Towards more spatially explicit assessments of virtual water flows: linking local water use and scarcity to global demand of Brazilian farming commodities

• Published in: Environmental research letters Vol. 11; no. 7; pp. 75003 - 75012
• Main Authors: Flach, Rafaela, Ran, Ylva, Godar, Javier, Karlberg, Louise, Suavet, Clement
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01-07-2016
• Subjects: Assessments; Brazil; Commodities; Consumption; Demand; Farming; Heterogeneity; International trade; material flow modelling; Municipalities; Sourcing; Spatial heterogeneity; Sugarcane; trade; virtual water; Water consumption; Water demand; water footprint; Water management; Water resources; Water scarcity; Water stress; Water use; Brazil; water footprint; Brazil; virtual water; trade; material flow modelling
• ISSN: 1748-9326; 1748-9326
• DOI: 10.1088/1748-9326/11/7/075003

Global consumption of farming commodities is an important driver of water demand in regions of production. This is the case in Brazil, which has emerged as one of the main producers of globally traded farming commodities. Traditional methods to assess environmental implications of this demand rely on international trade material flows at country resolution; we argue for the need of finer scales that capture spatial heterogeneity in environmental variables in the regions of production, and that account for differential sourcing within the borders of a country of production. To illustrate this, we obtain virtual water flows from Brazilian municipalities to countries of consumption, by allocating high-resolution water footprints of sugarcane and soy production to spatially-explicit material trade flows. We found that this approach results in differences of virtual water use estimations of over 20% when compared to approaches that disregard spatial heterogeneity in sourcing patterns, for three of the main consumers of the analysed crops. This discrepancy against methods using national resolution in trade flows is determined by national heterogeneity in water resources, and differential sourcing. To illustrate the practical implications of this approach, we relate virtual water flows to water stress, identifying where global demand for water coincides with high levels of water stress. For instance, the virtual water flows for Brazilian sugarcane sourced by China were disproportionally less associated to areas with higher water stress when compared to those of the EU, due to EU's much higher reliance on sugarcane from water scarce areas in Northeast Brazil. Our findings indicate that the policy relevance of current assessments of virtual water flows that rely on trade data aggregated at the national level may be hampered, as they do not capture the spatial heterogeneity in water resources, water use and water management options.