Resilience and reactivity of global food security

Abstract

The escalating food demand by a growing and increasingly affluent global population is placing unprecedented pressure on the limited land and water resources of the planet, underpinning concerns over global food security and its sensitivity to shocks arising from environmental fluctuations, trade policies, and market volatility. Here, we use country-specific demographic records along with food production and trade data for the past 25 y to evaluate the stability and reactivity of the relationship between population dynamics and food availability. We develop a framework for the assessment of the resilience and the reactivity of the coupled population-food system and suggest that over the past two decades both its sensitivity to external perturbations and susceptibility to instability have increased.

Keywords: Malthusian growth; food crisis; food trade network; stability.

Fig. 1.

Typical examples of population, food production, and trade dynamics for four countries representative of the four different groups presented in the text. Black dots indicate demographic records, and the continuous line represents our evaluation of $K=K_T$ (in red) and $K=K_L$ (in green).

Fig. 2.

Map displaying the geographic distribution of countries belonging to the four groups: (A) Exporting countries whose food trade has an impact on the carrying capacity, $K_T$. (B) Trade-dependent countries where population relies on food available through both domestic production and trade (import). (C) Countries where the impact of trade on food availability is negligible. (D) Countries exhibiting clear signs of food limitation as evidenced by the poorer diets.

Fig. 3.

(A) Total food excess (in calories) calculated as the sum of the difference between supply (through production and trade) and consumption for all countries in each group, g (i.e., ${\mathrm{ℛ}}_T\left(y\right)-\mathcal{R}\left(y\right)={\displaystyle {\sum }_{i\in g}\left(K_{T_i}\left(y\right)-x_i\right)\cdot ca{l}_i}$, where $ca{l}_i$ is the average daily per-capita diet of country i and $x_i$ is its population). (B) Ratio of the coefficients of variation (i.e., SD: mean) of food production ($K_L$) and trade-dependent supply ($K_T$) for each country group as a function of time. (C) Fraction of most sensitive (i.e., close to instability) countries within each group for different years. (D) Distribution of the most reactive countries [given by Max(Re(${\lambda }_H$))] for the four groups, considering all years from 1986 to 2010. Countries where the impact of trade on food availability is negligible (group C) and food trade-dependent countries (group B) are on average more reactive that group A and D nations. (Lower) Map of reactive countries (see also Fig. S3 for most unstable countries) for two different years (1987 and 2008). All calculation have been done with a delay τ = 1 y.

Fig. 4.

(A) Number of most sensitive (less resilient) countries (i.e., with $\mathrm{Max}\left[\mathrm{Re}\left(\mathrm{\lambda }\right)\right]\mathrm{>}-0.005\hspace{0.17em}\text{and}\hspace{0.17em}\text{Max}\left[\mathrm{Re}\left({\mathrm{\lambda }}_{\mathrm{{\rm H}}}\right)\right]\mathrm{>}-0.005$) as a function of time. (B) Localization of the most sensitive and reactive eigenvectors $\mathbf{v}$ and ${\mathbf{v}}_H$ (corresponding to the largest eigenvalues of J and H) for the year 1997. The larger the component of the eigenvector, the larger the impact of a given perturbation on that country.