Running out of oil, yes. We’ve all been concerned about that for many years and everyone anticipates a time when the world’s underground petroleum reserves will have been pumped dry. But oil is just an organic substance that was created by natural biological processes; we know that we have a lot of it, but we’re using it up very rapidly, no more is being created, and someday it’ll be gone. The disappearance of elements, though—that’s a different matter. I was taught long ago that the ninety-two elements found in nature are the essential building blocks of the universe. Take one away—or three, or six—and won’t the essential structure of things suffer a potent blow? Somehow I feel that there’s a powerful difference between running out of oil, or killing off all the dodos, and having elements go extinct.

As it happens, we are building a lot of flat-screen TV sets and computer monitors these days. Gallium is thought to make up 0.0015 percent of the Earth’s crust and there are no concentrated supplies of it. We get it by extracting it from zinc or aluminum ore or by smelting the dust of furnace flues. Dr. Reller says that by 2017 or so there’ll be none left to use. Indium, another endangered element—number 49 in the periodic table—is similar to gallium in many ways, has many of the same uses (plus some others—it’s a gasoline additive, for example, and a component of the control rods used in nuclear reactors) and is being consumed much faster than we are finding it. Dr. Reller gives it about another decade. Hafnium, element 72, is in only slightly better shape. There aren’t any hafnium mines around; it lurks hidden in minute quantities in minerals that contain zirconium, from which it is extracted by a complicated process that would take me three or four pages to explain. We use a lot of it in computer chips and, like indium, in the control rods of nuclear reactors, but the problem is that we don’t have a lot of it. Dr. Reller thinks it’ll be gone somewhere around 2017. Even zinc, commonplace old zinc that is alloyed with copper to make brass, and which the United States used for ordinary one-cent coins when copper was in short supply in World War II, has a Reller extinction date of 2037. (How does a novel called The Death of Brass grab you?)

Zinc was never rare. We mine millions of tons a year of it. But the supply is finite and the demand is infinite, and that’s bad news. Even copper, as I noted above, is deemed to be at risk. We humans move to and fro upon the earth, gobbling up everything in sight, and some things aren’t replaceable.

Solutions will be needed, if we want to go on having things like television screens and solar panels and computer chips. Synthesizing the necessary elements, or finding workable substitutes for them, is one obvious idea. Recycling these vanishing elements from discarded equipment is another. We can always try to make our high-tech devices more efficient, at least so far as their need for these substances goes. And discovering better ways of separating the rare elements from the matrices in which they exist as bare traces would help—the furnace-flue solution. (Platinum, for example, always in short supply, constitutes 1.5 parts per million of urban dust and grime, which is ever-abundant.)

But the sobering truth is that we still have millions of years to go before our own extinction date, or so we hope, and at our present rate of consumption we are likely to deplete most of the natural resources this planet has handed us. We have set up breeding and conservation programs to guard the few remaining whooping cranes, Indian rhinoceroses, and Siberian tigers. But we can’t exactly set up a reservation somewhere where the supply of gallium and hafnium can quietly replenish itself. And once the scientists have started talking about our chances of running out of copper, we know that the future is rapidly moving in on us and big changes lie ahead.