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Cropland use intensity was usually measured by output-input indicators. Yet these measurements cannot effectively represent the potentials for further cropland use intensification. As the theory of life expectancy suggests that a 3-year-old rat is “older” than a 30-year-old giant turtle, and we are “younger” than people at our age hundreds of years ago, the assessments on cropland use intensity should also consider the “gaps” toward the production capacity ceiling.
The authors, led by Prof. Wenbin Wu and Dr. Qiangyi Yu, measured the “cropping intensity gap (CIG)” and the “harvested area gap (HAG)” to understand the potentials for increasing multi-cropping practices on existing cropland. Globally, the average CIG around the year 2010 was 0.48 and 0.17 for the temperature- and temperature/precipitation limited scenarios, respectively, suggesting a range of 7.36 million km2 to 2.71 million km2 harvest areas would be possibly obtained, corresponding to a range of 37.55% to 13.83% of the current global cropland area. Notably, the country level average CIG values are closely related to the country level Hunger Index, implying the food-less-secured regions tend to have higher potentials for increasing cropland use intensity.
Figure 1 The country level cropping intensity gaps
In China, previous analyses have shown that the country’s cropland use is intensifying, leading to an increase in crop production. However, the current analyses indicate that HAG in China ranges from 13.5 to 36.3 million ha, equal to between 8% and 23% of currently harvested area in 2005. Moreover, HAG decreases between the 1980s and the 1990s, and subsequently increases between the 1990s and the 2000s, resulting in a small net increase for the entire study period (1980-2010). It suggests that despite observed increases in multi-cropping, changes in climatic factors has provided additional opportunities for intensification. Yet the potential is not fully exploited and the responses of land management to climate change are not linear.
Figure 2 The harvested area gap in China between 1980-2010
These studies demonstrate the applications of the CIG and HAG as a method to identify areas where crop production can be increased by increasing the multi-cropping practices. This provides a new perspective for understanding cropland use intensity, which is currently underexplored in scientific literature.
Wu, W., Yu, Q., You, L., Chen, K., Tang, H., Liu, J., 2018. Global cropping intensity gaps: Increasing food production without cropland expansion. Land Use Policy. In press.
Yu, Q., van Vliet, J., Verburg, P.H., You, L., Yang, P., Wu, W., 2018. Harvested area gaps in China between 1981 and 2010: effects of climatic and land management factors. Environmental Research Letters 13, 044006.
Yu, Q., Wu, W., You, L., Zhu, T., van Vliet, J., Verburg, P.H., Liu, Z., Li, Z., Yang, P., Zhou, Q., Tang, H., 2017. Assessing the harvested area gap in China. Agricultural Systems 153, 212-220.