Human Population: Where We Stand Now

As of 1983, the Earth supported a human population of 4.6 billion. The authors argue population needs to decline for the sake of ecological sustainability.

| March/April 1983

human population - illustration of population doubling generation by generation

The Earth's human population is growing at an unsustainable rate.

Illustration by Fotolia/bobyramone

In the 15 years since The Population Bomb was written, well over a billion people have been added to the human total. Amazingly, that number is greater than the entire population of the Earth at the time of the American Revolution.

Indeed, a short half-century ago there were just 2 billion people in the world. Now, there are 4.6 billion. In less than one brief lifetime, then, the human population of our planet has more than doubled.

Of course, such unprecedented growth might not be terribly serious were Earth not already overrun by people. In fact, today's human family is so large that it can survive only by behaving in a way no sane family would want to: by destroying its capital. The vast number of people now on this planet, you see, can be supported only by consuming or dispersing a one-time bonanza: our store of inherited wealth, which cannot be replenished on a time scale of any interest to society.

That capital includes, of course, nonrenewable energy resources such as petroleum and coal. It also includes soils (see Ecoscience: Topsoil Erosion); "fossil" fresh water (see Ecoscience: Pollution Problems With World Groundwater Supplies); and the living species of our planet, which are intimately involved in supplying ecosystem services to society (see Extinction Events). Furthermore, as those resources are depleted, the number of human beings that can be supported—Earth's "carrying capacity"—will be greatly diminished.

Therefore, one major concern of humanity must be to bring population growth to a halt as rapidly as is humanely possible, and then to start a gradual decline by keeping the birth rate (which is generally expressed as the number of people born annually per thousand people) slightly below the death rate. And that process must continue until a population is reached that can be supported indefinitely on renewable resources.

The size of the human population will depend upon, among other things, both the average level of affluence and the technology (and resources) used to support that affluence. However, it seems certain that, with foreseeable technologies and with a standard of living near that now enjoyed by the rich nations (and aspired to by the poor), our "optimum" population would be substantially smaller than today's — perhaps one billion or less.

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