The case for slowing population growth

Jeffrey D. Sachs, Project Syndicate

Global debates about population policy are confusing. One side argues that rising human populations threaten our environment and prosperity. Land, water, energy, and biodiversity all seem to be under greater stress than ever, and population growth appears to be a major source of that stress.

The other side of the debate, mainly in rich countries, argues that households are now having so few children that there won't be enough to care for aging parents.

Those who fret about population growth have the better argument. Issues confronting Europe, Japan, and to a lesser extent the United States and some middle-income countries concerning aging populations are manageable. Moreover, the benefits of slower population growth outweigh the adjustment costs.

By contrast, if global populations continue to rise rapidly, the stresses on the world's resources will worsen. Governments should therefore refrain from deliberate policies to raise birthrates, even in places where birth rates are low.

Part of the confusion of the public debate reflects different population trends in different parts of the world. The fastest population growth is taking place in the poorest regions. Poor people, especially poor people living on farms, tend to have the most children (often six or more per woman), and therefore the highest rates of population growth.

Poor farm families rely on their children for farm chores and for security when parents reach old age. Poor families lack access to contraception and family planning. Finally, poor families have many children as a kind of insurance policy against high child mortality rates.

As a result of high fertility rates in Africa, the UN Population Division predicts a doubling of Africa's population from around 900 million today to around 1.8 billion in 2050. Rapidly growing populations are also young populations, because of the high number of children per household. In Africa, the median age is now a mere 19 years and is projected to rise to around 28 years in 2050.

In Europe, the trends run in the other direction. The UN projects a decline in population to around 630 million in 2050, from around 725 million people today. With few children and longer life expectancy, the median age of the population rises sharply in this forecast, from 39 years in 2005 to around 48 years in 2050.

For the world as a whole, population is expected to continue to grow by another 2.5 billion people from 2005 to 2050. All of that growth will be in the developing world: 1.3 billion more people in Asia, 900 million more in Africa, the rest in Latin America and other regions.

Adding another 2.5 billion people to the planet will put enormous strains not only on societies with rising populations, but on the entire planet. Total energy use is soaring, reflecting the combined effect of rising per capita incomes -- and thus rising per capita energy use -- and population growth.

Higher energy use is already changing the world's climate in dangerous ways. Furthermore, the strains of increased global populations, combined with income growth, are leading to rapid deforestation, depletion of fisheries, land degradation, and the loss of habitat and extinction of a vast number of animal and plant species.

Population growth in developing regions -- especially Africa, India, and other parts of Asia -- needs to slow. Public policies can play an important role by extending access to family planning services to the poor, expanding social security systems, reducing child mortality through public health investments, and improving education and job opportunities for women.

A part of the European public, looking at Europe's looming population decline, wants to head in the other direction, promoting a return to larger families. That would be a big mistake. Advocates of faster European population growth worry that there won't be enough young workers to pay for public pensions. But this concern can be met through increased saving by today's young and middle-aged as they prepare for retirement, and by working past the age of 65.

These workers will reap large benefits from living in societies with stable or gradually declining populations. Most obviously, they will spend much less in direct household expenditures to raise children. They will also save on investments in new roads, power plants, schools, and other public services. They will enjoy less congested cities and fewer environmental pressures on the countryside. European economies will face lower costs in limiting emissions of greenhouse gases from energy use, leading to more effective control of climate change. The quality of life, in short, will tend to improve as Europe's population declines in coming decades.

There is nothing radical in calling for slower population growth. For tens of thousands of years, the human population tended to rise and fall without a substantial long-term trend. Only in the past two centuries, with the rise of modern economic life, did the world's population soar, from around one billion people in 1820 to 6.3 billion today and around nine billion by 2050.

This explosive growth was made possible by huge advances in science and technology. But this unprecedented growth has also put tremendous pressures on the planet. We should intensify our efforts to slow population growth through voluntary means, and we should recognize that leveling off of the Earth's population now would add to human happiness and strengthen environmental sustainability later.

The writer is Professor of Economics and Director of the Earth Institute at Columbia University.