Urban expansion poses severe threats to ecosystems. It is therefore important we better understand the impact of different urban expansion level on ecosystems for developing regionally differentiated ecological protection policies. Here, we proposed a conceptual framework to describe the impacts of urbanization on bundles of ecosystem services. Referred to as the concept of land use degree by nighttime light data, we put forward and verified an urban expansion level model. According to this model, study area was divided into a slow increase zone, increase zone, and rapid increase zone. Then, taking Taihu Lake Basin in China as a case, we used Zonal-statistics and Pearson correlation coefficients to reveal the impact in different zones of urban expansion level on multiple ecosystem services: crop production, freshwater supply, aquatic production, net primary productivity, soil conservation, water retention, flood regulation, and forest recreation index. Our results revealed that urban expansion levels significantly impacted all ecosystem services. In either increase zone or rapid increase zone, we found lowered values of crop production, net primary productivity, soil conservation, water retention, and flood regulation, while both aquatic production and forest recreation index increased in all zones from 1990 to 2010. Across the levels of urbanization, urban expansion level was always negatively correlated with provisioning services. This result suggests local governors should improve crop production per unit area and increase the cultivated land area to guarantee food security. In addition, urban expansion level had positive correlations with the trade-offs between flood regulation and forest recreation index, and those among crop production, freshwater supply, and net primary productivity. Therefore, policy-makers should effectively maintain the land use balance among ecological protection, agriculture development, and urban expansion to better coordinate relationships between development and protection. In acquiring quantitative knowledge of how urban expansion level drives ecosystem changes, our findings may help guide future sustainable urban planning with respect to ecosystem services, urban development, and human welfare benefits.

Determining the optimal granularity, which has often been ignored in the analysis of urban expansion and its landscape pattern, is the core problem in landscape ecology research. Here, we calculate the optimal granularities for differently sized cities in the Huaihe River Basin of China based on scale transformation and area loss evaluation. Accordingly, we construct a landscape index and urban land density function to analyze urban expansion and landscape pattern. The results can be summarized as follows. (1) Within the first scale domain of the landscape indices, the optimal granularities of Zhengzhou, Xuzhou, Yancheng, Xinyang, and Bozhou are 60 m, 50 m, 40 m, 40 m, and 40 m, respectively, which are the optimal units in the study of urban expansion. (2) The urban land density decreases from the urban center to the outskirts, the urban core of each city is more compact than the outskirts, and the land density curve parameter α of Zhengzhou is the largest at 4.693 and its urban core the most compact. (3) There are significant spatial and temporal differences in the urban land densities of differently sized cities. The urban land density functions of different cities are similar before 2000; after that, they are similar to the standard inverse S-shaped function and the land use density curve of large cities is closer to the standard inverse S-shaped function than that of small- and medium-sized cities. (4) Large cities have faster expansion, much larger land density curve parameter c than medium- and small-cities, stronger linkage development with surrounding areas, and a higher degree of urban centralization. Urban expansion compactness was influenced by urban locations and functions except for urban sizes. This study offers a method for identifying the optimal granularities for differently sized cities and also provides information for the decision-making efforts that concern the rapid urbanization in major grain-producing areas of China.

Rapid urbanization in the Huaihe River Basin has reshaped land use and intensified the tension between ecological protection and food security. A key gap is that most basin-scale ecosystem service value (ESV) assessments describe changes in land-cover composition but do not identify how landscape configuration–ESV associations vary across space. Using land use remote sensing images from 2000 to 2020, we quantitatively characterized the spatiotemporal evolution of land use via transfer matrices and landscape pattern indices. By integrating the equivalent value factor method, contribution analysis, spatial correlation analysis, and the geographically weighted regression (GWR) model, we examined the spatiotemporal dynamics and driving mechanisms of ecosystem service value (ESV). Key findings are as follows: (1) From 2000 to 2020, cropland area steadily decreased, while construction and forest land expanded markedly, with a synthetic land-use dynamic degree reaching 9.66%. (2) ESV first rose then fell, showing an overall decline. Forest land (18.882 billion CNY) and water areas (20.331 billion CNY) were the primary contributors. The ESV response to land use change manifested as a trade-off between short-term gains and long-term degradation. (3) Landscape patterns exhibited significant spatial heterogeneity, and ESV correlated strongly with patch number (NP) and landscape shape index (LSI). Class area (CA) emerged as the dominant factor, with CA of forest land, cropland, and water areas exerting the most pronounced effects. Based on the differential driving effects of landscape patterns and identified land use change hotspots, we propose enhancing ecosystem service values and mitigating conflicts between ecological conservation and food security through differentiated ecological engineering and ecological compensation strategies.