Copper limits: opportunity costs.

Abstract

In the News Focus story “The coming copper peak” (14 February, p. [722][1]), R. A. Kerr describes the public debate over the long-run availability of copper and other mineral commodities. What is troubling is that despite all we have learned since the publication of Limits to Growth ([ 1 ][2]) over four decades ago, we still focus on the fact that Earth contains a fixed stock of copper. Estimates of this stock are always a very tiny fraction of the total copper in Earth, for the logical reason that long before the last copper atoms are mined, costs become prohibitive. The fatal flaw of the fixed stock paradigm is that the amount of copper humans can ultimately produce—what the U.S. Geological Survey (USGS) refers to as resources—changes over time with new technology. For example, USGS in the early 1970s estimated global copper resources at 1.6 billion tons. Its latest figure—5.6 billions tons—has more than tripled ([ 2 ][3]). ![Figure][4] Chile's copper mines. CREDIT: SEBASTIAN KAWA, TOMASZ KAWA/WIKIMEDIA COMMONS More useful is the opportunity cost paradigm, which assesses long-run availability by what society has to give up for another ton of copper ([ 3 ][5], [ 4 ][6]). It focuses on real prices, and the race between the cost-increasing effects of depletion and the cost-reducing effects of new technology. Over the past century, new technology has kept depletion at bay ([ 5 ][7]). Will this continue over the 21st century? Given the erratic course of technological change, no one knows for certain. What we do know is that global population and copper consumption grew very rapidly during the 20th century; both will grow more slowly over the coming century. We also know that a lot of copper remains in marginal porphyry deposits with 0.4 to 0.5% copper equivalent. This should make it easier than in the past for new technology to keep copper readily available at reasonable costs. 1. [↵][8] 1. D. H. Meadows, 2. D. L. Meadows, 3. J. Randers, 4. W. W. Behrens , The Limits to Growth (Universe Books, New York, 1972). 2. [↵][9] 1. K. M. Johnson, 2. J. M. Hammarstrom, 3. M. L. Zientek, 4. C. L. Dicken , “Estimate of undiscovered copper resources of the world, 2013” (U.S. Geological Survey Fact Sheet 2014–3004, 2014); . 3. [↵][10] 1. J. E. Tilton , On Borrowed Time? Assessing the Threat of Mineral Depletion (Resources for the Future, Washington, DC, 2003). 4. [↵][11] 1. A. Yaksic, 2. J. E. Tilton , Res. Pol. 34, 185 (2009). [OpenUrl][12][CrossRef][13] 5. [↵][14] 1. P. Svedberg, 2. J. E. Tilton , World Dev. 34, 501 (2006). [OpenUrl][15][CrossRef][16][Web of Science][17] [1]: /lookup/doi/10.1126/science.343.6172.722 [2]: #ref-1 [3]: #ref-2 [4]: pending:yes [5]: #ref-3 [6]: #ref-4 [7]: #ref-5 [8]: #xref-ref-1-1 View reference 1 in text [9]: #xref-ref-2-1 View reference 2 in text [10]: #xref-ref-3-1 View reference 3 in text [11]: #xref-ref-4-1 View reference 4 in text [12]: {openurl}?query=rft.jtitle%253DRes.%2BPol.%26rft.volume%253D34%26rft.spage%253D185%26rft_id%253Dinfo%253Adoi%252F10.1016%252Fj.resourpol.2009.05.002%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [13]: /lookup/external-ref?access_num=10.1016/j.resourpol.2009.05.002&link_type=DOI [14]: #xref-ref-5-1 View reference 5 in text [15]: {openurl}?query=rft.jtitle%253DWorld%2BDev.%26rft.volume%253D34%26rft.spage%253D501%26rft_id%253Dinfo%253Adoi%252F10.1016%252Fj.worlddev.2005.07.018%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [16]: /lookup/external-ref?access_num=10.1016/j.worlddev.2005.07.018&link_type=DOI [17]: /lookup/external-ref?access_num=000236075500006&link_type=ISI