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Uneven agricultural contraction within fast-urbanizing urban agglomeration decreases the nitrogen use efficiency of crop production

Nature Food volume 5, pages 390–401 (2024)Cite this article

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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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Fig. 1: Concentration of food N production in less-urbanized cities.
Fig. 2: Sankey diagram for N flows in the food system of GBA in 1989 and 2018.
Fig. 3: Characteristics of N emissions in the food system of GBA.
Fig. 4: Variance in food-related N emissions across the 11 cities in GBA in 1989 and 2018.
Fig. 5: N pollution embedded in inter-city food trade within GBA during 1989–2018.
Fig. 6: Inter-city flows of embedded N pollution.

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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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Authors and Affiliations

  1. State Key Joint Laboratory of Environment Simulation and Pollution Control (SKLESPC), School of Environment, Tsinghua University, Beijing, China

    Chen Chen & Zongguo Wen

  2. Faculty of Architecture, The University of Hong Kong, Hong Kong, China

    Chen Chen

  3. School of Business, Macau University of Science and Technology, Macao, China

    Ni Sheng

  4. Macao Environmental Research Institute, Faculty of Innovation Engineering, Macau University of Science and Technology, Macao, China

    Qingbin Song

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Contributions

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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Correspondence to Zongguo Wen.

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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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