It’s the great taboo, I hear many environmentalists say. Population growth is the driving force behind our wrecking of the planet, but we are afraid to discuss it.
It sounds like a no-brainer. More people must inevitably be bad for the environment, taking more resources and causing more pollution, driving the planet ever farther beyond its carrying capacity. But hold on. This is a terribly convenient argument - “over-consumers” in rich countries can blame “over-breeders” in distant lands for the state of the planet. But what are the facts?
The world’s population quadrupled to six billion people during the 20th century. It is still rising and may reach 9 billion by 2050. Yet for at least the past century, rising per-capita incomes have outstripped the rising head count several times over. And while incomes don’t translate precisely into increased resource use and pollution, the correlation is distressingly strong.
Moreover, most of the extra consumption has been in rich countries that have long since given up adding substantial numbers to their population.
By almost any measure, a small proportion of the world’s people take the majority of the world’s resources and produce the majority of its pollution. Take carbon dioxide emissions - a measure of our impact on climate but also a surrogate for fossil fuel consumption. Stephen Pacala, director of the Princeton Environment Institute, calculates that the world’s richest half-billion people - that’s about 7 per cent of the global population - are responsible for 50 per cent of the world’s carbon dioxide emissions. Meanwhile the poorest 50 per cent are responsible for just 7 per cent of emissions.
Although overconsumption has a profound effect on greenhouse gas emissions, the impacts of our high standard of living extend beyond turning up the temperature of the planet. For a wider perspective of humanity’s effects on the planet's life support systems, the best available measure is the “ecological footprint”, which estimates the area of land required to provide each of us with food, clothing, and other resources, as well as to soak up our pollution. This analysis has its methodological problems, but its comparisons between nations are firm enough to be useful.
They show that sustaining the lifestyle of the average American takes 9.5 hectares, while Australians and Canadians require 7.8 and 7.1 hectares respectively; Britons, 5.3 hectares; Germans, 4.2; and the Japanese, 4.9. The world average is 2.7 hectares. China is still below that figure at 2.1, while India and most of Africa (where the majority of future world population growth will take place) are at or below 1.0.
The United States always gets singled out. But for good reason: It is the world’s largest consumer. Americans take the greatest share of most of the world’s major commodities: corn, coffee, copper, lead, zinc, aluminum, rubber, oil seeds, oil, and natural gas. For many others, Americans are the largest per-capita consumers. In “super-size-me” land, Americans gobble up more than 120kg of meat a year per person, compared to just 6kg in India, for instance.
I do not deny that fast-rising populations can create serious local environmental crises through overgrazing, destructive farming and fishing, and deforestation. My argument here is that viewed at the global scale, it is overconsumption that has been driving humanity’s impacts on the planet’s vital life-support systems during at least the past century. But what of the future?
We cannot be sure how the global economic downturn will play out. But let us assume that Jeffrey Sachs, in his book Common Wealth, is right to predict a 600 per cent increase in global economic output by 2050. Most projections put world population then at no more than 40 per cent above today’s level, so its contribution to future growth in economic activity will be small.
Of course, economic activity is not the same as ecological impact. So let’s go back to carbon dioxide emissions. Virtually all of the extra 2 billion or so people expected on this planet in the coming 40 years will be in the poor half of the world. They will raise the population of the poor world from approaching 3.5 billion to about 5.5 billion, making them the poor two-thirds.
Sounds nasty, but based on Pacala’s calculations - and if we assume for the purposes of the argument that per-capita emissions in every country stay roughly the same as today - those extra two billion people would raise the share of emissions contributed by the poor world from 7 per cent to 11 per cent.