Abstract
Agriculture strongly relies on irrigation. While irrigated land accounts for roughly 20% of the global cultivated area, it contributes to about 40% of crop production. In the last few decades, the growing demand for agricultural commodities has translated into an increasing pressure on the global freshwater resources, often leading to their unsustainable use. Here we investigate the sustainability of irrigation, balancing farmers’ profit generation objectives and the needs of ecological systems. We ask the question “sustainability of what?”, to stress how the sustainability of irrigation is often evaluated with respect the opposing needs of humans and nature. While from the farmers’ perspective irrigation is sustainable when it provides uninterrupted access to water resources at a price not exceeding the marginal revenue they generate (clearly without accounting for environmental externalities), from the standpoint of water resources, irrigation is sustainable if it does not deplete freshwater stocks or environmental flows. We invoke the notions of ‘weak’ and ‘strong’ sustainability to develop a novel framework for the evaluation of tradeoffs between human needs and the conservation of natural capital. Through the analysis of criteria of performance, we relate water deficit and irrigation overuse to the reliability and resilience of irrigation. This approach is applied to the case of Australia, a major agricultural country affected by water scarcity. The application of the framework to the case of Australia shows how this approach can be used to highlight areas in which irrigation contributes to a weakly sustainable use of water resources with impacts on environmental flows and groundwater stocks. Solutions, such as increasing efficiencies or reducing water applications through the adoption of deficit irrigation, can enhance water sustainability in some water scarce locations.
Highlights
The economic productivity of a number of human activities depends on access to water resources (Sullivan, 2002; D’Odorico et al, 2018)
Framework Application We evaluate environmental and socio-economic sustainability of irrigation water use in agriculture using a dataset of irrigation water use and crop production that allows us to analyse effective annual costs and incomes of irrigated agriculture, while for the hydrological analyses, we rely on the output from model simulations
These results show that the enhanced efficiency of irrigation systems has a positive impact on water productivity it has been reported that the farm-scale increase in irrigation efficiency may increase water consumption if farmers use the water savings resulting from the increased irrigation efficiency to plant crops that are more water-intense or irrigate more land (Grafton et al, 2018)
Summary
The economic productivity of a number of human activities depends on access to water resources (Sullivan, 2002; D’Odorico et al, 2018). About 70% of global freshwater withdrawals are used for irrigation to sustain global crop production (Rockström et al, 2017). At the same time 40% of global irrigation practices are unsustainable because they deplete environmental flows and/or groundwater stocks (Wada and Bierkens, 2014; Rosa et al, 2018). In the specific context of agriculture, sustainable irrigation strategies need to allow for an increase in crop production to meet rising food needs, while ensuring that natural resources (e.g., groundwater stocks, freshwater ecosystems, and water quality) are not irreversibly depleted (Borsato et al, 2019; Rosa et al, 2019)
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