Constraints and potentials of future irrigation water availability on agricultural production under climate change

TLDR

The study uses projections from the Inter‑Sectoral Impacts Model Intercomparison Project, coordinated by the Agricultural Model Intercomparison and Improvement Project, based on GCM outputs under RCP 8.5 from CMIP5. We compare ensembles of water supply and demand projections from 10 global hydrological models and six global gridded crop models. Models project that climate change will reduce global maize, soybean, wheat, and rice production by 8–43 % (400–2,600 Pcal) depending on CO₂ fertilization, that freshwater limits may force 20–60 Mha of irrigated land to revert to rainfed use and cut food production by 600–2,900 Pcal, while some regions could increase irrigation but require substantial infrastructure investment.

Abstract

We compare ensembles of water supply and demand projections from 10 global hydrological models and six global gridded crop models. These are produced as part of the Inter-Sectoral Impacts Model Intercomparison Project, with coordination from the Agricultural Model Intercomparison and Improvement Project, and driven by outputs of general circulation models run under representative concentration pathway 8.5 as part of the Fifth Coupled Model Intercomparison Project. Models project that direct climate impacts to maize, soybean, wheat, and rice involve losses of 400-1,400 Pcal (8-24% of present-day total) when CO2 fertilization effects are accounted for or 1,400-2,600 Pcal (24-43%) otherwise. Freshwater limitations in some irrigated regions (western United States; China; and West, South, and Central Asia) could necessitate the reversion of 20-60 Mha of cropland from irrigated to rainfed management by end-of-century, and a further loss of 600-2,900 Pcal of food production. In other regions (northern/eastern United States, parts of South America, much of Europe, and South East Asia) surplus water supply could in principle support a net increase in irrigation, although substantial investments in irrigation infrastructure would be required.