Population growth is, in many ways, the elephant in the environmental room. Climate change may continue to be the highest profile manifestation of pessimism about the environment, but underlying this and pretty much every other issue there is an assumption among many people that population is simply too high and that problems will not be properly tackled until there are fewer of us.
The issue has come to the forefront again this month with the publication by the UN of revised projections for global population over the rest of the century (World Population Prospects – the 2012 Revision). The headline figures, for the medium scenario, are 8.1 billion by 2025, 9.5bn by 2050 and nearly 11 billion by the end of the century.
The importance of this is that projections over the years have tended to come down as fertility rates were seen to decline rapidly in line with increased prosperity and better education. The disaster foreseen by Malthus and revived by Paul Ehrlich and the Club of Rome failed to materialise as the rate of population growth slowed and the green revolution brought relative food security.
For the last decade or so, the UN’s best estimates had been for the world’s population to grow to around 9 billion by mid-century, probably plateauing in following decades. Since stability would be highly improbable, the latter years of the 21st Century might then reasonably have been expected to see the first global decline in the number of people in the modern era. But their latest revision puts that in doubt; if correct, there would be perhaps a further two billion mouths to feed before the peak is reached.
The overall trends conceal much important detail, of course. For example, as the Guardian reported, Nigeria expected to have larger population than US by 2050. Not only that, but Africa as a whole is expected to be the region where more than half of the global increase occurs. The continent’s population is projected to rise from 1.1bn to 2.4bn over the next four decades, and to up to 4.2bn – more than one third of the global total – by 2100.
It seems that the reduced mortality arising from improved nutrition and better healthcare is likely to raise life expectancy for Africans to an extent which will only partially be offset by falling birth rates. Meanwhile, China’s relatively slow population growth and skewed demographics, both resulting from the ‘one child’ policy, make it probable that India will become the world’s most populous country by the end of the 2020s. From that point on, China’s population looks set to decline from a high point of about 1.45bn to around 1.1bn by 2100, or about 250 million fewer than today.
The native populations of a number of developed countries are expected to decline over coming decades, with the numbers likely to be offset by increased immigration. However things actually turn out, the large global population increase and the huge regional demographic shifts are likely to bring big changes, the consequences of which are difficult to foresee. But one thing is clear; they will certainly not lessen the argument that increasing numbers of humans are putting an intolerable burden on natural resources.
On one level, this sounds like a perfectly reasonable argument. After all, populations of other animal species wax and wane but are determined by a combination of the carrying capacity of their habitat and the extent of predation. Humans have no significant predators (arguably, other than other humans), but the question of carrying capacity cannot be simply ignored. Nitrogen fixation and more productive farming, a reliable supply of affordable energy and dramatic improvements in healthcare have enabled an unprecedented boom in population in modern times.
The sustainability of such populations is difficult to gauge, because the timescale for their persistence is by no means clear. It seems pretty certain that, at some time over the next hundred years, the global population will peak and start to decline. That generalisation is, of course, based purely on current trends and the timing and degree of any downward trend would depend on a number of technical and social issues which we simply cannot foresee.
Likely increases in life expectancy are already factored in, although it is not inconceivable that advances in the understanding of ageing and disease could push this even higher. Equally, there is an expected rate of decline of fertility, but no-one knows what might happen when births fall below replacement levels. Maybe birth rates would increase again after a time, but any estimates of population in another two or three centuries would be purely guesswork.
This leaves the current population explosion as a relatively short-term issue in a historical context, but none the less serious for that. What is needed to move to a position where population becomes benignly self-regulating over long periods – a truly sustainable situation – is to ensure that everyone is properly fed and has a reasonable quality of life. Without that, high population density could lead to conflict and large-scale famines would loom.
Fortunately, it should be quite possible to avoid such Malthusian catastrophes by assuring an affordable energy supply. Of course, continued advances would be needed in agricultural productivity, but harvests are also highly dependent on synthetic nitrogen fertilizer, which in turn requires large amounts of energy. Fresh water is often seen as a limiting resource, but in fact it is the ultimate example of continuous recycling. The main problem is that water is either in the wrong place or in the form of seawater. Cheap energy – maybe solar in the longer term – would enable large-scale desalination and transport.
As someone who tends to see the glass as being half-full, I regard expanding populations as a challenge rather than a problem. Our species has the intelligence, innovative skills and adaptability to manage the issues for the benefit of all and for the benefit of the natural environment. People who are well-off and well-fed take much more care of their surroundings than the poor and the hungry.
The Scientific Alliance
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