Will this help?
[link to www.worldwatch.org]

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Looking past the near-term concerns that have plagued population policy at the political level, it is increasingly apparent that the long-term sustainability of civilization will require not just a leveling-off of human numbers as projected over the coming half-century, but a colossal reduction in both population and consumption.

Certainly the rough-and-ready human carrying capacity estimates of the more distant past show considerable variation, ranging from fewer than 1 billion to over 20 billion. And it is obvious that it will be difficult to engender any sort of effective response to the crisis if the desired future population goals continue to be poorly understood and imperfectly articulated. It is, however, worthy of note that several investigators and organizations have developed reasonably well thought out positions on future global population optima, and those estimates have all clustered in the range of 1 to 3 billion.