Ecosystem service trade-offs and synergies based on the mechanical equilibrium model: A case study of the urban agglomeration on the northern slope of the Tianshan Mountains
Jiazhen Chen, Alimujiang Kasimu, Lina Tang, Fuqiang Han, Miyesier Jumai
Abstract
Understanding ecosystem service (ES) interactions is crucial for sustainable development. Rapid urbanization and industrialization have accelerated resource consumption, degrading ecological services and threatening ecological security and human well-being. This issue is prominent in the ecologically fragile and densely populated urban agglomeration on the northern slope of the Tianshan Mountains (UANSTM). Understanding the trade-offs and synergies of ESs is crucial for resolving conflicts among services, yet there is a lack of effective methods for comprehensively understanding the complex interactions among multiple ESs. This study evaluates six ESs in UANSTM: water yield (WY), habitat quality (HQ), carbon storage (CS), soil conservation (SC), food supply (FS), and air purification (AP). Sen’s slope and Mann-Kendall tests were used to analyze changes in these ESs from 2000 to 2020. The mechanical equilibrium model was used to visualize the interactions and trade-offs among ESs at the grid scale. The results showed that from 2000 to 2020, WY exhibited a non-significant decreasing trend in cropland and the eastern mountainous areas, while in the central and western mountainous areas as well as grassland, a non-significant increasing trend was also evident. HQ experienced a significant decline in cropland, which represented 8.13 % of the study area, while CS remained generally stable, with non-significant increases observed in 1.71 % of cropland and grassland areas. SC showed a non-significant increase in mountainous areas, occupying 14.40 % of the study area, while FS exhibited a significant increase in cropland. AP increased in grassland and cropland but decreased in built-up land and mountainous regions, with 24.81 % of the area seeing an increase in AP. The mechanical equilibrium model revealed that ES coordination was predominantly harmonious, covering 65.61 % of the region. Observable disparities existed across regions concerning the coordination levels’ distribution, with highly harmonious areas mainly located in bare land such as deserts and mountainous regions, moderately coordinated areas predominantly found in grassland, and transitional and imbalanced types mostly distributed predominantly in areas characterized by substantial human engagement, exemplified by built-up land and cropland. The polar angle (θ) of the coordination level is primarily located in Quadrant VI, covering 76.38 % of the UANSTM. Ecological optimization areas covered 9.22 % of the region, with the largest share in Quadrant VI (52.48 %). These results provide important guidance for ecological development and urban planning in arid-region agglomerations.