Liangzhi You
International Food Policy Research Institute
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Publication
Featured researches published by Liangzhi You.
Geophysical Research Letters | 2011
Steffen Fritz; Liangzhi You; Andriy Bun; Linda See; Ian McCallum; C. Schill; Christoph Perger; Junguo Liu; Matthew C. Hansen; Michael Obersteiner
This paper presents a methodology for the creation of a cropland map for Africa through the combination of five existing land cover products: GLC-2000, MODIS Land Cover, GlobCover, MODIS Crop Likelihood and AfriCover. A synergy map is created in which the products are ranked by experts, which reflects the likelihood or probability that a given pixel is cropland. The cropland map is then calibrated with national and sub-national crop statistics using a novel approach. Preliminary validation of the map was undertaken and the results are presented. The resulting cropland map has an accuracy of 83%, which is higher than the accuracy of any of the individual maps. The cropland map is freely available at agriculture.geo-wiki.org.
Eos, Transactions American Geophysical Union | 2013
Steffen Fritz; Linda See; Liangzhi You; Christopher O. Justice; Inbal Becker-Reshef; Lieven Bydekerke; Renato Cumani; Pierre Defourny; Karl-Heinz Erb; Jon Foley; Sven Gilliams; Peng Gong; Matthew C. Hansen; Thomas W. Hertel; Martin Herold; Mario Herrero; François Kayitakire; John Latham; Olivier Leo; Ian McCallum; Michael Obersteiner; Navin Ramankutty; Jansle V. Rocha; Huajun Tang; Philip K. Thornton; Christelle Vancutsem; Marijn van der Velde; Stan Wood; Curtis E. Woodcock
Food security is a key global concern. By 2050, the global population will exceed 9 billion, and a 50% increase in annual agricultural output will be required to keep up with demand. There are significant additional pressures on existing agricultural land through increased competition from the biofuel sector and the need to elevate feed production, which is being driven by higher levels of meat consumption in low- and middle-income countries.
Geophysical Research Letters | 2004
Guiling Wang; Liangzhi You
[1]xa0This study examines the relationship between the North Atlantic Oscillation (NAO) and vegetation productivity in Asia inferred from both provincial crop yields data in China and satellite-derived Normalized Difference Vegetation Index data. Our finding suggests that vegetation productivity in northern Asia during the main growing season correlates significantly to NAO, with a surprising long delay of 1.5 years. Correlation at shorter time lags, which was the focus of previous studies, is weak and not significant between the NAO index and vegetation activities in Asia. This suggests the existence of a so-far unrecognized mechanism that carries the NAO signal for multiple years. The lagged vegetation response also provides the potential for NAO to serve as a predictor for crop yields in China.
Cuadernos de Economía | 2004
Stanley Wood; Liangzhi You; Xiaobo Zhang
Because of the apparent slowdown in the growth of crop yield potential, the increasing share of farmers already using modern crop varieties, and the accelerating flow of knowledge on agricultural technology, one would expect to find gradual convergence in
PLOS ONE | 2016
Xiaoyun Li; Nianjie Liu; Liangzhi You; Xinli Ke; Haijun Liu; Malan Huang; Stephen R. Waddington
After a remarkable 86% increase in cereal production from 1980 to 2005, recent crop yield growth in China has been slow. County level crop production data between 1980 and 2010 from eastern and middle China were used to analyze spatial and temporal patterns of rice, wheat and maize yield in five major farming systems that include around 90% of Chinas cereal production. Site-specific yield trends were assessed in areas where those crops have experienced increasing yield or where yields have stagnated or declined. We find that rice yields have continued to increase on over 12.3 million hectares (m. ha) or 41.8% of the rice area in China between 1980 and 2010. However, yields stagnated on 50% of the rice area (around 14.7 m. ha) over this time period. Wheat yields increased on 13.8 m. ha (58.2% of the total harvest area), but stagnated on around 3.8 m. ha (15.8% of the harvest area). Yields increased on a smaller proportion of the maize area (17.7% of harvest area, 5.3 m. ha), while yields have stagnated on over 54% (16.3 m. ha). Many parts of the lowland rice and upland intensive sub-tropical farming systems were more prone to stagnation with rice, the upland intensive sub-tropical system with wheat, and maize in the temperate mixed system. Large areas where wheat yield continues to rise were found in the lowland rice and temperate mixed systems. Land and water constraints, climate variability, and other environmental limitations undermine increased crop yield and agricultural productivity in these systems and threaten future food security. Technology and policy innovations must be implemented to promote crop yields and the sustainable use of agricultural resources to maintain food security in China. In many production regions it is possible to better match the crop with input resources to raise crop yields and benefits. Investments may be especially useful to intensify production in areas where yields continue to improve. For example, increased support to maize production in southern China, where yields are still rising, seems justified.
PLOS ONE | 2012
Kun Ma; Liangzhi You; Junguo Liu; Ming-Xiang Zhang
Wetlands play important ecological, economic, and cultural roles in societies around the world. However, wetland degradation has become a serious ecological issue, raising the global sustainability concern. An accurate wetland map is essential for wetland management. Here we used a fuzzy method to create a hybrid wetland map for China through the combination of five existing wetlands datasets, including four spatially explicit wetland distribution data and one wetland census. Our results show the total wetland area is 384,864 km2, 4.08% of China’s national surface area. The hybrid wetland map also shows spatial distribution of wetlands with a spatial resolution of 1 km. The reliability of the map is demonstrated by comparing it with spatially explicit datasets on lakes and reservoirs. The hybrid wetland map is by far the first wetland mapping that is consistent with the statistical data at the national and provincial levels in China. It provides a benchmark map for research on wetland protection and management. The method presented here is applicable for not only wetland mapping but also for other thematic mapping in China and beyond.
Global Food Security | 2015
Linda See; Steffen Fritz; Liangzhi You; Navin Ramankutty; Mario Herrero; Christopher O. Justice; Inbal Becker-Reshef; Philip K. Thornton; Karl-Heinz Erb; Peng Gong; Huajun Tang; Marijn van der Velde; Polly J. Ericksen; Ian McCallum; F. Kraxner; Michael Obersteiner
China Economic Review | 2012
Liangzhi You
Archive | 2008
Samuel Benin; Liangzhi You
Archive | 2005
Liangzhi You; Mark W. Rosegrant; Cheng Fang; Stanley Wood