Impact of land use change on multiple ecosystem services in the rapidly urbanizing Kunshan City of China: Past trajectories and future projections

Formulation of suitable land use strategies for sustainable management of urban landscapes requires assessment of the potential impact of future urban expansion on ecosystem services. We assessed land use change in the rapidly urbanizing Kunshan City of China during 2006–2016 and projected future land uses in 2030 under three alternative scenarios: Business-As-Usual (BAU), Croplands Protection (CP), and Ecological Restoration (ER). Then we quantified the spatio-temporal variations of six ecosystem services (including crop production, carbon storage, habitat quality, flood regulation, and nitrogen and phosphorus retention) in response to urban land use change from 2006 to 2030 using the InVEST model. We also analyzed temporal variation of the tradeoffs and synergies among multiple ecosystem services throughout the period of study. Our estimates indicate that the urban land of Kunshan increased by 19% over the past decade and will continue to expand by 15% from 2016 to 2030 under the BAU scenario. As a result, crop production, carbon storage, habitat quality, and flood regulation capacity would all decrease tremendously. Crop production would remain stable under the CP scenario owing to the strict protection of croplands, but nitrogen and phosphorus loading would increase by 8%. In contrast, the ER scenario would decrease nutrient loading by over 35% with concomitant benefits to carbon storage, habitat quality, and flood regulation capacity. However, crop production would decrease dramatically under the ER scenario, primarily due to the transition of large areas of croplands to ecological zones. Although croplands were the major sources for nitrogen and phosphorus loading in Kunshan during the years 2006–2016, urban land would become the major source of pollution under all future scenarios. Crop production and habitat quality were not significantly correlated during the years 2006–2016, while they would be positively correlated under the BAU and CP scenarios. This implies that croplands would become increasingly important in providing habitats as urban land continues to expand by replacing ecological land from 2016 to 2030. We propose four major land use strategies, including compact urban growth, croplands protection, reforestation to build greenways, and wetlands restoration in the riparian areas of drinking water sources to improve ecosystem services in Kunshan.