As this turbulent decade draws to a close, what promises to be an even more critical one for progress in international development is about to begin.

We need not be reminded that the economic strains of the 1970s have been more severe than any since the disruption of World War II and the global depression that preceded it. But the truth is that the problems that will confront us all in the 1980s are almost certain to be more difficult. More difficult because with the loss of irrecoverably time the easier solutions to these problems have begun to disappear. What we will be left with in the decade ahead are increasingly painful dilemmas that can no longer be ignored or postponed. We are going to decide if we can really afford to continue temporizing with severe development problems that are getting worse rather than better.

If we focus on the ultimate objectives of development, it is obvious that an essential one must be the liberation of the 800 million individuals in the developing world who are trapped in absolute poverty -- a condition of life so limited by malnutrition, illiteracy, disease, high infant-mortality and low life-expectancy as to be below any rationsl definition of human decency.

Economic growth is absolutely essential to reducing this poverty, and every effort must be made to increase it in the developing societies. But absolute poverty is not going to be significantly reduced in an acceptable time frame by the growth rate alone -- whatever that rate can be made to be. It is naive to assume in any society that absolute poverty will automatically melt away simply because the gross national product is rising.

To reduce poverty, population growth will have to be slowed -- and soon. Short of nuclear war itself, this is the gravest issue that the world faces during the decades immediately ahead. It must be faced for what it inevitably is: a central determinant of humanity's future, and one requiring far more effective attention than it is currently receiving.

If current trends continue, the world as a whole will not reach replacement-level fertility -- in effect, an average of two children per family -- until about the year 2020. That means that some 70 years later the world's population would finally stabilize at about 10 billion individuals, compared to today's 4.3 billion.

We call it stabilized, but what kind of stability would be possible? Can we assume that the levels of poverty, hunger, stsress, crowding and frustration that such a situation could cause in the developing nations -- which by then would contain none out of every 10 human beings on earth -- would be likely to assure social stability? Or, for that matter, military stability?

Such a world is not inevitble, but there are only two possible ways in which it can be averted. Either the current birth rates must come down more quickly, or the current death rates must go up. There are, of course, many ways in which the death rates can go up. In a thermonuclear age, war can accomplish it very quickly and decisively. Famine and disease are nature's ancient checks on population growth, and neither one has disappeared from the scene. The United Nations Children's Fund estimates that more than 30 million children under the age of five died of starvation just last year.

But if our choice is for lower birth rates rather than higher death rates -- as it must be, for any other choice is inconceivable -- then we simply cannot continue the leisurely approach to the population problem that has characterized the past quarter-century. What must be grasped is the time factor involved. It is a point of immense importance, yet one that is most frequently misunderstood. For every decade of delay in achieving a net reporduction rate of 1.0 -- that is, replacement-level fertility about 11 percent greater. If, then, the date at which replacement-level fertility will be reached could be advanced from 2020 to 2000, the ultimate global population would be approximately two billion less -- a number equivalent to nearly half of today's world total.

That demographic fact reveals in startling terms the hidden penalities of failing to act, and act immediately, to reduct fertility. The time lost in temporizing with population problems is simply irrecoverably. It can never be made up.