Agriculture, bioenergy, and water implications of constrained cereal trade and climate change impacts

3.3 Regional results To explore the regional differences, we select four representative regions to evaluate the results in more detail: USA, Brazil, Middle East, and Western Africa. USA and Brazil are major cereal exporters in 2015, both with CIDR of -14%, while Middle East and Western Africa are major cereal importers, with CIDR of 59% and 24%, respectively (Fig 1). These regions also represent a wide range of income levels. Climate change has a small effect on CIDR over the projection periods in the four selected regions. In 2050, the CIDR is 2 percentage points higher in CC than RF for USA and Western Africa, and changes minimally for Brazil and Middle East. 3.3.1 Changes of cereal trade, production, and consumption under scenarios. Fig 3 shows regional changes in cereal imports and exports in 2050 in ID compared to RF. Not sur- prisingly, the regions with the largest changes in trade are those that are the heaviest importers and exporters in RF (S2a Fig in S1 File). For example, USA, Brazil, Argentina, and Austra- lia_NZ, which are the major cereal exporters in RF, show the largest decrease in cereal export in ID due to global trade restrictions. Correspondingly, being the major cereal importers in RF, Middle East, Northern and Western Africa show the largest decrease in cereal import in ID. These patterns are maintained in IC. Fig 4 shows the production and consumption patterns that underlie the changes in trade patterns. As expected, regions which have more cereal imports than exports in RF have lower

cereal consumption and higher cereal production in ID, and vice versa. That is, cereal import- ers in RF must increase cereal production in ID, with a resulting increase in price, as on the margin, production in these regions will be more expensive (e.g., Middle East and Western Africa in Fig 5), leading to a decrease in consumption. Cereal exporters in RF decrease produc- tion in ID due to lower global demand for their exports, lowering the domestic price of cereals, Fig 2. (a) Global total import (equivalent to global total export) of cereals, (b) global total consumption (equivalent to global total production) of cereals, and (c) global total land allocation to cereal crops over 2015–2050 in 5-year time steps under four model scenarios. Note that y-axes are in different scales. https://doi.org/10.1371/journal.pone.0291577.g002 PLOS ONE Agriculture, bioenergy, and water implications of constrained cereal trade and climate change impacts PLOS ONE | https://doi.org/10.1371/journal.pone.0291577 September 15, 2023 7 / 18