6 ideas
A shortage of a resource raises its price, and higher prices give people a reason to search for new deposits, find substitutes and cut waste. The long-run result is that the resource becomes more plentiful and cheaper than before the shortage began. Scarcity is therefore a temporary problem that sets off its own solution, not a fixed limit.
Physical estimates of 'known reserves' are misleading because reserves are only an inventory that firms find when it pays to look. The right test of whether a resource is getting scarcer is its real price, or the labor-hours needed to buy it, over the long run. By that measure most raw materials have become steadily less scarce over centuries.
Raw materials only become resources through human knowledge of how to find, extract and use them. Oil was sludge until someone found a use for it. Because more people means more minds producing ideas, population growth adds to the true resource base over the long run instead of draining it.
In 1980 Simon bet Paul Ehrlich that any raw materials Ehrlich chose would be cheaper in real terms ten years later. Ehrlich picked five metals: copper, chromium, nickel, tin and tungsten.
More people impose short-run costs, such as feeding, housing and educating children, before they contribute anything. In the long run they bring economies of scale, bigger markets and a larger pool of inventors. Judging population growth only by its short-run burden therefore systematically overstates its harm.
When forecasting resources, food, pollution or health, rely on long historical data series of the relevant measures rather than models built on assumed physical limits. Past trends in prices, life expectancy and food output per person have consistently beaten doom forecasts based on fixed-stock reasoning. A forecast that breaks with centuries of data needs strong evidence that the conditions producing that trend have actually changed.