Crop Diversity

Many of the same issues ecologists seek to understand in “natural” systems are equally applicable to agricultural and food systems. I recently collaborated with scientists at the Global Crop Diversity Trust and at the International Center for Tropical Agriculture to investigate how the diversity of global food supplies has changed over the past 50 years.

NMDS of diets
Diet composition for 151 countries in 1961, 1985, and 2009. Each dot is a country and the circles represent the magnitude of the country-to-country variation in diets in each year. This variation has declined dramatically (as evidenced by the size of the circles) over 50 years. The arrows show the trajectory of five countries over time as they move toward the center of the circle (which represents a standard “global mean” diet).

We found evidence that, at the country level, the diversity of crops contributing to diets has remained stable or increased over time. At the same time, there has been a fairly dramatic homogenization trend, such that countries are becoming more and more similar to each other in their diets.

The article is open-access and is available for download from PNAS. The story has also been covered by NPR, NBC News, the BBC, and TIME magazine.


Khoury, C., A.D. Bjorkman, H. Dempewolf, J. Ramirez-Villegas, L. Guarino, A. Jarvis, L. Rieseberg, P.C. Struik. 2014. Increasing homogeneity in global food supplies and the implications for food security. Proceedings of the National Academy of Sciences 111: 4001-4006. (open-access link)

We have continued to build on this study by conducting an assessment of the degree of interdependence among countries on plant genetic resources. This work was published as a research paper in Proceedings of the Royal Society B and as a complementary policy brief in advance of the 6th meeting of the Governing Body of The International Treaty on Plant Genetic Resources for Food and Agriculture (established by the Food and Agriculture Organization of the United Nations). There is a very nice blog post about the study here, as well as articles in the Washington PostBBCNational Geographic, and NPR.

origins of crop species
This map shows where many of our crop species originated – and where much of the genetic diversity of those species is still located. See links above for a larger version.


Khoury, C.K.H.A. AchicanoyA.D. BjorkmanC. Navarro-RacinesL. GuarinoX. Flores-PalaciosJ.M.M. EngelsJ.H. WiersemaH. DempewolfS. SoteloJ. Ramírez-VillegasN.P. Castañeda-ÁlvarezC. FowlerA. JarvisL.H. RiesebergP.C. Struik. 2016. Origins of food crops connect countries worldwide. Proceedings of the Royal Society B283: 20160792.