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 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. The neo-Malthusian view seems reasonable, especially when fortified by such statistics as these (published by the Population Institute): These charts show one of the most troubling trends in world demographics.
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.
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.
Ever-increasing numbers of people in the worlds poorest areas are moving into cities.
This has placed great pressures on already-troubled nations.