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Urbanization results in habitat loss and habitat fragmentation concurrently, both influencing biodiversity and ecological processes. To evaluate these impacts, it is important to understand the relationships between habitat loss and habitat fragmentation per se (HLHF) during urbanization. The objectives of this study were two-fold: 1) to quantify the different forms of the HLHF relationship during urbanization using multiple landscape metrics, and 2) to test the validity of the HLHF relations reported in the literature. Our analysis was based on a long-term urbanization dataset (1800-2000) of 16 large cities from around the world. Habitat area was represented as the percentage of non-built-up area in the landscape, while habitat fragmentation was measured using several landscape metrics. Our results show that the relationship between habitat loss and habitat fragmentation during urbanization is commonly monotonic-linear, exponential, or logarithmic, indicating that the degree of habitat fragmentation per se increases with habitat loss in general. We compared our results with 14 hypothesized HLHF relationships based on simulated landscapes found in the literature, and found that four of them were consistent with those of urbanization, whereas the other ten were not. Also, we identified six new HLHF relationships when fragmentation was measured by total core area, normalized total core area, patch density, edge density and landscape shape index, respectively. In addition, our study demonstrated that the \"space-for-time\" approach, frequently used in ecology and geography, generated specious HLHF relationships, suggesting that this approach is largely inappropriate for analyses of urban landscapes that are highly heterogeneous in space and unusually contingent in dynamics. Our results show both generalities and idiosyncrasies of the HLHF relationship, providing new insights for assessing ecological effects of urbanization.

Urbanization and climate change are together exacerbating water scarcity—where water demand exceeds availability—for the world’s cities. We quantify global urban water scarcity in 2016 and 2050 under four socioeconomic and climate change scenarios, and explored potential solutions. Here we show the global urban population facing water scarcity is projected to increase from 933 million (one third of global urban population) in 2016 to 1.693–2.373 billion people (one third to nearly half of global urban population) in 2050, with India projected to be most severely affected in terms of growth in water-scarce urban population (increase of 153–422 million people). The number of large cities exposed to water scarcity is projected to increase from 193 to 193–284, including 10–20 megacities. More than two thirds of water-scarce cities can relieve water scarcity by infrastructure investment, but the potentially significant environmental trade-offs associated with large-scale water scarcity solutions must be guarded against. This paper quantifies global urban water scarcity in 2016 and 2050 and explores potential solutions. One third to nearly half of the global urban population is projected to face water scarcity problems.

In spintronics, it is highly desirable to find new materials that can simultaneously possess complete spin-polarization, high-speed conduction electrons, large Curie temperature, and robust ferromagnetic ground states. Using first-principles calculations, we demonstrate that the stable YN2 monolayer with octahedral coordination is a novel p-state Dirac half metal （DHM）, which not only has a fully spin-polarized Dirac state, but also the highest Fermi velocity （3.74×10^5 m/s） of the DHMs reported to date. In addition, its half-metallic gap of 1.53 eV is large enough to prevent the spin-flip transition. Because of the strong nonlocal p orbitals of N atoms （N-p） direct exchange interaction, the Curie temperature reaches over 332 K. Moreover, its ferromagnetic ground state can be well preserved under carrier doping or external strain. Therefore, the YN2 monolayer is a promising DHM for high-speed spintronic devices and would lead to new opportunities in designing other p-state DHMs.

Urbanization has transformed the world’s landscapes, resulting in a series of ecological and environmental problems. To assess urbanization impacts and improve sustainability, one of the first questions that we must address is: how much of the world’s land has been urbanized? Unfortunately, the estimates of the global urban land reported in the literature vary widely from less than 1–3 % primarily because different definitions of urban land were used. To evade confusion, here we propose a hierarchical framework for representing and communicating the spatial extent of the world’s urbanized land at the global, regional, and more local levels. The hierarchical framework consists of three spatially nested definitions: “urban area” that is delineated by administrative boundaries, “built-up area” that is dominated by artificial surfaces, and “impervious surface area” that is devoid of life. These are really three different measures of urbanization. In 2010, the global urban land was close to 3 %, the global built-up area was about 0.65 %, and the global impervious surface area was merely 0.45 %, of the word’s total land area (excluding Antarctica and Greenland). We argue that this hierarchy of urban land measures, in particular the ratios between them, can also facilitate better understanding the biophysical and socioeconomic processes and impacts of urbanization.

Effective and timely quantification of the spatiotemporal pattern of urban expansion in China is important for the assessment of its environmental effects. However, the dynamics of the most recent urban expansions in China since 2012 have not yet been adequately explained due to a lack of current information. In this paper, our objective was to quantify spatiotemporal patterns of urban expansion in China between 1992 and 2015. First, we extracted information on urban expansion in China between 1992 and 2015 by integrating nighttime light data, vegetation index data, and land surface temperature data. Then we analyzed the spatiotemporal patterns of urban expansion at the national and regional scales, as well as at that of urban agglomerations. We found that China experienced a rapid and large-scale process of urban expansion between 1992 and 2015, with urban land increasing from 1.22 × 104 km2 to 7.29 × 104 km2, increasing in size nearly fivefold and with an average annual growth rate of 8.10%, almost 2.5 times as rapid as the global average. We also found that urban land in China expanded mainly by occupying 3.31 × 104 km2 of cropland, which comprised 54.67% of the total area of expanded urban land. Among the three modes of growth-infilling, edge expansion, and leapfrog-edge expansion was the main cause of cropland loss. Cropland loss resulting from edge expansion of urban land totalled 2.51 × 104 km2, accounting for over 75% of total cropland loss. We suggest that effective future management with respect to edge expansion of urban land is needed to protect cropland in China.

Land use/cover change (LUCC) is the foundation and frontier for integrating multiple land surface processes. This paper aims to systematically review LUCC research from 1990 to 2018. Based on qualitative and quantitative analyses, we delineated the history of LUCC research and summarized their characteristics and major progress at different stages. We also identified the main challenges and proposed future directions for LUCC research. We found that the number of publications on LUCC research and their total citations grew exponentially. The research foci shifted from the process of LUCC during 1990–2004 to the impact of LUCC during 2005–2013 and then to the sustainability of LUCC from 2014 onwards. Currently, LUCC research is facing theoretical, methodological and practical challenges ranging from integrating the framework of sustainability science, adopting emerging technologies to supporting territorial spatial planning. To move forward, LUCC research should be closely integrated with landscape sustainability science and geodesign and take the leading role in territorial spatial planning to achieve the related Sustainable Development Goals.

The effective detection of global urban expansion is the basis of understanding urban sustainability. We propose a fully convolutional network (FCN) and employ it to detect global urban expansion from 1992-2016. We found that the global urban land area increased from 274.7 thousand km2-621.1 thousand km2, which is an increase of 346.4 thousand km2 and a growth by 1.3 times. The results display a relatively high accuracy with an average kappa index of 0.5, which is 0.3 higher than those of existing global urban expansion datasets. Three major advantages of the proposed FCN contribute to the improved accuracy, including the integration of multi-source remotely sensed data, the combination of features at multiple scales, and the ability to address the lack of training samples for historical urban land. Thus, the proposed FCN has great potential to effectively detect global urban expansion.

As the Earth's Third Pole and the Asian water tower, the Qinghai‐Tibet Plateau (QTP) plays a key role in global climate regulation and biodiversity maintenance. Living in harmony with nature is vital for local and global sustainable development. Current research on the conflicted or coordinated relationship between humans and nature on the QTP at a fine spatial scale remains limited. To fill the gap, we developed the human activity intensity index (HAI) and eco‐environmental quality index (EQI) at 1‐km resolution and proposed a four‐quadrant diagram approach to explore the dynamics between them. The results show a coordinated development on the QTP as the HAI and EQI both increased from 2000 to 2020, and the ratio of coordinated areas to conflicted areas was 5:1. High HAI areas were mainly in big cities such as Xining, Lhasa, Haidong, Xigaze, and along traffic lines. The significant conflicted areas were mainly outside the Lhasa metropolitan, south of the Hengduan Mountains, and along some new roads, and reduced by 8% between 2000–2010 and 2010–2020. The area of high HAI but low EQI was the smallest proportion, mainly in southern Qinghai Lake, southern Brahlung Zangbo River, Gobi oases, and western transport lines, but it implies the highest risk of ecosystem degradation. This research expands the fundamental methodology to address complex human‐natural relationships and provides implications for the sustainable development of fragile ecosystems. Plain Language Summary The Qinghai‐Tibet Plateau (QTP), with an average altitude of over 4,000 m and 13 million residents, is the source of the nine rivers in Asia, providing fresh water, food, and other ecosystem services to more than 1.5 billion people, and is known as the Earth's Third Pole and Asian water tower. However, research on the relationship between humans and nature in that region is limited, especially at a fine spatial scale. To fill the gap, we developed the human activity intensity index (HAI) and eco‐environmental quality index (EQI) at 1‐km resolution and proposed a four‐quadrant diagram approach to explore the dynamics between them, addressing potential risks and sustainability pathways. We find that the relationship between humans and nature on the QTP tends to be harmonious from 2000 to 2020. The significant conflicted areas were mainly outside the Lhasa metropolitan, south of the Hengduan Mountains, and along new roads, and reduced by 8% between 2000–2010 and 2010–2020. However, the plateau's fragile ecosystem still faces great challenges with population growth, urbanization, infrastructure construction, and the threat of global climate change. This work expands the fundamental methodology and may support fine ecological restoration and environmental management for local governments. Key Points Human activity intensity and eco‐environmental quality were measured at the grid scale of 1‐km resolution on the Earth's Third Pole We proposed a four‐quadrant diagram approach to identify dynamic relationships between humans and nature Socioeconomic development and eco‐environment on the QTP tend to be coordinated during 2000–2020

This study aims to investigate the biological role of 6-methyladenine (m6A) methylation in inducing the carcinogenesis of glioma and its proliferation. Relative levels of ALKBH5 and glucose-6-phosphate dehydrogenase (G6PD) in glioma tissues and cell lines were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. Gain-of-function and loss-of-function approaches were used to investigate the role of ALKBH5 in mediating proliferation and energy metabolism of glioma cells. The regulatory effect of ALKBH5 on G6PD was analyzed using m6A-qRT-PCR. Our results showed that ALKBH5 was upregulated in glioma, which stimulated glioma cells to proliferate. Serving as a m6A eraser, ALKBH5 demethylated the target transcript G6PD and enhanced its mRNA stability, thereby promoting G6PD translation and activating the pentose phosphate pathway (PPP). Collectively, ALKBH5 stimulates glioma cells to proliferate through erasing the m6A methylation of G6PD, which can be utilized as a potential therapeutic target for glioma.

With global warming, extreme environmental heat is becoming a social issue of concern, which can cause adverse health results including heatstroke (HS). Severe heat stress is characterized by cell death of direct heat damage, excessive inflammatory responses, and coagulation disorders that can lead to multiple organ dysfunction (MODS) and even death. However, the significant pathophysiological mechanism and treatment of HS are still not fully clear. Various modes of cell death, including apoptosis, pyroptosis, ferroptosis, necroptosis and PANoptosis are involved in MODS induced by heatstroke. In this review, we summarized molecular mechanism, key transcriptional regulation as for HSF1, NRF2, NF-κB and PARP-1, and potential therapies of cell death resulting in CNS, liver, intestine, reproductive system and kidney injury induced by heat stress. Understanding the mechanism of cell death provides new targets to protect multi-organ function in HS.