Climate change will bring huge risks to human society and the economy. Regional climate change risk assessment is an important basic analysis for addressing climate change, which can be expressed as a regional system of comprehensive climate change risk. This study establishes regional systems of climate change risks under the proposed global warming targets. Results of this work are spatial patterns of climate change risks in China, indicated by the degree of climate change and the status of the risk receptors. Therefore, the risks show significant spatial differences. The high-risk regions are mainly distributed in East, South, and central China, while the medium-high risk regions are found in North and southwestern China. Under the 2°C warming target, more than 1/4 of China’s area would be at high and medium-high risk, which is more severe than under the 1.5°C warming target, and would extend to the western and northern regions. This work provides regional risk characteristics of climate change under different global warming targets as a foundation for dealing with climate change.
Climate change is expected to introduce more water demand in the face of diminishing water supplies, intensifying the degree of aridity observed in terrestrial ecosystems in the 21st century. This study investigated spatiotemporal variability within global aridity index (AI) values from 1970-2018. The results revealed an overall drying trend (0.0016 yr-1, p<0.01), with humid and semi-humid regions experiencing more significant drying than other regions, including those classified as arid or semi-arid. In addition, the Qinghai-Tibet Plateau has gotten wetter, largely due to the increases in precipitation (PPT) observed in that region. Global drying is driven primarily by decreasing and increasing PPT and potential evapotranspiration (PET), respectively. Decreases in PPT alone or increases in PET also drive global aridification, though to a lesser extent. PPT and increasing potential evapotranspiration (PET), with increasing PET alone or decreasing PPT alone. Slightly less than half of the world’s land area has exhibited a wetting trend, largely owing to increases in regional PPT. In some parts of the world, the combined effects of increased PPT and decreased PET drives wetting, with decreases in PET alone explaining wetting in others. These results indicate that, without consideration of other factors (e.g., CO2 fertilization), aridity may continue to intensify, especially in humid regions.
Phenology is an important indicator of climate change. Studying spatiotemporal variations in remote sensing phenology of vegetation can provide a basis for further analysis of global climate change. Based on time series data of MODIS-NDVI from 2000 to 2017, we extracted and analyzed four remote sensing phenological parameters of vegetation, including the Start of Season (SOS), the End of Season (EOS), the Middle of Season (MOS) and the Length of Season (LOS), in tundra-taiga transitional zone in the East Siberia, using asymmetric Gaussian function and dynamic threshold methods. Meanwhile, we analyzed the responses of the four phenological parameters to the temperature change based on the temperature change data from Climate Research Unit (CRU). The results show that: in regions south of 64°N, with the rise of temperature in April and May, the SOS in the corresponding area was 5-15 days ahead of schedule; in the area between 64°N and 72°N, with the rise of temperature in May and June, the SOS in the corresponding area was 10-25 days ahead of schedule; in the northernmost of the study area on the coast of the Arctic Ocean, with the drop of temperature in May and June, the SOS in the corresponding area was 15-25 days behind schedule; in the northwest of the study area in August and the southwest in September, with the drop of temperature, the EOS in the corresponding areas was 15-30 days ahead of schedule; in regions south of 67°N, with the rise of temperature in September and October, the EOS in the corresponding area was 5-30 days behind schedule; the change of the EOS in autumn was more sensitive to the change of the SOS in spring, because the smaller temperature fluctuation can cause the larger change of the EOS; the growth season of vegetation in the study area was generally moving forward, and the LOS in the northwest was shortened, while the LOS in the middle and south of the study area was prolonged.
Vegetation plays a key role in maintaining ecosystem stability, promoting biodiversity conservation, serving as windbreaks, and facilitating sand fixation in deserts. Based on the Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index (MODIS NDVI) and climate data, a Theil-Sen median trend analysis combined with the Mann-Kendall test and partial correlation and residual analyses were employed to explore spatiotemporal patterns of vegetation dynamics and key drivers in the Badain Jaran and Tengger deserts and Mu Us Sandy Land. Data were collected during the growing season between 2001 and 2020. Further analyses quantified the relative contribution of climate variation and anthropogenic activities to NDVI changes. Results revealed a predominantly increasing trend for average NDVI. The spread of average annual NDVI and growth trends of the vegetation were determined to be influenced by spatial differences. The area with improved vegetation was greater than that of the degraded region. Climate variability and human activities were driving forces controlling vegetation cover changes, and their effects on vegetation dynamics varied by region. The response of vegetation dynamics was stronger for precipitation than temperature, indicating that precipitation was the main climate variable influencing the NDVI changes. The relative role of human activities was responsible for > 70% of the changes, demonstrating that human activities were the main driving factor of the NDVI changes. The implementation of ecological engineering is a key driver of increased vegetation coverage and has improved regional environmental quality. These results enhance our knowledge regarding NDVI change affected by climate variation and human activities and can provide future theoretical guidance for ecological restoration in arid areas.
Vegetation change is of significant concern because it plays a crucial role in the global carbon cycle and climate. Many studies have examined recent changes in vegetation growth and the associated drivers. These drivers include both natural and human activities, but few studies have identified the regulation factors. By employing normalized difference vegetation index (NDVI) data, we analyzed the spatiotemporal pattern of vegetation change in China and then explored the driving factors. It was found that the overall greening of China has improved significantly, especially in the Loess Plateau and southwest China. The Yangtze River Delta and Bohai Rim, however, have not seen as much growth. Natural conditions are conducive to vegetation growth. Although socioeconomic development will be more beneficial for vegetation restoration, the current level and speed of development have a negative effect on vegetation. The regulation factors are considered separately since they affect both directly and indirectly. Regulation factors have accelerated vegetation growth. By understanding the factors affecting the current vegetation growth, we can provide a guide for future vegetation recovery in China and other similar countries.
Land degradation affects extensive drylands around the world. Due to long-term misuse, the Israeli Sde Zin dryland site has faced severe degradation. The study objective was to assess the feasibility of passive restoration in recovering the site. The study was conducted in four land-units along a preservation-degradation continuum: (1) an area that has not faced anthropogenic disturbances (Ecological land); (2) an area that was proclaimed as a national park in the 1970s (Rehabilitation); (3) an area that was prone, until recently, to moderate anthropogenic pressures (Triangle); and (4) a dirt road that was subjected to long-term off-road traffic (Dirtroad). Soil was sampled and analyzed for its properties. The soil physical quality followed the trend of Ecological land > Rehabilitation > Triangle > Dirtroad. Specifically, high soil salinity in the latter three land-units is attributed to long-term erosional processes that exposed the underlying salic horizons. Herbaceous and shrubby vegetation cover was also monitored. The herbaceous vegetation cover followed the trend of Ecological land (86.4%) > Rehabilitation (40.3%) > Triangle (26.2%) > Dirtroad (2.1%), while the shrubby cover was 2.8% in the Ecological land-unit, and practically zero in the other land-units. It seems that despite the effectiveness of passive restoration in recovering the soil’s physical properties, the recovery of vegetation is limited by the severe soil salinity.
Given the importance of waterway depths in river development, the effects of the evolution of bars and troughs on waterway expansion play an important role in river management and water depth conservation. This study aims to expand the waterway dimensions of the Jingjiang Reach of the Yangtze River. To achieve this objective, determining the relationship between river evolution processes and the potential for waterway depth improvement and navigation hindrances is vital. Therefore, the sedimentation, hydrological, and terrain data of the Jingjiang Reach from 1955 to 2020 are analysed to elucidate the above-mentioned relationship. Since the commissioning of the Three Gorges Dam, the scouring of the low-flow channel has accounted for 90%-95% of all scouring in the Jingjiang Reach. Furthermore, the central bars and beaches have shrunk by 9.4% and 24.9%, respectively, and 18.3% overall. Considering the bed scouring and waterway regulation projects in the Jingjiang Reach, we investigated the continuity of a 4.5 m × 200 m × 1050 m (depth × width × bend radius) waterway along the Jingjiang Reach, and find that navigation-hindering channels account for over 5.3% of the waterway length. Furthermore, part of the Jingjiang Reach is an important nature reserve and shelters numerous water-related facilities, which inhibits the implementation of waterway deepening projects. The findings of this study demonstrate that numerous challenges are associated with increasing the waterway depths of the Jingjiang Reach.
Delayed response behaviour commonly occurs in conjunction with changes in riverbed scouring and sediment deposition and is a key component in understanding the intrinsic behaviour of reservoir siltation. Due to the complexity of the riverbed siltation process, the variability in the factors that influence siltation and the limitations of available research methods, the understanding of the delayed response behaviour of the sedimentation process in the Three Gorges Reservoir (TGR) is currently merely qualitative, and there is a lack of quantitative in-depth understanding. In addition, the effects of changes in water and sediment conditions on sedimentation in the TGR before and after cascade reservoir impoundment have not been quantified, so further studies are needed to provide a reference for better understanding the intrinsic behaviour of sedimentation in the TGR and the implications for the long-term use of the reservoir. Based on measured water and sediment data from 2003 to 2020 and topographic data from 2003 to 2018, a delayed response model for sedimentation in the TGR is constructed and combined with theoretical derivation to analyse the changes in the delayed response behaviour of the TGR before and after the impoundment of the cascade reservoirs and the associated causes. Then, the influence of changes in water and sediment conditions in previous years on sedimentation in the reservoir area is determined. The results show that (1) the improved delayed response model of sedimentation, which considers variations in external water and sediment conditions, reservoir scheduling, and riverbed adjustment rates, can effectively reflect the sedimentation process in the TGR, especially after the impoundment of the cascade reservoirs. Additionally, the typical section elevation delayed response model can simulate the section elevation adjustment process. (2) After the impoundment of the cascade reservoirs, the decreased variation in incoming water and sediment and more concentrated incoming sediment in the flood season increased the adjustment rate of the riverbed, and the delayed response time of TGR sedimentation was shortened from the previous 5 years to the previous 3 years. The impact of the previous water and sediment conditions is not negligible for the sedimentation process in the TGR, and the cumulative proportion of the previous influence reaches more than 60%. (3) The influence of incoming sediment on the sedimentation process and typical section adjustment process in the reservoir area increased after the impoundment of the cascade reservoirs, and the influence of the water level in front of the dam on sedimentation remained the largest.
Studies investigating innovation networks shaped by large innovative enterprises (LI-ENTs), which play a very important role in intercity diffusion of technology and knowledge, are rather thin on the ground. Using location information of LI-ENTs in China, we performed a headquarter-branch analysis to generate intercity innovation linkages and analyzed the patterns and dynamics of the generated network of knowledge diffusion. Although the network covers 353 cities across China, its spatial distribution is extremely uneven, with a few cities and city-dyads dominating the structure of the network. Furthermore, intercity linkages of innovation within and of urban agglomerations, as well as their central cities, stand out. With regard to network dynamics, the economic development level, innovation ability, and administrative level of cities, as well as the geographical, institutional, and technological proximity between cities are all found to have a positive impact on intercity linkages of innovations, whilst the impact of FDI on the national distribution of Chinese innovative enterprises is negative. Most importantly, the status of cities within the urban agglomeration exerts a significant positive effect in relation to the innovative enterprises’ expansions, which reflects that the top-down forces of government and the bottom-up forces of market function together.
As China’s economy and society continue to expand, urbanization in China has reached a new stage. In this context, China’s characteristic town development plans, from the national to the local level, provide a new impetus for the expansion of towns and cities, and contribute to rural revitalization. When assessing the universality of regional dynamics, China exhibits high diversity for regional development. This highlights a complex scientific problem associated with describing the underlying linkages and influencing variables between distinct regional characteristic towns. It also complicates the application of tools that support spatial orientation and spatial decision-making. To address this problem, this study proposes a cross-platform analytical framework that unifies data, geography information systems (GIS), unsupervised analysis, visualization, and Geodetector, with Orange as the core. Based on a review of distribution patterns and multi-hierarchical spatial clustering features, this paper focuses on the rise of characteristic towns in China and investigates the primary environmental and human factors influencing spatial heterogeneity in small towns. The findings show that the development level of characteristic towns under the “city-town” system varies across China. Multi-hierarchical cluster analysis effectively reveals the intrinsic features of characteristic towns and facilitates precise spatially-oriented decision-making under different scenarios. In the framework of the “natural-humanistic” and “city-town” systems, the Geodetector effectively measures the spatial stratified heterogeneity of each indicator in the characteristic towns. This reveals an inner logic among the diverse non-linear spatial correlations. Ultimately, the study deeply investigates the individual development of characteristic towns, and the synergistic construction of “city-town” systems, arguing that characteristic towns have the potential to create “city-town” interactive spaces, and the ability to realize “Orange+GIS” cross-platform synergies.
Urbanization of the Tibetan Plateau is a part of the strategies to strengthen China’s national security shield as well as to enhance its national ecological safety barrier and the “water tower” of Asia. It also plays an irreplaceable role in protecting one of the last unspoiled regions in the world, ensuring that the “third pole” achieves modernization in step with the rest of China, and improving the lives of all ethnic groups that live in “roof of the world.” This study discusses in detail the distinctive drivers, development path, development goals, development dynamic, and green development model and strategy of the new type of urbanization in the Tibetan Plateau, which differs markedly from the rest of China. This author asserts that urbanization of the Tibetan Plateau should involve low-intensity development, cultural transmission, protection of land and borders, conservation of water resources, small concentrations and wide dispersion of the population, social inclusivity, and improvements to the environment that benefit the people, driven by domestic investment, tourism, services, and paired assistance. The plans for the region’s future development are as follows. In terms of the protection of land and borders, the Tibetan Plateau will safeguard China’s national security with fast and stable development and ensure sufficient populations inhabit border and rural areas. By 2035, the permanent population of the plateau will be 16 million, and the level of urbanization will reach 52.5%, with stability in the middle stage of urbanization, thereby comprehensively improving the quality of urbanization. In terms of green development, it is necessary to improve the quality of ecological products and the capacity and level of ecological services, accentuate local features and folk customs, promote culture, and encourage people to tend livestock in rural areas and live in towns, thereby creating beautiful cities and towns in the Tibetan Plateau. In terms of the small concentrations and wide dispersion of the population, the overall urban pattern will be “three clusters, four belts, and multiple nodes.” The “three clusters” are the Xining, Lhasa, and Qaidam metropolitan areas; the “four belts” are along the Qinghai-Tibet Railway, the Sichuan-Tibet Railway, the Ancient Tang (China)-Tibet Road, and border areas; and “multiple nodes” refers to major urban nodes and border towns. In terms of ensuring connectivity, the Qinghai-Tibet Railway was completed ahead of schedule, national security lines are being strengthened, and new infrastructure and smart cities are being built. Additionally, the land system of border cities is being reformed, a special zone for experimental border land reform is being constructed, and border towns are being prioritized in national strategies and territorial space planning.
Human activities in the marginal zone of the Changtang Plateau (CTP) uninhabited area are important research topics in China and globally. Based on the core-periphery theory of geography, this paper selected three counties in the marginal zone of the CTP uninhabited area with significant transitional physical geography features and socio-economic conditions as case areas. We used the data set of settlement patches identified by visual interpretation in Google Earth Pro, combining them with field survey data to study the evolution of human settlements on the CTP, the characteristics of settlement layout, and their socio-economic roots. The study found that: (1) Since the democratic reform in Tibet, the production mode of herders on the CTP has transitioned from four-season nomadic herding to cold-season sedentary grazing, warm-season rotational grazing, and then to a combination of sedentary grazing and forage supplementation. In structural changes of grassroots organizations, village boundaries were clarified, grazing ranges were fixed, and settlement systems were formed. (2) On a large scale, the settlement layout on the CTP showed a certain degree of agglomeration in local areas, but the settlements’ spatial agglomeration decreased as the observation scale decreased. The settlement size structure matched the typical rank-size rule of rural settlements. (3) The settlement layout of the CTP showed significant traffic lines and dominant location orientation. These orientation characteristics revealed “core-periphery” regional differences. Changes in production conditions, such as artificial grass cultivation and part-time employment, affected the dependence on traditional grazing points. Settlements moved from resource dependence to dependence on multiple elements, such as resources and facilities. The religious, cultural heritage of the sacred mountains, lakes, and temples influenced the settlement layout, leading to clustering in local areas and to group format. This study expands our understanding of the settlement pattern in the marginal zone of uninhabited areas and provides valuable references for advancing the optimization of the CTP human settlement system in the new era.
