Diaz, R. J., & Rosenberg, R. (2008). Spreading dead zones and consequences for marine ecosystems. Science, 321(5891), 926-929.
FAO (Food and Agriculture Organization). (2011). The state of the world’s land and water resources for food and agriculture. http://www.fao.org/docrep/015/i1688e/i1688e00.pdf. Viewed 1 May 2014.
FAO (Food and Agriculture Organization). (2014). FAOSTAT. http://faostat3.fao.org/faostat-gateway/go/to/download/E/EL/E. Viewed 1 May 2014
Lal, R. (2006). Enhancing crop yields in the developing countries through restoration of the soil organic carbon pool in agricultural lands. Land Degradation & Development, 17(2), 197-209.
Lobell, D. B., Burke, M. B., Tebaldi, C., Mastrandrea, M. D., Falcon, W. P., & Naylor, R. L. (2008). Prioritizing climate change adaptation needs for food security in 2030. Science, 319(5863), 607-610.
Loveland, T. R., & Acevedo, W. (2006). Land cover change in the Eastern United States. Status and Trends in Eastern United States Land Cover. Pretty J, Noble AD, Bossio D, Dixon J, Hine RE, Penning de Vries FWT, and Morison JIL. (2006).
Resource-Conserving Agriculture Increases Yields in Developing Countries. Environmental Science and Technology, 40(4), 1114-1119.
Ray, D. K., Mueller, N. D., West, P. C., & Foley, J. A. (2013). Yield trends are insufficient to double global crop production by 2050. PLoS One, 8(6), e66428.
There are several potential concerns with the data used for this analysis. It is reported to the UN by each country, and it is possible that the methodologies used to generate the data within each country vary over time (especially as governments change). By looking at the percentage of global land area devoted to agriculture and the total land area devoted to agriculture, you can see that the FAO estimate of global land area varies by about 2%. This is troubling as global land area should be relatively static (with small changes coming from sea level rise, coastal erosion and deposition, etc.). On the other hand, some of the errors in each country’s data may average out in the global summary, and this is the best data available. Finally, saying that we would need 34 million new km2 of farms and ranches is useful as a thought experiment, but is certainly not intended to be an accurate prediction. I simply multiplied current total agricultural area by 0.7 to get the estimate, despite the fact that the actual suitability of newly converted lands for agriculture would vary widely, and that many other factors would influence how much land would be needed. Some of the pasture included in that figure could be viable grassland habitat, just as TNC manages several ranches that are grazed as a conservation management strategy.