Is global warming caused by too many people? This begins a series of articles in which Climate & Capitalism editor Ian Angus shows that population numbers can conceal far more than they reveal.

by Ian Angus

A recent Washington Post article criticized three new books on global warming because “none of these authors discusses population growth in any kind of depth.”

To reduce emissions, the reviewer wrote, we should be “helping people to have smaller families …[by] providing the means for family planning to those who want it but don’t have access.” That, he assures us, is “a lot easier than retooling the global economic system.” [1]

Like many environmentalists, the Post writer firmly believes that population growth worsens global warming by increasing greenhouse gas emissions, and that the solution is to slow or reverse population growth by providing birth control to people “who don’t have access” – that is, to people in the Third World.

And yet, anyone who carefully reads the many websites, articles, speeches and books that argue the “too many people” thesis will find that they offer little or no evidence to support such conclusions.

That’s not to say that they don’t offer impressive arrays of facts, usually in the form of a scary paragraph about global population growth.

This, from Optimum Population Trust, is typical:

“The world’s population is still exploding. Human numbers, which reached 6.8 billion in 2009, are expected to reach 9.15 billion in 2050, and we’re growing by 78 million a year. The 2.3 billion increase from 2008 to 2050 is almost as much as the entire population of the world in 1950 … Every week 1.58 million extra people are added to the planet – a sizeable city – with nearly 10,000 arriving each hour.” [2]

And so is this, from Global Population Speak Out:

“It took virtually all of human history for our numbers to reach 1 billion in the 1800s. It took only about a century to add the second billion in 1930. We added the third billion in just 30 years and the fourth in only 15 years. We are now at 6.7 billion with projections of over 2 billion more to come in the next 40 years. The size and growth of the human population is linked closely to nearly all forms of environmental degradation we see today.” [3]

Such statements – many more could be quoted – present gross population figures as the most important measure of humanity’s impact on the earth. Advocates of population reduction rarely take their analysis any further. When it comes to human numbers, populationist arguments begin and end with big is bad and bigger is worse.

Correlation isn’t causation

Typically, such arguments point to the substantial increases in both population and greenhouse gases in the past two centuries, and conclude that emissions growth has been driven by population growth.

The underlying argument is summarized in a recent textbook on climate change:

“Generally, if one person has an environmental impact of some arbitrary quantification, x, then it is not unreasonable to suppose that two people will have an impact of 2x, three people an impact of 3x, etc; in other words, that environmental impact is proportional to population ….”[4]

But this simplistic logic only works if every additional person causes the environmental impact to increase by “some arbitrary quantification, x.” The populationist argument assumes that, but doesn’t prove it.

At some point in every introductory statistics course, the instructor tells students about a European city where increases in the stork population were supposedly matched by increases in the number of new babies. The point is, that correlation isn’t causation – storks don’t bring babies, no matter what the numbers say.

This lesson is all too rarely applied to debates on population and emissions. To determine whether population growth really drives emission levels, or if the correlation is a coincidence, or if the numbers are in some other way misleading, we need to go beyond big numbers and examine real connections and relationships.

With population, the correlation-or-causation problem is further complicated by the fact that big scary numbers (6.7 billion people, 10,000 births per hour) actually tell us very little unless we examine them in context. Population statistics are useful only if we understand how they are determined, what they include and what they leave out, what their strengths and limitations are for any specific purpose. As Karl Marx wrote 150 years ago, “population” is an abstraction, not a real thing.

“It seems to be correct to begin with the real and the concrete, with the real precondition, thus to begin, in economics, with e.g. the population, which is the foundation and the subject of the entire social act of production. However, on closer examination this proves false. The population is an abstraction if I leave out, for example, the classes of which it is composed.” [5]

This is a profound insight, one that activists who are concerned about the complex relationship between humanity and the world we live in must understand. “Population” is just a number, one that can conceal far more than it reveals. To understand the relationship between “population” and climate change, we need to dissect the big numbers.

Population where?

As a first step towards exposing the concrete reality behind the abstraction, this article considers some differences between rich and poor countries that the “too many people” argument usually ignores. The table below compares two groups of countries:

  • The G20 countries, self-described as “the systemically significant industrial and emerging-market economies.” These countries include two-thirds of the world’s population and account for 90% of the world’s Gross National Product. [6]
  • The 19 countries with the lowest per capita CO2 emissions. All but one (Afghanistan) are in Africa.

In each group, the countries are listed in descending order by Per Capita CO2 emissions in 2006, the most recent year for which I could find numbers.

The second column from the right shows population density – the average number of people per square kilometre. This is a rough measure of how “populated” (over or under) the country is.

The right-hand column shows how fast the population is growing. “Total Fertility Rate” is the number of children, on average, born to each woman in the country during her lifetime. The higher this number is, the faster the country’s population is growing. The Total Fertility Rate at which a country’s total population would be stable, not growing or declining, is generally taken to be about 2.3 – ranging from 2.1 in rich countries where infant mortality is lowest, to as high as 3.3 in the global south.

CO2 Emissions, Population Density, and Total Fertility Rate
CO2 Emissions Population
Per Capita (tonnes) Total

(million tonnes)


(per sq. km)


Fertility Rate

G20 Countries U.S.A. 19.7 5975.1 30.71 2.05
Australia 19.0 390.44 3.0 1.79
Canada 17.2 560.39 3.0 1.53
Saudi Arabia 15.78 381.56 13.47 3.35
Russia 11.0 1577.69 8.0 1.34
Germany 10.7 880.25 230.89 1.36
Japan 10.0 1273.6 337.23 1.27
South Korea 9.89 475.25 491.7 1.21
U.K. 9.2 557.86 246.88 1.82
South Africa 8.59 414.65 36.35 2.64
Italy 8.3 488.04 192.89 1.38
France 6.7 408.69 110.88 1.89
China 4.62 6103.49 136.12 1.73
Argentina 4.43 173.54 14.29 2.25
Mexico 4.14 436.15 53.84 2.21
Turkey 3.7 273.71 89.24 2.14
Brazil 1.86 352.52 21.86 1.9
Indonesia 1.46 333.48 126.06 2.18
India 1.31 1510.35 328.59 2.81
Total CO2 Emissions 22566.76
Low Emission Countries Sierra Leone 0.17 0.99 83.88 5.0
Madagascar 0.15 2.83 30.73 5.14
Guinea 0.15 1.36 38.51 5.2
Tanzania 0.14 5.37 38.9 4.46
Eritrea 0.12 0.55 37.6 5.05
Mozambique 0.1 2.04 24.21 5.18
Uganda 0.09 2.71 115.53 6.46
Rwanda 0.08 0.8 320.48 5.12
Malawi 0.08 1.05 102.62 5.59
Niger 0.07 0.94 9.0 7.75
Ethiopia 0.07 6.01 64.81 5.29
Central African Republic 0.06 0.25 6.0 4.14
Mali 0.05 0.57 9.91 6.62
Burkina Faso 0.05 0.79 50.79 6
Dem. Rep. of Congo 0.04 2.2 25.62 6.2
Chad 0.04 0.4 8.0 5.31
Afghanistan 0.03 0.07 46.22 7.07
Somalia 0.02 0.17 13.47 6.04
Burundi 0.02 0.2 228.91 6.33
Total CO2 Emissions 29.3
Emissions Source: United Nations Statistical Division. CO2 Emissions in 2006.
Fertility Source: World Population Prospects The 2006 Revision. (PDF)
Pop. Density Source: World Atlas.

This table leads to three inescapable conclusions.

1. CO2 emissions are a problem of rich countries, not poor ones. The G20 countries produced more than 22,500 million tonnes of CO2 in 2006. That’s 78% of the worldwide total – nearly four times as much as all other countries combined. It is more than 770 times as much CO2 as the 19 lowest emitting countries produced.

Per capita CO2 emissions in the United States are 98 times greater than in Gambia, 132 times greater than in Madagascar, 197 times greater than in Mozambique, and 400 times greater than in Mali or Burkino Faso.

These figures, it’s important to note, significantly understate the case, because they don’t include some of the major emission sources that are concentrated in rich countries, such as military activity and international air travel.

So the idea that “providing the means for family planning to those who want it but don’t have access” will somehow slow global warming makes no sense. With few exceptions, birth control has long been available in the countries that are doing the most to destroy the earth’s climate.

2. There is no correspondence between emissions and population density. The high-emitting G20 group includes countries such as India, Japan, and South Korea, which are home to high numbers of people per square kilometer – but it also includes countries with low population density, such as Australia, Canada and Russia.

Exactly the same is true of the low-emission group, which includes countries with high population density (Rwanda, Burundi) and countries with low population density (Niger, Chad).

So it is clearly possible to have low population density with high emissions, or high population density with low emissions.

It’s also worth noting that almost all of the low-emission countries have far fewer people per square kilometre than the United Kingdom, where Optimum Population Trust is promoting Third World birth control as a means of slowing global warming. [7]

3. Population growth rates do not correspond to CO2 emissions. In fact, there’s a negative correlation. Broadly speaking, the countries with the highest per capita emissions are those whose population is growing most slowly or even declining, while the countries with the lowest emissions have the highest growth rates.

In fact, in most G20 countries the birth rate is at or below replacement level. If it weren’t for immigration, their total population would be falling. According to some estimates, by the end of this century the population of Italy (excluding immigration) will fall by 86%, Spain will decline 85%, Germany 83% and Greece 74%. [8]

Only three G20 countries (Saudi Arabia, South Africa, and India) have fertility rates that are clearly above replacement level, and even they are growing far more slowly than the 19 lowest emitting countries.

If we were to adopt the usual populationist correlation=causation stance, we’d have to conclude that high emissions cause low population growth, or that high population growth causes low emissions. Of course that’s absurd: both emissions levels and population growth are shaped by other social and economic causes.

The real conclusion is, that there’s something seriously wrong with the more people equals more emissions argument, and something even more wrong with the idea that Third World birth control will slow global warming. [9]

In his recent book, Peoplequake, environmental writer Fred Pearce makes this point dramatically:

“The poorest three billion or so people on the planet (roughly 45 per cent of the total) are currently responsible for only 7 per cent of emissions, while the richest 7 per cent (about half a billion people) are responsible for 50 per cent of emissions.

“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 Manchester or Munich. In the unlikely event that her ten children live to adulthood and all have ten children of their own, the entire clan of more than a hundred will still be emitting only about as much carbon dioxide each year as you or me.

“So to suggest, as some do, that the real threat to the planet arises from too many children in Ethiopia, or rice-growing Bangladeshis on the Ganges delta, or Quechua alpaca herders in the Andes, or cow-pea farmers on the edge of the Sahara, or chai-wallas in Mumbai, is both preposterous and dangerous.” [10]

Preposterous and dangerous. Amen.

To be continued



[1]Thomas Hayden. “Environmental books suggest save-the-Earth climate may be entering a new phase.” Washington Post, April 20, 2010. Accessed April 21, 2010 at

[2] Optimum Population Trust website. Accessed April 10, 2010 at

[3] Global Population Speak Out website. Accessed April 10, 2010 at

[4] Jonathon Cowie. Climate Change: Biological and Human Aspects. Cambridge University Press, Cambridge, 2007. p. 310

[5] Karl Marx. Grundrisse: Introduction to the Critique of Political Economy. Penguin Books, 1973. p. 100

[6] Despite its name, the G20 includes only 19 countries – the twentieth member is the European Union, which is omitted from this table to avoid double-counting.

[7] Optimum Population Trust recently launched a program called PopOffsets that lets people in rich countries “offset” their emissions by contributing to birth control programs in the Third World. OPT particularly mentions a program in Madagascar, which is one of the 19 lowest-emitting countries.

[8] Fred Pearce. Peoplequake: Mass Migration, Ageing Nations and the Coming Population Crash. Eden Project Books, London, 2010. p. 122

[9] To avoid misunderstanding: I strongly support making birth control, abortion and other maternal health services available to women everywhere, as a basic human right. What I oppose is blaming third world women for global warming, and promoting reduced fertility as a solution. That’s not only inaccurate, it has dangerous implications, as the history of population control programs in the last 40 years has shown.

[10] Fred Pearce. Peoplequake. p.242.