The United Nations has identified Danica May Camacho, born just before midnight Oct. 30 in a Philippine hospital, as the 7 billionth inhabitant of our planet. According to the United Nations Population Division, the Earth was to welcome its 7 billionth person on Oct. 31.

While some would see the birth on Halloween as ill-omened, trends are positive. Some even believe that we are entering an era of population decline. While that will help ease strains on the planet, it creates problems of its own as Japan knows well.

The world’s population has been growing at an explosive rate. The U.N. estimates that about 4.5 billion people have been added to the world population in the last 60 years. In the last decade alone, world population has grown by around a billion people.

The specter of an inexorable rise in the number of planetary inhabitants prompted fears of Malthusian catastrophes as the number of people on the Earth outstripped the planet’s capacity to support them. But something odd happened in the last few decades: Population growth actually slowed down. In 1969, the U.S. State Department forecast a world population of 7.5 billion people by 2000. In 1994, the U.N. medium estimate put the arrival of the world’s 7 billionth inhabitant at around 2009. Instead, we hit that milestone toward the end of 2011.

(Of course, all the numbers are a little fuzzy. The U.N. admits that its margin of error could be as high as 56 million people. The U.S Census Bureau gives the world until March to hit 7 billion. And Ms. Camacho is only the 7 billionth person to be alive today; in all our history, 108 billion humans have walked the Earth.)

The real story today is not the unrelenting growth, but the moderating of its pace. The growth rate has been cut in half in the last half century and is expected to hit zero sometime around 2070. The U.N. forecasts that the global population will rise to 10 billion by 2083 from 6 billion in 2000. That means that the growth rate would have been about 66 percent in four-fifths of the 21st century, a stark contrast to the four-fold increase of the whole 20th century.

Demographers tell us that a fertility rate of 2.2 to 2.3 is needed to keep population levels steady. But population growth is declining significantly in many places, with fertility rates — the average number of children a woman has in her lifetime — falling below 2.0 in 75 countries. Most of that decline is occurring in developed countries in Europe and North America, but it is also happening in Japan, which has a fertility rate of 1.4, and South Korea (1.2). China’s fertility rate is just 1.5, meaning that it will be the first country in history to get old before it gets rich.

Most scientists attribute the shift to rising prosperity. As families get wealthier, there is less incentive to have children. Income equates with health and lessens the need to have children to carry on the family line or support parents in their dotage. Once survival is assured, parents try to prepare their children for better lives, acquiring education. The spread of birth control has contributed to this shift. Indeed, one of the elements of this trajectory is the rising affluence of the world’s nations. Population is increasing while the rate of the poverty is not.

Today, the same number of people are living in absolute poverty — 890 million people — as there were in 1804, when the world’s population first hit 1 billion. In 1804, that constituted 84 percent of the total population; today it is just 12.7 percent.

In East Asia, the numbers are even more striking. In 1987, more than half of East Asia lived in absolute poverty; today, it’s just 7 percent, while the total population has climbed by 400 million.

Falling growth rates lessen population pressures, but they create new dilemmas for societies. While the elderly may not consume resources as rapaciously as the young, they still leave a footprint. More significantly, the elderly do not save; rather, they consume the resources they have spent their lives accumulating — and rightly so.

These population patterns — less children, people living longer — are new. Societies have not experienced the precedent of fashioning ways to adjust. Our pension plans, for example, are premised on industrial models in which future workers contribute today for withdrawal tomorrow. A shrinking labor pool means that fewer contributors support more retiring workers. It is no wonder that social security plans around the world are under strain.

While the Malthusian disaster has been averted, we must be far more careful in how we use resources. A more affluent population has a much larger footprint. Just as troubling, trends have been set in motion — such as climate change — that oblige us to adopt drastic behavioral changes if we are to reverse those patterns.

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