“reserve” estimates refer to current economic viability.

The lithium production market is still a fairly new market, so even though USGS and others have made some reserve and resource estimates already, it is premature to make any firm conclusions about future resource discovery and production. We’ve learned at least one lesson from the peak oil debate: higher prices do indeed spur innovation and increased production, at least they have in the U.S. Interestingly, almost the entire increase in global oil production has come from an increase in U.S. oil production. That is, the rest of the world has barely managed to stay in place on the treadmill of oil production, even in the face of far higher oil prices.

With respect to the notion of peak lithium, there is a substantial difference between this commodity and oil because there are many ready substitutes for lithium that can be used in the manufacture of batteries. The USGS report cited by OP states: “Substitution for lithium compounds is possible in batteries, ceramics, greases, and manufactured glass. Examples are calcium and aluminum soaps as substitutes for stearates in greases; calcium, magnesium, mercury, and zinc as anode material in primary batteries; and sodic and potassic fluxes in ceramics and glass manufacture.” These substitutes may all face similar resource constraints as lithium, but there is a fundamental difference between changing battery chemistries and finding substitutes for oil more generally.

Source: https://www.greentechmedia.com/articles/read/is-there-enough...