KEY POINTS:
As a young architecture student, Richard Grant heard a statistic that would change his life. "I heard on the [radio] a gentleman speaking who said the world's population, the way it was going, would double. That frightened me because I was a student looking at structures - you can't just double things, the structure must change. If you double the size of a man, his bones won't support him."
Back then, just after World War II, the population of the world was nearly 2.5 billion. By the late 1980s it had doubled, and it has now reached 6.6 billion. By the middle of this century, the United Nations' mid-range forecast is that there will be 9.2 billion people living on the planet - nearly four times the number that scared Grant when he was a teenager.
A few years later Grant married Irma who, fortunately, agreed they should, in the words of so many people who share their concerns, just "replace themselves", not add to the growing population.
"We wanted to have a family," says Grant, whose first child was a son, Simon. "We had a daughter, a second child, because I thought it was important to have two to help each other, and we were a complete family, and we ensured we did not have another child. People are important, and children are very, very important; we must therefore bring them into a world that's good and not going to collapse."
The Grants' son followed his parents in deciding to have only two children; others have gone further still and have no children at all as part of their commitment to do their bit to "save the environment".
The Optimum Population Trust (OPT), which was set up in 1991, has now launched a voluntary campaign to "stop at two".
But there are others who object to the premise that we should not have children as a way to protect the planet, and not just for religious or ethical reasons. They argue that the central premise is wrong - that it is not too many people who are destroying the planet, but the lives of a rich, profligate few, mostly in the Western "developed" world. Some even detect a worrying threat that the incipient debate on curbing consumptive lifestyles is being undermined by the renewed focus on population.
One of those is Tony Juniper, executive director of the environmental lobby group Friends of the Earth.
"When I'm doing public meetings and the population question is raised, as it often is, the way the question is posed gives the impression ... they are saying the population in Africa or India is an issue," says Juniper. "You immediately put the pressure away from what you can do to what somebody else can do."
In the late 1700s, Thomas Malthus worried that the strain of feeding a growing population could hasten the "premature death" of the human race. The basic human anxiety with feeding ourselves later morphed into a more complicated concern with the methods humans found of solving the food problem - mass agriculture, industrialisation and global trade.
We have cut down forests, denuded soils, drained and poisoned water tables, raped the seas of fish and polluted the air, destroyed resources - or more accurately put them out of reach - and so, progressively, made Earth a less comfortable place to live.
Today, the debate has been given new urgency by the potentially catastrophic climate change threatened by burning fossil fuels, and the swelling of China. As China's economy has boomed, growing demand from the world's most populous country for energy, food, buildings, even gold, has forced up prices of commodities.
Then, this year came the news everybody expected - but just not so soon - that China is thought to have surpassed the US as the planet's biggest emitter of greenhouse gases.
The average Chinese citizen is responsible for a fraction of the emissions of the average American, but the sheer size of China's population had to be recognised.
For populationists, the mathematics are simple: the more people there are who need water, food, fuel and shelter, the greater the stress on the planet. These days, the equation is expressed in terms of carbon - since the ability of the Earth's atmosphere to absorb carbon dioxide, the biggest source of greenhouse gasses, is at the top of the political agenda.
Thus the OPT calculates that every family that decides to "stop at two" will save 750 tonnes of CO2 for each child that is not born - equivalent to 620 return flights between London and New York.
To put this into perspective, when TV reporter Justin Rowlatt spent a year as the "Ethical Man" on the BBC's late-night current affairs show Newsnight, all his family's efforts to change lightbulbs, ditch the car and even have wife Bee walk to hospital to give birth cut their carbon footprint by two tonnes. But the birth of Elsa, their third child, meant their footprint ended up "worse off than when we started", said Rowlatt.
Globally, the numbers add up to a significant environmental impact. Worldwide, the average "total fertility rate" was estimated by the UN Population Fund this year at 2.7. If every second couple had one fewer children, says the OPT, by the middle of this century there would be 1.4 billion fewer people than the UN forecasts.
The combined environmental impact of 1.4 billion people surely dwarfs the combined efforts of Western governments to install renewable energy and persuade people to insulate their boilers and buy smaller cars.
And the solutions - improving contraception, education and healthcare - are much cheaper than the alternatives, says Chris Rapley, head of the Science Museum in London and a patron of the OPT.
But there is widespread public awkwardness about discussing population. Perhaps with good reason: last year, Ethical Consumer magazine's Eco Worrier column posed the question, "Is it ethical to have children?"; several readers cancelled their subscriptions. Meanwhile, conferences discuss renewable energy, energy efficiency, public transport, low-wattage lightbulbs and low-carbon cars, but almost never timetable debates on population.
Most of Ethical Consumer's offended readers objected on religious grounds, says writer Mary Rayner. Other oft-cited reasons are prudishness at discussing sex, discomfort over equating children with carbon, and the shadow of coercive one-child policies in China and, formerly, India. There are also fears the debate will be co-opted by anti-immigration groups in developed countries, where populations would be falling if not for hundreds of thousands of people arriving from abroad.
"There's a continuing sense among liberals that there's something coercive and 'right-wing' about this that sits uneasily with the standard liberal/progressive mindset in the development and environmental world," says Jonathon Porritt, one of Britain's best-known environment campaigners and one of the few who has talked publicly about population as a problem since the 1970s. "I think that perception is completely wrong, but the longer you go on allowing it, the more it fulfils itself."
Oxfam's head of research, Duncan Green, confirms the populationists' claim that the most powerful ways to drive down birth rates are better living standards, education and healthcare - especially for women. He adds a fourth: urbanisation.
Such policies clearly have huge potential - the UN estimates 200 million women in the world do not have access to "safe and effective" contraceptive services - but these are primarily development and healthcare policies.
"The things we're concerned about, such as rights, also happen to deal with population by allowing [women] to chose their family size," says Green.
It is not the solutions that critics of the population argument disagree with - it is the diagnosis of the problem itself.
Fundamentally, some object to the initial premise that, as Phil Harding puts it, we are living beyond the "carrying capacity" of the planet.
Technological advances and a fairer distribution of resources mean the idea of a finite world is questionable, they argue. "Absurd, even," says Julian Baggini, editor of The Philosophers' Magazine. "Clearly there's an absolute limit somewhere, which despite all our efforts couldn't sustain that population, but the idea that's coming soon is rather dubious."
Humans are unquestionably damaging their environment, sometimes with fatal consequences. However, those who argue against a population policy do not accept that growing numbers are the problem. To understand why, you have to look in more detail at the statistics, which reveal two crucial trends.
The first is that populations are mostly growing in countries where consumption is a fraction of that in the developed world.
At almost the two extremes, the average person in the poorest parts of Africa is responsible for one 200th of the CO2 emissions of the average American. Even with their booming economy and heavy use of coal, the average Chinese person generates a quarter of the CO2 of an American.
Overall, the world's richest nations account for nearly a fifth of the world's people, but nearly half of global CO2 emissions. And the real disparity is even greater because a large proportion of China's building and energy boom is making goods for America, Europe and other developed nations, which have, in effect, exported much of their carbon footprint by moving manufacturing to cheaper markets. And these figures do not include international aviation.
Such disparities extend to other resources too, says John Sauven, Greenpeace's executive director: "If we had nine billion people who were all vegetarian and walking to work, that's very different to nine billion Americans driving to work and having hamburgers every day. For sure, if there were one billion people we wouldn't have the problems we do today, but numbers per se are not the problem alone - we have to look at the other side: consumption."
Rosamund McDougall of the OPT's advisory council agrees, but says those 1.4 million children the organisation wants to avoid are future consumers, and future consumers who will, understandably, want better lives than their mothers and fathers.
"Most of them will be born in the developing world, but do you want to keep them that way?"challenges McDougall. "What people who are saying that are saying is they must be kept in poverty. In nearly 50 years' time they'll want to be using a lot of resources."
To make matters more complicated, one of the most effective policies to reduce birth rates is raising living standards, because, as former Tanzanian President Julius Nyerere put it: "The greatest contraceptive one can have in the developing world is the knowledge that your children will live."
The second important trend is that birth rates have already fallen in every region of the world, and globally have nearly halved since the 1950s.
The UN's mid-range forecast of 9.2 billion people by 2050 assumes the total fertility rate falling below the replacement rate by that date. And the UN has a history of over-projecting population, claim critics. Much of this decline in population growth is being offset by people living longer - and nobody is seriously advocating anybody be denied life-saving medical help to stop some CO2 going into the atmosphere.
The OPT accepts world population should reach a turning point around the middle of the century, but warns that it will take much longer to swing the other way and start falling.
In the meantime, it says, more family planning and education would still make a big difference if they could speed up the peak or reduce it.
- Observer
