It's long been a truism of environmental thinking that human population increase is going to have negative environmental consequences. But a survey of current demographic thinking and analysis has some surprising ideas.
SAN DIEGO OR TOKYO?
Which of these cities has the largest carbon footprint: Tokyo with a population of almost 13 million, or San Diego with a population of 3 million in a milder climate? If you're a student of American culture, you must know that San Diego has a far greater carbon footprint. Not just per capita, but cumulative. All those cars, all that air conditioning, all that cement, all that irrigated lawn.
OTHER DEMOGRAPHIC "DISCOVERIES"
Apparently it is not writ in stone that more developed countries will have continuously lowering birth rates. That only poor countries will reproduce. This has been known in population studies as "the demopraphic divide." Some develoed countries are now seeing a rise in the birthrate, not simply growth by immigration.
In some wealthier cultures it now seems that well-off couples may decide to opt for children rather than another car or more expensive vacations. Imagine that.
In temperate climates, say some political demographers, it may be beneficial to have increasing population so you don't end up with a tiny working age segment trying to support a larger number of aged retirees. They also note that most political schemes to pump up the national birth rate in places like France and Italy have not worked. China's negative birthrate pressure does have an effect there.
A couple interesting references: Developed nations and population decline.
Population growth, urbanization and global warming.