Incorporating suburban cropland into urban green infrastructure: A perspective of nature-based solutions in China

Urban green infrastructure (GI) addresses human social development issues and challenges through urban green space ecosystem services. However, the ecosystem service functions of suburban cropland, especially regulating services and cultural services, have been seriously underestimated. The distribution of green spaces and suburban cropland varies in different regions of China, as well as their potential development methods. This article examines the potential of integrating suburban cropland into urban green infrastructure, offering a perspective on nature-based solutions in China. We divided the suburban cropland in China into three parts: peri‑suburban, mid-suburban, and outer-suburban by the concept of 15-minute living circle based on different travel modes of people. Based on statistical yearbook data, satellite remote sensing images and the fragstats 4.2 programme, a quantitative analysis was conducted on the spatial distribution, landscape pattern and social development of suburban farmland and green space in four cities. Then, the potential for improving the exposure level of suburban cropland after incorporating suburban cropland into urban green infrastructure was quantified and compared. Finally, we explored the potential development of the three kinds of suburban cropland as green infrastructure based on the concept of NbS. We found the spatial pattern of cropland and green space in the mid-suburban is greatly affected by regional geographical conditions, the green exposure level, i.e., green space availability indicators, in Beijing, Shanghai, Guangzhou, and Xi'an increased by 83 %, 300 %, 24 %, and 612 %, respectively, after incorporating suburban cropland into urban green infrastructure. The potential development models for suburban cropland should be based on NbS and China's national conditions: peri‑suburban cropland should be fully utilized for cultural and social functions, the mid-suburban cropland should focus on multifunctional utilization of cropland, and the outer-suburban is prioritized for ecological functions. Our study provides scientific insights for deep exploration of the functions of suburban cropland in China.