The U.S. birthrate is at replacement level, or about 2.1 children per woman on average. This birthrate would bring about population stabilization over a relatively short time. Yet we won't stabilize our population as long as immigrants to the United States continue to add 1.3 million people to the population each year -- 300,000 of them entering the country illegally. It is a fact that until we address this growing influx of immigrants, who account for about one third of our annual population growth, the population will continue to grow indefinitely despite the nation's success at achieving a replacement level birthrate.

Never has an issue with such major consequences for this country been so ignored. Never before has there been such a significant failure by the president, Congress, and the political infrastructure to address such an important problem. We are faced with the most important challenge of our time -- the challenge of sustainability -- and we refuse to confront it. It is the biggest default in our history.

The reason for this silence is simple. In order to bring a halt to exponential growth, the number of legal immigrants entering this country would have to match the number of emigrants leaving it -- about 220,000 people per year. Yet, while federal actions have increased the immigration rate dramatically during the last four decades, any suggestion that the rate be decreased to some previously acceptable level is met with charges of "nativism," "racism," and the like. Unfortunately, such opposition has silenced much-needed discussion of the issue -- recalling the political smear tactics of the late Senator Joe McCarthy. The first time around it was "soft on communism." This time the charge is "racism" because a significant number of immigrants are of Hispanic descent. Demagogic rhetoric of this sort has succeeded in silencing the environmental and academic communities and has tainted any discussion of population-immigration issues as "politically incorrect." As frustrating as it is to see the president and members of Congress running for cover on such a monumental issue, it is nothing short of astonishing to see the great American free press, with its raft of syndicated columnists, frightened into silence by political correctness.

The issue is not racism, nativism, or any other "ism," however. The real issue: numbers of people and the implications for freedom of choice and sustainability as our numbers continue to grow. Population stabilization will be a major determinant of our future, how we live and in what condition; talk of it should not be muzzled by McCarthyism or any other demagogic contrivance. Rather, the issue must be brought forth and explored in public hearings and discussions precisely because it is a subject of great consequence.

Noting that the United States consumes more resources than any other country in the world, the task force of the President's Council on Sustainable Development warned of "enormous implications" for the environment, economic progress, and quality of life if U.S. population growth continues at current rates or higher. "Coupled with the technologies and resource consumption patterns that underlie the U.S. standard of living, population growth in America produces an environmental impact unparalleled by any other country at this time," the task force wrote in 1996.

Adding more and more people to the U.S. population base will do nothing to relieve the overload in this country, nor will it significantly relieve the overload on those nations sending immigrants. Indeed, if we don't set limits and stabilize our population, we'll continue to grow until we reach the point where conditions are as bad in the receiving countries as in the sending countries. For their part, overpopulated nations will fail to take the steps necessary to protect their own natural resources, and the global environmental will be increasingly stressed.

As Garrett Hardin, an author and professor emeritus of human ecology at the University of California, has said: "Admitting immigrants from overpopulated countries amounts to taking on their problems which they haven't solved. If we take on their problems, they will never solve them by other means."

The fact that lower birth rates are found in industrialized countries where women have access to education, job opportunities, and family planning services means we should do everything we can to provide education, family planning, economic advice, and technical aid and assistance to those countries where such opportunities are lacking.

But we also must consider the causes of the refugees' flight and see therein the environmental and social conflicts that often accompany overpopulation. Many immigrants to the United States are refugees because environmental problems are not being dealt with in their native countries. For example, a large number of immigrants in recent years are from places with diminishing croplands -- Central and South America and the Philippines, for example. Others come from nations such as India, where the ecological systems have been ravaged.

Indeed, many of the world's violent conflicts are heavily influenced by -- if not caused by -- overpopulation and environmental mismanagement of agriculture, water, and forestry resources. Environment and overpopulation problems often cause these resources to be in short supply, a tenuous situation that leaves the populace vulnerable to those using ethnic and religious differences to gain power.

We don't often think of warfare, civil war, and violent internal conflicts as being caused by excessive population. The political interpretation and media reports in the United States typically characterize these conflicts as religious, ethnic, tribal, or peasant disputes, or the result of some failing in the moral status of the cultures in which they occur. Were there not overwhelming environmental problems in these nations, however, many of these conflicts would be smaller or wouldn't have happened at all.

That population will stabilize sometime is inevitable. Unfortunately, if left to its own devices, this stabilization will occur when crowding, crime, inconvenience, noise, polluted air, congestion, and food and water shortages confront us wherever we turn.