With the growth of the global population and rapid socio-economic development, global warming, glacial melting, and other environmental pollution issues, especially greenhouse gases, are becoming increasingly prominent (Green 2020; Dragan et al., 2021). Since the release of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) in 2007, the global academic community has made many new findings on various aspects of climate change (Frank et al., 2002), among which the “land use change plays an important role in the increase in global atmospheric carbon dioxide levels, second only to fossil fuel combustion,” is a very important conclusion (Houghton, 2010; Sreekanth 2021). According to the carbon emission calculator of the World Resources Organization, the global carbon emissions between 1850 and 1998, land use change, and the carbon emissions caused by it are 1/3 of the total emissions influenced by human activities; and the cumulative carbon emission from land use change in China from 1950 to 2005 is 10.6 PGC, accounting for the cumulative carbon emissions from land use change in China from 1950 to 2005, which accounted for 30% of all carbon emissions from anthropogenic sources and 12% of global carbon emissions from land use change in the same period. China is the largest carbon emitter in the world, with greenhouse gas emissions of 14 billion tons of CO₂ equivalent in 2019, accounting for 26.7% of the total global emissions (Ahmad et al., 2020). In September 2020, President Xi Jinping proposed at the 75th session of the United Nations General Assembly that China would increase its national contribution, adopt more vigorous policies and measures, strive to peak CO₂ emissions by 2030, and achieve carbon neutrality by 2060. In September 2021, the “Opinions of the Central Committee of the Communist Party of China (CPC) and the State Council on the Complete and Accurate Implementation of the New Development Concept to Achieve Carbon Neutrality” made systematic planning and overall planning for China to achieve peak carbon and carbon neutrality. In October 2021, the State Council issued the “Action Plan for Achieving Carbon Neutrality by 2030,” which further elaborated the requirements for achieving carbon neutrality in various key areas (Shi and Guo, 2022) such as how to accelerate the improvement of all-factor carbon emission efficiency and effectively reduce total carbon emissions and climate change (Elahi et al., 2021; Elahi et al., 2022). It would help achieve the goal of carbon peaking and carbon neutrality which is an inevitable requirement for high-quality economic and social development and a hot topic of widespread concern from all walks of life (Anser et al., 2020; Chandio et al., 2020; Booth et al., 2021; Foster et al., 2021).

Urbanization is not only a process of continuous industrial, population concentration and rapid economic and social development but also a process of massive energy consumption and a high concentration of carbon emissions (Liu and Yang, 2022). Since the reform and opening up, China has experienced rapid urbanization and industrialization, and its total economic volume has increased rapidly (Wang and Pu, 2022). This crude urbanization development model has brought about serious negative resource and environmental effects, which in turn have fed back into the speed and quality of urbanization development (Chen et al., 2019). According to the seventh census data (as of November 2020), from 1978 to 2020, the urbanization rate of China increased from 17.9 to 63.89. Based on the general rule of urbanization development in the world, China is still in the rapid development interval of an urbanization rate of 30%–70%. In March 2014, the State Council released the National New Urbanization Plan (2014–2020), the first urbanization plan promulgated by the central government. The plan clearly puts forward the new urbanization construction strategy of “Green development, recycling development, and low-carbon development,” aiming to change the original “rough and loose” urbanization, whose theoretical connotation includes human-centeredness, synergy, and sustainability. It is a major change to realize the development concept from “urbanization of population” to “urbanization of people” (Chen et al., 2019). It points out that during the rapid development of China’s urbanization, there are some outstanding contradictions and problems that must be highly valued and addressed, one of which is that “urbanization of land” is faster than “urbanization of the population,” and construction land is sloppy and inefficient. From 2000 to 2011, the national urban built-up area grew by 76.4%, much faster than the urban population growth rate of 50.5% (National New Urbanization Plan, 2014–2020), which reflects the problem that the lack of synergy among multiple elements in the urbanization process, such as population, land, economy, and society, hinders the healthy development of urbanization. The multidimensional elements in urbanization should maintain a compatible and matching rate of evolution and also match the spatial set-up process in order to facilitate the realization of new urbanization. In addition, sustainability is also an important connotation of the new type of urbanization, which must fully consider new issues such as resource and environmental bearing and adaptation to climate change (Martínez-Zarzoso, 2011; Nathaniel and Adeleye, 2021). Therefore, it is instructive to consider the dual objectives of rational urbanization development and climate protection and adjust urbanization development to adapt to the changing climate to strengthen the exploration of new urbanization with green and low-carbon energy.

Empirical studies conducted by domestic and foreign scholars based on several perspectives show that urbanization and carbon emission growth are interactively and dynamically coupled in several aspects (Zhou et al., 2003; Pahunang et al., 2021; Elahi et al., 2022). Hanif (2018) explored the impact of economic growth, urban expansion, and energy consumption on environmental degradation in developing economies in sub-Saharan Africa. The findings suggest an inverted U-shaped relationship between per capita economic growth and carbon emissions, which is consistent with the findings of Zarzoso et al. (2011). However, in Ansell (2021), by analyzing the effects of urbanization, economic growth, and population size on residential carbon emissions in the South Asian Association for Regional Cooperation (SAARC) member countries between 1994 and 2013, the empirical results showed a U-shaped relationship between urbanization and residential carbon emissions and residential carbon emissions initially decrease with increasing urbanization, reaching a turning point at 25.33% and then increases with urbanization. Suo and Li (2020) suggested that there are regional differences in the effect of urbanization on carbon emissions, with a positive correlation between high-income groups and a negative correlation among low-income groups. Elsewhere, Wang et al. (2017) showed that the urban population size has both an impact and a spatial spillover effect on carbon emissions in the province in a study of 30 prefecture-level cities. Zhang et al. (2013) showed that for every 1 km² increase in urban construction land on the East and West sides of the Hu Huanyong line, the average annual carbon emissions increased by 1.79 million t and 2.58 million t, respectively (Musah et al., 2021). The study examined the relationship between urbanization and carbon emissions in West Africa. Economic growth has a substantial positive effect on CO₂ emissions, while renewable energy consumption has a substantial negative effect on CO₂ emissions. Lin (2016) argued that developing the tertiary sector, increasing investment in human capital, improving market competition, and reducing energy intensity are effective measures to achieve a win-win situation for both carbon intensity reduction and economic growth during urbanization.

In a comprehensive view, there are still shortcomings in the previous studies. First, most of the relevant studies have focused on the national and provincial scales, and not enough attention has been paid to the ecologically fragile and less developed cities in the Yellow River basin. Second, urbanization is essentially a change in economic, social, and spatial structures, which affects CO₂ emissions in various ways (Wang and Pu, 2022). In the process of urbanization, the agglomeration of population and economic and other factors contribute to carbon emissions, and their joint efforts shape the dynamic relationship between urbanization and carbon emissions. Therefore, mapping the coupled and coordinated relationship between urbanization and carbon emissions is an effective path to explore the carbon emission reduction of urbanization.

In this study, Ningxia is chosen as the research object. The Ningxia Hui Autonomous region is located in the arid-semi-arid region and desert-steppe transition zone in inland northwest China. Surrounded by deserts in the East, West, and North, the unique geographical location and climatic conditions make Ningxia with sparse vegetation and severe soil erosion one of the most fragile ecological regions in China. Due to the rough use and disorderly development of land in the historical period, the degree of intensive land use in the region is low, the per capita urban construction land is 1.85 times the national average, and the average investment intensity and output intensity per mu of the 23 industrial zones are 35.77 and 11.39% of the national average, respectively, and the non-construction land such as arable land, grassland, and wetland is commonly occupied. The degree of exploitation of mineral resources is insufficient, and the energy structure dominated by coal is difficult to change in the short term. In this case, the pressure to complete the energy consumption per unit of GDP, the proportion of non-fossil energy, and other energy-saving emission reduction targets is very high. With the continuous development of the economy and society, the intensity of energy development and utilization in Ningxia will further increase. Clarifying the relationship between the spatial and temporal effects of land use carbon emissions and urbanization development is conducive to scientifically grasping the law of carbon emission growth and spatial expansion and providing a theoretical basis for formulating regional differentiated energy conservation and emission reduction policies in the future.

The remainder of the study is organized as follows. Section 2 describes the study area, methodology, and data sources, including the selection of new urbanization evaluation indicators, the measurement of land use carbon emissions, and the coupling coordination degree model. Section 3 uses the approach described in Section 2 to empirically investigate the coupling relationship between the level of new urbanization and land-use carbon emissions in Ningxia since 2009. In Section 4, the innovation points and limitations to this study are analyzed by comparing them with existing studies. Section 5 summarizes the study and proposes policy recommendations from the perspective of balanced urbanization development and a low carbon economy.

According to the aforementioned analysis, the spatial and temporal patterns of coupling and coordination between urbanization and land use carbon emissions in Ningxia vary significantly, with the spatial dimension showing the spatial characteristics of high North and low South, and the temporal dimension showing the wave-like evolution characteristics from low-level coupling to high-level coupling. Further analysis of the coupling and coordination relationship between the elements of urbanization and land use carbon emissions shows that the highest coupling degree is economic urbanization, which reaches a high level of coupling, while population urbanization is in the grinding stage, and land urbanization and social urbanization are less coupled, indicating that the most important factor affecting land use carbon emissions in Ningxia during the study period is the development of the economic level.

On the one hand, Ningxia’s economic volume is small and its growth rate is slow. In 2020, the region’s gross domestic product will be 392.055 billion yuan, 1.16 times higher than in 2010, ranking at the bottom of the nine provinces in the Yellow River Basin. As an important coal chemical and thermal power base in China, Ningxia undertakes the task of national strategic energy reserves. Since the 13th Five-Year Plan, Ningxia has focused on the development of a large number of energy-intensive industries such as the coal chemical industry, resulting in the continuous expansion of carbon emissions. At present, Ningxia wind power, photovoltaic, and other renewable energy development sources is difficult to support the effective transformation of the energy structure; in the short term, this high-carbon energy and industrial structure is hardly a significant adjustment, and low-carbon development is facing a very serious situation. In addition, economic development will also cause the built-up area to expand outward. After the 12th Five-Year Plan, Ningxia entered into a period of high-speed development and began to undertake the transfer of chemical industries from the East to the West, which occupied a large number of ecological lands such as the grassland and forest land, and the ecological land decreased by 84,279.22 hectares or 2.08% in 10 years. This led to a decrease in the carbon sink scale and the expansion of the carbon source area, which resulted in an increase in net carbon emissions from land use.

On the other hand, the distribution of population-scale and economic level in the North and South of Ningxia is unbalanced. Regional differences lead to large spatial differences in the degree of coordination of urbanization and carbon emission coupling across the region. The northern part of Ningxia along the Yellow River concentrates 57% of the region’s population and 80% of the towns, creates 90% of the total economic volume and 94% of the fiscal revenue, and is an important energy, chemical, raw material and basic industrial base with increasing population and industrial agglomeration capacity. In the central region, there is drought and water shortage, serious land sanding, and the industries are mainly mining and special agricultural product processing industry, and the population share is basically stable. The southern region has prominent soil erosion problems, poor agricultural cultivation conditions, insufficient industrial development momentum, and a declining trend in population share.

Therefore, this study makes the following suggestions from the perspective of balanced urbanization development and a low carbon economy. First, the energy utilization efficiency is improved, and the development of clean energy is increased. Ningxia is located in the intersection and transition zone of three natural regions in China, rich in wind and solar energy resources, which provides favorable conditions for increasing the proportion of renewable energy in the energy system. Second, Ningxia needs to implement a differentiated strategy of zoning development. In the northern cities along the Yellow River, industrial policies that promote rapid population concentration should be implemented, the core driving role of the provincial capital Yinchuan should be strengthened further, the land should be planned rationally, comprehensive industries led by manufacturing and service industries should be developed, the dependence of the secondary industry on energy should be reduced, and energy efficiency should be improved. In the central and southern regions, ecological function zones with distinctive features will be formed in accordance with their ecological carrying capacity, so as to promote the gradual evacuation of the population and the development of tourism, logistics, agricultural and sideline product processing and other industries. In addition, based on improving the carrying capacity of city clusters and central cities, more efforts should be made to build medium-sized cities, increase the allocation of resources to medium-sized cities, make up for the development shortcomings of these cities, and enhance their attractiveness.

There are also some uncertainties in this study. Due to differences in geographic location, latitude and longitude, and climatic conditions, there are large differences in land-use carbon emission factors across regions. In fact, it is difficult to determine the particular coefficients for each land type in each city. This study followed the practice of previous studies (Fang et al., 2007; Huang, 2013; Zhang et al., 2013; Zhao et al., 2013) and used the same coefficients to estimate the carbon emission levels of different cities in Ningxia. In addition, seasonal variations and long-term changes in carbon emissions were not considered. This study assessed carbon emissions and carbon sink levels on an annual basis without identifying their changes in different seasons of the year. Third, this study has a more objective control on the coordination of carbon emission and urbanization coupling in Ningxia and their spatial correlation characteristics, but it is necessary to further explore how to coordinate the level of carbon emission and urbanization development in Ningxia by indicators and multiple dimensions, which are uncertainties and limitations that need to be studied in depth in the next direction.

This study constructs a regional urbanization comprehensive development evaluation index system, analyzes the urbanization development level and land use carbon emission of each county and district in Ningxia from 2009 to 2019, and further explores the coupling relationship between the two. The main conclusion is as follows.

The comprehensive evaluation index of the Ningxia urbanization system and land use carbon emission both showed an increasing trend during the decade and showed a spatial pattern of being high in the North and low in the South. The coupling degree of the two increases from 0.51 in 2009 to 0.62 in 2019, with an average annual increase of 1.1%. The coupling coordination degree increases from 0.22 to 0.37, with a low overall level, indicating that Ningxia’s low level of urbanization, low energy utilization, and sloppy development patterns lead to the growth of carbon emissions in Ningxia, which in turn restricts the development of urbanization. Ningxia should promote the construction of a new type of urbanization and facilitate its transformation from economic urbanization to comprehensive development.