I'm happy to see that the survey got a significant proportion of people thinking. It's also fascinating that meat-eaters would be more pessimistic than others on farmed animal suffering.
While I have the same intuition as you, I wonder if the author means other kinds of metal could be the bottleneck. Also, my intuition points that minerals are not a bottleneck if we can make it cost-efficient to extract extraterrestrial minerals (ie, asteroids and comets). But can we?
I described it more in post 1, but the constraints on minerals are on the timing (the time required to open mines) and on scale (the quantities required are too big, the large majority of metals is expected to peak by 2100 given exponential growth).
What matters the most, though, is energy - mining, refining and smelting require a lot of energy (mostly from diesel trucks and coal for high heat manufacturing, both very difficult to substitute). The grade of ores is already declining. Given infinite energy, we could mine common ground and get anything we want, but this is of course impossible. Mining from common ground would actually be the prospect of space mining, since there is no geological process that makes concentrated ore on asteroids and other planets.
Overall, the amount of metals we can mine depends on the amount of energy at our disposal. Which is a problem since it will decline.
As said above, you can find in the additional doc a full section on metals.
Thank you Julia for this well-written post! I had been considering writing something along these lines (because of the increase in EAs working in policy and under public scrutinee), and I am very, very glad that this is not only taken seriously, but also actively being worked on.
That is a great initiative! I'm a graduate student focusing on international relations, and it's not obvious what I should be doing next to maximise my impact. I'll make sure to look it up and contact you once I've gotten a few things out of the way.
I am not American, but may I share on my feed your message ?