Ecological restoration projects offset negative impacts of unsustainable land use and its interaction with climate change on ecological security network in Northeast China

• Clarifies LUCC components to reveal mechanisms driving ESN dynamics. • Quantifies the role of restoration projects in shaping regional ESN evolution. • Ecological restoration projects offset the impacts of negative LUCC on ESN. A robust ecological security network (ESN) is crucial for ecological security and sustainable development. The dynamics of the regional ESN are driven by land use/land cover change (LUCC) and climate change, which influence the ESN by altering ecosystem services, ecological sensitivity, and landscape patterns. Previous studies primarily focused on the overall effects of climate change and LUCC on ESN changes, while largely overlooking the role of detailed LUCC and its interaction with climate change. In this study, we constructed and evaluated ESN in Northeast China from the 2000s to 2020s using the methods of circuit theory and graph theory. We further quantified the effects of climate change, LUCC, and ecological restoration projects (positive LUCC) and unsustainable land use (negative LUCC) on ESN changes through factorial control experiments. Results revealed that the ESN declined initially but significantly enhanced in the last decade due to the implementation of large-scale ecological restoration projects (e.g., Grain for Green Program and Wetland Conservation Projects). The changes of structure, connectivity, and robustness in the ESN were most primarily influenced by LUCC effects, followed by interactive effects of climate change and LUCC, and then climate change effects. Both LUCC and climate change exhibited positive effects on the changes in structure, connectivity, and robustness of ESN, while their interactive effects showed negative effects. We further found that the negative effects of LUCC intensified when combined with climate change, exceeding the effects of negative LUCC alone on the ESN. Notably, positive LUCC partially offset the negative impacts of unsustainable land use and its interaction with climate change on the ESN under the modeled historical conditions. These findings offer valuable insights for formulating land management policies and implementing ecological projects.