As the global population hits seven billion, should we be worrying?

There will be those who say that the “population bomb” will explode and engulf us all; and there will be those who argue that it has been defused.

What is certain is that an expanding population creates challenges. The world first reached one billion people in 1804, and it took 123 years to get to two billion in 1927.

But then the growth accelerated, with six billion being reached in 1998 and seven billion just 13 years later. In May the UN predicted a global population of 9.3 billion by 2050 and more than 10 billion by the end of the century.

Since the Reverend Thomas Malthus started warning of the dire consequences of Britain’s burgeoning population 200 years ago – wrongly, as it turned out – there have been deep disagreements about how fast the population will expand, and what the impact will be.

The arguments first flared with the publication of Paul Ehrlich’s The Population Bomb in 1968, and returned again as evidence has mounted of climate change due to pollution.

Aubrey Manning, emeritus professor of natural history at the University of Edinburgh, has long been worried about population growth. “Whatever your cause, it’s a lost cause unless we limit population,” he says. “People don’t like talking about population control, but we have to.”

He argues that the number of humans is “out of balance” with the natural world, and that almost every country is over-populated. Others, however, take a more optimistic view. Fred Pearce, a science writer and author of the book, Peoplequake, points out that half of the world’s women are now having two or less children.

“If you are over 45, you have lived through a period when the world population has doubled. No past generation has lived though such an era – and probably no future generation will either,” he says.

“But if you are under 45, you will almost certainly live to see a world population that is declining – for the first time since the Black Death almost 700 years ago.”

Pearce argues that the education of women coupled with rising standards of living and reduced infant mortality is driving down the birth rate, meaning that “peak population” may not be far away.

“Women have always wanted freedom, not domestic drudgery and the childbirth treadmill,” he says. “And, now that most of their babies survive to adulthood, they are having it.”

Pearce believes the problem is not over-population, but is instead over-consumption by the rich, industrialised nations like Britain and the US. He goes further and suggests some of the demands for population control are tainted by racism.

“You can see it as underpinning the notion [of population control] that it’s people in countries far away, with dark skin, breeding, that are damaging planetary systems and are causing greenhouse gases emissions,” he says. “Is there racism in that? I suspect there is a bit.”

Advocates of population control would reject this criticism. But there is still a clear divide between those who want to put population growth at the top of the political agenda, and those who don’t.

“People tend to overlook population when talking about climate change,” said Roger-Mark De Souza from Population Action International in Washington DC. “Yet, rapid population growth expands and exacerbates people’s vulnerability to climate change impacts.

“Ensuring women have access to the contraceptives they want, starting today, is the first step toward creating healthier lives for the seven billion, and protecting our planet for those yet to come.”

Development charities like Oxfam and Christian Aid, however, argue that there is too much focus on population, ignoring the bigger problem of consumption. “The balance of current population growth occurs in those countries where consumption is lowest, that is in poorer countries,” says Alex Cobham, the chief policy adviser with Christian Aid. “By far the greatest increases in unsustainable consumption occur in rich countries like the UK.”

The solution is not to seek to limit “fertility choices” in developing countries, Cobham argues. “The fundamental obstacle to sustainable consumption is not population growth, but inequality,” he says.

For the executive director of the UN Population Fund, former Nigerian health minister Babatunde Osotimehin, reaching a population of seven billion is a call to action. He wants teenage girls to stay at school and become empowered to control the number of children they have.

“It’s an opportunity to bring the issues of population, women’s rights and family planning back to centre stage,” he said. “There are 215 million women worldwide who need family planning and don’t get it. If we can change that, and these women can take charge of their lives, we’ll have a better world.”

We tend to blame people in far away places with dark skin