Many environmentalists believe that environmental destruction is a product of "overpopulation", and that the world is already "full up". So are population reduction strategies essential to solving the climate crisis?
At best, population control schemes focus on treating a symptom of an irrational, polluting social and economic system rather than the causes. In China, for instance, such measures haven't solved that country's environmental problems.
At worst, populationist theories shift the blame for climate change onto the poorest and most vulnerable people in the Third World.
They do not address the reasons why environmental damage, or even instances of overpopulation, happen in the first place and they divert attention away from the main challenge facing the climate movement — the urgent need to construct a new economy based on environmentally sustainable technologies and the rising of living standards globally.
For at least 200 years, "overpopulation" has been used to explain a host of social problems such as poverty, famine, unemployment and — more recently — environmental destruction.
Between 1798-1826, the conservative English economist and clergyman Thomas Malthus published six editions of his influential Essay on the Principle of Population, which argued that population growth inevitably outstrips food production.
Malthus' argument was that the English working class was poor because they were too numerous, not because they were exploited. He opposed welfare or higher wages because, he said, that would allow the poor to survive, and breed, compounding "overpopulation" and leading to more poverty.
Malthus was wrong about food production. In the last two centuries, food production has grown faster than population — his theories nevertheless gained wide acceptance among the English elite of the day because they provided a convenient excuse to blame the poor for their own predicament.
In the 1960s, Malthus' anti-human ideas were resuscitated by a new generation of conservative theorists who argued that the people of the global South remained hungry because there were too many to feed. US environmentalist Paul Erlich, in his 1968 bestseller The Population Bomb, argued for population control measures in the Third World to, he said, avert an ecological crisis.
Populationists like Erlich usually don't question the unequal allocation of resources on a global scale. Nor do they admit that high birth rates in the Third World are largely a response to dire poverty.
Instead, they look at the world's resources as though they were dividing up a pie: reduce the world's population and those remaining will each get a bigger slice. They fail to address the question of power and, therefore, unequal access to global resources.
Most environmentalists who believe that population control is necessary would still reject the most extreme forms of the populationist argument.
But the fact remains that the real driver of climate change is not population growth but a market economy locked into burning fossil fuels for energy. The corporations that profit most from taking the lion's share of global resources are the same polluting industries that, today, are resisting the necessary shift away from carbon-based economies.
Populationists tend to downplay the question of power. As renowned US ecologist Barry Commoner commented, populationist solutions to environmental destruction are "equivalent to attempting to save a leaking ship by lightening the load by forcing passengers overboard".
He went on to ask the question that populationists tend to ignore: "One is constrained to ask if there is not something wrong with the ship".
The world is not experiencing runaway population growth. Global population is growing, but the rate of growth is slowing. It peaked in the 1960s and has been in decline ever since. Global population grew by 140% between 1950 and 2000. Experts predict a further rise of 50% between 2000 and 2050, and just 11% in the 50 years after that.
The simplistic view that population control is the main way to reverse runaway climate change can obscure debate over other measures. These include: the rapid replacement of fossil fuel-generated energy with renewables; improvements in energy efficiency; and the introduction of sustainable agricultural methods.
In rich countries such as Australia, we need to campaign for environmental outcomes that sharply reduce Third World poverty, including cancelling debt owed to First World nations.
It is well documented — including in the wealthy countries — that birth rates fall as living standards rise. Furthermore, the greater economic independence women have, and the more control women have over their own bodies, the fewer children they have. Development, along with women's emancipation, is the best contraception.
It is undeniable that parts of the world are overcrowded, and that land degradation through over-logging, erosion, over-hunting, over-fishing and poor waste disposal are massive problems in the countries of the global South.
These social, economic and environment problems are interlinked, and point to the real causes of overpopulation and environmental destruction of the Third World — extreme poverty. Liberty and justice and rights for the poor, especially women, have to be our concern.