Seriously Now, What Do You Think Is Going to Happen?
In view of the unlikeliness of the scenarios in the preceding post, I suppose I should mention what I think is the most likely effect of our civilization getting close to a carrying capacity: Rents will rise. There's lots of evidence increasing rents cause lower birth rates. In other words, we can expect population to level off long before any catastrophe.
The real question
The real question isn't whether there's clear evidence of current overpopulation (there isn't). It isn't even whether overpopulation is theoretically possible (it isn't the slam dunk that Malthusians think, but it's “the way to bet”). The real question is whether overshoot is likely.
Let's consider the consequences either way. If overshoot is unlikely, we don't have to worry about overpopulation until it actually happens. Since it's not actually happening, we don't have to worry about it. If overshoot is likely, we have to worry about overpopulation even if it doesn't look like a problem. In particular, we should be sensitive to even the slightest hint of population problems, even if they're anecdotal.
There are three main reasons to take overshoot seriously. First, overshoot is a phenomenon frequently observed in animals. It is rarely seen in plants. As far as ecology is concerned, humans are, of course, plants. When there are more of a species of animal there is less of what that animal eats. When there are more of a species of plant, the resources the plant needs either increase (soil) or stay the same (sunlight). The only resources that humans treat the way animals do are fossil fuels and wild fish. Both of those should be obsolete soon.
Second, in the past overpopulation theorists tended to underestimate carrying capacity. When they predicted population would level off soon, the population increased past the point they predicted. Rather than admit they made a mistake, some of them started to claim that the population would not level off but instead crash. On the other hand, now that some countries are declining in population, that theory may disappear.
Lucy: Well, look here. A big yellow butterfly. It's unusual to see one of those at THIS time of year, unless of course, it flew up from Brazil. I'll bet that's it. They DO that sometimes, you know. They fly up from Brazil.Overshoot looks like a potato chip from Brazil.
Linus: That's no butterfly! That's a potato chip.
Lucy: Well, I'll be. I wonder how a potato chip got all the way down here from Brazil!