Back in 1980, two scientists made a famous wager. Biologist Paul Ehrlich thought that the planet's growing population was going to run out of natural resources. Economist Julian Simon, in contrast, thought that human ingenuity would prevent a crisis. So they bet on how the price of five metals would change over a decade. Ehrlich predicted that shortages would kick in, and prices would skyrocket. But, as Thomas Graedel of Yale University explains, "The prices fell, and Ehrlich paid Simon $576.07."
That bet got a lot of publicity. Graedel points out, however, that it really didn't settle the issue: "They were both betting from positions of professional philosophy and not knowledge of the amount of resources ultimately available in the ground."
Now, a new study by Graedel and others is trying to add some numbers on the world's metal supply to the debate. And although it concludes we are nowhere near running out of some rare, economically important ores, it does suggest that humans are having a major impact on supplies. Nearly two-thirds of known copper in the United States, for instance, can now be found in landfills or products such as pipes.
Graedel says data on metal supplies is hard to come by. In part, that's because mining companies tend to look at the short term, focusing on known, accessible reserves of ore. "Basically, the effort goes into what one might be doing in the next five or 10 years, not what is likely to happen in the next 30 or 40," he says.
So Graedel and his colleagues decided to take that long view. They looked at metals important to industry that are relatively scarce, like copper and zinc. They wanted to know: How much does the entire planet have, and how much have we already dug up? "It's a giant accounting problem. And we get information from a lot of different places, realizing that this is never going to be totally accurate," Graedel explains.
Still, it's accurate enough to come to some provocative conclusions. Take copper. It's in everything from electrical wires to coins. The United States is a major producer. But Robert Gordon, another Yale researcher, says look for copper in this country and you'll find "roughly a third in the ground, a third in use, and a third in the trash."
That's right — the researchers estimate that two-thirds of our copper is in things like landfills, gadgets and plumbing. Worldwide, the report estimates that a quarter of the planet's copper has already been mined. Gordon says that if the entire population of the planet wanted to use copper the way Americans do now, "you would end up using all the copper that even the optimistic geochemists think is in the Earth's lithosphere and ore."
Some experts question a few of the study's numbers, like an estimate that the planet has just over 1.5 billion tons of copper. A recent report from the U. S. Geological Survey suggests that there's probably more. Still, the report in the Proceedings of the National Academy of Sciences is fueling discussion, with its estimates that humans have probably gone through about 26 percent of the world's copper and 19 percent of the zinc.
William Clark, who studies resource sustainability at Harvard, says he was stunned when he saw those numbers. "The observation that human activity on the planet has become so ubiquitous and large that we've shifted half the stock of a major metal from natural locations to human locations is just a different way of thinking about things," Clark says.
Yale's Graedel says that's all they were trying to do: make people think about the future of these metals in a new way. "I would hope that this wouldn't be viewed as sort of a Chicken Little-type, 'sky is falling' situation. What we've tried to do is to put numbers on a discussion about the rate at which we're using materials and the ways in which we're using materials."
He and his colleagues say that a supply crunch could come first for the rarest metals that industry finds useful, like platinum, which has a unique ability to catalyze chemical reactions. This can make it hard to find substitute metals to replace it.
But the researchers don't believe the planet is on the brink of a metals crisis. For one thing, the metal hasn't disappeared, it's just moved to a different location. So it could be recycled. Or, new technology might reduce demand. Still, the scientists are betting that — ultimately--metals will become scarcer, and prices will rise.