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Compact cities, characterized by high density and accessibility with fully developed inner-city public transport, are widely discussed and practiced around the world in response to the challenges of sustainable development and global warming. On this basis, we are committed to answering the question of how cities with varying urban growth rates adopt different policy practices, and whether these practices contribute to achieving the goal of building a sustainable, low-carbon city. Specifically, this study assesses the theoretical evidence and practical experiences on the effect of compact city characteristics and policies on urban CO2 emissions using a focused literature review and representative case studies. The results illustrate that public transportation is often strengthened in compact city policies and the density and spatial configuration of cities has a significant impact on urban carbon emissions. Moreover, there are significant differences within the impact mechanisms of compact cities on carbon emissions between small-medium-sized cities (dealing with aging populations and resource waste) and megacities (dealing with excessive urban sprawl). However, there is still insufficient quantitative evidence on the effectiveness of compact city policies and this review provides insights into future compact city planning toward policy approaches which yield lower carbon emissions.

Improving the quality of forest, water, farmland, and other types of land use with outstanding ecosystem optimization, restoration functions (ecological lands) and reducing anthropogenic carbon emissions are recognized as the two main approaches of current mainstream climate change policies. The paper aims to evaluate and compare the value neutrality within these two main types of policy responses to climate change. To do that, a case study was conducted at the Yangtze River Economic Belt, China. We first summarized the implementation status of all climate change policies in the study area and collected data related to climate and economy at the policy pilot sites. Next, the coupling relationship between climate and socio-economic conditions at policy pilot sites was calculated by the Tapio model. Finally, we constructed dummy variables that reflected the status of policy implementation, to estimate the value neutrality of mainstream climate change policies and their impact on the coupling relationship by DID models. The results showed that the proportion of policies related to ecological lands that significantly improved the coupling degree between climate and socio-economic conditions of the pilot sites is more than that of carbon emission-related ones. Moreover, the average coupling degree between climate and socio-economic conditions of the pilot sites of ecological land policies was significantly increased by 3.99 units after policy implementation, which is 27.8% higher than that of carbon emission reduction policies. Generally, the two main findings directly evidenced that the climate change policies aimed at improving the area and quality of ecological lands were more conducive to the coupling development of the climate–economy nexus than the policies focusing on restricting carbon emissions, which provides important enlightenment for the establishment of relevant environmental policies around the world.

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