Assessment the impact of urban expansion on cropland net primary productivity in Northeast China

Urban development inevitably comes with the loss of prime agricultural land, leading to a decline in cropland productivity. The Northeast region is an important grain-producing region in China, and agricultural land is of great significance in ensuring national food security. Here, land use and cover data and MODIS-NPP data were used to comprehensively understand the direct and adverse influence of urban land growth on cropland net primary productivity (NPP) in Northeast China. The results indicated that (1) in Northeast China, the urban land area increased by a total of 5230.00 km2 since 2000. The urban land growth phenomenon was particularly notable in the cities near the central transportation trunk line and along the southern coastal regions. (2) more than half of the newly added urban land patches originated from cropland. Between 2000 and 2020, urban expansion in Northeast China resulted in a 0. 85 Tg C loss of cropland NPP. (3) there was significant regional variation in cropland NPP loss. The low altitude and low slope regions experienced the most significant NPP loss. Meanwhile, large and developed cities caused more NPP losses, and cities with dispersed expansion had a broader impact on cropland productivity than cities with concentrated expansion. (4) when converting the loss of cropland NPP to crop yield, it revealed a reduction of 0.91 million tons in grain yield in Northeast China. These findings provide valuable insights for urban development and cropland protection strategies in Northeast China, offering crucial guidance for sustainable land use practices.