Increasing global food demand, low grain reserves and climate change threaten the stability of food systems on national to global scales1,2,3,4,5. Policies to increase yields, irrigation and tolerance of crops to drought have been proposed as stability-enhancing solutions1,6,7. Here we evaluate a complementary possibility—that greater diversity of crops at the national level may increase the year-to-year stability of the total national harvest of all crops combined. We test this crop diversity–stability hypothesis using 5 decades of data on annual yields of 176 crop species in 91 nations. We find that greater effective diversity of crops at the national level is associated with increased temporal stability of total national harvest. Crop diversity has stabilizing effects that are similar in magnitude to the observed destabilizing effects of variability in precipitation. This greater stability reflects markedly lower frequencies of years with sharp harvest losses. Diversity effects remained robust after statistically controlling for irrigation, fertilization, precipitation, temperature and other variables, and are consistent with the variance-scaling characteristics of individual crops required by theory8,9 for diversity to lead to stability. Ensuring stable food supplies is a challenge that will probably require multiple solutions. Our results suggest that increasing national effective crop diversity may be an additional way to address this challenge.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
The sources of all data used in this study are referenced in the Methods and all raw data are freely accessible at the URLs provided in Extended Data Table 1. The dataset used for the analyses is available from the corresponding author upon request.
Rosenzweig, C. & Parry, M. L. Potential impact of climate change on world food supply. Nature 367, 133–138 (1994).
Fraser, E. D. G., Legwegoh, A. & Krishna, K. C. Food stocks and grain reserves: evaluating whether storing food creates resilient food systems. J. Environ. Stud. Sci. 5, 445–458 (2015).
Ray, D. K., Gerber, J. S., MacDonald, G. K. & West, P. C. Climate variation explains a third of global crop yield variability. Nat. Commun. 6, 5989 (2015).
Marchand, P. et al. Reserves and trade jointly determine exposure to food supply shocks. Environ. Res. Lett. 11, 095009 (2016).
Challinor, A. J. et al. Transmission of climate risks across sectors and borders. Phil. Trans. R. Soc. A 376, 20170301 (2018).
Lobell, D. B. et al. Prioritizing climate change adaptation needs for food security in 2030. Science 319, 607–610 (2008).
Bailey, R. et al. Extreme Weather and Resilience of the Global Food System. Final Project Report from the UK–US Taskforce on Extreme Weather and Global Food System Resilience https://www.foodsecurity.ac.uk/publications/archive/page/4/ (The Global Food Security Programme, 2015).
Doak, D. F. et al. The statistical inevitability of stability–diversity relationships in community ecology. Am. Nat. 151, 264–276 (1998).
Tilman, D. The ecological consequences of changes in biodiversity: a search for general principles. Ecology 80, 1455–1474 (1999).
Huai, J. Dynamics of resilience of wheat to drought in Australia from 1991–2010. Sci. Rep. 7, 9532 (2017).
Bren d’Amour, C., Wenz, L., Kalkuhl, M., Steckel, J. C. & Creutzig, F. Teleconnected food supply shocks. Environ. Res. Lett. 11, 035007 (2016).
Rippey, B. R. The US drought of 2012. Weather Clim. Extrem. 10, 57–64 (2015).
Harvey, C. A. et al. Extreme vulnerability of smallholder farmers to agricultural risks and climate change in Madagascar. Phil. Trans. R. Soc. B 369, 20130089 (2014).
Sternberg, T. Chinese drought, bread and the Arab Spring. Appl. Geogr. 34, 519–524 (2012).
Rosset, P. Food sovereignty and the contemporary food crisis. Development 51, 460–463 (2008).
Fader, M., Gerten, D., Krause, M., Lucht, W. & Cramer, W. Spatial decoupling of agricultural production and consumption: quantifying dependences of countries on food imports due to domestic land and water constraints. Environ. Res. Lett. 8, 014046 (2013).
Puma, M. J., Bose, S., Chon, S. Y. & Cook, B. I. Assessing the evolving fragility of the global food system. Environ. Manage. 10, 024007 (2015).
IPCC. Climate Change 2007: The Physical Science Basis (eds Solomon, S. et al.) (Cambridge Univ. Press, 2007).
FAO. Soaring Food Prices: Guide for Policy and Programmatic Actions at Country Level to address High Food Prices. http://www.fao.org/fileadmin/user_upload/ISFP/revisedISFP_guide_web.pdf (2011).
Cardinale, B. J. et al. Impacts of plant diversity on biomass production increase through time because of species complementarity. Proc. Natl Acad. Sci. USA 104, 18123–18128 (2007).
Gross, K. et al. Species richness and the temporal stability of biomass production: a new analysis of recent biodiversity experiments. Am. Nat. 183, 1–12 (2014).
Tubiello, F. N. Make better use of UN food and agriculture stats. Nature 563, 35 (2018).
Davis, A. S., Hill, J. D., Chase, C. A., Johanns, A. M. & Liebman, M. Increasing cropping system diversity balances productivity, profitability and environmental health. PLoS ONE 7, e47149 (2012).
Lin, B. B. Resilience in agriculture through crop diversification: adaptive management for environmental change. Bioscience 61, 183–193 (2011).
Snapp, S. S., Blackie, M. J., Gilbert, R. A., Bezner-Kerr, R. & Kanyama-Phiri, G. Y. Biodiversity can support a greener revolution in Africa. Proc. Natl Acad. Sci. USA 107, 20840–20845 (2010).
Gaudin, A. C. M. et al. Increasing crop diversity mitigates weather variations and improves yield stability. PLoS ONE 10, e0113261 (2015).
Abson, D. J., Fraser, E. D. & Benton, T. G. Landscape diversity and the resilience of agricultural returns: a portfolio analysis of land-use patterns and economic returns from lowland agriculture. Agric. Food Secur. 2, 2 (2013).
Challinor, A. J., Koehler, A.-K., Ramirez-Villegas, J., Whitfield, S. & Das, B. Current warming will reduce yields unless maize breeding and seed systems adapt immediately. Nat. Clim. Change 6, 954–958 (2016).
Raseduzzaman, M. & Jensen, E. S. Does intercropping enhance yield stability in arable crop production? A meta-analysis. Eur. J. Agron. 91, 25–33 (2017).
Lesk, C., Rowhani, P. & Ramankutty, N. Influence of extreme weather disasters on global crop production. Nature 529, 84–87 (2016).
United States Department of Agriculture. National Nutrient Database. https://ndb.nal.usda.gov/ (2013).
Hill, M. O. Diversity and evenness: a unifying notation and its consequences. Ecology 54, 427–432 (1973).
Marshall, M. G. Codebook: Major Episodes of Political Violence (MEPV) and Conflict Regions, 1946–2015. http://www.systemicpeace.org/inscr/MEPVcodebook2015.pdf (2016).
Harris, I., Jones, P. D., Osborn, T. J. & Lister, D. H. Updated high-resolution grids of monthly climatic observations - the CRU TS3.10 dataset. Int. J. Climatol. 34, 623–642 (2014).
Monfreda, C., Ramankutty, N. & Foley, J. A. Farming the planet: 2. Geographic distribution of crop areas, yields, physiological types, and net primary production in the year 2000. Glob. Biogeochem. Cycles 22, GB1022 (2008).
Sacks, W. J., Deryng, D., Foley, J. A. & Ramankutty, N. Crop planting dates: an analysis of global patterns. Glob. Ecol. Biogeogr. 19, 607–620 (2010).
Danielson, J. J. & Gesch, D. B. Global Multi-Resolution Terrain Elevation Data 2010 (GMTED2010). https://pubs.usgs.gov/of/2011/1073/pdf/of2011-1073.pdf (US Geological Survey, 2011).
FAO-UNESCO. Soil Map of the World: Revised Legend (with Corrections and Updates). World Soil Resources Report 60 http://www.fao.org/soils-portal/soil-survey/soil-maps-and-databases/faounesco-soil-map-of-the-world/en/ (FAO, 1988).
Simons, G. F. & Fennig, C. D. Ethnologues: Languages of the World 21st edn (SIL International, 2017).
MacDonald, G. K. et al. Rethinking agricultural trade relationships in an era of globalization. Bioscience 65, 275–289 (2015).
JMP v.12.0.1 (SAS Institute, 2007).
Quantum GIS Development Team. Quantum GIS Geographic Information. version 2.13 (2016).
Tilman, D. Global environmental impacts of agricultural expansion: the need for sustainable and efficient practices. Proc. Natl Acad. Sci. USA 96, 5995–6000 (1999).
We thank the Bren School of Environment Science and Management of the University of California Santa Barbara for support. This work was also supported by a grant overseen by the French National Research Agency (ANR) as part of the ‘Make Our Planet Great Again’ program (17-MPGA-0004) and by a National Science Foundation grant (LTER-1831944). We thank the FAO and its member countries, the University of East Anglia and the Center for Systematic Peace for data collection, dissemination and guidance on data use.
The authors declare no competing interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data figures and tables
Extended Data Fig. 1 Relationship between effective crop species diversity and crop species number per nation.
a, Black dots are mean effective crop species diversities and bars show the σ for nations grouped as planting 1–20, 20–40, 40–60, 60–80 or 80–100 crop species during 2001–2010 (n = 91). Data for each nation are shown as grey dots. Note that for a given number of crop species, there is a wide range in their effective crop species diversity caused by some nations having only a few dominant crops (and thus having a low effective diversity) and other nations having many crops of more similar abundances (and thus a high effective diversity). The two circled dots highlight 2 such nations, both growing 30 crop species but either very unevenly (that is, the dot with low effective diversity) or more evenly (that is, the dot high effective diversity). b, The frequency distribution of the effective crop species diversity values for this same time period.
a–f, Magnitude of the change in national yield stability as dependent on effective crop group diversity (a) and effective species diversity (d), precipitation instability (b, e) and irrigation (c, f). a–c, Values of national yield stability are predictions from the multiple regression model using effective crop group diversity (Extended Data Table 2a). d–f, Values of national yield stability are predictions from the multiple regression model using effective crop species diversity (Extended Data Table 2b). Predicted values were back-transformed from log-transformation, calculated using the observed range of the three predictors and keeping all the other predictors at their mean values. The grey bands represent the regression 95% confidence interval.
Extended Data Fig. 3 Contribution of crop groups to national caloric yield stability for each of six geographical regions.
A positive value of the log-transformed response ratio of yield stability for a crop group indicates that the presence of that crop group has a stabilizing effect. A negative value indicates a destabilizing effect. National log response ratios are represented per geographical region. In most regions, the presence of a given crop group is associated with increased national yield stability (n = 819).