Circular visualization of virtual-land flows along with international cereal trade

Distant human and environmental systems are likely to be closely connected in the era of globalization, often resulting in positive outcomes for sustainability (Liu et al., 2013). Continued population growth and limited land resources lead to many countries to be increasingly dependent on international cereal trade to meet their domestic demand for grain (Zhang et al., 2016). Cereal commodities are land-intensive and in high demand. Thus, international cereal trade triggers a huge area of virtual land (land resources used to produce goods) flowing across different human–environmental systems and intensely affect reallocations of global land resources (Würtenberger et al., 2006). Following Zhang et al.’s (2016) approach and selection, we retrieved import and export quantities, yields, and harvested areas of nine kinds of cereals (i.e. barley, buckwheat, maize, oats, rice, rye, sorghum, soybean, and wheat) of 202 countries/regions from the Food and Agriculture Organization of the United Nations (available from http://www.fao.org/faostat/ en/#data, last accessed 31 July 2017) and then calculated the areas of virtual land embodied in the international cereal trade occurring between 2009 and 2013. Finally, we selected 16 countries with the largest areas of net imported/exported virtual land (i.e. eight largest