SPEAK of overpopulation in the world, and many people think of India - where some 900 million people live on a land mass one-third the size of the United States.
What would be the social and environmental impact if India's population were to double? That was the question asked by a group of Indian scholars brought together by the Ford Foundation in 1970 to produce the eight-volume ``Second India Study.''
Since then, India's population has climbed steadily such that a ``Second India'' will have been added to the 1971 figure of 548 million just 13 years from now. And because of the increasing number of women of child-bearing age, another doubling - a ``third'' and even ``fourth'' India - is likely to occur before population stabilizes.
The World Resources Institute, a nonprofit research organization in Washington, recently published ``The `Second India' Revisited: Population, Poverty, and Environmental Stress over Two Decades.'' It looks back at the Ford Foundation report of 24 years ago, checks its predecessor's predictions, and makes some observations and forecasts of its own that should be most helpful as nations prepare for next month's United Nations-sponsored conference on population and development in Cairo.
There is some good news. The proportion of couples using contraceptives has risen from 10 percent to more than 40 percent. In the south Indian states of Kerala and Tamil Nadu, where women are better educated and have higher social status, fertility rates have dropped to replacement levels.
But in most respects, writes institute vice president Robert Repetto and his Indian research colleagues, ``India continues to wrestle with the same problems that were obvious in 1970.''
Back then, there was hope that the so-called ``Green Revolution'' would produce enough high-yield wheat and rice to feed a growing population that suffered high rates of malnutrition. But per capita production of food grains in India has increased less than 6 percent since then, despite the modernization of Indian agriculture, and there are troubling indications that food scarcity around the world may be increasing as population numbers continue to rise.
Over the weekend, the Worldwatch Institute reported that world grain production had dropped from a 3 percent annual rate of increase to just 1 percent a year since 1984. This is well below the annual population growth, which means that worldwide per capita grain production is decreasing.
Meanwhile, reports the World Resources Institute, ``India's environment has deteriorated markedly since the Second India Study was written.''
Upstream deforestation is causing rapid siltation of dams. Improper irrigation has waterlogged or salinized millions of acres. Water tables are falling. Saltwater along the coasts is intruding into freshwater aquifers. Cutting of wood for fuel and livestock grazing have stripped vegetation from much of the rural landscape.
``Most of India's varied native ecosystems now exist only in remnant patches, under great pressure from surrounding populations and commercial interests,'' the report states.
``Shrinking habitats have reduced the numbers and the ranges of India's magnificent and diverse plant, animal, and bird populations, endangering many,'' the report continues.
The social implications of overpopulation are clear as well. Nearly 40 percent of the populace lives below the official poverty level. ``India faces a further huge increase in the labor force,'' reports World Resources Institute, ``and there remains a massive backlog of workers in low-productivity, low-skill jobs.''
Clearer now than when the Ford Foundation study was done in 1970 is that the answers to India's population problem range far beyond family planning to such things as health services and education - especially for women. This is true of many other countries if ``Second Indias'' are to be prevented elsewhere.