Water resources transfers through southern African food trade: water efficiency and climate signals

Temporal and spatial variability of precipitation in southern Africa is particularly high. The associated drought and flood risks, combined with a largely rain-fed agriculture, pose a challenge for water and food security in the region. As regional collaboration strengthens through the Southern Africa Development Community and trade with other regions increases, it is thus important to understand both how climate variability affects agricultural productivity and how food trade (regional and extra-regional) can contribute to the region's capacity to deal with climate-related shocks. We combine global hydrological model simulations with international food trade data to quantify the water resources embedded in international food trade in southern Africa and with the rest of the world, from 1986-2011. We analyze the impacts of socio-economic changes and climatic variability on agricultural trade and embedded water resources during this period. We find that regional food trade is efficient in terms of water use but may be unsustainable because water-productive exporters, like South Africa, rely on increasingly stressed water resources. The role of imports from the rest of the world in the region's food supply is important, in particular during severe droughts. This reflects how trade can efficiently redistribute water resources across continents in response to a sudden gap in food production. In a context of regional and global integration, our results highlight opportunities for improved water-efficiency and sustainability of the region's food supply via trade.

南部非洲降水的时空变异性特别高。相关的干旱和洪水风险，加上主要依赖雨水灌溉的农业，对该地区的水和粮食安全构成了挑战。随着通过南部非洲发展共同体加强区域合作以及与其他地区的贸易增加，了解气候变异性如何影响农业生产力以及粮食贸易（区域内和区域外）如何有助于该地区应对与气候相关的冲击的能力就变得非常重要。我们将全球水文模型模拟与国际粮食贸易数据相结合，以量化1986 - 2011年期间南部非洲与世界其他地区的国际粮食贸易中所蕴含的水资源。我们分析了这一时期社会经济变化和气候变异性对农产品贸易和蕴含水资源的影响。我们发现，区域粮食贸易在用水方面是高效的，但可能不可持续，因为像南非这样的水资源高效利用的出口国依赖的是日益紧张的水资源。世界其他地区的进口在该地区粮食供应中的作用很重要，特别是在严重干旱期间。这反映了贸易如何能够有效地在各大洲之间重新分配水资源，以应对粮食生产的突然缺口。在区域和全球一体化的背景下，我们的研究结果凸显了通过贸易提高该地区粮食供应的水资源利用效率和可持续性的机会。