The World in 2050_ Four Forces Shaping Civilization's Northern Future - Laurence C. Smith [27]
To enter this debate it is simplest to start off with finite, nonrenewable raw commodities that are essential to modern human enterprise, like metals and fossil hydrocarbons (we will take up water, food, and renewable hydrocarbons later). Are we running out?
Let us tabulate estimates of known geological deposits that we have already discovered and know to be of sufficiently high grade that they could be profitably developed tomorrow if necessary. These quantities are called proved reserves, or simply reserves. It is then a simple calculation to divide the world’s total reserves by their current rate of depletion (i.e., their annual production rate) to see how many years are left until the remaining reserves run out. This simple measure is called the “R/P” (reserve-to-production) ratio or the “life-index” of a resource. On the following page are some examples of global proved reserves (both in total and per capita) and R/P ratios for twenty-two of the Earth’s especially useful nonrenewable resources.
Two observations leap from these data. The first is that the absolute abundance of a reserve is not always a good predictor of when it might be depleted. The current world reserve of oil—despite being the second-largest at nearly two hundred billion metric tons (about twenty-four metric tons for every man, woman, and child alive on Earth)—is scheduled to run out in just 42 years at current production rates, whereas the supply of magnesium would appear to last for 4,481 more years, despite having only 1/75th the abundance of oil. Platinum would appear to have 150 years left despite being more than two million times scarcer (just 100 grams for every man, woman, and child).
The second observation is that there is an enormous range in R/P ratios, with some reserves projected to be exhausted as soon as eight years from now and others not for hundreds or even thousands of years. The known proved reserves of magnesium, for example, appear sufficient to carry us to the year 6491 at today’s rate of consumption. Interestingly, commodity prices do not necessarily reflect this. For example, one can buy silver and lead much more cheaply than platinum, despite their having shorter index lifetimes.
Proved World Reserves of Some Important Natural Resources
(Sources: PB 2008; British Geological Survey 2005)98
Why is this? Can the markets be wrong? Before you rush off to hoard lead ingots, note that there are serious flaws with the use of this simple “fixed-stock” approach to project future resource scarcity. An obvious one is that not all “nonrenewable” resources are irreparably destroyed when used, meaning they can be recycled. This is particularly true for metals. Lead and aluminum are highly recycled today, for example. A second flaw is that the size of proved reserves is not truly fixed but tends to rise over time as new deposits are found, extraction technologies improve, and commodity prices go up. The latter can make a low-grade deposit become economically viable, thus adding it to the list of proved reserves despite no new geological discoveries whatsoever. And to an economist, a big problem with the R/P ratio is its implicit assumption that the cost of production for all those tons is equal around the world, when we know that is not the case.
In principle there is sufficient aluminum, iron, zinc, and copper within the Earth’s crust to last humanity for millions of years, if we had the energy and technology and desire to extract such dilute materials and didn’t object to mining away vast portions of the planet from beneath our feet. Mineral “depletion,” at least in the strictly