Many folks conflate overpopulation with overcrowding, but while the two terms do overlap, they are far from synonymous.
Overcrowding is a much simpler phenomenon than overpopulation. It refers to a situation in which the area or volume of people (or their “extrasomatic extensions” like cars or dwellings) occupy a large fraction of the available two-dimensional area or three-dimensional space, to the extent that people feel pressed and often stressed. Overcrowding implies little or no “elbow room.”
Stadiums, classrooms, hallways, buses, subways, elevators, dwellings, slums, restaurants, bars, streets, sidewalks, stores, markets, rock concerts and Disneyland can all be overcrowded. Note that each of these is an artificial facility or event, not a natural setting, although more natural environments like popular recreation areas – city parks, Yosemite Valley in July or Southern California beaches – can also be overcrowded.
In contrast, overpopulation is getting at not the shortage of sheer space alone, but rather the much more complex relationship between the size of a population and the capability of the environment and all its resources – including its “sinks” into which we expel wastes – to support this population and its aggregate consumption.
Overpopulation occurs when a population exceeds the carrying capacity of its environment. When carrying capacity is surpassed, the environment, habitat and “natural capital” (e.g., renewable and nonrenewable natural resources) are worn down and used up, reducing the ability of the environment to support that population.
Surpassing carrying capacity is a precarious, temporary condition known as “overshoot.” Overshoot can occur because the carrying capacity is not a hard ceiling up against which a growing population bumps and cannot transgress. Rather, it is more like a porous boundary that can be overshot by a rapidly growing population with substantial momentum, but only fleetingly.
Arguably, at 7.2 billion and counting, hard-charging humanity has already overshot the long-term carrying capacity of the Earth. This occurred once we learned how (i.e., developed the technology) to exploit depletable, nonrenewable, energy-dense concentrations of fossil fuels and the high-grade mineral ores that provide, as geologist Walter Youngquist puts it in his marvelous book Geodestinies, the “material basis of civilization.” Modern civilization burst into being, but now our day of reckoning approaches.
The number of people that can be supported sustainably by an environment and its resources, even a high-quality environment richly endowed with resources, is always – always – far, far fewer than the sheer number of human bodies that could hypothetically be squeezed into the available space.
Yet this has not stopped ecological ignoramuses from proclaiming again and again that “we could put the world’s entire population into Texas [or Manhattan, or San Francisco] with room to spare” or words to that effect. Anyone who voices this ridiculous canard has betrayed a profound ignorance of the fundamental distinction between overpopulation and overcrowding. While mathematically true, the “Texas fallacy” is utterly beside the point. Those 7.2 billion people stuffed into an area of, say, 7.2 billion square yards (less than three square miles), wouldn’t last three (very miserable) days.
In part, the popular confusion between overcrowding and overpopulation is the fault of environmentalists and population activists themselves, as well as the news media. Whenever we publicize images that we intend to convey overpopulation, what we show are images that in fact convey overcrowding, not overpopulation. That’s why we show images like the overcrowded train in Bangladesh rather than the solitary skier atop an Alaskan icefield.
It just so happens that Bangladesh is actually one of the many places on Earth that is overpopulated as well as overcrowded. Its 155 million people – about half the U.S. population – are crammed into a vulnerable, low-lying area the size of Iowa at a population density of 2,700 per square mile, more than double that of New Jersey, our most densely populated state. Environments can support larger numbers of poor people who consume little than rich people who consume much. But poor people understandably want to be richer, and therein lies the dilemma.
Let me close this essay with a question. When just two Apollo astronauts at a time stood on the surface of the Moon, was it already overpopulated?