By the time you’ve finished reading this sentence, the human population of Earth will have increased by approximately 12 people. As you continue reading, the average number of births will, every second, eclipse the average number of deaths. If we assume a typical reading speed of 250 words per minute, in the time it takes you to reach the end of this article, there will be around 1800 more people living on the planet than when you started.
But is that something to worry about?


Human numbers have been rising ever since the end of the Black Death in the Middle Ages. We currently pack in an extra 78 million people every year. The current population is 6.8 billion, and we’re expected to stampede through the 7 billion mark in 2012. According to the UN, the world population in 2050 will be 9.1 billion – a rise of over 6.6 billion in the 100 years since 1950.

The question is, can the Earth cope with that many people? Warnings that humans are overcrowding the planet have been sounding for centuries. Up until now, human progress and scientific ingenuity have staved off global catastrophe. Despite famines, most people have been fed and, taken as a whole, health and living standards have improved. And if the climate really is doomed, the consequences haven’t derailed us. At least not yet.

But now, a decade into what most scientists believe is a crunch century for the environment, some campaigners are desperately trying to put population growth back on the global agenda. Their argument is simple: there are too many of us. Continued growth, they say, is at the root of every environmental challenge we face, from cutting CO2 emissions to sharing the world’s limited fresh water. If we don’t do something soon, the natural resources we all depend on will vanish.

“The world needs to wake up to the fact that population growth is a driver of all environmental problems, on a par in importance with climate change,” says Roger Martin, one of the UK’s most strident campaigners on the issue. “It is the third element in every single environmental equation, where total impact equals the average impact per head, multiplied by the number of
people on Earth.”

Martin is chairman of the Optimum Population Trust, a think tank concerned with the impact human numbers have on sustainability. It campaigns for stabilisation of the population and, eventually, its gradual decline.

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“Space and resources on this planet are finite, so we know that growth will end one day because it cannot go on forever,” he says. “And when growth does end, it will come from one of two causes – fewer births through contraception and humane population policy [promoting family planning rather than forcing people to have fewer children], or more deaths through famine, disease and war. There is no third way of indefinite population growth.”

Earlier this year, David Attenborough became a patron of the Optimum Population Trust. Following the likes of James Lovelock in publicly calling for action on population growth, Sir David’s feelings were clear. He said, “I’ve never seen a problem that wouldn’t be easier to solve with fewer people, or harder, and ultimately impossible, with more.”

9.1 billion elephants

Although environmental heavyweights like Attenborough and Lovelock have spoken out, some campaigners believe that population remains a taboo subject. It’s the 9.1 billion elephants in the room that nobody wants to talk about. In some ways, it’s no surprise. Anyone who does talk about population has to deal with sensitive connotations concerning religion, immigration, racism, eugenics and coercive population control such as the enforced sterilisation programme of 1970s India. And part of what complicates the matter is that the most rapid growth in human numbers is occurring in the poorest countries.

The vast majority of the additional 2.3 billion people that the world will harbour in 2050 will live in the developing world. And most of the fastest-growing countries are among the 49 classed by the UN as the world’s least developed. Some, such as Liberia, Niger and other sub-Saharan nations, are projected to swell by 150 per cent or more.

In these arid countries, already starved of resources, the total fertility today is catastrophic. In Liberia, at current fertility levels, women have an average of 5.14 children over their lifetime. In Niger, the number is 7.15. And in the coming decades, countries such as these will face what John Beddington, the UK Government’s chief science advisor, describes as a “perfect storm” of food, energy and water shortages.

Beddington warns that, globally, the demand for food and energy will increase by 50 per cent by 2030. The need for water will go up by 30 per cent. The bigger the population, the thinner the world’s resources are spread – and it’s still unclear what effect climate change will have on the problem.

“The worst-affected countries tend to be the poorest,” says Hania Zlotnik, director of the UN Population Division. “The high population growth that they’re experiencing is contributing to a vicious circle that is hindering development.”

As well as publishing all of the UN’s official population estimates and projections, Zlotnik’s division advises governments on population issues, including the need for family planning and – crucially – access to a wide range of modern contraception for women. However, communicating the benefits of slowing population growth can too often sound elitist: the arrogant, high consumers of the developed world telling the poor that they have to change. But that’s not the case, Zlotnik says.

“The argument is that in almost every country that has managed to increase its economic growth, fertility decline has usually preceded it or gone hand-in-hand with that growth.” Simply put, food, water, healthcare and education are easier to provide for a population that is not growing too fast. And in turn, that population is likely to be more productive with better infrastructure.

“Some countries need to be convinced that declines in fertility are good, not for the developed world or even the planet, but for themselves,” Zlotnik says.

Boom and bust

Population growth is not restricted to the poorest countries. But elsewhere in the world, the rate of growth is not nearly as extreme. Below-replacement fertility, where the number of children born fails to counterbalance the number of deaths, has been a fact of life in most developed countries for several decades. Even in China, the world’s most populous country with 1.33 billion, fertility has been below-replacement level for more than a decade and authorities in Shanghai have recently relaxed the one-child policy for urban-dwellers “Partly as a consequence of the development of the economy and education, and partly as a consequence of family planning programmes, birth rates in most countries are coming down,” says Professor David Coleman, a demographer at Oxford University. “In parts of southern India, the birth rate is now about the same as that in northwestern Europe. In Thailand, Sri Lanka, Brazil, Indonesia, it’s becoming really rather low and many people feel that it’s going to go below the level required to replace the population in the long run. The general expectation is that most countries will follow in due course.”

Provided all populations reach a fertility below-replacement level, the UN projects that the world population could peak late in the 21st century, and then begin declining for the first time in hundreds of years. But to achieve that we have to put the brakes on population before 2050. The trouble is, population increase until mid-century cannot be avoided. High fertility in the past, especially in the developing world, has built an inevitable momentum that fuels population growth – like a car braking at high speed, it’s going to take longer to come to a complete stop. There is still a high concentration of women of child-bearing age alive, so even if global fertility rates suddenly dropped to replacement level, it would take ageneration or two for the population to finally stabilise.

The developed world is not immune. Despite having fertility rates way below 2.1 births per woman – the average for replacement – 42 million more people will live in the developed world in 2050 compared with today. Here in the UK, the Office for National Statistics says the population will be 77 million people in 2051, up from today’s 61 million. The United States, meanwhile, will be home to an additional 89 million. In both cases, the increase will be down to migration.

According to the UN, the UK will receive a net average of 174,000 migrants a year between now and 2050, a statistic that will undoubtedly ignite fierce debate. For some, the additional numbers will provide a guarantee of economic growth, markets and labour forces in a world where the number of pensioners is set to triple. For others, that’s the same mentality as a pyramid cash scheme, in which growth only happens by a never-ending stream of new people entering.

“People argue that scientific progress will always find a way to support the extra numbers,” Coleman says. “But these are terrible increases that have been very frivolously accepted as projections when they’ll mean a big difference in quality of life if they are allowed to come to pass.”

Numbers vs consumption

As far as the environment is concerned, the last thing we need is more rich people. Population growth in the developed world may be marginal compared to that in some countries, butalong with every new inhabitant of a developed nation comes a vast appetite for consuming resources. Earlier this year, Fred Pearce, one of the world’s leading writers on environmental issues, drew attention to calculations made by Stephen Pacala, director of the Princeton Environment Institute. Pacala says that the richest seven per cent of the global population are responsible for 50 per cent of the world’s carbon dioxide emissions. In comparison, the poorest 50 per cent of the world are responsible for just seven per cent of emissions.

“Every additional Brit, let alone American, is a rich consumer of countless resources with a very heavy carbon footprint,” says Roger Martin. “In Bangladesh, it’s absolutely tiny by comparison. So we want all countries to adopt population policies.”

He’s serious. The Optimum Population Trust promotes a ‘Stop at Two’ pledge by which people promise not to have more than two children. Having a third, Martin argues, is now a matter of morality. “Two children is fractionally below replacement level. Most of us in the developed world have a choice, whereas many people in the least developed world do not,” he says.

“For the average family, it is a fact and not an opinion that, by having a third child, they will increase the global population, and therefore increase global pressure on the environment and decrease everyone’s share of the natural resources on which we ultimately depend to survive.”
For campaigners like Martin, unless measures such as these are taken, we could sabotage our own efforts to fix the environment. Any reduction in consumption of resources or emissions of CO2 per head could be cancelled out by an overall population that’s out of control. Of course, nobody really believes that if you solve the ‘population problem’, all other environmental issues will simply disappear, but they should be easier to deal with. That’s why some environmentalists are adamant that population be up for discussion.

They might have a point. If there’s going to be nine billion of us each trying to carve out enough space for a life, the least we can do is talk to each other.


The website for the UN Population Division, including official projections

The website for the Optimum Population Trust

Blogs, videos and other media on what the world will be like in 2050

Ian Taylor is a London-based journalist, and former deputy editor of BBC Science Focus


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A former deputy editor at Science Focus, Ian once undertook a scientific ranking of the UK's best rollercoasters on behalf of the magazine. He is now a freelance writer, which is frankly a lot less fun.