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Building an ecological security pattern is an important way to relieve ecological pressure and promote the harmonious development of human and ecosystem in the context of rapid urbanization. The article takes Qingdao, Shandong Province as the study area, and firstly identifies ecological sources by the Morphological Spatial Pattern Analysis (MSPA) method combined with the ecological red line of Qingdao City. Secondly, the potential ecological corridors are identified based on the Minimum Cumulative Resistance model (MCR) method, and the potential corridors are classified by gravity model. According to the research paradigm of "point-line-area", the ecological security pattern of "Four Zones, One Axis and One Belt" in Qingdao is constructed. The results show that the ecological security pattern of Qingdao consists of 22 ecological source areas, 128 ecological corridors and 16 stepping stones, with a total area of ecological source areas is 753.28 km 2 , mainly forest land and water, showing a spatial distribution pattern of "clustering from north to South and East and connecting in the middle"; the overall ecological network is well connected, but the spatial span between the north and south ecological source areas is large, and the construction cost of the ecological network is high; forest land and water are the main landscape types of the ecological corridor, and forest land has the largest area, accounting for 34.02% of the total area of the ecological corridor; in addition, arable land, as the main land for living and production, is seriously disturbed by man, accounting for 27.30% of the total area of the ecological corridor. Therefore, we should strengthen the ecological corridor protection and avoid excessive human interference with ecological sources, ecological corridors and stepping stones. As an important ecological barrier along the southeast coast of Shandong Peninsula, Qingdao takes its whole elements of ecological land as the life community, fully considers the ecological functions of ecological source areas and the spatial structure of ecological networks, and constructs the

Aiming at the traditional ecological footprint model, the improved ecological footprint of the carbon footprint effectively makes up for the singularity of the ecological footprint's consideration of carbon emissions, and plays an important role in promoting high-quality development and ecological sustainability. This paper selects 2015, 2018 and 2020 as important time points for the study, corrects the ecological footprint parameter factors based on net primary productivity (NPP), measures the ecological footprint after the improvement of the carbon footprint, studies the spatial and temporal variation in the ecological footprint at the 100-m grid scale with the support of IPCC greenhouse gas inventory analysis, and analyzes the current ecological conservation status of the Yellow River Delta. Additionally, in the context of a low carbon economy, the decoupling index of carbon emissions and GDP is extended to the evaluation and analysis of high-quality development. The study showed that (1) the ecological footprint of the Yellow River Delta has increased year by year, from 0.721 hm2·person− 1 to 0.758 hm2·person− 1, an average annual increase of 2.9%; the ecological carrying capacity has decreased from 0.40 hm2·person− 1 to 0.31 hm2·person− 1, an overall decrease of 28.59%. (2) The overall ecological deficit of the Yellow River Delta grid is lightly overloaded, with most of the ecological surplus occurring in the northern and eastern parts of the study area and a few moderate and heavy overloads in the center of the core area where there is a lot of built-up land and the area is small and easy to gather. (3) Based on the low-carbon economy analysis, 2015, 2017 and 2020 reach absolute decoupling and are in the ideal scenario. However, in the rest of the years, carbon emissions and economic development are still in a large contradiction, and decoupling has fluctuated and varied greatly in the last six years. The effective combination of ecological footprint and low carbon economy analysis provides an important theoretical basis for improving ecological conservation and achieving high-quality development.

Exploring the coordinated relationship between built-up area expansion and population growth in the urbanization process is important for the planning and sustainable development of cities. The article took Shandong Peninsula urban agglomeration as the study area, which was divided into the Provincial Capital Economic Circle, Jiaodong Economic Circle, and Lunan Economic Circle according to the plan named the Implementation Plan for Implementing the Opinions of the CPC Central Committee and the State Council on Establishing a New Mechanism for More Effective Regional Co-ordinated Development. The people–land coordination relationship in the region was analyzed from the perspective of spatio-temporal integration through indices such as fractal dimension, spatial autocorrelation, population sprawl, and city land expansion and population growth coordination index (CPI) The results showed that (1) the relationship between built-up area expansion and population growth in the Shandong Peninsula urban agglomeration was uncoordinated. The three economic circles mainly changed from rapid population growth to significant expansion of built-up areas. (2) The development patterns of the three economic circles were different. The Provincial Capital and Jiaodong showed a pattern with Jinan and Qingdao as the core, driving the periphery area. Lunan showed a multi-point scattered development; there was no central city, but Linyi City was developing faster. (3) Jiaodong had the biggest changes in terms of population and built-up area. This study provides a scientific reference for the urban planning and sustainable development of the Shandong Peninsula urban agglomeration.