One of my associates is currently involved in a study to determine the ceiling population of this country. And to a lesser extent the capacity of the planet! Have read some of the initial briefing material and its very interesting, as the audience is mostly department of environment and sustainability, which is sponsoring a symposium next year in August. Main drivers are around new and emergent technologies (including GM crops and animals). Also, you guessed it. The effects of climate change (which for some reason they qualify as cyclical :-k , so much for anthropogenic). Lastly and most interesting are questions around the future of the human population. Look forward to the bibliography they are putting together, but would be interested if anyone else has seen papers that discuss this. Have searched goggle and other network sites, but not much around. Who else can find some material (legit) around this kind of work).