Large-scale Land Reclamation Research Articles

Maize-Straw Biochar Enhances Soil Properties and Grain Yield of Foxtail Millet in a Newly Reclaimed Land

Large-scale land reclamation has become common in northwestern China; however, low soil fertility and poor soil water-holding capacity limit agricultural production on these reclaimed lands, requiring increased fertilizer and irrigation inputs. Biochar, produced from agricultural waste, has shown potential in improving soil quality and water-holding capacity. In this two-year field study (2021 and 2022), we investigated the effects of biochar produced from maize straw on soil properties and grain yield of foxtail millet grown on newly reclaimed land. Three biochar treatments (3000, 4500, and 6000 kg ha−1) were compared to a control (CK) with no biochar application. Biochar application resulted in increased soil organic matter, total phosphorus, total nitrogen, soil enzyme activity, and soil organic acid content. It also significantly decreased soil pH and bulk density. Compared with the CK, biochar increased available nitrogen from 29.7% to 108% in 2021 and 37.0% to 88.4% in 2022. Similarly, biochar increased available phosphorus from 64.7% to 143% in 2021 and 41.9% to 96.5% in 2022. Grain yields ranged from 3092 to 4753 kg ha−1. Biochar treatments increased grain yield compared to the CK, ranging from 12.2% to 24.6% in 2021 and 27.1% to 53.7% in 2022. Correlation analysis revealed that soil pH was negatively related to soil oxalic acid content, phosphorus content, and sucrase activity. Available nitrogen and phosphorus contents were negatively related to soil bulk density and positively related to catalase activity. Soil water content was negatively correlated with soil bulk density and positively correlated with organic matter. In conclusion, biochar improved the rhizosphere soil pH and the effectiveness of soil fertility in the newly reclaimed soil, resulting in an enhanced grain yield of foxtail millet.

Response of hydrodynamic environment to land reclamation in Sanmen Bay, China over the last half-century

Sanmen Bay (SMB) is one of the important harbors in Zhejiang Province. It is a semi-enclosed shallow bay that has undergone large-scale land reclamation activities. Long-term reclamation has changed the hydrodynamic conditions of SMB, such as tide, residual current, tidal prism, water exchange capacity, and tidal asymmetry. In this study, three typical periods of numerical models, based on historical charts and remote sensing, were established to investigate the influence of reclamation activities on the hydrodynamic conditions of SMB from 1971 to 2020. These model results reveal that the amplitude and phase of M2, the main tidal components in SMB, decreased by ~0.1–0.3 m and ~ 5°–15°, respectively, over the last half-century. Additionally, under the influence of ~200 km2 reclamation, many hydrodynamic conditions in SMB also changed. This includes the reduction of a residual current and tidal prism, an increase in residence time, and a change in tidal asymmetry characteristics. The residence time in nearby Xiayangtu exhibited a downward trend from 2003 to 2020, because land reclamation squeezed, and thus, enhanced the residual current eddy. The water-exchange capacity of the bay became weaker with the reduction of tidal prism to one-third and an increase in residence time. The tidal asymmetry characteristic of SMB changed from half of flood dominant to fully flood dominant by the influence of shoreline and bathymetry, which raised the flood risk. Research on the response of the hydrodynamic environment to reclamation activities in SMB reminds the local government to reassess the impact of land reclamation on the hydrodynamic environment.

Rapid seagrass meadow expansion in an Indian Ocean bright spot

The areal extent of seagrass meadows is in rapid global decline, yet they provide highly valuable societal benefits. However, their conservation is hindered by data gaps on current and historic spatial extents. Here, we outline an approach for national-scale seagrass mapping and monitoring using an open-source platform (Google Earth Engine) and freely available satellite data (Landsat, Sentinel-2) that can be readily applied in other countries globally. Specifically, we map contemporary (2021) and historical (2000–2021; n = 10 maps) shallow water seagrass extent across the Maldives. We found contemporary Maldivian seagrass extent was ~ 105 km2 (overall accuracy = 82.04%) and, notably, that seagrass area increased threefold between 2000 and 2021 (linear model, + 4.6 km2 year−1, r2 = 0.93, p < 0.001). There was a strongly significant association between seagrass and anthropogenic activity (p < 0.001) that we hypothesize to be driven by nutrient loading and/or altered sediment dynamics (from large scale land reclamation), which would represent a beneficial anthropogenic influence on Maldivian seagrass meadows. National-scale tropical seagrass expansion is unique against the backdrop of global seagrass decline and we therefore highlight the Maldives as a rare global seagrass ‘bright spot’ highly worthy of increased attention across scientific, commercial, and conservation policy contexts.

Public Health and Political Governance

Abstract In the light of the Covid-19 pandemic, its mutations, concealment by people and the resistance to vaccines against it, it is relevant to examine the outbreak of bubonic plague in colonial Lagos during the early twentieth century and the response by the British colonial authorities. The methodology applied to this study is historical, drawing information from medical, sanitary, land use and physical planning documents accessed from various archives as well as some secondary sources. It is clear that the colonial government’s housing and public health regulations, which allowed authorities to inspect people’s homes for cases of infectious disease, drove people to escape into the hinterland, increasing the spread of the plague. Consequently, the colonial authorities carried out a massive structural and physical reorganisation of towns and villages. They also embarked on large-scale land reclamation, decongested overcrowded houses and introduced sanitary measures to make the environment more habitable. This paper argues that through effective political governance structures the colonial government strategically eliminated the bubonic plague in Lagos.

Groundwater Level Dynamic Impacted by Land-Cover Change in the Desert Regions of Tarim Basin, Central Asia

Groundwater is essential to residents, ecology, agriculture, and industry. The depletion of groundwater impacted by climatic variability and intense human activities could threaten water, food, and socioeconomic security in arid regions. A thorough understanding of groundwater level dynamics and its response to land-cover change is necessary for groundwater management and ecosystem improvement, which are poorly understood in arid desert regions due to a scarcity of field monitoring data. In our study, spatiotemporal characteristics of groundwater level impacted by land-cover change and its relationship with vegetation were examined using 3-years in-situ monitoring data of 30 wells in the desert regions of Tarim Basin during 2019–2021. The results showed that the depth to groundwater level (DGL) exhibited obvious spatial and seasonal variations, and the fluctuation of DGL differed significantly among the wells. The cultivated land area increased by 1174.6, 638.0, and 732.2 km2 during 2000–2020 in the plains of Yarkand, Weigan-Kuqa, and Dina Rivers, respectively, mainly transferring from bare land and grassland. Annual average Normalized Difference Vegetation Index (NDVI) values increased with time during the period in the plains. DGL generally exhibited a weakly increasing trend from 2019 to 2021, mainly due to human activities. Land-cover change significantly affected the groundwater level dynamic. Generally, the groundwater system was in negative equilibrium near the oasis due to agricultural irrigation, was basically in dynamic equilibrium in the desert region, and was in positive equilibrium near the Tarim River Mainstream due to irrigation return water and streamflow. NDVI of natural desert vegetation was negatively correlated with DGL in the desert regions (R2 = 0.78, p &lt; 0.05). Large-scale land reclamation and groundwater overexploitation associated with water-saving irrigation agriculture development have caused groundwater level decline in arid oasis-desert regions. Hence, controlling groundwater extraction intensity, strengthening groundwater monitoring, and promoting water-saving technology would be viable methods to sustainably manage groundwater and maintain the ecological environment in arid areas.

Spatiotemporal Variation and Future Predictions of Soil Salinization in the Werigan–Kuqa River Delta Oasis of China

Soil salinization is a serious global issue; by 2050, without intervention, 50% of the cultivated land area will be affected by salinization. Therefore, estimating and predicting future soil salinity is crucial for preventing soil salinization and investigating potential arable land resources. In this study, several machine learning methods (random forest (RF), Light Gradient Boosting Machine (LightGBM), Gradient Boosting Decision Tree (GBDT), and eXtreme Gradient Boosting (XGBoost)) were used to estimate the soil salinity in the Werigan–Kuqa River Delta Oasis region of China from 2001 to 2021. The cellular automata (CA)–Markov model was used to predict soil salinity types from 2020 to 2050. The LightGBM method exhibited the highest accuracy, and the overall prediction accuracy of the methods had the following order: LightGBM &gt; RF &gt; GBRT &gt; XGBoost. Moderately saline, severely saline, and saline soils were dominant in the east and south of the research area, while non-saline and mildly saline soils were widely distributed in the inner oasis area. A marked decreasing trend in the soil salt content was observed from 2001 to 2021, with a decreasing rate of 4.28 g/kg·10 a−1. The primary change included the conversion of mildly and severely saline soil types to non-saline soil. The generalized difference vegetation index (51%), Bio (30%), and temperature vegetation drought index (27%) had the greatest influence, followed by variables associated with soil attributes (soil organic carbon and soil organic carbon stock) and terrain (topographic wetness index, slope, aspect, curvature, and topographic relief index). Overall, the CA–Markov simulation resulted exhibited suitable accuracy (kappa = 0.6736). Furthermore, areas with non-saline and mildly saline soils will increase while areas with other salinity levels will continue to decrease from 2020 to 2050. From 2046 to 2050, numerous areas with saline soil will be converted to non-saline soil. These results can provide support for salinization control, agricultural production, and soil investigations in the future. The gradual decline in soil salinization in the research area in the past 20 years may have resulted from large-scale land reclamation, which has turned saline alkali land into arable land and is also related to effective measures taken by the local government to control salinization.

Introducing ICEDAP: An ‘Iterative Coastal Embayment Delineation and Analysis Process’ with Applications for the Management of Coastal Change

Coastal embayments provide vital benefits to both nature and humans alike in the form of ecosystem services, access to waterways, and general aesthetic appeal. These coastal interfaces are therefore often subject to human development and modifications, with estuarine embayments especially likely to have been anthropogenically altered. Frequent alterations include damming to eliminate tidal influx, backfilling to create new land, and development for the sake of economic gain, which may cause profound damage to local habitats. By providing a record of transitions in surface waters over time, satellite imagery is essential to monitoring these coastal changes, especially on regional to global scales. However, prior work has not provided a straightforward way to use these satellite-derived datasets to specifically delineate embayed waters, limiting researchers’ ability to focus their analyses on this ecologically and economically important subset of coastal waters. Here, we created ICEDAP, a geometry-based ArcGIS toolbox to automatically delineate coastal embayments and quantify coastal surface water change. We then applied ICEDAP to the coast of South Korea, and found that coastal habitat change was particularly profound within embayed regions identified using an 8 km epsilon convexity setting (denoting a moderate distance from the coast and degree of enclosure by surrounding land areas). In the mapped coastal embayments, more than 1400 km2 of coastal habitats were lost during the past 38 years, primarily due to human modification such as large-scale land reclamation projects and the construction of impoundments. Our results suggest that anthropogenic alterations have resulted in the widespread loss of more than USD 70 million of valuable coastal ecosystem services. Together, ICEDAP provides a new innovative tool for both coastal scientists and managers to automatically identify hotspots of coastal change over large spatial and temporal scales in an epoch where anthropogenic and climate-driven changes commonly threaten the stability of coastal habitats.

Large scale land reclamation and the effects on hydro-mechanical behavior in loess and loess-derived fill

To discover the complex hydro-mechanical evolution on Loess Plateau that accompany large-scale land reclamation project, we tracked changes of moisture, matric suction, anisotropic displacements and stresses in geological interfaces of natural loess and deep man-made fill during a comprehensive process of construction and the subsequent three years rest period. Results indicate that vertical stress increases during emplacement of thick fill, while the lateral earth pressure first increases and then gradually decreases with elapsed time. There was a non-linear increase in lateral earth pressure with depth of infill during construction. Whereas lateral earth pressure decreased with depth in lengthy rest period. The fill vertically compressesed and laterally extended during construction, while the geological interface of fill and loess laterally rebounded during construction pause. The primary vertical displacement occurred at the contact zone between the original loess slope and fill. The lateral earth pressure coefficient of infill is influenced by lateral compression and extension of contact zone during land reclamation process. It mirrors the observation that variations in lateral earth pressure with depth are dependent on deformation of natural slope materials. Interestingly, vertical stress and lateral earth pressure periodically fluctuated during rest period, correlating to creeping and shrinkage in loess influenced by moisture content change under different environmental relative humidity. The volumetric moisture contents in fill and contact zone significantly increased during construction. The moisture content of contact zone is 10% higher than the overlying higher density fill after construction, which is attribute to the process of matric suction equilibrium. Considering a constant moisture content, the ratio of historical mean principal stress to deviatoric stress in fill and interface are under the principal stress failure line during construction. However, water diffusion potentially threats the stability of this man-made geological structure.

Socio-natural aspects of the causes and consequences of the famine of 1921–1923 in the Volga region

This paper analyzes socio-natural aspects of the causes and consequences of the famine in the early 1920s in the Volga region. Ecological problems of anthropogenic nature, which appeared in this region in the second half of the 19th century, are considered as an essential cause of famine. It was those problems that largely caused periodic droughts and crop failures that led to famine. The author considers large-scale irrigation and land reclamation, construction of waterworks and reservoirs, as well as afforestation, which began in the Middle Volga region in the 1930s, to be important consequences of the famine. Thanks to the interaction of the authorities and society in the implementation of state programs to combat drought and crop failures, in the second half of the twentieth century, it was possible to eliminate the threat of food shortages and the emergence of severe social problems in this regard. The research is based on a number of published and unpublished documents, including archival materials, which contain evidence of contemporaries of the events and processes described. The content of the paper and the conclusions formulated by its author correspond to the current trends in the development of socio-economic and environmental history of Russia.

Wave and storm surge evolutions in the Pearl River Estuary with large-scale land reclamation impacts

Globally, many estuarine areas are suffering from large-scale land reclamations to fulfill the land demands of city expansion. Understanding the wave and storm surge evolutions in response to human reclamations in estuaries is of vital importance regarding estuarine management (e.g., reclamation plan formulation, flood mitigation). The wave and storm characteristics, and their responses to 1990–2020 land reclamations in the Pearl River Estuary (PRE) were investigated by a storm surge model. Besides, the impacts of increasing typhoon intensity (TI) on the changes of waves and storm surges caused by reclamations were also illustrated under the background of global warming. Simulated results show that reclamations cause apparent variations of wave height and storm surge fields in the PRE. The wave height and surge height also increase with the enhancement of TI, consequently influencing the wave height and surge height change rates caused by reclamations. Furthermore, the combined actions of land reclamation and increased TI conduct the most remarkable effects and bring the highest surge height compared with other scenarios. Particularly, the maximum wave height and surge height can reach 0.88–2.31 m and 2.71–3.77 m along the seawalls of Zhuhai, respectively, indicating more enormous seawall submersion and inland flooding.

A review of theriological research in the Polissia in the XIX–XXI centuries

The history of theriological research in the territory of Polissia from the 19th century to the present is considered (authors, works, and contributions to the study of the mammal fauna of the region). A review of the most significant publications on the theriofauna of the Polissia region is presented. The material is considered in chronological order, in four sections: ‘The period before systematic collecting’ (from the 19th century to 1920), ‘The period of field expeditionary research’ (1920–1940), ‘The resumption of theriological research at a new level’ (1945–1970), ‘Period of detailed stationary studies’ (1971–2000), ‘Modern stage of research’ (from 2001 to the present). A list of the most famous researchers of Polissia is given in accordance with the proposed periodization. The authors conclude that the number of studies and publications for the analysed period is connected, first, with state projects for the economic development of this territory (the construction of the Brest–Moscow railway at the end of the 19th century, large-scale land reclamation of Polissia throughout almost the entire 20th century). The key role of A. V. Fedyushin and I. N. Serzhanin for the development of theriological research is noted. The role of nature reserves created in the Chernobyl territory in the study of the mammal fauna of this region is discussed. The complete list of Polissia mammals including 80 species is given. It is concluded that the Polissia theriofauna has not been fully studied (insectivorans, bats, and rodents). The theriological studies in various parts of the Polissia region were carried out unevenly: from single visits and local expeditions to stationary and long-term monitoring studies. The insufficient level of theriological monitoring and, as a result, the lack of proper analysis of changes in mammal assemblages are indicated. The existing scientific collections, where specimens of mammals from Polissia are stored, are not catalogued into a single database and are difficult to study. In Belarus, theriologists are divided and do not have a common platform for the exchange of information and experience. The positive experience of Ukrainian colleagues in the creation and maintenance of the long-term activity of the Theriological School is presented.

Water quality and interaction between groundwater and surface water impacted by agricultural activities in an oasis-desert region

A comprehensive understanding of groundwater dynamics and its interaction with surface water under the influence of agricultural activities is essential for local agriculture, ecology and resident in arid regions, which is poorly understood in arid oasis-desert region. In our study, with emphasis on a comparison of hydrogeochemical characteristics between the oasis (irrigated) and desert (non-irrigated) areas, the water quality and groundwater-surface water interaction of a typical oasis-desert system with a rapid irrigation agriculture development were examined to clarify the effects of agricultural activities on groundwater level and quality using stable isotopic and hydrochemical data of 83 water samples. Results showed that cultivated land area increased by 121.8 % (732.4 km2) during 2000 to 2020, mainly transferring from grassland and bare land. Groundwater EC ranged from 786 to 49,400 μS/cm, with weakly alkaline. Shallow groundwater had a much higher EC than other water components. Stable isotopic and EC values of shallow groundwater in the non-irrigation areas were much greater than those in the irrigation areas, whereas middle groundwater isotopic values were more depleted in the desert than in the oasis. Shallow groundwater EC value was lower in summer, middle groundwater had higher EC in summer. Streamflow and confined water in the study area are suitable for agricultural irrigation, but phreatic water in the oasis is generally not suitable for irrigation at present. The groundwater chemistry was mainly controlled by strong evaporation, dilution, mixing, water-rock interaction and agricultural drainage. Groundwater in the irrigation areas was recharged by ephemeral runoff seepage, irrigation return flow and subsurface lateral inflow. Long-term development of irrigation agriculture (large-scale land reclamation, irrigation and groundwater pumping) in arid region has caused groundwater level decline and salinization, with a strong interaction between phreatic water and surface water. Hence, decreasing irrigation area and groundwater exploitation, carrying out gradual ecological restoration, improving water-saving efficiency and agricultural drainage system would be the viable method to restore groundwater and maintain the oasis-desert ecosystem coexistence in arid regions in the context of climate change.

Future climate imposes pressure on vulnerable ecological regions in China

Ecological regions of medium fragility account for 55 % of China's land. Large-scale afforestation and land reclamation have been carried out in these areas over the past few decades. However, how future climate change poses risks and challenges to them remains unclear. By establishing a multi-algorithm framework combining machine learning algorithms with multi-source dataset, our work predicts Normalized Difference Vegetation Index (NDVI, a proxy for vegetation greenness) and its variations in the 21st century under different climate scenarios. We find that vegetation greening (i.e., NDVI increase) in northern and southwestern China is unstable over four 20-year periods from 2020 to 2100. However, a strikingly prominent greening is expected to occur on the Qinghai-Tibet Plateau until the end of this century. Future warming can not only exacerbate the difficulties of vegetation conservation and restoration in vulnerable ecological regions, also threaten these new croplands, stymieing ambitions to increase crop production in China. Our results underscore the crucible that a warming climate presents to current restoration projects. We highlight the urgency of adapting to climate change to achieve ambitious goals of carbon sequestration and food security in China.

Signals, Deterrence, and the Quad

Signals, Deterrence, and the Quad Ketian Zhang (bio) The United States and its allies have the capability to deter China, and have successfully done so, from their worst-case scenario—a major militarized conflict. However, three factors reduce the effectiveness of their deterrence: the lack of clear signals, excessive media exposure, and divergent interests among Quad members. The Quad can be useful, but only if the United States maintains well-defined signals of commitment while clarifying the stakes. As it currently stands, the Quad does not successfully deter Chinese actions in territorial disputes. China has not shied away from using military coercion in its land border disputes with India. In June 2020, for instance, Chinese and Indian troops clashed violently along the disputed land border in the Galwan Valley, resulting in casualties on both sides.1 Chinese foreign minister Wang Yi told India to "stop transgressions into China-controlled territories" and to "refrain from actions changing the status quo along the border," representing a clear indication of coercive intent.2 Moreover, although China prefers to utilize nonmilitary—or so-called gray-zone—coercion in maritime disputes in the South and East China Seas, such coercive measures can themselves be destabilizing.3 This essay assesses factors influencing the likelihood of successful deterrence in the Indo-Pacific region by using China's land and maritime territorial disputes as examples. It addresses two questions: what signals of resolve are necessary for effective deterrence, and does the Quad enhance [End Page 43] deterrence? Finally, it uses the Sino-Indian border and South China Sea disputes to illustrate the conditions under which deterrence can be effective. The Need for Clearer Signals The United States and its allies have the capability to potentially deter China's territorial challenges. However, clearer signals of resolve and reassurance are necessary to achieve successful deterrence. First and foremost, the United States should set clearer red lines; otherwise, the signals sent to China are mixed and ineffective. For example, during its first term, the Obama administration was not sufficiently clear in signaling red lines to China regarding Chinese behavior in the South China Sea. A 2013 Chinese Academy of Social Sciences report on China's regional security environment stated that the implementation of U.S. rebalancing "had a problem of divergence between willingness and capability," citing the lack of U.S. commitment during the Scarborough Shoal incident of April 2012.4 This lack of clear U.S. red lines led Beijing to proceed with large-scale land reclamation activities in late 2013 and 2014. One Chinese scholar this author interviewed who was often in conversation with the then South China Sea section of China's State Oceanic Administration noted that "China first started reclamation at the Johnson South Reef and was watching the reaction from the international society carefully; it proceeded with large-scale reclamation after realizing that there was not much of a reaction internationally."5 By "international," this interviewee meant the United States. The U.S. response in 2014 was relatively muted: Washington did not call out China's land reclamation from the outset. Instead, the White House and, importantly, President Barack Obama himself remained silent. Obama's second term, however, saw the drawing of clearer red lines. During the November 2015 Asia-Pacific Economic Cooperation (APEC) summit in Manila, Obama called on China to halt its land reclamation activities in the South China Sea.6 He subsequently warned Beijing in March 2016 that there would be "serious consequences if China reclaimed land [End Page 44] at the Scarborough Shoal."7 Local Chinese government documents from 2013 noted explicitly that China would implement land reclamation on the Scarborough Shoal.8 Yet following Obama's 2015–16 warnings, subsequent government documents cease to mention reclamation on the Scarborough Shoal. This suggests that without the clear red line from the United States, it is quite plausible that China would have proceeded to reclaim the Scarborough Shoal, making this episode a successful case of U.S. deterrence. The Trump administration pressed Beijing to halt militarization of the South China Sea, but Trump himself did not issue a clearly stated red line. This lack of clarity could have had adverse effects. Chinese analyst...

Impacts of land reclamation projects on hydrodynamics and morphodynamics in the highly altered North Branch of the Changjiang Estuary

The estuary is highly dynamic and sensitive to external and internal forcing. We examine a chain reaction of hydrodynamic and morphodynamic responses to a series of land reclamation projects during the period 1997 to 2017 in the North Branch of the Changjiang Estuary through the Digital Elevation Model (DEM) comparison and the numerical simulation by the Finite Volume Community Ocean Model (FVCOM). The results show that tidal amplification was further strengthened by the artificially reduced channel volume in the middle and upper segments of the North Branch due to the implementation of several large-scale land-reclamation projects in the first stage (1997–2007), and the channel siltation in the middle and upper segments was in turn further promoted by the increased tidal flows with flood dominance. In the second stage (2007–2017), tidal amplification was relaxed by the channel narrowing project at the lower segment and the waterway improvement project through channel dredging works at the middle and upper segments. Contemporary erosion volume was almost balanced by the accretion volume in the North Branch because of the weakening dominance of flood over ebb flows. Spatiotemporal variation in channel accretion and erosion patterns in response to estuarine engineering projects was vividly mirrored by the change of simulated bed shear stress in that the areas with increased (decreased) bed shear stress underwent severe erosion (accretion). These findings highlight again the dynamic feature of tide-dominated estuaries and the importance of simulation tools to the estuarine management.

Impact of major nearshore land reclamation project on offshore groundwater system

Offshore groundwater (OG) systems are widely distributed in the coastal areas, where nearshore land reclamation projects are constructed for seaports, airports, and urban other infrastructures. However, there is almost no study on the interaction between these projects and the OG system. This paper presents the first such an effort using the Hong Kong International Airport near Lantau Island, as a case study by developing a three-dimensional density-dependent flow and transport model to investigate the interaction between the reclaimed airport and the OG system. Results show that the offshore relatively fresh groundwater may flow from the nearby Lantau Island through the submarine confined aquifer. The higher pore water pressure in the basal aquifer beneath the airport is generated by the regional groundwater system of the nearby Lantau Island. Besides, the reclaimed airport also serves as extra aquifer space for the storage of fresh groundwater resources. The expansion of the 3rd runway will further increase the water table and move the center of the water mound toward the 3rd runway area. The groundwater system in the airport will reach a new steady state 50 years after the expansion, and the volume of the fresh groundwater lens is calculated to be ~5.2 × 107 m3 with a maximum water table of 1.4 m above mean sea level. The findings of this study have implications on the large-scale nearshore land reclamation which may be affected by the OG system in other coastal areas.

Explaining China’s large-scale land reclamation in the South China Sea: Timing and rationale

ABSTRACT Since 2013, China has undertaken extensive reclamation and construction on several reefs in the Spratly Island chain in the South China Sea. China has since been adding new construction and fortifications to the land features that had undergone reclamation between late 2013 and 2015, but none of the new projects rivalled the large-scale reclamation from 2014–15, and nor has China reclaimed any new land features. Land reclamation has theoretical and empirical implications. The literature regarding maritime disputes in the South China Sea is rich and plenty. Many studies, however, focus on China’s bilateral assertive or coercive behaviour as well as China’s general strategy in the South China Sea, not land reclamation per se. What explains the timing of China’s large-scale land reclamation in the South China Sea? Why did China decide to initiate large-scale land reclamation in the first place? This paper, therefore, conducts a comprehensive case study analysing China’s land reclamation decisions. I argue that China’s land reclamation is a result of capability, rationale, and opportunities which include a calculation of U.S. resolve. This study has implications for understanding Chinese foreign policy decision-making and contributes to the credibility debate in the coercion literature.

Response of Water Environment to Land Reclamation in Jiaozhou Bay, China Over the Last 150 Years

Jiaozhou Bay (JZB), located at Qingdao City, north China, is a semi-enclosed shallow bay that has undergone large-scale land reclamation and is suffering from a deteriorated water environment. Long-term evolution of JZB with respect of coastline, tidal prism, tidal dynamics, water-exchange capacity, and pollutant transport from 1863 to 2020 was investigated in this paper, using remote sensing images, historical charts, and a numerical model. The JZB was predominated by natural evolution from 1863 to 1935, during which the coastline barely changed. Thereafter, human intervention became intense and more and more natural tidal flats were replaced by salt ponds, aquaculture area, and reclamation very quickly. As a result, tidal prism, area of tidal flats, and area of JZB decreased sharply by 0.290 km3, 182 km2, and 223 km2, respectively, from 1935 to 2020, corresponding to annual decreasing rates being of 123 times, 10 times, 12 times, respectively, as that of before 1935. A numerical model showed that the residual current in JZB tended to be weaker due to the change of coastline and bathymetry, which is not favoring the water-exchange and pollutant transport, especially in the northeast of JZB. The basin residence time increased from 15.5 days in 1935 to 17.6 days in 2020, because of weaker residual tidal current and smaller tidal prism. Local residence time increased significantly near the area with large land reclamation, especially in the northeast and west of JZB. Distribution of dissolved inorganic nitrogen (DIN), in each year, which is the dominant pollutant in JZB, indicated higher DIN concentration and weaker transport along with reclamation. The research on JZB evolution over the last 150 years can provide useful suggestions for the decision-makers of the local government to improve the marine ecosystem. The systematic method to investigate long-term water environment evolution of JZB can be used to study other semi-closed bays.

Epidemic process and influencing factors of hemorrhagic fever with renal syndrome: a review

Hemorrhagic fever with renal syndrome (HFRS) is a category B infectious disease caused by hantaviruses that cause acute kidney injury and has a high mortality rate, and HFRS control has been given a high priority in China. It has been found that hantavirus types are closely associated with selective host transformation and regional adaption, and continue to evolve in the form of gene recombination. The severity of HFRS varies in hantavirus types. In addition, global environmental changes and alteration of host animal behaviors accelerate Hantavirus genome variations, and large-scale land reclamation and infrastructure building increases the likelihood of human contacts with hosts and disease-transmitting vectors, thereby increasing the risk of HFRS development. This review summarizes the main characteristics and influencing factors pertaining to the epidemic process of HFRS, so as to provide insights into effective prevention and control of this infectious disease.

Impacts of Human Activities on Hydrodynamic Structures during the Dry Season in the Modaomen Estuary

Over the past few decades, the topography and river-tide-salt dynamic characteristics of the Pearl River Delta (PRD) have undergone a myriad of changes due to the unnatural evolution process induced by diverse human activities, such as dam construction, land reclamation, sand excavation, and dredging for navigation. To investigate the impact of human activities on hydrodynamic structures in the PRD of the Modaomen Estuary (ME) during the dry season, a three-dimensional river-tide-salt dynamic model was used to simulate the hydrodynamic characteristics of the ME for different historical periods. The model results indicate that large-scale land reclamation weakened the tidal dynamics and mixing effects in the ME, promoting gravity circulation with opposite velocity directions at the surface and bottom within 15 km downstream of the estuary. Additionally, riverbed downcutting enhanced the tidal dynamics, which intensified saltwater intrusion, leading to the spatial scale-of-gravity circulation expanding 1–2 times. The enhancement of riverbed downcutting on the tidal dynamics in the ME was significantly greater than the weakening effect of land reclamation. Hence, due to the comprehensive influence of human activities between the 1970s and 2010, the hydrodynamic structures in the ME changed from a state of atypical gravity circulation, with nonobvious stratification, to a state of highly stratified and large-scale gravity circulation. The pollutant diffusion in the ME under different scenarios is also discussed in this paper. The results show that reclamation results in weakening of tidal dynamics, which is not conducive to the mixing and diffusion of pollutants in the estuary. However, the narrowed estuary due to land reclamation is conducive to the rapid entry of pollutants into the open sea.