How are the Green Lungs of Urumqi's Oasis Cities Changing?

Oasis cities such as Urumqi act as green lungs for the environment. In the last thirty years, desertification and rapid urban growth have stressed these spaces. Researchers examined green landscape changes from 1990 to 2020 using satellite images and a random forest classifier. They found that unused land, urban green spaces, and built‑up areas dominate, together covering over 80% of the surface. Between 1990 and 2020, urban green areas shrank by 0.38%, water bodies by 37.41%, cropland by 0.57% and unused land by 4.58%. At the same time, built‑up land expanded sharply, fragmenting city parks further. Diversity (Shannon) and evenness indices rose, while contagion and connectivity indices fell, showing a greener network that is more scattered and less linked. The drivers are both natural and social. Elevation shapes the overall green distribution, while precipitation and temperature dominate changes in the north and south. Economic and demographic factors such as GDP, population, and distance to rivers or towns shape the green core of the city. Understanding these mechanisms is key to designing sustainable management strategies and safeguarding the ecological security of urban oases.

The analysis employed a Random Forest classifier to differentiate eight land‑cover classes, achieving over 90% accuracy thanks to a large training sample set. Geographic detectors quantified each independent variable's influence on the spatial variability of green patterns, revealing that elevation accounts for roughly 45% of the overall urban green distribution. Geographically Weighted Regression (GWR) then showed precipitation's effect as positive in the north (average coefficient +0.23) and negative in the south (average coefficient -0.15), indicating an asymmetric vegetation response to water availability. Socio‑economic factors, especially per‑capita GDP, correlate positively with green expansion in wealthier districts but negatively in peripheral zones where building pressure is higher. The contagion index, dropping by 4.3 points, signals a loss of continuity among green patches, potentially impairing ecological connectivity and heat‑island mitigation. The rise in Shannon's index (+0.12) reflects greater plant species heterogeneity, likely due to ornamental species introduced in new urban parks. These findings suggest green‑planning policies should prioritize ecological corridors and the preservation of high‑elevation areas, where vegetation is more climate‑resilient. Moreover, integrating high‑resolution climate data with socio‑economic indicators can enhance forecasts of future urban green scenarios, supporting more informed decisions for the sustainability of oasis cities.