WITHIN A WEEK or so, the Census Bureau will declare that the population of the United States has reached the 300 million mark. As I write this sentence, the bureau's Population Clock, found at www.census.gov, reads 299,901,023. It took thousands of years for the population of what's now called the United States to reach 100 million, a milestone achieved in 1915; 52 years, to 1967, to add the next 100 million; and 39 years, to 2006, to add the next 100 million. And there are more coming, as the U.S. population is projected to reach perhaps 400 million around mid-century, and may continue climbing beyond that. Whoops, the Population Clock now says 299,901,426. I must learn to type faster!
The rising population will bring with it more: more of everything. More people, more sprawl, more creativity, more traffic, more love, more noise, more diversity, more energy use, more happiness, more loneliness, more fast food, more art, more knowledge, maybe even more wisdom. Today the United States is 50% larger in population and development footprint than a mere four decades ago, and if current trends hold, four decades from now it will be a third larger still. That means our national infrastructure must grow by at least another third to accommodate further population -- a third more highways, housing subdivisions, schools, trash landfills and everything else. I hope you like the United States, because there is a great deal more of it coming.
First, let's contemplate what should not worry us about continuing U.S. population growth. One is the question of whether we can handle it: We can. Physical resources remain plentiful in the United States and globally, with no primary physical resource (other than groundwater in China) currently near depletion. Today, there are about 1 trillion barrels of petroleum in the world's "proven reserve," according to U.S. Geological Survey estimates, about a 40-year supply at present rates of consumption, and there may be decades or even centuries' worth of oil still to be found in deep-ocean deposits about which little is known. The global economy is likely to have moved beyond petroleum before the oil runs out. Centuries worth of coal and uranium are in current reserves. Even assuming substantial future increases in global demand, most basic commodities are in good supply worldwide and expected to remain so. Resource consumption engages all manner of problems, including the danger of artificially triggered climate change. But for the moment at least, running out of the stuff we need does not seem to be a big danger.
Nor should we worry about running out of land, at least in the United States. The U.S. is among the world's least-populous nations, with one-eighth the population density of, say, Britain. The "built-up" area of the United States is far smaller than most would guess, with about 7% of the U.S. land mass converted to cities, roads and similar uses. Even if you include agriculture as a built-up use (modern high-yield agriculture is far from a natural condition for land), only about one-quarter of the United States has been converted to suit the wishes of people. Subtract the parts of the Rocky Mountains, Southwestern deserts and Alaska that aren't suitable for most kinds of habitation, and there remains plenty of land in the U.S. for substantial future population increases. Some nations -- Bangladesh, China, India and Japan -- already are approaching their usable-land limits. America's lies far in the distance.
Globally, it is astonishing that the world's population has roughly doubled, from 3 billion to 6 billion, in the four decades since Paul Ehrlich's influential book, "The Population Bomb," predicted global mass starvation beginning as early as the 1970s. Instead, by 2005, malnutrition had declined to the lowest level in human history, according to United Nations figures. How could forecasts of population doom have been so wrong? The core Malthusian assumption is that population would always increase faster than technology can respond. Instead, during the postwar era, it's been the other way around. High-yield agriculture has increased food production faster than the global population has grown; energy production and industrial production have risen much faster than global population.
Now, maybe there is a limit to the numbers the globe can sustain, and here at home we may not necessarily like a nation of more people, homes, cars and roads. Everyone hates tract housing, strip malls and traffic, all of which are fated to multiply. But before you say, "I hate sprawl," remember that sprawl is caused by more people and more affluence. And which of these, precisely, do you propose to ban?