Spatial heterogeneity of landscapes and land cover in Sulawesi Island in relation to water regulation ecosystem services.

Land cover change on Sulawesi Island was analyzed to assess changes in the potential capacity of water regulation ecosystem services from 1990 to 2022. Potential water regulation capacity was mapped using a weighted spatial index based on a Simple Additive Weighting approach that integrates natural landscape, natural vegetation, and land cover datasets for 1990, 2006, and 2022. In 1990, areas with very high or high water regulation capacity covered 59.5% of Sulawesi, but by 2022 this share had declined to 44.9%, indicating a net contraction of higher potential regulation classes. Central Sulawesi and South Sulawesi contributed most strongly to this decline, while Southeast Sulawesi and North Sulawesi showed partial recovery of high-capacity classes in the later period. Over the same interval, vegetated land cover types that strongly support water regulation decreased from 75 to 54% of the island, largely due to conversion to agricultural and built-up areas. These changes suggest a reduced potential capacity of landscapes to support water regulation functions, including rainfall retention, baseflow support, and watershed resilience, particularly in areas experiencing extensive forest conversion and expansion of agricultural and built-up land. The spatial outputs identify provincial- and watershed-level hotspots where forest protection, restoration, and ecosystem service-based zoning could be prioritized. The study demonstrates the value of regional-scale ecosystem service mapping in a tropical island context to support land use policy and long-term ecological resilience.