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Contributed by Andrea Rinaldo, December 22, 2012 (sent for review August 7, 2012)
Abstract
Population growth is in general constrained by food production, which in turn depends on the access to water resources. At a country level, some populations use more water than they control because of their ability to import food and the virtual water required for its production. Here, we investigate the dependence of demographic growth on available water resources for exporting and importing nations. By quantifying the carrying capacity of nations on the basis of calculations of the virtual water available through the food trade network, we point to the existence of a global water unbalance. We suggest that current export rates will not be maintained and consequently we question the long-term sustainability of the food trade system as a whole. Water-rich regions are likely to soon reduce the amount of virtual water they export, thus leaving import-dependent regions without enough water to sustain their populations. We also investigate the potential impact of possible scenarios that might mitigate these effects through (i) cooperative interactions among nations whereby water-rich countries maintain a tiny fraction of their food production available for export, (ii) changes in consumption patterns, and (iii) a positive feedback between demographic growth and technological innovations. We find that these strategies may indeed reduce the vulnerability of water-controlled societies.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: andrea.rinaldo{at}epfl.ch.
Author contributions: S.S., A.R., and P.D. designed the research; S.S., A.M., and P.D. developed the analytic methods; S.S. and P.D. analyzed the data and performed numerical simulations; A.R. and A.M. provided additional ideas and concepts; and S.S., A.R., A.M., and P.D. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1222452110/-/DCSupplemental.
See Commentary on page 4161.
Freely available online through the PNAS open access option.
- aDepartment of Physics and Astronomy, University of Padua, Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia and Istituto Nazionale di Fisica Nucleare, 35131 Padova, Italy;
- bLaboratory of Ecohydrology, École Polytechnique Fédérale Lausanne, 1015 Lausanne, Switzerland;
- cDipartimento di Ingegneria Civile, Edile ed Ambientale, University of Padua, 35131 Padova, Italy;
- dDepartment of Environmental Sciences, University of Virginia, Charlottesville, VA 22904-4123; and
- eLaboratory of Environmental Fluid Mechanics and Hydrology Laboratory, École Polytechnique Fédérale Lausanne, 1015 Lausanne, Switzerland
Contributed by Andrea Rinaldo, December 22, 2012 (sent for review August 7, 2012)
Abstract
Population growth is in general constrained by food production, which in turn depends on the access to water resources. At a country level, some populations use more water than they control because of their ability to import food and the virtual water required for its production. Here, we investigate the dependence of demographic growth on available water resources for exporting and importing nations. By quantifying the carrying capacity of nations on the basis of calculations of the virtual water available through the food trade network, we point to the existence of a global water unbalance. We suggest that current export rates will not be maintained and consequently we question the long-term sustainability of the food trade system as a whole. Water-rich regions are likely to soon reduce the amount of virtual water they export, thus leaving import-dependent regions without enough water to sustain their populations. We also investigate the potential impact of possible scenarios that might mitigate these effects through (i) cooperative interactions among nations whereby water-rich countries maintain a tiny fraction of their food production available for export, (ii) changes in consumption patterns, and (iii) a positive feedback between demographic growth and technological innovations. We find that these strategies may indeed reduce the vulnerability of water-controlled societies.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: andrea.rinaldo{at}epfl.ch.
Author contributions: S.S., A.R., and P.D. designed the research; S.S., A.M., and P.D. developed the analytic methods; S.S. and P.D. analyzed the data and performed numerical simulations; A.R. and A.M. provided additional ideas and concepts; and S.S., A.R., A.M., and P.D. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1222452110/-/DCSupplemental.
See Commentary on page 4161.
Freely available online through the PNAS open access option.
Water-controlled wealth of nations
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