The population challenge

I don't really know what the answer is. In Washington we see the reports roll in; they are all impressive, all in formal language, all crying for action of one sort or another. A month ago the Conference on the Long-Term Worldwide Biological Consequences of Nuclear War explained that devastation by nuclear war would be more serious than supposed, that it might cut off sunlight and produce nuclear winter. Exit mankind.

Later came another warning from another quarter. An authoritative gathering set up by Georgetown University's Center for Strategic and International Studies issued its findings. The speaker was former Ambassador Marshall Green, erstwhile US coordinator of population affairs. He grimly warned of overpopulation. Figures of growth on the planet were detailed and frightening. Will there be food enough? Other speakers noted famine and malnutrition already present in many underdeveloped countries. Danger this way, too.

Let me recite some of the figures on population, because there has been a tendency recently to put the threat aside. There are about 4.7 billion people on earth today, or (since the estimate is taken from a speech by Paul R. Ehrlich, Stanford University, of last October) we can probably level that off at 5 billion. World population is growing around 80 million a year. ''Between now and the end of the century, the population equivalent of the United States will join us about every three years,'' says Mr. Ehrlich.

''These numbers represent an enormous challenge to humanity. A world that already cannot provide decent living conditions for much of its human population is going to be faced with an unprecedented further increase in the size of its population. What's even worse, the wherewithal to provide that care has not increased; it is dwindling. The human family is doing something collectively that no sane family would ever do. It is living off its capital while it is destroying its earning capacity.'' So much for Ehrlich.

Most of these learned studies are written in formal jargon of their own about ''exponential growth'' and ''macro-economic projections,'' (whatever that means) but the stark facts are there. They are not concealed by demographics; practically everybody can see them except, it appeared last October,House Speaker Tip O'Neill. Then heexercised a kind of legislative veto power of his own and torpedoed the Simpson-Mazzoli immigration reform bill, which conscientious congressmen had been working on for years. The Speaker apparently has changed his view, and plans to bring the bill before the House next year. Mexico has a rapidly growing population and may be sending a million legal and illegal immigrants across the border annually to the US. The bill was designed to check the illegal flow.

Back in 1972 the Rockefeller Commission reported that increasing population ''has multiplied and intensified many of our domestic problems and made their solutions more difficult.'' Says Ambassador Green, ''Even the US, which has been receiving for permanent residence every year more immigrants than all the other countries of the world combined, is now beginning to give long overdue attention to illegal immigration.''

But it won't be easy. The House Speaker has checked one earnest effort at reform. On Sept. 22, the Immigration and Naturalization Service announced that the Border Patrol had reached the million mark in apprehending illegal aliens during the previous 12-month period. America faces a number of threats: one from the skies, another from across the borders.