Overpopulation of Earth is a tragedy unfolding in slow motion. Babies, after all, are born one at a time in all corners of nations large and small. We can barely comprehend that the natural increase totals 212,000 souls a day, 6.5 million a month, 77.7 million a year. And the magic of compound interest works in human as well as financial affairs.

An opportunity to revisit the population issue comes on Oct. 12 when, according to the United Nations, humanity will reach the 6 billion mark. This may be confusing to those who recall that the U.S. Census Bureau's world population clock hit 6 billion at 7 24 p.m. CDT on July 18. No matter. Both estimates are similar enough to deserve our attention. But the Census Bureau's milestone passed with little notice, and the United Nations estimate also is likely to get short shrift with the public and media.

The birth of the planet's 6 billionth current inhabitant also marks another first World population has doubled in less than 40 years. And exponential growth is adding 1 billion people every 12 to 14 years. Ninety percent of this growth is in the developing world. The consequences are grave. Environmental destruction escalates as more people compete for water, land, clean air, food, fuel and amenities. Civil conflicts and ethnic wars roil societies as Balkanized peoples attempt to gain advantage through resource grabs at the expense of neighbors. Millions of the dispossessed are forced to migrate, straining the resources and goodwill of richer nations.

The disconnect between such disasters and population awareness is most obvious in media coverage. In May 1998, slash-and-burn fires swept Mexico and Central America, creating clouds of smoke that drifted as far north as North Dakota and as far east as Florida for almost a month. A study of 349 news articles by Michael Maher of the University of Louisiana, Lafayette, concluded that reporters framed the event chiefly in terms of human health, safety and convenience. Only three percent of the news framed the fires in terms of global biodiversity loss. And only 1 percent of the total coverage mentioned population growth in the region as a cause of the fires. Mexico's population, approaching 100 million, has nearly quadrupled in the last 50 years.

'Scientists looked up and saw irrefutable evidence of a well-established, long-documented trend of global deforestation and tropical species loss, a trend driven chiefly by human population growth,' Maher writes. 'Journalists looked up at the smoke and saw - smoke. They saw anything but a population- driven Sixth Extinction. Journalists gave more salience to connecting the smoke to pet health than to population growth. Americans are portrayed as either prudently saying indoors or bravely continuing to entertain themselves despite the irritating smoke.'

Five of the 349 stories examined by Maher mentioned human population growth as a cause of the fires. All references to population were brief and buried in the bottom third of the story. Of the five, the most complete explanation of the popula- tion/deforestation connection was four sentences long. These appeared in paragraphs 41 and 42 of the story. Why did so much smoke get in the journalists' eyes and cause them to overlook the root cause of the 1998 fires?

One reason is that population growth appears beyond the capacity of humankind to control. Indeed, population momentum almost guarantees that world population will reach 9 billion by 2050. It takes about 70 years for the population to stabilize after a nation reaches a replacement-level fertility rate of 2.1 births per woman. Worse, the articles appearing about population have a new theme not to worry; in the next century the world is in for some rapid downsizing. An example is an article by Max Singer, 'The Population Surprise,' in The Atlantic Monthly (August).

'Fifty years from now the world's population will be declining, with no end in sight,' Singer writes. 'Unless people's values change greatly, several centuries from now there could be fewer people living in the entire world than live in the United States today... The evidence now indicates that within 50 years or so world population will peak at about 8 billion before starting a fairly rapid decline.' Singer slides over the problem associated with at least 2 billion more people in the next half-century, as well as the fact that his estimate is 1 billion short of that projected by other demographers. We are supposed to stop worrying and love the population bomb because it will be defused somewhere down the road. He makes an astounding leap of faith to predict that world population growth will head into negative numbers as modernity spreads to the less developed world.

I will not be present in 2050 to see if projections of a world of 9 billion people come to pass or, if they do, whether humankind's general condition is better or worse. I will never know whether the worst predictions about the greenhouse effect on ice-cap melt and weather prove to be true. Nor can I ever expect to learn how rich nations coped with a flood of political and economic refugees from the Malthusian misery engulfing poor nations.

But as a 68-year-old college teacher, I am only too aware that the fresh-faced students in my class will be among those who will see the scenarios played out in the first half of the new century. As is true of each generation, they are the ones-who-will-be-left. Will they care and, even if they do, will they have the time and conviction necessary to the task? I fall back on a speech made 31 years ago by C.P. Snow, the British physicist and philosopher 'One hears young people asking for a cause. The cause is here. It is the biggest single cause in history, simply because history has never presented us with such a danger. It is a very difficult cause to fight, because it will be long-drawn out... It is the duty of all the generations which are going to live in what is now the future, to keep before the world its long-term fate. Peace. Food. No more people than the earth can take. That is the cause.'

Snow's emphasis on young people remains relevant. Anyone traveling around the world today encounters a sea of young men and women, the spawn of the post-World War II generation encouraged (sometimes coerced) to multiply and populate the earth. Even in the industrial nations of Western Europe, youth unemployment is a grave social irritant. In the poorer nations of Asia, Africa, Latin America and the Middle East, fundamentalist revolutions and unrest find their acolytes among jobless young males. Birthrates may well be falling, but geometric imperatives guarantee the escalation of population nearly everywhere, if not through natural increase then through immigration. When the U.N. population clock hits 6 billion, it will be a cause not for celebration but for contemplation.