Malthus was wrong but that doesn't mean we can relax
If you believe the United Nations' projections, then at some point today, somewhere on the planet, a baby will be born, who will push the world's population above the seven billion mark.
Now, seven billion is a big number, representing an awful lot of people. What's more, it's a number that is rising with disconcerting rapidity. The world's population passed the six billion barrier just 12 years ago, and has now doubled in just 43 years, within the lifetime of this columnist.
And it's set to carry on climbing. According to the UN's statisticians, humanity is set to reach the 10 billion mark by 2085. Although if they've underestimated our enthusiasm for reproducing, the world's population could double again to hit 14 billion within the lifespan of the babies born today (see chart).
These forecasts have prompted some extravagant hand-wringing among the world's media, with commentators inevitably citing the work of 18th century clergyman Thomas Malthus to evoke apocalyptic visions of the perils of overpopulation.
Malthus, who wrote when the world's population was fewer than one billion, argued that while populations rose exponentially, their food supplies could only grow in a linear fashion. As a result, he concluded that material advances were impossible, and unrestrained reproduction must inevitably lead to famine, war and extinction.
Obviously he was wrong. But that hasn't discouraged a new generation of neo-Malthusians, who believe that the world's growing population faces a whole array of fatal resource constraints.
In the past week, we have heard fresh warnings that India will be unable to feed its growing population over the coming decades. And in recent years, a whole mini-industry of doomsayers has sprung up, dourly forecasting that the world is about to run out of fresh water, oil and gas, and any number of essential minerals.
They are wrong, too. Thanks to greatly improved farming techniques, food production has far outstripped population growth. In 1950, the world grew 249 kilograms of grain for each person alive. By the 1980s, per capita grain production exceeded 320kg. Despite the growth of the world's population, food has never been as abundant or cheap as it has been at the beginning of the 21st century.
Much the same applies to other resources. China is chronically short of water. But about half of the country's total supply goes to watering the annual grain crop, and more than half of that is wasted through inefficient irrigation.
Simple technological improvements can go a long way to solving the shortages.
Similarly, pessimistic types have warned since the 1970s that the world's supplies of hydrocarbons are running out. But in recent years, advances in sideways drilling and hydraulic fracturing have allowed the exploitation of vast new reserves in the world's oil and gas shales that will last for decades, possibly centuries, to come. In short, technology has consistently allowed us to overcome resource constraints.
As last week's edition of New Scientist pointed out, if you had built the equivalent of an iPhone from the components available in 1986, you would have needed several large trucks to carry it around. Today's iPhone weighs just 130 grams, about as much as an apple. As a result, whatever problems the world's population is likely to face over the coming decades, a shortage of resources will not be among them.
But that doesn't mean the neo-Malthusians are entirely wide of the mark. The chart showing exponential growth in the human population is unnervingly reminiscent of similar charts from the natural world.
Periodically, we see the same sort of growth patterns among the populations of algae that inhabit many of the planet's lakes. After years of apparent stability, the population begins to grow. The growth accelerates. The population doubles, then doubles again and again, until the lake is taken over entirely by algae. And then the algae die off, killed not by a lack of resources but by the toxic waste products of their own runaway metabolisms.
Similarly, the risk of human population growth is not that we will run out of food, minerals or energy, but that we will be poisoned by our own waste products. Either we will be poisoned directly by pollutants, or indirectly, as our waste products alter the chemical and physical processes of our biosphere, for example, by changing the climate, so that it can no longer support such a large population.
Admittedly, no one likes to think of themselves as akin to pond scum. But it's sobering to think that we may yet suffer the same fate if we fail to understand the real dangers of exponential population growth.