Complementary mechanisms stabilize national food production

Abstract

Ensuring the temporal stability of national food production is crucial for avoiding sharp drops in domestic food availability. The average stability of individual crop yields and asynchrony among crop yield fluctuations are two candidate mechanisms to stabilize national food production. However, the quantification of their respective influence on the stability of national food production is lacking, as is the identification of the factors regulating both mechanisms. Using yield data for 138 crops and 115 countries over a 50-year period, we first show that the stability of total national yield mostly relies on the fluctuations of the yield of crops covering the largest share of cropland. The average yield stability of these crops exert a stabilizing effect on national food production that is twice as important as the one of the asynchronous yield fluctuations among them. Climate variability reduces the stability of national food production by synchronizing yield fluctuations among crops and destabilizing the yield of individual crops. However, our results suggest that increasing crop diversity can counteract the synchronizing effects of climate variability by enhancing asynchronous dynamics among crops. Irrigation can promote the average stability of individual crop yields but cannot compensate for the destabilizing effect of climate variability. Considering both the response of each crop to climatic variations and the dynamics emerging from crop baskets will help agricultural policies to ensure stable food supply at the national level.

Potential, attainable, and current levels of global crop diversity

“…Crop diversity in space depends on the area of the unit at which diversity estimations are made (Aramburu Merlos and Hijmans 2020). Much analysis of crop diversity and effects relies on national statistics (Khoury et al 2014, Mahaut et al 2021, in which the country-total diversity (Dγ) is computed. However, most interest in diversification is related to expected effects at farm or landscape levels (Sirami et al 2019).…”

“…While there can be benefits of diversity at the national level (Renard and Tilman 2019), the national to local-average diversity ratio (i.e. Dβ), an indicator of regional heterogeneity, should also be considered when assessing diversity effects on the stability of food production (Mahaut et al 2021).…”

Matches and mismatches between the global distribution of major food crops and climate suitability

“…Although temporal changes in the global distribution of crop harvested areas can mitigate the negative effects of climate on agricultural production [13], the extent to which these dynamics do affect the magnitude of the harvested areas-climate suitability mismatch remains to be quantified. Another promising extension of this work will be to consider the temporal variability of crop yields, yield stability being key for the adaptation of global agriculture to climate change [53].…”

Cultivate biodiversity to harvest food security and sustainability

“…As would be expected, greater year-toyear variation in rainfall and growing season temperature decreased the stability of total national crop harvests. These results suggest that for many countries, increases in national crop species diversity could signifi cantly promote the year-to-year stability of the total food harvest in a nation in the face of current and likely increasing climatic variability, without a cost to mean yield 19,20 .…”

“…Analyzing 50 years of data across 91 nations, Renard and Tilman 19 found, for instance, that countries with an effective crop diversity of 4 had severe crop harvest declines about once every 7 years, whereas those countries with an effective crop diversity of 10 had such declines only about once every 60 years (Figure 1). This stabilizing effect of crop species diversity is explained by what is called the portfolio or insurance effect 19,20 . Because different crop species exhibit different responses to hot, cold, wet, or dry weather, and to pests or diseases, greater crop diversity is better at buffering out the impact of environmental variation on the total harvest of all crops in a country.…”