An integrated connectivity-structure assessment reveals the effects of large-scale afforestation on landscape fragmentation patterns

Large-scale afforestation is a cornerstone of global ecological restoration, yet its impact on landscape connectivity remains poorly quantified, limiting our understanding of its long-term ecological effectiveness. Traditional assessments rely on structure-based metrics can misrepresent fragmentation trends by overlooking ecological connectivity.

Here, we present a comprehensive analysis of forest dynamics in China's Yellow River Basin, a globally significant restoration region, employing a multi-metric framework that integrates the Connectivity-based Fragmentation Index (CFI) with structure- and aggregation-based indices (SFI, AFI). The results reveal that despite three decades of massive afforestation (1991-2023) driving an 81.6% net forest expansion, this greening has induced a nuanced reorganization of the landscape. Crucially, the perceived trend in fragmentation depended entirely on the metric applied. SFI which sensitive to patch proliferation indicated increased fragmentation for 60% of the forest area, aligning with the widespread establishment of new, often small patches. In stark contrast, CFI which prioritizes functional connectivity revealed a markedly lower proportion (40%) of forest area undergoing increased fragmentation. The finding that CFI indicates less severe fragmentation here than globally observed (>50%) reveals that afforestation has substantially preserved, or even enhanced, functional connectivity amidst growing landscape complexity. Our findings highlight the necessity of integrating connectivity, aggregation, and structural-focused metrics into global fragmentation assessments to accurately evaluate the ecological outcomes of restoration efforts.