[Construction and Optimization Strategies of Ecological Security Pattern in Mega Urban Agglomerations of Eastern...

The three mega urban agglomerations of Beijing-Tianjin-Hebei (BTH), the Yangtze River Delta (YRD), and the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in eastern China serve as core economic hubs and focal areas for ecological challenges. Establishing an ecological security pattern (ESP) is crucial for balancing economic growth with ecological sustainability. However, previous studies have often overlooked the resilience of ecosystems in recovering to a stable state, which undermines the robustness of ESPs in addressing future risks. Additionally, limited research has focused on enhancing the spatial connectivity of ESPs by incorporating the intrinsic characteristics and spatial configurations of ecological sources (ESs) and ecological corridors (ECs), hindering the development of functionally robust and structurally integrated ESPs. This study assessed ecological resilience using 2020 land use data. Following the framework of "ecological source identification-ecological resistance surface setting-ecological corridor extraction, " areas with high ecological resilience were identified as ESs, and the minimum cumulative resistance (MCR) model was applied to extract ECs that connect these ESs. A multi-indicator system was then developed to evaluate the ESPs. By determining critical thresholds for downgrading ESs and ECs and analyzing the spatial configuration of the ESPs within these urban agglomerations, optimized strategies were proposed. The results showed that: ① The mega urban agglomerations exhibited moderate ecological resilience, with GBA leading at 0.59, followed by YRD at 0.51, and BTH at 0.50. Urban areas generally demonstrated low resilience, while forests, grasslands, and water bodies were characterized by higher resilience. ② ESs were identified within the three mega urban agglomerations, covering 14.7%, 13.9%, and 24.7% of their respective areas. A total of 112, 145, and 57 ECs were extracted. Each urban agglomeration contained several small, low-grade ESs (numbering 11, 9, and 2) and longer low-grade ECs (numbering 10, 8, and 5). ③ To enhance indicators such as the resilience and permeability of low-grade ESs and ECs, it is recommended that BTH and GBA prioritize reinforcing high-quality ECs to leverage the "strong supporting weak" effect between high- and low-grade ESs. BTH and YRD should focus on land use planning and water resource management. All three urban agglomerations should establish ecological buffer zones and "stepping stones." Additionally, new ESs should be added in the ESP gap areas of BTH and GBA to improve overall coverage, uniformity, and spatial connectivity. Optimized ESP strategies integrating enhanced ecological resilience with improved spatial connectivity include: "three horizontal, two vertical, one belt" for BTH; "three sides, multiple cores, multiple corridors" for YRD; and "two horizontal, two vertical, three areas" for GBA. These findings provide valuable insights for the strategic management of ecosystems within urban agglomerations.