Changes in global cropland area and cereal production: An inter-country comparison
Introduction
Global demand for food is increasing with the fast-growing population and changed dietary structure; therefore, how to feed the world successfully has always been a big challenge (Foley et al., 2011; Tilman et al., 2011; Yu et al., 2012). Cereals – including wheat, rice, maize, and barley – are essential to global food security (Godfray et al., 2010) because they are not only staple crops with a rich source of proteins, carbohydrates, vitamins, minerals, fats and oils but also crops grown in greater quantities and provide more food energy worldwide than any other type of crop (World Bank Databank, 2018; Parry et al., 2004; Pfeiffer and McClafferty, 2007). Global cereal supply and demand, in terms of production, utilization, stock and trade, have been steadily increasing in the past decades (Dorosh, 2009; West et al., 2014; To and Grafton, 2015; FAO, 2017), and of these, maintaining cereal production has played an even more important role amid the process of global environmental change (Li et al., 2016; Reynolds et al., 2016; Wei et al., 2017).
Crop production (ton) is a linear function of cropland area (hectare) and productivity (ton per hectare), suggesting that any changes in cropland area or productivity could influence the total production (Foley et al., 2011; Reynolds et al., 2017). The production of cereal crops has tripled over the past five decades, with only a small increase in the land area cultivated (Rudel et al., 2009; Pingali, 2012). However, these small changes in area have contributed to approximately 12% of the total cereal production increase globally (Foley et al., 2005), suggesting that the relationship between changes in cropland area and cereal production is nonlinear at a larger geographical scale. This is mainly due to the spatially heterogeneous use of land, e.g., the quality, suitability and management intensity of cropland used for cereal production differ from place to place, causing that the same amount of change in area in different locations would probably have different consequences on cereal production. For example, urban sprawl and cropland retirement both lead to cropland area loss. The former is more likely taking place on existing fertile cropland; thus, a greater production loss is expected (Bren d’Amour et al., 2017; van Vliet et al., 2017), while the latter usually results in converting marginal cropland for ecological restoration; thus, only a limited production loss is expected (Xu et al., 2006). This example demonstrates that at a larger geographical scale, cropland area change would have not only a direct effect on crop production but also indirect effects, which would be induced by the reallocated cropland area and changed average cropland productivity during the process of cropland change.
Due to insufficient data availability in terms of mapping the quality, suitability and management intensity of global cereal croplands, the relationship between cropland area change and cereal production, especially the indirect effects induced by cropland change, is largely unknown at the global level (Verburg et al., 2013). Moreover, given the lack of effective global land governance and compensation mechanisms (Egli et al., 2018), it is likely that more regional-level case studies were designed for domestic policy-making, as the consequences of land use on food, social and ecological systems are largely territory-specific (Sikor et al., 2013). For example, case studies can be found from China (Liu et al., 2015; Li et al., 2017), Brazil (Dias et al., 2016), and India (Behera et al., 2016). Thus comparative analyses, which extend the country-specific perspective by assessing the relative performance to each other, could be helpful to optimizing a country’s domestic land use by comparing it to another country's land use (Chen et al., 2018).
In this study, in terms of the difficulties in upscaling a detailed regional-level analysis to the global level, we use the existing data and implement an inter-country comparative analysis to understand the different cropland use models implemented across countries for cereal production during the last decade. Specifically, we aim to understand the indirect effects of cropland area change on cereal production for individual countries, including (i) how much cropland area has been changed? and how much of this change occurred in primary locations and marginal locations respectively? (ii) how many changes in potential production are expected (i.e., directly induced by area change) against the observed changes in actual production? Using this information, a topology is developed to highlight the different cropland use models, aiming to help develop national-level strategies for sustainable cereal production (e.g., maximizing production while minimizing environmental effects) by comparing one country’s performance to that of others.
Section snippets
The research framework
The assessment is performed quantitatively for the world’s major cereal producing countries, aiming to understand which countries have better allocated cropland area for cereal production and which countries have better improved actual average cereal productivity considering the changes in cropland area. According to the Food and Agriculture Organization of the United Nations (FAO)’s definition, the cereal crops included in the study are wheat, rice, maize, barley, pearl millet, small millet,
Changes in net cropland area and their composition
The rank of net cropland area changes for the major cereal producers is presented in Fig. 2. It shows that Brazil has experienced a marked net increase in cropland area for cereal production (approximately 3.9 million hectares), and 63% of this increase is allocated to primary locations (i.e., locations that cereal productivity is above the country’s average). Nigeria and Australia ranked the second and the third, respectively, in terms of net cropland area increase, and 43% and 26%,
Discussion
The typology of different models in utilizing land for cereal production is found to be relevant to the global food security assessment released by the International Food Policy Research Institute (von Grebmer et al., 2017). The assessment applied the Global Hunger Index (GHI) to measure the severity of food insecurity for developing countries, which means that some cereal producing countries included in the current study, e.g., countries in Europe and North America, are not included in the
Conclusion
The changes in cropland area and cereal production between 2000 and 2010 are compared for the world’s major cereal producers. In addition to the direct effects of cropland area increase/decrease on cereal production, the indirect effects – as a result of the reallocated cropland area and the change in average cropland productivity – have been examined. Although an obvious trend of increased actual cereal production and reduced hunger has been observed globally, the contributions are
Acknowledgements
The Agricultural Land System group at AGRIRS provided valuable support throughout the study. QY thanks Prof. Peter Verburg for his early comments. This work is financed by the National Key Research and Development Program of China (2017YFE0104600), by the National Natural Science Foundation of China (41501111) and by the Fundamental Research Funds for Central Non-profit Scientific Institution (IARRP-2017-27 and IARRP-2017-65). The authors thank three anonymous reviewers for their valuable
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