The world's population reached six billion this month. Further, India now has one billion people. Should we celebrate, or are these milestones en route to environmental disaster?
The irony is that, while population growth has vastly outstripped anything that the Reverend Thomas Malthus could have imagined in 1798, the spectre of Malthusian catastrophe has receded. The expansion in the productivity of land and the more efficient use of mineral resources are the major achievements of, in particular, the 20th century.
Malthus warned of the dangers of exponential growth. Unless we developed habits of fertility control (he favoured sexual continence) we faced nature's "positive checks" - namely war, famine and disease - as means of ensuring that population growth would be sustainable in the long run.
Despite a number of regional population crises in the eighteenth and nineteenth centuries - eg in Eastern Polynesia, Ireland and China - by 1900 population growth had accelerated, famines had diminished, public health had improved, and war had ceased to be endemic. Industrialisation had proved Malthus wrong, or had it?
In 1900, neoclassical economists feared the onset of diminishing returns to land. They saw the nineteenth century expansion as a fluke, made possible not by industrialisation but by the diaspora of Europe into the "New World" (the neo-Europes of the Americas and Australasia). Growth in the nineteenth century was linked to the increased supply of land; not to increased productivity.
In 1900, British economists considered Britain to be dependent on its empire. After 1850, Britain had relied on food imports from the USA. With the expansion, urbanisation and industrialisation of America from the 1870s, the British expected to have to rely on their Dominions for food as American food would be increasingly consumed by Americans.
The British feared starvation if the Dominions industrialised in the wake of the United States; they feared the prospect of economic self-sufficiency in places like New Zealand. Optimists like Alfred Marshall defused the fears by suggesting that it would take a very long time before Canada, Australia and New Zealand would be rivals of rather than suppliers to Britain. Yet even Marshall accepted the basic premise that the spectre of Malthus would return some time this century.
The South African War that began in 1899 signalled the end of the frontier expansion and a new kind of warfare - a return to zero-sum struggles over territory. From 1900 to 1950, the German, Spanish and Japanese Wars suggested that the anticipated Malthusian tragedy was unfolding. Nations fought for empires, for "land and freedom", and for lebensraum.
Yet by 1950, the world's population had only reached 2.5 billion. Further, the world passed through a kind of anti-Malthusian economic crisis in the 1920s and 1930s, when primary producers failed because their production outstripped the growth of demand for food and raw materials. The terms of trade for agricultural products fell markedly in the 1920s, despite the closure of the agricultural frontier. The supply of food outstripped population growth, turning Malthus' arithmetic on its head.
In 1999, most of us have perceptions that are diametrically opposite of the perceptions that predominated in 1900. We believe that the twentieth century pattern of falling world food prices will continue. We see food production as a sunset industry, despite the rapid growth in world population and the even faster growth in average real incomes.
The world continues to have plenty of reproductive potential, at least in the 2000s and 2010s. 1.3 billion of those 6 billion are aged 15-24. Nevertheless, current projections suggest that world population will increase by just fifty percent in the next fifty years and will probably settle at about $10 billion around 2080.
Economic development, in part a consequence of population growth, is itself the cause of reduced fertility, and poverty generates fertility. Malthus got it wrong. He believed affluence would lead to increased fertility, and that fertility growth consigned humanity to endemic poverty.
Economic growth is the main single cause of the introduction of sustainable production techniques. In the nineteenth century, when the world had just over 1 billion people, we ravaged the environment: exterminating, burning, chopping, contaminating, extracting, polluting. Land then seemed super-abundant. We did not value it because it was abundant and we were few. We used natural resources in a profligate way. We didn't care. By the 1950s, through the burning of wood and coal, we created vastly more smoke pollution in our cities than we do now. Indeed, the 1950s was a decade of unusual global warming.
In the 1960s we started to value our planet. Higher population, economic development and technological creativity created the conditions for a stable affluent and equitable society. By using our natural assets as if we valued them, it has become possible to raise living standards - even in third world countries - without overloading the environment.
However, the optimistic scenario may not eventuate. Growth that is accompanied by growing poverty places huge pressures on the environment. The most poor will trade-off tomorrow for today in order to survive. The less poor seek to mimic the consumption patterns of the affluent. Inequality is the enemy of sustainable development. It is also a prescription for increased fertility as too many of us look once again to our own children to support us when we are old.
No discussion of world population can omit the vital question of the intergenerational contract, through which those of working age support their elders. In the developed world, there is huge concern about the growing ratio between old and young. Yet, from a global perspective, this remains far from being a problem. What we can say is that, with the young of the world being distributed predominantly in the world's 'provinces' (ie the third world) then demography itself will ensure that the pace of globalisation will continue. (We might note that provinces always have a comparative advantage in the production of people.) National demographic ratios are irrelevant to the global superannuation debate.
A projection of the key trends of the twentieth century into the twenty-first gives us much ground for optimism. Those trends are diminished war, improved human rights, increased environmental values, globalisation, democratisation, more-sustainable economic growth, and smaller families.
Yet the pessimists have a point. If we don't allow the majority to share in the productive potential of today's post-industrial global economy, then the unanticipated gains of the twentieth century will unravel. Just as a Malthusian tragedy was averted in a world of rapid population growth, a future world of increased poverty amidst plenty could lead to a zero-sum struggle for resources and its Malthusian outcome.
In the 21st century, we can choose to go down the road of increased inequality. Or we can choose the path of sustainable and equitable economic growth. Such a path can lead to a stable world population of 10 billion economically secure people by the time today's babies reach their twilight years.