We monitored the last remaining Asian elephant populations in China over the past decade. Using DNA tools and repeat genotyping, we estimated the population sizes from 654 dung samples collected from various areas. Combined with morphological individual identifications from over 6,300 elephant photographs taken in the wild, we estimated that the total Asian elephant population size in China is between 221 and 245. Population genetic structure and diversity were examined using a 556-bp fragment of mitochondrial DNA, and 24 unique haplotypes were detected from DNA analysis of 178 individuals. A phylogenetic analysis revealed two highly divergent clades of Asian elephants, α and β, present in Chinese populations. Four populations (Mengla, Shangyong, Mengyang, and Pu’Er) carried mtDNA from the α clade, and only one population (Nangunhe) carried mtDNA belonging to the β clade. Moreover, high genetic divergence was observed between the Nangunhe population and the other four populations; however, genetic diversity among the five populations was low, possibly due to limited gene flow because of habitat fragmentation. The expansion of rubber plantations, crop cultivation, and villages along rivers and roads had caused extensive degradation of natural forest in these areas. This had resulted in the loss and fragmentation of elephant habitats and had formed artificial barriers that inhibited elephant migration. Using Geographic Information System, Global Positioning System, and Remote Sensing technology, we found that the area occupied by rubber plantations, tea farms, and urban settlements had dramatically increased over the past 40 years, resulting in the loss and fragmentation of elephant habitats and forming artificial barriers that inhibit elephant migration. The restoration of ecological corridors to facilitate gene exchange among isolated elephant populations and the establishment of cross-boundary protected areas between China and Laos to secure their natural habitats are critical for the survival of Asian elephants in this region.

Over the last 4 decades, China has undergone major economic development, resulting in considerable impacts on its wildlife populations and habitats. It is essential to quantify the conflict between development and conservation to assist with policy-making because forestry policies and market trends affected indirectly the distribution of Asian elephants. Here, we mapped the historical distribution of elephants versus human land use. Elephant distributions appear to occur in unbroken natural forests only. However, over the 40-year period, the distribution ranges have become smaller and fragmented, with natural forest area also declining by 16%. The monoculture of cash trees is encroaching on natural forests. Over the past 10 years, rubber plantations have become concentrated in the south, with extensive natural forests and scattered rubber farms being converted to tea plantations, due to changes in governmental policies and product prices. Through mapping the spatial changes in the distribution of rubber and tea plantations, our study is expected to help local managers to incorporate the needs of endangered elephants through creating space when planning plantations, especially in Xishuangbanna and the south part of Pu’er. In conclusion, restoring elephant habitat and establishing ecological corridors are critical for the survival of elephants in this region.

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As an indispensable energy source, ammonia plays a significant role in industrial and agricultural production. Given that the current ammonia production is still dominated by the energy-intensive and high-carbon-footprint Haber–Bosch process, photocatalysts for nitrogen reduction represent a low-energy-consuming and sustainable approach to generate ammonia, which have received extensive attention and research. However, photocatalytic nitrogen fixation materials have limitations, such as the difficulty in N2 adsorption and activation and the recombination of photogenerated carriers. It is still a serious challenge to improve the photocatalytic nitrogen fixation performance to realize its industrial application. It is crucial to master and explore the strategies for improving the performance of photocatalysts. Therefore, this paper reviews the traditional and emerging strategies for improving the performance of photocatalytic nitrogen fixation and briefly prospects the existing challenges and future opportunities. This review is expected to provide momentous breakthroughs on photocatalysts for artificial nitrogen fixation in the next stage.

The hybrid materials prepared by the controlled fumigation polymerization of pyrrole on the surface of activated carbon derived from carbon dots combined the stability of carbon materials, the wettability of...

Green rusts (GRs), which are important intermediate phases during Fe 2+ oxidation, are commonly associated with various metal cations during their crystallization in soils and sediments, but the effects of these foreign metal cations on the formation of GRs and on their subsequent transformation to Fe (hydr)oxides remain unclear. In the present study, the effects of Mn 2+ , Ni 2+ , and Cu 2+ on the evolution processes of hydrosulfate green rust (GR2) are documented under various conditions and the mechanisms leading to cation incorporation in the reaction products are determined. The rates of GR2 formation and of its transformation to Fe (hydr)oxides both decrease in the order of Cu 2+ > Ni 2+ > Mn 2+ and increase with increasing metal cation concentration. During GR2 crystallization, a small fraction of foreign metal cations is structurally incorporated in GR2 by replacing Fe 2+ , and their amount in the mineral follows the order of Cu 2+ > Ni 2+ > Mn 2+ . Under all conditions, the final reaction products are a mixture of lepidocrocite and goethite; a slow oxidation rate of mineral Fe 2+ and a strong catalytic effect of surface Fe 2+ both facilitate the goethite formation from GR2, reversely, favorable to lepidocrocite formation. Additionally, the three cations possess different speciation and distribution in lepidocrocite and goethite: Mn exists mainly as Mn(III) and probably minor Mn(II)−Mn(III) molecular clusters and occurs mainly in the mineral interior by isomorphic substitution or coated by the Fe (hydr)oxides crystals; Ni is present as Ni(II) and uniformly distributed in the newly formed minerals by either isomorphic substitution or surface adsorption; finally, Cu is mainly sorbed at the mineral surface as Cu(II) with minor Cu(I). These cations may thus be structurally incorporated in Fe oxides in the order of Mn(III) > Ni(II) > Cu(II). These new insights into the interaction between GR2 and trace metal cations improve our understanding of Fe oxide crystallization processes and of the environmental geochemical behavior of associated metal cations in redox alternating soils and sediments.

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