Abstract
Diverse development paths among cities within an urban agglomeration can lead to uneven changes in their agricultural production scale, which reshape the inter-city food supply patterns and the spatiotemporal characteristics of nitrogen (N) pollution from the food system. Here, using Guangdong–Hong Kong–Macao Greater Bay Area of China as a case, we found a substantial decrease in N use efficiency of crop production from 45.2% to 29.3% during 1989–2007, along with a growing level of concentration of food N production in less-urbanized cities. From 1989 to 2018, 12.3% to 42.2% of total N pollution in food production became embedded in inter-city trade, leading to aggregation of N pollution in peripheral cities with relatively low levels of economic development. We suggest that protection and intensification of cropland from urban encroachment, as well as enhancing the economic and technical synergies among cities, can serve the sustainable transition of the food system with coordinated N pollution mitigation.
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Data availability
Data supporting the findings of this study are available in the article and supplementary information file. Material flow data in the food system and socio-economic data are publicly available from Statistical Yearbook of Urban Construction in China (https://www.mohurd.gov.cn/gongkai/fdzdgknr/sjfb/tjxx/jstjnj/index.html), Guangdong Statistical Yearbook (https://stats.gd.gov.cn/gdtjnj/), Guangdong Rural Statistical Yearbook (https://stats.gd.gov.cn/gdnctjnj/), Statistical Yearbook of each city in PRD (https://stats.gd.gov.cn/), Hong Kong Annual Digest of Statistics (https://www.censtatd.gov.hk/en/EIndexbySubject.html?pcode=B1010003&scode=460), Monitoring of Solid Waste in Hong Kong (https://www.wastereduction.gov.hk/en-hk/resources-centre/waste-statistics), Yearbook of Statistics of Macao (https://www.dsec.gov.mo/en-US/Home/Publication/YearbookOfStatistics), and FAOSTAT (https://www.fao.org/faostat/en/#data). Parameters used for calculation of N flows as well as their sources are provided in the supplementary information file. Source data are provided with this paper.
Code availability
The code and algorithm developed in the study are available in Methods and Supplementary Information. Code for calculating the inter-city food N flows is available via Zenodo at https://zenodo.org/records/10868557 (ref. 60).
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Acknowledgements
This work was supported by the Joint Scientific Research Fund of the National Natural Science Foundation of China (NSFC) and the Science and Technology Development Fund of Macao (FDCT) (72261160655) (Z.W.), National Science Fund for Distinguished Young Scientists of China (71825006) (Z.W.) and Research project of China Rural Research Institute, Tsinghua University (CIRS2024-6) (Z.W.).
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Z.W. and C.C. co-designed the study. C.C. and Q.S. contributed to data collection, C.C. and Z.W. conducted technical analysis and results interpretation. C.C. wrote the paper; Z.W., Q.S. and N.S. supervised the research and revised the paper.
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Nature Food thanks Yunfeng Huang, Erik Mathijs and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Chen, C., Wen, Z., Sheng, N. et al. Uneven agricultural contraction within fast-urbanizing urban agglomeration decreases the nitrogen use efficiency of crop production. Nat Food 5, 390–401 (2024). https://doi.org/10.1038/s43016-024-00980-5
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DOI: https://doi.org/10.1038/s43016-024-00980-5
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