In the context of high-quality economic development and coordinated regional development, this paper measures the urban land use efficiency of 275 prefecture-level cities in China from 2003 to 2016, taking into account the unexpected output (environmental pollution), and explores the temporal and spatial evolution of urban land use efficiency through kernel density estimation and spatial autocorrelation analysis. The results show that: (1) From 2003 to 2016, China’s urban land use efficiency showed an overall fluctuating growth, but it remained at a low level. The mean value of urban land use efficiency has been gradually decreasing in east, west and central regions. (2) In the whole country and the eastern, central and western regions, the regional differences have been increasing, and the efficiency values of the whole country and the east have become polarized. (3) Urban land use efficiency shows a weak spatial positive correlation, but the degree of spatial agglomeration is increasing. High-high agglomeration areas are mostly distributed in the southeastern coastal areas, and extend into the central region, while most of the high-low polarized areas are the capital cities of the central and western regions. The low-high depressed areas are scattered around the high-value accumulation areas, some of which have turned into high-high agglomeration areas during the study period, while the low-low homogeneous areas are mainly distributed in the central, western and northeastern regions. Therefore, it is proposed that strengthening the utilization of urban stock land, strengthening the regional cooperation mechanism, and formulating policies which improve the efficiency of land use are effective ways to promote the intensive and economical use of urban land, as well as regional coordinated development.

Economic development, resource utilization, and environmental protection have always presented clear dilemmas for many countries at the national level. It is clear that the related concepts of eco-efficiency and the evaluation index can help in evaluating these associated issues. Thus, based on the use of undesirable output super Slacks-Based Measure models, this study evaluated the eco-efficiency of 30 Chinese provinces during the period between 2005 and 2016. This evaluation was conducted by analyzing the spatiotemporal dynamics and key factors influencing these changes using a panel regression model. The results of this analysis reveal that eco-efficiency gradually increased over the course of the study period, peaking at different levels among the regions. We used the conventional CV evolutionary method to show that inequalities in eco-efficiency gradually decreased at the national level. Indeed, our estimations of the factors affecting this variable suggest that industrial structure, degree of openness, urbanization, technical innovation, and environmental governance all exert significant positive influences, while energy consumption and traffic exert negative effects. The extent of the impacts of these factors on eco-efficiency varied between the different regions.

Using bibliometric methods, this paper analyzes the total amount and keyword composition among 910 studies in the field of farmland abandonment published in the Web of Science database from 1992 to 2019. According to the usage of keywords, existing studies are reviewed from the three aspects of monitoring and mapping, driving forces and influencing factors, and effects assessment and trade-off. The results show that: (1) At present, the extraction and mapping of abandoned farmland data mainly rely on household surveys and remote sensing technology, and combing NDVI time series with spatial information can provide abandoned farmland data with high precision. (2) The driving forces and influencing factors of cultivated land abandonment have been summarized in terms of extent, sources and attributes, respectively. Cultivated land marginalization is the fundamental driving force of cultivated land abandonment, labor migration is the direct driving force, and changes in socio-economic factors are the main driving forces. (3) The environmental effects of cultivated land abandonment are spatially heterogeneous, and temporal-spatial differences, the landscape environment, climate, cultivation and topographic features will all play decisive roles in shaping the ultimate environmental effects. Studies of trade-offs between the impacts of cultivated land abandonment mainly focus on ecosystem service function and value, while the role of spatial background is often ignored. Based on a systematic review of existing literature, this paper suggests that future efforts should carry out large-scale investigations on abandoned cultivated land at the national level, conduct multi-scale research on the driving forces of land abandonment, and conduct trade-off research on the effects of land abandonment based on national conditions.