How long 'til we're barely surviving?

Noam Chomsky was in Chapel Hill a couple of weeks ago. I read in the October 6 Independent Weekly yesterday that Dr. Chomsky predicts, according to reporter David Fellerath, that "in 500 years, humans will be barely surviving." Fellerath writes that Chomsky cited nuclear war and global warming as the biggest threats.
    Chomsky doesn't define "barely surviving." Perhaps a precipitously declining human population? Or a much diminished quality of life for all but the remaining rich? The latter might lead to the former, in any case, as the have-nots rise up and rabble (some with those nuclear weapons Chomsky cites).
    In either case, I wouldn't have given us 500 years myself, but Chomsky is much better read than I am, so maybe he's right. Not that he or I (or you) will be around to find out.
    I suspect that "barely surviving" will come sooner, on the evidence of the sharp recent upward trending of one particular curve, the graph of human population growth (the thick red line in the chart below:

    The curve has been very steep for several decades and is accelerating; it's frankly a wonder that we're not just barely surviving already. Maybe we are but just haven't noticed it yet?

That's certainly true for other species on the planet. The effect on other species is and will continue to be catastrophic in terms of the size (or existence) of their populations. Another way of stating human population growth is in terms of humans' biomass relative to the total biomass on the planet. From the article, "Differential Reproduction - An Exponentialist View":

A sobering [Malthusian¹] thought is that as the global human population increases its percentage of the total biomass so many other species are going extinct [emphasis mine].

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1. The Reverend Thomas Robert Malthus (1766-1834), who "observed that sooner or later population gets checked by famine, disease, and widespread mortality."