Spatial change of peri-urban expansion and potential land degradation in Yogyakarta and Surakarta

Abstract

This study investigates the spatial change of peri-urban expansion in Yogyakarta and Surakarta, Indonesia, quantifying the characteristics of urban sprawl between 2013 and 2023. Four core metrics - Cohesion, Dependency, Accessibility, and Spatial Equilibrium - were utilized to analyze the patterns of new built-up development outside the constrained administrative cores. Analysis indicates that the functional urban reach of both cities extends approximately 15 kilometers from their centers (Dependency). However, their expansion morphology differs significantly. Yogyakarta exhibits a more spatially balanced distribution (Spatial Equilibrium) and generally compact growth (Cohesion), yet its primary growth node, Depok, shows a dispersed pattern (Cohesion) and high accessibility. Conversely, Surakarta's growth is uneven (Spatial Equilibrium) and is characterized by a mix of high dispersion (e.g., Colomadu, Mojolaban) and strong clustering (e.g., Gondangrejo) (Cohesion), reflecting distinct, localized growth dynamics. This rapid and often fragmented spatial expansion - evidenced by the conversion of agricultural land into built-up areas - poses a significant, immediate threat to the region's sustainability.