In the context of the global climate change problem intensifying due to a dramatic increase in carbon emissions, smart cities, as a topical application of digitalization and intelligence, have become a new urban governance mode for countries, which helps to achieve sustainable development. This research studies the relationship between smart city construction (SCC) and carbon dioxide emissions based on the differences-in-differences model (DID) and propensity score matching (PSM) to promote China to achieve dual carbon goals and high-quality development. The findings are as follows: (a) SCC could promote carbon emission reduction by reducing urban carbon dioxide emissions by an average of 11.4%, which also has significant long-term dynamic effects. Specifically, SCC has more obvious emission reduction effects on activities, such as industrial production and waste treatment. (b) Mechanism verification shows that green technology progress is a significant booster for the carbon reduction effect in SCC. The pilot project can increase output of green patents, which helps transfer production mode and consumption patterns in an environmentally friendly manner. SCC could increase the total factor productivity (TFP) through the rational allocation and efficient use of resources, and thus reducing carbon emissions. (c) Research on city heterogeneity shows that a high level of human capital, material, and financial resources can provide support for smart cities to better achieve the carbon reduction effect. Among them, material resources have the best carbon reduction effect in the process of SCC, which could reduce carbon dioxide emissions by about 6.6–17.7%. This study is useful for policymakers to continuously and dynamically adjust urban development strategies in the future, to achieve a balance between socioeconomic prosperity and environmental sustainability.

In the requirement of the “double carbon” goal, China has confronted the lack of a driving force for the low-carbon transformation of socioeconomic development, which requires a comprehensive law and strategy support system for supporting a circular economy. In this study, a framework associated with a multi-level quantitative index system associated with legislative support for a circular economy (MILC) through the entropy TOPSIS method was developed. It can not only reflect the legal support for a circular economy in four areas based on the “3R” principle, but also respond to the process of environmental law improvement dynamically. The legislative support effect can be applied and analyzed in China’s circular economy for the period from 2009 to 2022, which can respond to the process of legal improvement on the environment dynamically. The obtained results show that China’s circular economy and its rule-of-law guarantee system are still facing many challenges, such as the low systematic degree of legalization for industrial development, unmatched supporting legal system, and backward concepts and consciousness of circular economy legalization. Various suggestions according to the identification of the importance of a legal support system for the circular economy were obtained, which can not only encourage a reduction in resource consumption and carbon reduction from the view of systematic legalization, but also promote socioeconomic transformation to match the goal of “double carbon”.

Balancing ecological conservation and rural livelihoods in protected areas remains a global challenge, particularly under strict land use regulations and economic development constraints. Territorial spatial planning (TSP) in an ecological function area (EFA) faces constraints such as land use restrictions, ecological redlines, and economic development limits. This study investigates how ecological land resources influence farmers’ incomes in ecological function areas (EFAs), with a focus on the moderating role of advanced livelihoods (ALI). Using an integrated Fixed-Effects–SVM–Genetic Algorithm framework, we quantify nonlinear policy-livelihood interactions and simulate multi-scenario governmental interventions (e.g., ecological investment, returning farmland to forest/RFF) across Beijing’s EFA, which can obtain the key findings as follows: (a) Ecological land resources have a significant positive effect on farmers’ incomes due to production-manner adjustment guided by governmental green strategy and corresponding TSP in an ecological restoration area of an EFA, while they have a non-significant impact in the core ecological reserve areas on account of the strict environmental protection restrictions on economic activities. (b) Differences in financial support between lower and higher economic development zones can bring about adverse impact results on farmers’ incomes in an EFA. (c) ALI significantly amplifies the positive impact of ecological land use on farmers’ incomes, demonstrating its critical role in bridging ecological and economic goals. (d) Sensitivity analysis results under RFF, targeted government investment, and ALI can maximize income gains through policy interaction from the government and farmer sides jointly. The above obtained results are beneficial to balance ecological protection and economic interests of farmers’ sustainably in an EFA.