Abstract
Food supply shocks are increasing worldwide1,2, particularly the type of shock wherein food production or distribution loss in one location propagates through the food supply chain to other locations3,4. Analogous to biodiversity buffering ecosystems against external shocks5,6, ecological theory suggests that food supply chain diversity is crucial for managing the risk of food shock to human populations7,8. Here we show that boosting a city's food supply chain diversity increases the resistance of a city to food shocks of mild to moderate severity by up to 15 per cent. We develop an intensity-duration-frequency model linking food shock risk to supply chain diversity. The empirical-statistical model is based on annual food inflow observations from all metropolitan areas in the USA during the years 2012 to 2015, years when most of the country experienced moderate to severe droughts. The model explains a city's resistance to food shocks of a given frequency, intensity and duration as a monotonically declining function of the city's food inflow supply chain's Shannon diversity. This model is simple, operationally useful and addresses any kind of hazard. Using this method, cities can improve their resistance to food supply shocks with policies that increase the food supply chain's diversity.
Highlights
Global and national food supply chains increase exposure to shocks compared with local food supply chains[4,7,15,16], and add diversity and resilience[15,17]
Using annual timescale food inflow supply networks for the cities of the USA, we extracted the annual intranational food inflow subgraph of each metropolitan area for the period 2012−2015, which is the period with available data[30] and when food production systems were substantially affected by drought and agricultural production shocks on the Great Plains and in the western USA31,32
Analogous to biodiversity buffering ecosystems against external shocks[5,6], our results show that cities with a greater diversity of food suppliers have a lower probability of suffering a food supply shock for any reason
Summary
Global and national food supply chains increase exposure to shocks compared with local food supply chains[4,7,15,16], and add diversity and resilience[15,17]. From ecological and resilience theory[23,24], a food shock resilience model should relate the diversity and/or connectivity of the food supply chain network to explain a city’s resistance to food shocks. Companies and nations had access to a model estimating their ability to buffer food supply chain shocks, this model could be used in policy and management to optimize supply chains and control the risk of shocks[26,28]. We propose a statistical−empirical model meeting these ideal criteria, explaining the resistance of USA cities to food supply shocks as a function of the topological diversity of the city’s food supplier network
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