食料：サプライチェーンの多様化によって食料の供給途絶から都市を守る

Improving a city’s food supply chain diversity enhances its resilience to disruptions to supply, known as food shocks, reports a study published in Nature. This relationship is demonstrated with a statistical model — constructed using four years of data from 284 cities across the United States — that may guide policymakers.

Food supply shocks — such as those caused by extreme weather, political factors and disease pandemics — are becoming more common worldwide. Ecological theory suggests that to manage the risk of these shocks, food supply chains should be as diverse as possible. What has been missing, however, is a simple, quantitative model that can be used to visualize the risk of shock in relation to factors that can be actively controlled by a city, company or nation.

Alfonso Mejia and colleagues examined observations of annual food supply to 284 cities in the United States across four food sectors (crops, live animals, animal feed and meat) during a period when moderate to severe droughts were afflicting a large proportion of the country (2012–2015). These data were used to create a statistical-empirical model that explains how a city’s capacity to resist a food supply shock of a certain frequency, intensity and duration correlates with the diversity of its supply chains. Strikingly, boosting this diversity can increase resilience to shocks of mild to moderate severity by up to 15%.

The authors hope that by creating a simple, operationally useful model that is generalizable to different hazards, cities will be able to use it to guide policies aimed at increasing food supply chain diversity. This could help buffer against future disruptions.