Consumption Dwarfs Population as Main Environmental Threat

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 percent
of the global population - are responsible for 50 percent of the
world's carbon dioxide emissions. Meanwhile the poorest 50 percent are
responsible for just 7 percent 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 120 kilograms of meat a year per person, compared to just 6 kilos
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 percent increase in global economic
output by 2050. Most projections put world population then at no more
than 40 percent 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 percent to 11 percent.

Look
at it another way. Just five countries are likely to produce most of
the world's population growth in the coming decades: India, China,
Pakistan, Nigeria, and Ethiopia. The carbon emissions of one American
today are equivalent to those of around four Chinese, 20 Indians, 30
Pakistanis, 40 Nigerians, or 250 Ethiopians.

Even if we could
today achieve zero population growth, that would barely touch the
climate problem - where we need to cut emissions by 50 to 80 percent by
mid-century. Given existing income inequalities, it is inescapable that
overconsumption by the rich few is the key problem, rather than
overpopulation of the poor many.

But, you ask, what about future
generations? All those big families in Africa begetting yet-bigger
families. They may not consume much today, but they soon will.

Well,
first let's be clear about the scale of the difference involved. A
woman in rural Ethiopia can have ten children and her family will still
do less damage, and consume fewer resources, than the family of the
average soccer mom in Minnesota or Munich. In the unlikely event that
her ten children live to adulthood and have ten children of their own,
the entire clan of more than a hundred will still be emitting less
carbon dioxide than you or I.

And second, it won't happen.
Wherever most kids survive to adulthood, women stop having so many.
That is the main reason why the number of children born to an average
woman around the world has been in decline for half a century now.
After peaking at between 5 and 6 per woman, it is now down to 2.6.

This
is getting close to the "replacement fertility level" which, after
allowing for a natural excess of boys born and women who don't reach
adulthood, is about 2.3. The UN expects global fertility to fall to
1.85 children per woman by mid-century. While a demographic "bulge" of
women of child-bearing age keeps the world's population rising for now,
continuing declines in fertility will cause the world's population to
stabilize by mid-century and then probably to begin falling.

Far
from ballooning, each generation will be smaller than the last. So the
ecological footprint of future generations could diminish. That means
we can have a shot at estimating the long-term impact of children from
different countries down the generations.

The best analysis of
this phenomenon I have seen is by Paul Murtaugh, a statistician at
Oregon State University. He recently calculated the climatic
"intergenerational legacy" of today's children. He assumed current
per-capita emissions and UN fertility projections. He found that an
extra child in the United States today will, down the generations,
produce an eventual carbon footprint seven times that of an extra
Chinese child, 46 times that of a Pakistan child, 55 times that of an
Indian child, and 86 times that of a Nigerian child.

Of course
those assumptions may not pan out. I have some confidence in the
population projections, but per-capita emissions of carbon dioxide will
likely rise in poor countries for some time yet, even in optimistic
scenarios. But that is an issue of consumption, not population.

In
any event, it strikes me as the height of hubris to downgrade the
culpability of the rich world's environmental footprint because
generations of poor people not yet born might one day get to be as rich
and destructive as us. Overpopulation is not driving environmental
destruction at the global level; overconsumption is. Every time we talk
about too many babies in Africa or India, we are denying that simple
fact.

At root this is an ethical issue. Back in 1974, the famous
environmental scientist Garret Hardin proposed something he called
"lifeboat ethics". In the modern, resource-constrained world, he said,
"each rich nation can be seen as a lifeboat full of comparatively rich
people. In the ocean outside each lifeboat swim the poor of the world,
who would like to get in." But there were, he said, not enough places
to go around. If any were let on board, there would be chaos and all
would drown. The people in the lifeboat had a duty to their species to
be selfish - to keep the poor out.

Hardin's metaphor had a
certain ruthless logic. What he omitted to mention was that each of the
people in the lifeboat was occupying ten places, whereas the people in
the water only wanted one each. I think that changes the argument
somewhat.