How overpopulated is the planet, really?

[Jim Lane]

18. Why is your upper limit "a non-energy-assisted society of hunter-forager-gardeners"?

Even without resort to any fossil fuels, we can have "energy assistance" through renewables. For example, your calculation of habitable land excludes deserts, but uninhabited deserts can be the sites of large-scale solar energy arrays that would assist people living elsewhere.

Please don't lump me in with the technological deus ex machina types who think that we can keep growing indefinitely because science will always be there with a new fix -- nuclear power or "Green Revolution" crops or whatever. There's absolutely no question that the human population is now far too high and that the problem is getting worse. The only open question is how the correction will come, and I would have to side with the pessimists who foresee famine, plague, and war as the most likely "solutions" (as opposed to a population that declines because higher living standards mean people don't need to have a lot of children to ensure survival in their old age).

Nevertheless, there's a big gap between saying that seven billion is too high and saying that anything over 50 million is too high. I recall seeing some other analysis that settled on one billion as the sustainable human population. Of course, just getting to one billion (without the widespread famine etc.) will be difficult enough.