Compared to personal pronoun use, especially in situations with multiple potential referents, "less" and "fewer" have a lesser (heh!) potential for creating confusion because changing one for the other doesn't obviously change the amount or kind of information. Even if the use feels wrong ("there were less people") it's still clear what was meant.
Also, there's nothing implicitly wrong with liberal arts, as mathematics is one of them.
The population doubled over the last 50 years, and civilization spread in the same time period. You're not going to see the same pattern over the next fifty years as the current decadal growth rate is one third of what it used to be fifty years ago, and unlikely to increase again. Likewise, the same doubling of installed PV capacity, for example, took only something like three years in the recent decade, so even your doubling or even quadrupling of needs over five decades would amount to almost a blip in the short term. Fifty year predictions or social and technical development are completely off anyway so I'm not going to discuss them.
Also, PV panels require no rare earth elements and even wind turbines could manage without them, except that for some wind turbine manufacturers it's apparently more convenient at the moment to use them. I've already responded to this bullshit so many times that I've ultimately come to regard any mention of "rare earths" in connection to solar power as the shibboleth of the ignorant masses that never bother to educate themselves on things they're so eager to complain about.
"The value of marriage is not that adults produce children, but that children produce adults." -- Peter De Vries