Land degradation is a global issue receiving much attention currently. In order to objectively reveal the research situation of land degradation, bibliometrix and biblioshiny software packages have been used to conduct data mining and quantitative analysis on research papers in the fields of land degradation during 1990–2019 (data update time was 8 April 2019) in the Web of Science core collection database. The results show that: (1) during the past 20 years, the number of papers on land degradation has increased. According to the number of articles, it is divided into four stages: a low-production exploration period, a developmental sprout period, expansion of the promotion period, and a high-yield active period. (2) Land-degradation research covers 93 countries or regions. The top five countries in terms of research volume are China, the United States, the United Kingdom, Germany, and Australia. China, the United States, and the United Kingdom are the most important countries for international cooperation in the field of land degradation. However, cooperation between countries is not very close overall. (3) Land degradation, degradation, desertification, remote sensing, soil erosion, and soil degradation are high-frequency keywords in the field of land degradation in recent years. (4) The research hotspots in the field of land degradation mainly focus on research directions such as restoration and reconstruction of land degradation, and sustainable management of land resources. (5) The themes of various periods in the field of land degradation are diversified, and the evolutionary relationship is complex. There are 15 evolutionary paths with regard to dynamic monitoring of land degradation, environmental governance of land degradation, and responses of land degradation to land-use change. Finally, the paper concludes that the research directions on land degradation in future include the process, mechanism, and effect of land degradation, the application of new technologies, new monitoring methods for land degradation, theory enhancement, methods and models of ecological restoration, reconstruction of degraded land, multidisciplinary integrated system research, constructing a policy guarantee system for the reconstruction of degraded land, and strengthening research on land resource engineering.

Land use/land cover change has been attracting increasing attention in the field of global environmental change research because of its role in the social and ecological environment. To explore the ecological risk characteristics of land use change in the Poyang Lake Eco-economic Zone of China, an eco-risk index was established in this study by the combination of a landscape disturbance index with a landscape fragmentation index. Spatial distribution and gradient difference of land use eco-risk are analyzed by using the methods of spatial autocorrelation and semivariance. Results show that ecological risk in the study area has a positive correlation, and there is a decreasing trend with the increase of grain size both in 1995 and 2005. Because the area of high eco-risk value increased from 1995 to 2005, eco-environment quality declined slightly in the study area. There are distinct spatial changes in the concentrated areas with high land use eco-risk values from 1995 to 2005. The step length of spatial separation of land use eco-risk is comparatively long — 58 km in 1995 and 11 km in 2005 — respectively. There are still nonstructural factors affecting the quality of the regional ecological environment at some small-scales. Our research results can provide some useful information for land eco-management, eco-environmental harnessing and restoration. In the future, some measures should be put forward in the regions with high eco-risk value, which include strengthening land use management, avoiding unreasonable types of land use and reducing the degree of fragmentation and separation.

In recent years, as a way to achieve higher agricultural output while reducing the negative impact of agricultural production on the environment, agricultural sustainable intensification has attracted worldwide attention. Under the framework of "connotation definition-measuring method-influencing factor-implementation path", this paper systematically sorts out the main research results in the field of agricultural sustainable intensification. The results show that: (1) The connotation of agricultural sustainable intensification has not been clearly defined. It is widely believed that sustainable intensification has the characteristics of increasing production and reducing environmental damage, and is widely used in agricultural, biological and environmental sciences; (2) The measurement methods and indicators of agricultural sustainable intensification are diverse, and the measurement cases are mainly distributed in Europe, Asia, Africa and America; (3) The influencing factors of agricultural sustainable intensification can be roughly divided into four aspects: socio-economic factors, farmers’ own characteristics and natural factors, among which population pressure is the potential driving force for agricultural sustainable intensification; (4) The most obvious feature of agricultural sustainable intensification is the reduction of the yield gap. The strategy of implementing agricultural sustainable intensification can be attributed to the effective use of inputs and the adoption of sustainable practices and technologies. Therefore, the implementation path can be summarized as enhancing the effectiveness of external inputs to the agricultural system and optimizing the practice and technology mix within the crop production system. Finally, this paper concludes that research on connotation definition, influencing mechanism, different regional models, incentive mechanism for farmers, impact evaluation and system design of agricultural sustainable intensification should be strengthened in future.

Farmland abandonment has important impacts on biodiversity and ecosystem recovery, as well as food security and rural sustainable development. Due to rapid urbanization and industrialization, farmland abandonment has become an increasingly important problem in many countries, particularly in China. To promote sustainable land-use management and environmental sustainability, it is important to understand the socioeconomic causes and spatial patterns of farmland abandonment. In this study, we explored the dynamic mechanisms of farmland abandonment in Jiangxi province of China using a spatially explicit economical model. The results show that the variables associated with the agricultural products yield are significantly correlated with farmland abandonment. The increasing opportunity cost of farming labor is the main factor in farmland abandonment in conjunction with a rural labor shortage due to rural-to-urban population migration and regional industrialization. Farmlands are more likely to be abandoned in areas located far from the villages and towns due to higher transportation costs. Additionally, farmers with more land but lower net income are more likely to abandon poor-quality farmland. Our results support the hypothesis that farmland abandonment takes place in locations in which the costs of cultivation are high and the potential crop yield is low. In addition, our study also demonstrates that a spatially explicit economic model is necessary to distinguish between the main driving forces of farmland abandonment. Policy implications are also provided for potential future policy decisions.