Tracing the water footprint of food losses the in trade network: the case of wheat

Food loss and waste is increasingly becoming a topic of great public concern: in 2011, FAO presented the estimate that around one third of the world’s food was lost or wasted every year and SDG 12 (“Sustainable consumption and production”) from Agenda 2030 includes among its targets to “halve per capita global food waste” and to “reduce food losses”. The impact on environmental resources is significant: in particular, 24% of total freshwater resources used in food crop production are lost in the different stages of food loss and waste. While in high-income countries food is mainly wasted at the consumer level, low-income ones record losses concentrated in the agricultural and post-harvest stages. Globally, food markets are telecoupled and globalized, so wasted food has effects on water resources in the whole supply chain, propagating along the trade network up to the countries of initial production, where water resources have been utilized, often through irrigation, altering the local hydrological cycle. The reconstruction of such network is one of the most challenging aspects of tracing the impact of food waste on water resources. The difficulties are due to the numerous food re-exports and nested supply chains, to the different origins of food waste (from production to distribution and consumption), and to the marked variability of the country-specific unit water footprints. As a key hypothesis, we assumed that in each country the ratio between imports and domestic production would be the same in both domestic consumption and exports, to cope with re-export feedbacks in the network. Focusing on the emblematic case of wheat and its derivatives (e.g., flour, bread, pasta), we were able to reconstruct the complex global network that connects losses and wastes at any stage along the supply chain with the corresponding wasted water resources.

Our results show that, for most countries, the network is very extensive and involves many states around the world. For example, in 2016 over 20 foreign countries employed their water resources to produce wheat which in turn was wasted as bread in Italy at the consumer level, accounting for around 15% of the bread’s water footprint (870 m³/t).  This highlights how much water resources are now globalized and that the waste of food in a country can impact even very distant water resources. We also quantify the contribution of each waste component, from agriculture’s field losses to consumers’ household wastes. For Italy, 54% of losses related to bread are at the consumption stage, while only 6% occur at the agricultural stage. Eventually, we present how the relative importance of each component varies, depending on the network of countries involved in the production, storing, processing, distribution and consumption of food.