries. Nine are in China and another nine in India.
Dr. Speidel emphasizes that the growth of the cities is due more to high urban birth rates than the movement of population to metropolitan centers.
``Governments know that they must do something, but they are still not investing in meeting the real problem, which is population growth,'' Dr. Speidel says. ``Our study shows that, in many developing countries, 60 percent or more of urban expansion is due to the excess of urban births over deaths, and only about 40 percent is related to rural-urban migration.''
The study calls urbanization ``the dominant demographic trend of the late 20th century'' and says it will continue well into the 21st century, ``when population growth is expected to moderate.''
Nafis Sadik, executive director of the UN Population Fund, says she is ``very impressed with the concise and intelligent way'' in which the Population Crisis Committee investigation dealt with the facts about urbanization. It is an issue that affects society everywhere, Dr. Sadik notes.
Ruth Otte, president of the Discovery Cable Channel, which carries many documentaries about population and the environment, says she found the study ``a strong reminder of our common human concern in spite of our different histories around the planet. This is such a compelling way to portray the imperative,'' she adds.
Ramachandran points out the close links between urban and rural areas in advocating the establishment and growth of small and intermediate cities as a kind of solution to the trend towards the vast metropolis.
``One cannot improve the rural areas and neglect the urban areas,'' he says, ``or do it the other way 'round and then complain that the urban areas are given too many resources at the expense of the rural regions. The two are totally interlinked.''
The Population Crisis Committee shows Tokyo-Yokohama; Mexico City; New York; Sao Paulo, Brazil; Osaka-Kobe-Kyoto, Japan; and Seoul with more than 15 million people (see chart).
Using 10 criteria to judge living standards, the committee rates Melbourne, Montreal, and Seattle-Tacoma at the top, with Atlanta and Essen-Dortmund-Duisburg, Germany, in second place. On the bottom of that list one finds Recife, Brazil; Dhaka, Bangladesh; Kinshasa; Lagos, Nigeria; Bucharest, Romania; and Yangon (Rangoon), Burma.
Noting the growth of megacities (population of more than 15 million), the committee says some have reached ``a size off the scale of human experience. Some experts believe that traditional urban economies of scale are becoming dwarfed by the problems of congestion, that some cities are simply too large to be efficient.''