Abstract
Recent studies have highlighted the reliance of global food production on unsustainable irrigation practices, which deplete freshwater stocks and environmental flows, and consequently impair aquatic ecosystems. Unsustainable irrigation is driven by domestic and international demand for agricultural products. Research on the environmental consequences of trade has often concentrated on the global displacement of pollution and land use, while the effect of trade on water sustainability and the drying of over-depleted watercourses has seldom been recognized and quantified. Here we evaluate unsustainable irrigation water consumption (UWC) associated with global crop production and determine the share of UWC embedded in international trade. We find that, while about 52% of global irrigation is unsustainable, 15% of it is virtually exported, with an average 18% increase between year 2000 and 2015. About 60% of global virtual transfers of UWC are driven by exports of cotton, sugar cane, fruits, and vegetables. One third of UWC in Mexico, Spain, Turkmenistan, South Africa, Morocco, and Australia is associated with demand from the export markets. The globalization of water through trade contributes to running rivers dry, an environmental externality commonly overlooked by trade policies. By identifying the producing and consuming countries that are responsible for unsustainable irrigation embedded in virtual water trade, this study highlights trade links in which policies are needed to achieve sustainable water and food security goals in the coming decades.
Highlights
In the last decade, many studies have shown that some of the world’s major agricultural baskets rely on unsustainable water use for irrigation (Gleick and Palaniappan 2010, Konikow 2011, Gleeson et al 2012, Scanlon et al 2012, Kummu et al 2016, Mekonnen and Hoekstra 2016)
The unsustainability of irrigation We find that 52% (569 km3) of global irrigation practices are unsustainable because they deplete freshwater stocks and/or environmental flows
The impact of agriculture on unsustainable irrigation water consumption (UWC) strongly varies with crop type and geographic location with wheat, maize, rice, cotton, and fruits and vegetables collectively contributing to 73% of global UWC
Summary
Many studies have shown that some of the world’s major agricultural baskets rely on unsustainable water use for irrigation (Gleick and Palaniappan 2010, Konikow 2011, Gleeson et al 2012, Scanlon et al 2012, Kummu et al 2016, Mekonnen and Hoekstra 2016). Irrigation practices are classified as unsustainable when their water consumption exceeds local renewable water availability. In these conditions, irrigation uses water that should be allocated to environmental flows and contributes to environmental degradation and groundwater depletion (Rosa et al 2018a). About 20% of irrigation water use worldwide is from non-renewable groundwater abstractions (Wada et al 2012). Irrigation water withdrawals may deplete freshwater stocks (both surface water bodies and aquifers) when their abstraction rates exceed those of natural recharge (Wada et al 2010, Famiglietti 2014, AghaKouchak et al 2015, Richey et al 2015, Rodell et al 2018, Wang et al 2018)
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