The Malthusian theory was once thought to be, pretty much, relegated to the status of a curious footnote in the history of economic thought. Henry George's chapters on poverty and subsistence in Progress and Poverty stand as the definitive marshalling of the abundant logical ammunition against it. Toward the end of the 20th century A.D., however, an influential crew of neo-Malthusians brought the theory back. Also, modern Malthusians such as Paul Ehrlich, Lester Brown and the happy fun guys that called themselves the Club of Rome have added a wrinkle, claiming that subsistence can only keep ahead of population growth at the cost of an unsustainable level of envronmental harm.
Seven+ billion people is a lot of people, no doubt about it. Is it too many? The neo-Malthusian view seems reasonable, especially when fortified by such statistics as these (published by the Population Institute):
Indeed, these statistics show that there is plenty of poverty. But do they indicate overpopulation? We mustn't let ourselves be bamboozled by numbers. A hundred million people is an increase of roughly half a percentage point. The Earth has the capacity to absorb such numbers. Today, vast capacities of the earth's resources lie unused. Still more arable land is being destroyed by unsustainable farming or settlement practices. And even more of the earth"s "carrying capacity" is being used to make weapons, or toys, or crops for export — all manner of things that, despite the wretched poverty of so many of the world's people, no one needs for survival.
The United Nations Food and Agriculture Organization estimates the earth has the capacity to grow food for some 33 billion people. Critics will protest that such tremendous yields would require the dubious efficiencies of monoculture, petrochemical fertilizers and genetic engineering — and that is probably true. Yet it is also true that, in all liklihood, we'll never need to grow anywhere near that much. Current UN estimates project a plateau population of around 9 billion people about midway through this century (and it's worth noting that every time this top figure has been estimated, it has been lower). Modern "industrial" farming techniques make it easier to run large-scale, remotely-managed corporate farms, but they are not needed to create high yields of nutritious food.
The total area or arable land in the world today, according to the CIA World Factbook, is 3.98 billion acres. The definition used is land that is under cultivation, or temporarily fallow (for less than five years) — but it excludes abandoned land resulting from shifting cultivation. Enough arable land exists in India to give each person in the country approximately half an acre. In famine-ravaged Ethiopia, each person could have three-quarters of an acre of arable land. Africa, the poorest continent, has 20.2% of the world's land area, and only 13% of its population. North America has a whopping 2.1 acres of arable land per person!
While it is true that many regions have experienced frightening rates of deforestation and topsoil loss, these problems result from land hoarding, not overpopulation. Around the world, deforestation and desertification result from peasants pushing into sub-marginal land while high-quality farmland is either held out of use entirely, or used to grow export crops. In Brazil, for example, the situation became so acute that squatters have been massacred for occupying remote, unused areas of privately-held ranches. A large, organized movement has grown around the peasants' demand simply to be allowed to use land that others don't feel like using, just now.
Two factors consistently correlate with high birth rates: poverty, and poor education. It has long been known that when living standards rise in a community, birth rates tend to decline; this widely-documented phenomenon is called the "demographic shift" (Henry George referred to it in 1879). Recently, however, another kind of demographic shift has been observed. Where women have had access to education and media, birth rates have showed significant declines — even when income levels had not increased. It is instructive to note, in the table below, the correlations between lower life-expectancy and literacy figures for women, and the standard measures of poverty.
The most distasteful part of the recent spate of neo-Malthusian cant has been the notion that irresponsible poor people should be forcibly stopped from procreating, lest their hungry numbers start to wrest control of the resources held by more "civilized" sorts. In an economy where more energy and resources are spent in taking pictures of children than are used to feed children in the rest of the world, such advice is preposterous. It is true that the developing world cannot raise its standard of living to "Western" standards, using the same wasteful methods, without causing horrible damage to the natural environment. However, "Western standards" are by no means the only game in town. The long-term trend has been for more human satisfaction to be provided with less pollution. Environmentally sustainable technology for industry, food and energy production is available today. The reasons why it is not used extensively have more to do with politics and economics than with technical feasibility. (It could be that the rise of truly global environmental dangers, in the form of climate change, will accelerate these trends.)
It remains an unfortunate fact that the world's poorest, most corrupt, most disorganized and environmentally endangered nations are the ones with the highest birth rates (of course, they have fairly high death rates as well; Africa's population actually decreased in the 1990s). The neo-Malthusians identify genuinely dire problems. But it is time we got it straight: poverty is not caused by overpopulation. The syndrome of social problems commonly called "overpopulation" is actually caused by poverty. Therefore, the problem cannot be solved by forcing people to restrict their fertility. Our world still has sufficient resources exist to feed every new child — but those resources are held idle, or devoted to frivolous uses.
For further reading: Malthus: Still Wrong After All These Years