There are probably 1 billion people in the developed world enjoying a life of "consumerism, fossil-fuel burning and so on", plus a tiny minority composed of the elites of the global south. You may add roughly another billion people from the emerging economies (i.e. the BRIC countries), who have lesser, but rapidly growing, rates of per capita consumption.
We are already 1-2 billion people living what we'd consider a "normal life" by modern standards, maybe another 3-4 billion with tolerably low levels of resources, and 1 more billion in the most absolute poverty. Heck, I have not seen any study to confirm, but I suspect that the average pet in the US is better taken care off that the average child in a 3rd world shanty town (and probably have a longer expected lifespan too)!
So, yes, the population bomb is a problem, but it gets amplified by the per-capita expenditure, and the 80-96 percentile have a disproportionate weight on the overall effect.
(Contrary to OWS retoric, my opinion is that the "one percenters" are not the main part of the problem. They are not only too few, but subject to time and space limitations that prevent them to consume as much as their wealth would predict. At the end of day, they will use most of their money to make more money or gain political influence. What they use that influence for is yet another dimension of our predicament).