Over much of the earth a precarious balance exists between food and people. There are too many people and not enough food. The disparity appears to be growing. Beginning Aug. 6 the United Nations Conference on Population will meet in Mexico City to review the matter. It is a delicate issue. The Roman Catholic Church, and other denominations, is against government involvement. On the other hand China, a nation with a population of more than a billion, had adopted policies of strong government restriction. Overpopulation in one country affects relations with its neighbors (look at the Mexican border). The world is confronted with a new, growing, and explosive problem.
The World Bank's annual report is focused on population. Says president A. W. Clausen, ''Population growth does not provide the drama of financial crisis or political upheaval, but its significance for shaping the world of our children and grandchildren is at least as great ... Failure to act now to slow growth is likely to mean a lower quality of life for millions of people.''
The problem is that poor countries generally have the highest birthrate: ''among the poorest groups within countries,'' says Mr. Clausen, ''poverty contributes to high mortality and even higher fertility.''
The Washington-based Population Reports International estimates that population growth for the world has recently increased to 1.8 percent after remaining nearly stationary for a decade at 1.7 percent. In the developing world of low-income countries (excluding China), population growth rates remained stationary at 2.4 percent annually between 1960 and 1977; since then the rates have increased to 2.5 percent.
Global population is around 4.6 billion. The United States has a population of about 232 million and an annual natural increase of 0.7 percent. By contrast, Mexico is around 713 million, with an estimated annual increase of an enormous 2 .5 percent. Contrasts like this cause militant groups like Population Reports International to argue that ''if one- or two-child policies are not effectively implemented within the next five to 10 years there will be massive famine and social upheaval.''
Such issues are bound to come up at the Mexico City conference; in fact they have already surfaced in Washington in debates over US policy. One matter of intense interest is China. A discussion appears in the UN World Development report. China is alarmed at its own size and wonders if it can feed its own people. Says the UN report:
''Birth Control has been a national priority in China since 1971 when the government launched a new program to promote later marriage, longer spacing between births, and fewer children.'' But it wasn't enough. ''It became clear that even compliance with a two-child family norm would not reduce the rate of population growth enough to meet the national goal of 1.2 billion people by the year 2000.''
The rest of the world shudders at the restrictive powers of the Chinese government. But will they work? In 1979, says the UN report, the province of Sichuan started a policy designed to persuade married couples to have no more than one child. There were economic rewards and punishments. The pattern was picked up by other provinces. In 1980 the government set up the goal of only one child.
''Early results of the one-child campaign seem striking,'' the UN report says rather vaguely. Birthrates have indeed fallen. ''But,'' it continues, ''several factors are working against the one-child policy.''
* The compulsory pension systems omit many elderly people, and they depend on their children for old-age security.
* Then again there is a bureaucratic tangle, it appears, between allocation of land for household use and size of family.
The regulations confront folk patterns as, for example, ''a preference for sons (which) is a strong cultural impediment to having only one child.'' There are strong suspicions of infanticide.
The report says financing incentives fall on local areas, not on the central government, ''and there is a great variation'' as a consequence. Here's what happened in Jilin Province in 1981:
''Families pledging to have only one child were granted annual bonuses of almost 50 yuan - equivalent to 7 percent of average rural income - to last for 15 years, and received a double-size private plot. For their single child they received an adult grain allowance and a special health care allowance.
''Yet in Hofei city in Anhui Province bonuses paid to parents were much lower - a one-time payment of 10 or 20 yuan, a few towels, a thermos bottle, some toys , a wash basin, or even nothing at all.''
The world rubs its eyes. Can any state control such matters?