WHY IS IT that no one in America seems to know anything about the population crisis or even to care? I can see four reasons. First, excessive population growth on a worldwide scale is a new problem. Its symptoms--starvation, unemployment, illiteracy, environmental destruction, international conflict, and even racism--are so familiar and tidily classified that we often diagnose them as the disease itself. Second, it is 'their' disease, not ours. They won't bother us by dying on our doorsteps. In fact, if the news industry decides it is better business to inform us about rapes, murders, and Jackie Onassis than the children in Bolivia who are being blinded and crippled by protein starvation, we need never hear about 'them' at all. Third, the population problem is bad politics. Anyone even vaguely familiar with demography knows that industrial development prompts massive fertility declines. But which presidential contender will address the National Association of Manufacturers testimonial crowd on our pressing need to give away billions to foreigners so they can build businesses to compete against our own? Fourth, the clowns and fanatics who have appointed themselves the heads of the population stabilization movement's public relations department have turned the population crisis into an entertainment special. Entertainers are seldom taken seriously.

Lester Brown, who is one of America's best agricultural economists, does not try to cajole, shock, or threaten his audience into action. He does not preach apocalypse, or even seem to fear it. Instead, he warns that standards of living around the world must fall if the world's population keeps doubling every thirty-five years. In The Human Interest offers a sketch of today's population problems and a prescription for stabilization.

THE POPULATION explosion, as Peter Adamson once wrote, has hit us "not because we have suddenly started multiplying like rabbits; it's just that we have stopped dying like flies." For most of man's history, early winters, droughts, epidemics and wolves stabilized his population. As Brown notes, but for our high fertility rates our species might have died off. We have lowered our death rates so successfully that our well-being now depends upon lowering birth rates. The world's population is slightly under four billion today; moderate U.N. projections suggest that unless fertility patterns change drastically it will break six billion by the end of the century and eleven billion by the year 2050.

The population explosion does not directly threaten Russia, Japan, Europe, Australia, Canada or the United States, the "rich nations." As they industrialized they broke the fertility barrier. Most of them are growing less than one per cent a year, and can expect to reach zero population growth within a generation or two. At worst population pressure will cause job and housing shortages. For the rest of the world, however, population growth is a problem on an entirely different scale. They are growing on average two and a half per cent a year, which works out to twelve times a century, if that kind of growth can keep up. Brazil adds more people to the world each year than Russia and Great Britain put together; Ethiopia, more than France, Italy, West Germany and the Philippines.

Hypothetical situation: if a rich country has a four per cent rate of economic growth and a one per cent rate of population growth, per capita G.N.P. increases three per cent a year, nineteen times a century. But with the same economic growth rate and a two and half per cent rate of population growth, G.N.P. per capita rises in a poor country only one and a half per cent a year, or five times a century. The greater population growth in the poor country effectively eliminated its chances of catching up. And in the real world, of course, there is no guarantee that economic growth will outpace population growth.

Population growth, in fact, may actually slow down economic growth because it impedes human development. Sri Lanka had to shut down its free medical services this year because too many people needed them. Ghana's schools must turn away one child in three, and even then can barely afford to teach the other two to read.

BROWN WARNS US that "we may be on the verge of one of the great discontinuities of history." What he means is that demand for food and natural resources has once again outstripped production; this time, he thinks, for good, not only because of exponential population growth, but because "rising affluence is emerging as a major claimant of world resources." We have a food shortage today not only because population growth has eaten away the gains from the Green Revolution Third World hybrid seed program, but because rich countries are upgrading their diets. Each year at least eight million tons of grain--enough to feed thirty five million people well--are diverted from human to animal mouths to provide more meat for the rich.

Besides endangering lives in poor countries, "superaffluence"--this is Brown's term--threatens the natural balance. Pollution is no longer a localized problem: auto and factory exhausts in North America and Europe seem to be changing the winds, pushing the monsoon rains off Asian cropland into the sea. Poor countries are destroying their share of their environment too: woodcutters are stripping India of its forests; herders in the Subsahara are helping the desert spread; careless farmers in Pakistan are washing away their best soil and its covering, parlaying their land into a dust bowl.

HOW DOES BROWN plan to save everyone? After running through the usual homilies about understanding and international cooperation he gets down to specifics. Spend the billions necessary to provide family planning for everyone; at least one out of three pregnancies is unwanted. Spend $8 billion to teach the world's billion illiterates to read; educated people have fewer children. Embrace women's rights. Spread health care; poor families have so many children partly because they expect a few to die. Brown's most interesting suggestion is that "reform" (he carefully avoids specific proposals here) will bring down fertility levels. Although Brazil's per capita G.N.P. is almost twice as high as Taiwan's, and family size usually shrinks as incomes rise, Brazil has hardly dented its birth rate in the last 20 years; Taiwan has halved its own. The reason, according to Brown: illiteracy, unemployment, and infant mortality are low in Taiwan, high in Brazil; Taiwan has reformed its land tenure and income distribution systems, Brazil has not. Parenthetically Brown appeals to rich countries to "reject" superaffluence.

In The Human Interest is probably the best popular book that has ever been written on the population crisis. This isn't to say there isn't a lot wrong with it. Brown is in the habit of writing a book a year; it shows. This one reads like transcribed dictation. It reflects phony-scientific jargon ("superaffluence") and is often simply inaccurate (the world has not run out of arable land, fish catches can be increased, perhaps even doubled.) The material is so sloppily organized that I had to skip back and forth through the book to prove to myself that all his ideas connected.

WHILE BROWN may not entertain his audience, he does manage to entertain a couple of useless ideas. He seems to feel that population growth, and poverty, and every other human affliction would vanish if we were all kinder to each other or more understanding; the world's social system, as he sees it, is basically sound. In fact, it is often the system itself which is the problem. Excessive population growth is not a metaphysical condition, it is a social sickness which has stricken countries ravaged by colonialism, or which ignore extreme internal inequalities. A landless laborer in Indonesia would be crazy not to have all the children he could: he gets paid by the hand. Trying to institute "reforms" such as literacy to lower fertility without removing the social causes of high fertility rates is like trying to lower casualty rates without stopping a war. Like so many population experts who live in exclusive suburbs and write about poor people, Brown seems to feel more revulsion than compassion for his subject. He seems more concerned with keeping the numbers of poor (and--I dare say--nonwhite) to a minimum than with improving their lives through population policy. In the past, such thinking has led to "health clinics" which can handle abortions but not medical problems, and state programs which pay men to undergo sterilization, but refuse to provide them steady work.

If Brown is worried enough about environmental stress and resource depletion to devote a third of his book to these issues, why doesn't he think out proposals to curb 'the explosion in the consumption of nonrenewable resources' as well as 'the population explosion'? Does he want population growth in the poor countries to stop so that the poor can lead decent and dignified lives--or so that the rich countries can consume even more? His observation that population growth may endanger the skier and take the fun out of golfing might make a Nigerian wonder how serious Brown's stake in his interest really is.