The carnage and chaos that have wracked Rwanda and Haiti in recent months would seem to be unrelated, sparked by distinctly different ethnic or political rivalries in sub-Saharan Africa and the Caribbean.
Could each country be the victim of a common underlying malady, one that has fanned long-standing tensions into conflict? Consider:
Before massacres and mass exodus depopulated Rwanda, the Maryland-sized nation had more people per square mile than almost any other African country, and declining food production. With each woman of child-bearing age having more than eight children, it also had one of the highest fertility rates.
In Haiti, where 7 million people are crammed into a similarly small area, the economy is in shambles and the land badly deforested. With a fertility rate of nearly five children per woman, the country's population is projected to double in just 18 years.
"Resource scarcities are a root cause of the violent conflicts that have convulsed civil society" in countries like Rwanda and Haiti, asserts Timothy E. Wirth, U.S. undersecretary of state. Such conflicts could intensify and widen, he adds, "as ever-growing populations compete for an ever-dwindling supply of land, fuel and water."
Thus, in a major policy switch from previous Republican presidencies, the Clinton administration is pushing for an international commitment to slow the world's surging population growth at a coming United Nations conference in Cairo, Egypt.
"Current conflicts are a grim foreshadowing of the anarchy that could engulf more and more nations if we fail to act," Mr. Wirth warns. Nor would the United States be immune, he adds, noting that "environmental devastation and disease do not stop at national borders."
When they gather in Cairo Sept. 5, delegates from the world's nations are expected to act on a plan intended to stabilize global population at 7.8 billion by 2050. Unless something is done, U.N. planners predict, today's 5.6 billion people could more than double, to 12.5 billion, by that time.
In a draft "program of action" hammered out earlier this year, the United States and most other nations have agreed that the the best way to stabilize population is to provide more family planning and contraceptives, and to enhance women's education, employment and political rights.
But the U.N. plan is generating its own conflict. Pope John Paul II and the hierarchy of the Roman Catholic Church charge that the policy statement promotes abortion on demand and homosexuality. Church leaders also have accused drafters of "cultural imperialism" and of sanctioning sexual promiscuity in pushing for wider access to contraceptives.
Moreover, some church leaders and others have questioned whether population growth is a problem at all. The Pontifical Academy for Life, an arm of the Catholic church, decried "the alarmist campaign," pointing out that "the so-called 'demographic explosion' is actually subsiding" and some countries -- notably Russia and some in Western Europe -- are even experiencing declines in population.
Few issues have sparked more intense debate than how many people the Earth can support.
Long before the English cleric Thomas Malthus earned lasting fame for his gloomy predictions in 1798, thinkers were worrying about whether the land could support all the people on it, says Joel Cohen, a population expert at Rockefeller University in New York.
But for the last 50 years, the question has taken on increasing urgency, as world population grew at a record pace. After reaching 2 billion during the 1930s, global population growth has mushroomed to where another 1 billion people are being added every 10 years.
That increase -- roughly 10,000 new people every hour -- is akin to populating another Baltimore City every 36 hours, another New York City every month or another country the size of Mexico every year.
Environmentalists and economists hotly debate whether population growth is a bane or boon to nations that are struggling to get out, or stay out, of poverty.
The world's swelling ranks represent "a triumph of human knowledge and organization over the raw forces of nature," argues Julian L. Simon, professor of business and management at the University of Maryland College Park and a widely quoted optimist on population matters. As the landscape becomes more crowded, people will figure out how to solve whatever problems or shortages might arise.
Dr. Simon maintains that "there is no statistical evidence to show population growth has negative effects" on human welfare or the environment. "Every single trend in human welfare shows improvement in the long run," he says.
"You can't grow forever on a finite planet," counters Donella H. Meadows, an adjunct professor at Dartmouth College who has co-authored two books warning that the world is near or past its carrying capacity. "Resources are being drained down everywhere," she adds. "Pollution is building everywhere. We can't go on like this very much longer." "There is no consensus," notes Barbara Torrey, former president of the Population Reference Bureau, now on the staff of the National Academy of Sciences.
But many scientists, while unable to pinpoint the limits to human growth, still worry that environmental trends may be worsening because of increasing population and because of consumption habits.
"As human numbers further increase, the potential for irreversible changes of far-reaching magnitude also increases," warns a joint statement issued last year by 58 of the world's scientific academies, including the U.S. National Academy of Sciences. It cites "a growing loss of biodiversity, increasing greenhouse gas emissions, acid rain, loss of topsoil and shortages of water, food and fuel-wood in many parts of the world."
Indeed, demographers predict that 95 percent of the world's population growth will occur in developing countries that are probably least able to support it, in Africa, Latin America and Asia.
As it is, nearly 20 percent of the people in developing countries -- 700 million people worldwide -- do not have enough food to stay healthy and productive, according to the International Food Policy Research Institute in Washington. Per capita food production declined in 75 countries during the 1980s, and two-thirds of developing nations reported stagnant or reduced production just two years ago.
Many experts think it is possible to feed a global population of 10 billion people or more, concluded John Bongaarts of the Population Council in a Scientific American article earlier this year. But some of the most undernourished countries are least able to boost food production because they have little or no reserves of fertile land or water, and they are too poor to buy enough food from other nations.
About 130 million people in 20 countries also do not have enough renewable fresh water to drink now, according to a study by Population Action International in Washington. In 30 years, the group predicts, water scarcities could spread to some 30 countries, afflicting up to 1 billion people.
Population growth is not limited to the Third World, demographers note. The United States, with 260 million people, is the third most populous country, and it is the most rapidly growing industrialized nation. At current rates, the U.S. population could double in 63 years, says Martha Riche of the Population Reference Bureau.
Much of the U.S. growth stems from a huge new wave of immigration, which has generated political tensions in some border states. But American women also have been having bigger families than their counterparts in other developed nations -- 2.1 children, on average. The birth rate for maintaining a stable population is two per woman.
In terms of environmental impact, Americans and other citizens of the industrialized world consume far more resources per person, and produce far more waste and pollution, than their poorer neighbors. The one-fifth of the world population living in developed countries consumes two-thirds of all resources and generates 75 percent of the wastes, environmentalists note.
As grim as such statistics may seem, the trends are not all bad. Population growth has slowed in recent years, as fertility rates have dropped.
Conventional economic wisdom once had it that prosperity is the key to reducing population growth, as better-educated couples would choose to have fewer children.
But birth rates in developing countries have dropped by one-third since the mid-1960, even without improved living conditions, Scientific American reported last year. Women who once had six children on average now have four.
The biggest reason for the decline is increased access to family planning and contraception, or voluntary sterilization, concluded the article's authors, who included Bryant Robey of the Johns Hopkins School of Hygiene and Public Health.
Even so, experts say there remains a serious shortage of family planning in many countries. By one estimate, more than 120 million married women of child-bearing age would like to avoid pregnancy but are practicing no form of birth control.
That is one of the reasons why the United States and other nations have pledged increased international aid for family planning. As the largest contributor, the United States has boosted its share from $400 million to $600 million. Mr. Wirth says other industrial nations will follow suit.
The Vatican has objected that "family planning" is a smoke screen for encouraging teen sex and abortion on demand. Other vague references to family that do not specify monogamous couples smack of support for homosexual marriage, other critics maintain.
Supporters say the U.N. document calls for reducing abortion, ,, while ensuring access to safe abortions in countries where it is legally permitted. References to family are broad enough to encompass the reality of varied cultural practices around the world, they say.
Despite the Vatican's objections, there seems to be broad agreement among nations on the need to stabilize population growth. Only a handful of countries, with predominantly Catholic populations, have objected to portions of the proposed accord.
That is a dramatic change from previous U.N. population summits. In Bucharest, Romania, in 1974, developing countries viewed the population controls advocated by the United States and other industrialized nations as a conspiracy to keep the Third World under economic subjugation. An Indian health minister asserted that "development is the best contraceptive."
By 1984, many developing countries had decided they needed help in reducing their population growth. But the United States, with the Reagan administration opposed to abortion, took the position that population was a "neutral" factor in countries' economic and social development. The Reagan administration also withdrew U.S. funding for international family planning programs because they supported some groups that performed abortion.
The Bush administration continued the freeze on family planning, and abortion politics even suppressed a scientific report on global population. A report drafted in 1991 by the president's council of science advisers warned that population growth was outstripping some countries' ability to feed their people.
But Alan Bromley, President George Bush's chief science adviser, said he never released the council's population report because of the White House's "tremendous political sensitivity" over abortion.
The timing was significant because the next year, Mr. Bush attended the U.N. "Earth Summit" in Brazil, where world leaders debated how to promote environmentally sensitive development. Population was barely mentioned.
In hindsight, Dr. Bromley, now dean of engineering at Yale University, said he wishes he had not buried his council's population warning.
"Every year counts," he said. "When you are adding a million people every four days, every year that you delay action puts more pressure on the planet."
Timothy B. Wheeler covers the environment for The Baltimore Sun.