We propose a theoretical framework for assessing the ecological benefits provided by national key ecological projects in China over the past 20 years. A dataset consisting of six primary indicators and nine secondary indicators of ecosystem structure, ecosystem quality, and ecosystem services for the period 2000-2019 was generated using ground survey and remote sensing data. Ecological benefits were quantitatively evaluated following the implementation of national key ecological projects in China. Areas with medium, relatively high, and high degrees of ecological restoration accounted for 24.1%, 11.9%, and 1.7% of the national land area, respectively. Degrees of ecological restoration were higher in areas with a greater number of ecological projects. Areas with relatively high and high degrees of ecological restoration were mainly concentrated in the Loess Plateau, the farming-pastoral zone of northern China, the Northeast China Plain, and an area spanning the border areas of Sichuan, Yunnan, Guizhou, Chongqing, and Hunan. The relative contributions of climatic factors and ecological projects to changes in vegetation net primary productivity were 85.4% and 14.6%, respectively, and the relative contributions of climatic factors and ecological projects to changes in water erosion modulus were 69.5% and 30.5%, respectively. The restoration potential of national vegetation coverage was 20%, and the restoration potential percentages of forest and grassland vegetation coverage were 6.4% and 23%, respectively. Climatic conditions can inhibit ecological restoration. Areas with relatively high and high degrees of ecological restoration were mainly distributed in areas with an annual average temperature greater than 0 ℃ and annual precipitation greater than 300 mm. Therefore, the limitations associated with climate conditions should be considered during the implementation of national ecological projects. The implementation of single ecological projects or single ecological restoration measures should be avoided, the use of combined measures should be emphasized, and the benefits of ecological investment funds should be maximized.

Water shortage, unmatched combination of resources and unbalanced regional development are acute problems in northwest China. This region has a strategic location in promoting coordinated regional development, communicating international and domestic markets, adjusting economic structure and building ecological barriers. Therefore, the construction of eco-economic pivotal zones in northwest China would contribute to relieving the eco-environmental dilemma and improving the level of regional ecological security, which has a positive influence on the national economic development. Based on the analysis of human-environment interaction, urban agglomeration and development system, population distribution and ethnic composition in northwest China under the "Three Water Lines" pattern, this study firstly interprets the basic connotation of the eco-economic pivotal zones in this region. We propose that the eco-economic pivotal zone is a strategic area for national and global man-land coordination, which could be defined from the perspectives of ecological function zone, economic hub zone, cultural integration zone and deep-land passage zone. Based on the needs of national macro-strategic layout and land-sea coordination, we clarify the multi-functional orientations of eco-economic pivotal zones. Furthermore, this paper constructs a comprehensive development pattern in northwest China under "Three Water Lines" strategy, which is composed of 9 urban growth poles, 71 city nodes, 4 development axes and 4 eco-economic pivotal zones. And the construction layout as well as the development paths of Hexi, Lanzhou-Xining, north slope of Tianshan Mountains and circum-Tarim Basin eco-economic pivotal zones are also proposed. Finally, this paper discusses the interactive mode between the eco-economic pivotal zones and China's national development strategy layout, which would help the formation of a new pattern of development in western China, and provide a scientific basis for a better understanding of the Belt and Road Initiative.

Spatial and temporal variations in ecosystem services (ESs) are driven by two dimensions, environmental factors and trade-off/synergy between services. In the ecological conservation red line area that can guarantee regional and national ecological security and sustainable economic and social development, it is particularly important to clarify the driving mechanism of ESs for the management and optimization of ecosystem. Taking Beijing's ecological conservation red line area as an example, this study considers soil conservation, water yield and vegetation carbon sequestration, and uses Geodetector to identify the influencing factors of the relationship between the three ESs. Then, based on the partial correlation method, the impact of the net relationship between services and environmental variables on ESs is quantitatively separated and compared. Results show that trade-offs and environmental variables have varying degrees of influence on the spatial heterogeneity of ESs, and their interactions can enhance the decisive power of the corresponding individual variable. The differences in the formation process of various services make the factors that affect the relationship between services different, but the land use intensity is the most important factor for the spatial relationship between the three services, indicating that the rational planning of land use is crucial to the coordinated optimization of ESs in the Beijing's ecological conservation red line area. After removing the extremely important factors, the net relationship between services and the impact of environmental variables on ESs were compared. It is found that environmental variables (slope and precipitation) had stronger driving force on the spatio-temporal change of soil conservation. Precipitation and vegetation carbon sequestration have similar effects on water yield. Spatial and temporal changes in vegetation carbon sequestration, with relatively small effects from environmental variables, were closely related to the other two services.

Scientifically predicting and analyzing China's carbon neutrality pathways under different scenarios is helpful for the reasonable advancement of carbon neutrality goals, but there has been limited comprehensive analysis that combines carbon emission-sink change trend and a systematic analysis that uses international scenarios for climate change research. Our research simulates China's carbon emission-sink paths in the 21st century under the shared social economic paths, with the usage of WITCH integrated assessment model and IBIS vegetation dynamic model. We also predict and analyze the timetable and paths of China's carbon neutralization. We find that: (1) China's carbon aggregates show that there is a 3-4 year cyclical fluctuation. Under the RCP6.0 climate scenario, China's average carbon sinks are stable at about 0.30 Gt C/a. Under the RCP2.6 climate scenario, the amount shows a downward trend, and it is predicted to drop to about 0.18 Gt C/a in 2065-2100. (2) China's carbon emissions are jointly affected by world's economic and social development path and policy intensity. Under medium or high intensity emission reduction policies, China's carbon emissions will show a downward trend after reaching the peak in 2025-2030, and under SSP1 or SSP4 with high intensity carbon emission reduction policy, carbon emissions will be reduced to about 0.30 Gt C/a in 2060 and achieve the goal of carbon neutrality. (3) The research of pathways based on typical carbon neutral scenarios finds that, it is required to actively promote the progress and application of clean energy technology, the transformation of non-electric energy to electric energy, the popularity of biomass energy and CCS technology, and advocate the development of electric vehicles in order to realize carbon neutrality goals.

Clarifying the link between economic growth and environmental pollution is an essential issue to achieve regional high-quality development and establish "dual circulation" development patterns. Using the size of industrial economies and industrial pollution index in the Yangtze River Delta (YRD) region during 2000-2018 as the research object, this study constructs allometric growth models based on the size of industrial economies and industrial pollution index to reveal their spatio-temporal changes. We also investigate the influence mechanism of allometric growth using a boosted regression tree model. The results showed that: (1) The spatial pattern of the size of industrial economies and industrial pollution index in the study region has strong stability and high similarity, demonstrating a decreasing trend from east to west. Moreover, the industrial pollution index shows a decreasing trend with the increase in the size of industrial economies. (2) In terms of the vertical direction, the allometric growth in the YRD changes along with the pattern of the economic environment coordinated basically-the weak economic expansion-the economic environment coordinated basically. For the horizontal direction, the rate of industrial pollution index is lower than the size growth rate of the industrial economy and shows a downward trend in most of the cities. (3) Urban ecological foundation, energy efficiency, industrial development level, technological development level, opening-up level and financial investment level are the main factors affecting allometric growth, and these factors have positive impacts on allometric growth in the early stage, while turn into negative impacts during the later stage. (4) The misaligned relationship between market-driven economic growth and government-driven environmental protection induces the allometric growth of the economy and environment, and promotes regional integration. Regional integration and the allometric growth of the economic environment promote each other. Promoting economic and ecological integration in the YRD, as well as realizing the coordination of lucid waters-lush mountains and mountains of gold and silver, is the only way to accomplish regional high-quality development.

Revealing the driving factors and scale effects of water pollutant discharges is of great importance in the study of the environmental consequences of urban agglomeration evolution. It is also a prerequisite for ensuring collaborative water pollutant reduction and environmental governance in urban agglomerations. This study, taking 305 counties in the Yangtze River Delta (YRD) as an example, selects Chemical Oxygen Demand (COD) and Ammonia Nitrogen (NH₃-N) as two distinctive pollutant indicators, and uses the Spatial Lag Model (SLM) and Spatial Error Model (SEM) to estimate the driving factors of water pollutant discharges in 2011 and 2016. Then the Multiscale Geographically Weighted Regression (MGWR) model is constructed to diagnose the scale effect and spatial heterogeneity of the driving factors. The findings show that the size of permanent population, the level of urbanization, and economic development level show positive global-scale impacts on water pollutant discharges, while the level of industrialization, social fixed assets investment, foreign direct investment, and local fiscal decentralization are dominated by micro impacts at the local scale. The spatial heterogeneity of local influencing factors mainly presents the following characteristics. Social fixed assets investment has a strong positive effect on both COD and NH₃-N discharges in the Hangzhou-Jiaxing-Huzhou region and coastal area of the YRD; industrialization has a positive effect on COD discharges in the Taihu Lake basin and Zhejiang province; foreign direct investment has a local inhibitory effect on NH₃-N discharge, and the "pollution halo" effect of foreign investment is more prominent in the marginal areas of the YRD such as northern Jiangsu, northern Anhui, and southern Zhejiang; local fiscal decentralization has a noticeable inhibitory effect on COD discharge in the central part of the YRD, reflecting the positive impacts of improved local environmental awareness and stronger constraints of multi-level environmental regulations in the urban agglomeration. Therefore, it is recommended to take green production and living style to reduce the discharge base of water pollutants, to embed environmental push-back mechanism in the fields of industrial production, capital investment and financial income and expenditure, and to establish systematically a high-quality development pattern of urban agglomerations that is compatible with the carrying capacity of the water environment.