Reply #12: There are widely varying estimates

[bananas]

Here are two references.
The first lists a bunch of estimates - take your pick.
The second is a quote from Paul Ehrlich, famous author of "The Population Bomb", who doesn't consider population the #1 problem anymore - which is the point I was trying to make in my post.

"Ecologists, economists and other scientists and policy makers from all over the world have attempted to estimate the human carrying capacity of the planet. The results vary dramatically depending on the methods used and the assumptions made. The variety of methods employed and assumptions made result in a broad range of estimates varying from as low as fewer than one billion people to as high as 1,000 billion."
http://www.ilea.org/leaf/richard2002.html

"Paul Ehrlich, famed ecologist, answers readers' questions
Q. Do you still believe -- as you've said in the past -- that population growth is the No. 1 environmental problem, and that coercion "for a good cause" to slow population growth should still be our first priority? -- Peter Walker, Eugene, Ore.
A. I think trends in population are in the right direction, but still too slow. China, of course, has done miracles with a relatively coercive program, but I think now we could get birthrates where they belong without much coercion. The worst population problems are in rich nations, especially the U.S., because of their very high rates of consumption. Consumption is, in Anne's and my view, the single most difficult problem to deal with now -- as we discuss extensively in One With Nineveh. Times have changed -- population control, especially among the rich, is critical, but consumption control today is probably more critical and certainly tougher to achieve."
http://www.grist.org/comments/interactivist/2004/08/09/ehrlich/index1.html