Articles | Volume 8, issue 3
https://doi.org/10.5194/esd-8-875-2017
https://doi.org/10.5194/esd-8-875-2017
Research article
 | 
27 Sep 2017
Research article |  | 27 Sep 2017

Estimating global cropland production from 1961 to 2010

Pengfei Han, Ning Zeng, Fang Zhao, and Xiaohui Lin

Abstract. Global cropland net primary production (NPP) has tripled over the last 50 years, contributing 17–45 % to the increase in global atmospheric CO2 seasonal amplitude. Although many regional-scale comparisons have been made between statistical data and modeling results, long-term national comparisons across global croplands are scarce due to the lack of detailed spatiotemporal management data. Here, we conducted a simulation study of global cropland NPP from 1961 to 2010 using a process-based model called Vegetation–Global Atmosphere–Soil (VEGAS) and compared the results with Food and Agriculture Organization of the United Nations (FAO) statistical data on both continental and country scales. According to the FAO data, the global cropland NPP was 1.3, 1.8, 2.2, 2.6, 3.0, and 3.6 PgC yr−1 in the 1960s, 1970s, 1980s, 1990s, 2000s, and 2010s, respectively. The VEGAS model captured these major trends on global and continental scales. The NPP increased most notably in the US Midwest, western Europe, and the North China Plain and increased modestly in Africa and Oceania. However, significant biases remained in some regions such as Africa and Oceania, especially in temporal evolution. This finding is not surprising as VEGAS is the first global carbon cycle model with full parameterization representing the Green Revolution. To improve model performance for different major regions, we modified the default values of management intensity associated with the agricultural Green Revolution differences across various regions to better match the FAO statistical data at the continental level and for selected countries. Across all the selected countries, the updated results reduced the RMSE from 19.0 to 10.5 TgC yr−1 (∼  45 % decrease). The results suggest that these regional differences in model parameterization are due to differences in socioeconomic development. To better explain the past changes and predict the future trends, it is important to calibrate key parameters on regional scales and develop data sets for land management history.

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Short summary
Global cropland net primary production has tripled over the last 50 years. However, long-term comparisons across global croplands are scarce due to the lack of detailed management data. Here, we conducted a simulation study of global cropland production from 1961 to 2010 using the VEGAS model. We modified the key parameter associated with the Green Revolution. The updated results decreased the RMSE by ~ 45 %, suggesting it is important to calibrate key parameters on regional scales.
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