Overpopulation and depopulation are like almost no other "unmentionable" subjects because they evoke major speculation, fears and strong opinions. As we are constantly using "ten Earth’s" worth of the planet's useable photosynthetic energy in the industrial age, by drawing upon the ancient solar deposits known as fossil fuels, this could indicate we are ten times overpopulated as ecological carrying capacity would allow.

But "too many people" sounds antisocial and harsh. Some folk like having so many "companions" (strangers around). Cities are commonly thought to be the greatest thing on Earth, despite such grave drawbacks as there being little public space anymore that isn’t fenced or paved.

No one wants to lessen the collective burden by being the one to "check out." Even so, some of us are looking at massive, involuntary die-off as a consequence of fast-dwindling petroleum for growing and distributing food. The bursting of the housing bubble could actually result from depopulation: fewer people in the cities as a result of starvation or an exodus to the rural areas.