Spatiotemporal evolution of land use and habitat quality in the Three-River source region.

Investigating spatial-temporal variations in land use/cover change (LUCC) and habitat quality (HQ) is essential for evaluating ecosystem integrity and advancing sustainable development objectives. The Three-River Source Region (TRSR) has distinctive LUCC characteristics that reveal intricate relationships between land utilization patterns and environmental deterioration. Through an integrated PLUS-InVEST modeling framework, this research assesses historical LUCC and HQ transformations in the TRSR spanning three decades (1990-2020) while forecasting ecological patterns through mid-century projections (2050). Analysis indicates that grasslands dominate the TRSR landscape and constitute the core of its ecosystem. Over the past three decades, grassland, water body, and cropland areas increased by 14,593.43 km², 1,888.67 km², and 319.81 km², respectively, while the proportion of unused land declined from 22.24% to 17.79%. Projections forecast continued expansion of grassland and water body extents, accompanied by further reduction in unused land. Observed spatial shifts and reciprocal transformations among land-cover types underscore dynamic landscape processes. HQ exhibited an overall decline, with 0.67% of the region experiencing deterioration, which exceeded areas of improvement. In the absence of intervention, HQ degradation is projected to intensify, potentially doubling in spatial extent. Notably, HQ fluctuations occurred even in areas without LUCC, although more pronounced changes were detected where significant land-use conversions took place. These findings underscore the complex linkages between LUCC and HQ. Future strategies for the TRSR should prioritize limiting unused land expansion, conserving grasslands, and deepening understanding of regional ecological dynamics, thereby enabling more precise and targeted planning and management of unused land categories. Further elucidation of mechanisms relating land use to HQ will be critical for advancing research and guiding ecological restoration efforts.