About ‘Where our food crops come from’

by Colin K. Khoury, Harold A. Achicanoy, Carlos Navarro-Racines, Steven Sotelo, and Andy Jarvis at the International Center for Tropical Agriculture (CIAT). Version 1.0 (May 2016). This work is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0).

This work is associated with the publication:

Khoury CK, Achicanoy HA, Bjorkman AD, Navarro-Racines C, Guarino L, Flores-Palacios X, Engels JMM, Wiersema JH, Dempewolf H, Sotelo S, Ramírez-Villegas J, Castañeda-Álvarez NP, Fowler C, Jarvis A, Rieseberg LH, and Struik PC (2016). Origins of food crops connect countries worldwide. Proc. R. Soc. B 283: 20160792. Available online at: https://dx.doi.org/10.1098/rspb.2016.0792

About the circular plots

The circular plots link the “primary regions of diversity” of crops (regions where crops were initially domesticated and evolved over long periods of time, and where the diversity of traditional crop varieties and related wild plants is especially high) with crops’ current importance in regional food supplies, measured in terms of calories (kcal/capita/day), protein (g/capita/day), fat (g/capita/day), and food weight (g/capita/day), and in regional agricultural production, measured in terms of total production quantity (tonnes), harvested area (ha), and gross production value (current million US$).

Each region has a color representing its own “native” crops and those colors are connected to other regions due the importance of those crops in the diets/agricultural production in other regions. The direction of the contribution is indicated by both the “native” region’s color and a gap between the connecting line and the consuming/producing region’s segment. The magnitude of contribution is indicated by the width of the connecting line. Because the line width is nonlinearly adapted to the curvature, it corresponds to the contribution size only at the start and end points. Regional food supply values (per capita/day) were formed by deriving a weighted average of national food supply values across countries comprising each region, with national values weighted by population. Regional production values were formed by summing national production values across countries comprising each region.

Methods and code for the plots were derived from The Global Flow of People by Nikola Sander, Guy J. Abel and Ramon Bauer at the Wittgenstein Centre for Demography and Global Human Capital. Their human migration source code and our source code are both available on Github.

About the data

We analyzed the full set of food crop commodities reported in national food supply and pertinent national production data provided by FAO (1) [for food supplies- calories (kcal/capita/day), protein (g/capita/day), fat (g/capita/day), and food weight (g/capita/day); for production systems- production quantity (tonnes), harvested area (ha), and gross production value (current million US$). National food supply from plants represents national production plus imports plus or minus food reserve changes over the survey period; minus exports, quantities used for seed, animal feed, and in the manufacture of non-food products, and losses during storage and transport. While food supply data accounts for direct human consumption, production data for crops such as maize and soybean are potentially inclusive of livestock and industrial uses as well as human food. In the production analysis we also included agricultural crops indirectly contributing to human food supplies via livestock production (i.e., alfalfa, clover, and vetch). Non-food (e.g., fibre for clothing) crops as well as animal product commodities were not included in the analysis. Plant commodities comprised of the same crop species were aggregated into single commodities representing the crop, e.g., sesame seed oil and sesame seed. After aggregation, 53 crop commodities remained in food supplies data, and 132 crop commodities in production data.

We analyzed data for each crop commodity per country per measurement over the most recent three years for which sufficient data were available (2009-2011). All (177) countries consistently reported during the time period were included for food supplies variables, as well as for production quantity and harvested area, covering 98.5% of the world’s population. All (141) countries reported for (current million US$) production value were included, covering 94.1% of the world’s population.

Regions were delineated following national borders in order to form manageable units for the assignment of primary regions of diversity of all crops, and at a scale enabling comparison with national food supply and production data. Regional classifications followed those listed in Annex 2 of the FAO State of the World’s Plant Genetic Resources for Food and Agriculture (2), modified to more accurately represent eco-geographic parameters driving plant species distributions. Specifically, both western and eastern Europe were split into north and south regions to account for cold temperate versus Mediterranean ecologies; Australia and New Zealand were segregated from the remaining (tropical) islands of the Pacific region; and South America was split into Andean, temperate, and tropical regions. A total of 23 regions were delineated worldwide. To account for eco-geographic variation within countries, those countries whose boundaries included more than one region were included in all appropriate regions (e.g., Colombia was assigned both to Andean and to tropical South American regions). See the countries-regions table for a listing of all countries and their associated eco-geographic regions.

Primary regions of diversity were assigned to crops based on published studies regarding origins and centres of crop diversity and species richness of closely related wild plants (3-18). The primary region of diversity unit was chosen for this analysis due to its greater overall applicability across the literature in comparison to more precisely proposed centres of origin or centres of diversity. To be inclusive with regard to primary regions of diversity of crops, those crops whose primary diversity encompassed more than one designated region were listed in all appropriate regions (e.g., wheat was listed in Central Asia, West Asia, and the South and East Mediterranean due to the high diversity of traditional crop varieties and wild relatives in each of these regions). Forty-two of the total 53 crop commodities treated in food supplies data, and 116 of the total 132 crops in production data were attributable to primary regions of diversity. The remaining commodities that were not clearly recognizable as specific crop species (e.g., “Fruits, other”) were listed as “not specified”. See the crops-regions table for a listing of all crops and their primary regions of diversity. The crop map displays primary regions of diversity for selected major agricultural crops.

For each country, we determined the importance of each primary region of diversity around the world to its national food supply and national production by summing the contribution of consumed/produced crops by their primary regions of diversity. Country level information on the importance of primary regions of diversity is available for download for both national food supplies and national production systems. The circular plots display this data, with consuming/producing countries aggregated to the regional level.