Landscape aggregation enhances soil conservation service: Insights from the grain for green program on the Loess...

Soil conservation service (SCS) plays a fundamental role in maintaining land productivity, preventing land degradation, and safeguarding long-term food and ecological security. Traditional assessments of SCS typically focus on individual pixels or plots, often overlooking the influence of landscape connectivity on SCS delivery. This study aims to quantify the hidden effects of landscape patterns governing SCS improvement during a large-scale ecological restoration program. Using multivariate statistical methods, we analyzed land use, landscape metrics, and observed sediment yield from 30 watersheds participating in China's Grain for Green Program (GGP) on the Loess Plateau between 2000 and 2020. Our results revealed four key findings: (1) The GGP drove significant land use transitions inducing a critical shift toward greater landscape aggregation; (2) 93.3 % of watersheds showed significant improvements in SCS closely synchronized with increased landscape aggregation; and (3) Variance partitioning analysis identified Landscape Pattern as the dominant unique contributor to SCS improvement (16.53 %), outperforming Ecological Engineering (12.17 %), Human Activities (7.36 %), and Climate (3.68 %); (4) SEM further confirmed that SCS enhancement was primarily driven by increased landscape aggregation (standardized path coefficient: 0.307, p < 0.01), followed by reduced fragmentation and improved connectivity. Notably, the GGP exerted its effects on SCS indirectly-by promoting landscape aggregation and vegetation dynamics-rather than through direct vegetation area expansion alone. These findings demonstrate that optimizing landscape aggregation is a critical, yet often overlooked, strategy for enhancing soil conservation, underscoring the need for restoration policies to move beyond area-based targets toward strategic, pattern-oriented landscape planning that maximizes conservation outcomes.