Before we move on from our starting point, I wanted to have a closer look at one claim made on Hanson's website that I found particularly worrying. The claim goes like this: "With sustainable agriculture and economy, the Earth could only feed 1 billion people. We can currently only support a population of more than 6 billion because we're using non-sustainable agriculture that's dependent on oil. So, when oil runs out, we have a big problem."
Now, I wanted to know moure about the source of that claim - in particular, where that number of 1 billion comes from. Hanson links to this page for reference: http://www.paulchefurka.ca/Population.html (By the way, the whole website http://www.paulchefurka.ca/ seems interesting - but that's a different story, I haven't had the time yet myself to take a closer look at it). Now when you go through that text, you'll find that it just observes a correlation between the population "explosion" on Earth and the onset of the "Oil Age" around the year 1900, and concludes that the number of people the Earth can support without oil is the number of people back then, somewhat more than 1 billion. Now, we know that correlation doesn't mean causality - just because more and more people started populating this planet around the time the wide-spread use of oil began, it doesn't necessarily mean that the latter development caused the former. (For example, there is no mention of the role of advances in medicine like the use of antibiotics.) And even if that were the case, it wouldn't mean that world population was already at it's possible maximum before the advent of oil. So, the good news is that the number of 1 billion is questionable, to say the least. It's not much more than an assumption.
What do we learn from this? Firstly, stay critical. Don't just believe things you read, try to get to the source of statements and see if they're plausible. Secondly, however, even if the concrete number doesn't turn out to be true, the underlying concepts of "carrying capacity" and "overshoot" that are explained on Paul Chefurka's page are worth keeping in mind. It is plausible that our finite planet can only feed a limited number of people. It is possible that the use of non-sustainable resources and techniques can increase the planet's carrying capacity for a limited amount of time. (Regardless of the question if our food industry is sustainable or not, people who have seen the movie "We feed the world" - I haven't, yet - tell me that you don't really want your food to be produced that way.) And it is thus possible that an "overshoot" occurs, which might end badly once the point comes when that "artificial" increase of carrying capacity can't be sustained any more. The question is if there are more scientific studies of these issues out there, which might give a more unbiased picture of where we stand, and if, given the current and projected world population, we already have a problem or not. If anyone reading this is knowledgeable with regard to that question, I'd be interested to learn more.
(As a small aside, ironically in Germany we have problems with a declining population that brings our old-age pension system into trouble because fewer young people have to pay for more old people's pensions. Which is why the younger people - me included - now have to save some money for their own retirement, and are looking for profitable ways to invest that money. If you want to see some strange effects that come from loads of money looking for ways to be invested profitably, go see the movie "Let's make money". If you're thinking about adding some alternative investments to your portfolio, maybe giving microcredits to people in developing countries or investing in companies listed in a "green" index such as the German NAI may be worth taking into consideration.)