The year is 2000. The earth is polluted, overrun by a teeming, seething population. The anonymous masses are stripping the land of food and fuel. Most of them have been wrenched off the land and hurled into swelling slums where the struggle for existence is harsh.

That is the stark picture that U.S. experts have drawn of the world 22 years from now. President Carter last year directed them to "assess potential global environmental changes and their impact on the United States." Various government agencies, their efforts coordinated by the White House Council on Environmental Quality, contributed to the study.

They compiled hundreds of pages of excrutiatingly detailed findings and summarized them in a confidential report entitled "Global 2000 Study." It is against the nature of politicians, however, to release bad news unless they can also offer a happy ending. The project managers, therefore, feared the report might be too bitter for the president to swallow. They prepared a second, more palatable version that tells essentially the same story but disguises the ugly facts by making them deliberately dull.

We have seen both versions, which may yet undergo further revisions before the final report is delivered to the Oval Office. But from the ant bed of print a warning emerges that the over-burdening population, rather than a nuclear holocaust, may cause man's final Armageddon.

The president's population experts estimate that the world population will increase at least 56 percent by the year 2000; as many as 2.3 billion more people may be swarming over the earth. But it will be the underdeveloped nations that will absorb a catastrophic 90 percent of the population growth.

By the end of the century, four-fifths of the world's people will be living in under-industrialized, poverty-plagued economies. This great, faceless mass will gravitate into sprawling urban ghettos, which will become breeding grounds for disease and despair, crime and rebellion. Thus the world will become sharply divided between the haves and the have-nots, with the have-not nations bursting at the borders.

The population demands will create severe shortages of food and water. Intelligence reports predict that "if present trends continue, the world will have lost one-third of its agricultural lands to desertification by the year 2000 because of human mismanagement which is often associated with intense population pressure."

But the second, more optimistic draft quotes other experts as predicting that arable land will increase by 18 percent, thus enabling food production to keep pace with population growth if conditions are good. Most of the authorities, however, anticipate the worst.

Thus the prospects are for more mouths to feed and less food to fill them. Even the existing crops, agricultural experts fear, may become more vulnerable. Insect pests will be more difficult to control as they become immune to man's chemical warfare. Swarms of insects miles long, such as the locusts already plaguing Africa, may become commonplace in many regions, "with resulting losses in farm output."

The human hordes are also expected to defoliate the world's forests, with disastrous results. Twenty years ago, forests covered one-fourth of the world's surface; by 2000, the woodlands will be cut back to one-sixth of the globe, predict CIA and State Department analysts. The effects: "Prices and absolute scarcity will put fuel wood and charcoal out of economic reach of not only the subsistence sector, but also much of the market sector of the lesser-developed countries."

The oceans have been held out as a source of more nourishment, but "technological and social developments by 2000 will not cause an increase in sustained yields of the traditional marine fisheries," predict Commerce Department officials. Indeed, "if pollution continues unabated, as appears to be the prognosis, the effect will be significant reduction in fishery yields."

The fresh-water supply will also be jeopardized. "Water shortages . . . can be expected to appear with increasing frequency and severity in the future," the study warns. Water may also become a disease carrier. As more water is used for irrigation to increase crop production, the flow may spread "debilitating, if not fatal, diseases."

Air pollution, already an unhealthy aggravation, could become a deadly threat. Increasing industrialization and overpopulation causes a nasty phenomenon called "acid rain," a mixture of sulphur dioxide and water-vapor pollutants deadly to plant life, which already threatens many areas.

The analysts also believe that the world will remain dependent on fossil fuel until 2000, despite the skyrocketing costs. The surplus capacity of the oil producing nations will disappear "as early as 1985 and as late as 1990." Coal isn't regarded as an acceptable substitute because of its environmental and climatic pollutants. Other alternatives such as nuclear and solar power, have "potential" to replace oil but "smoothly bridging the transition from fossil fuels appears difficult."

All in all, the final "Global 2000 Study," despite some optimistic predictions, will make disturbing reading for President Carter. The analysts, meanwhile seem more concerned over what to tell the president than what to do about the problem.