Soil has garnered global attention for its role in food security and climate change.Fine-scale soil-mapping techniques are urgently needed to support food,water,and biodiversity services.A global soil dataset integrat...Soil has garnered global attention for its role in food security and climate change.Fine-scale soil-mapping techniques are urgently needed to support food,water,and biodiversity services.A global soil dataset integrated into an Earth observation system and supported by cloud computing enabled the development of the first global soil grid of six key properties at a 90-m spatial resolution.Assessing them from environmental and socioeconomic perspectives,we demonstrated that 64%of the world’s topsoils are primarily sandy,with low fertility and high susceptibility to degradation.These conditions limit crop productivity and highlight potential risks to food security.Results reveal that approximately 900 Gt of soil organic carbon(SOC)is stored up to 20 cm deep.Arid biomes store three times more SOC than mangroves based on total areas.SOC content in agricultural soils is reduced by at least 60%compared to soils under natural vegetation.Most agricultural areas are being fertilized while simultaneously experiencing a depletion of the carbon pool.By integrating soil capacity with economic and social factors,we highlight the critical role of soil in supporting societal prosperity.The top 10 largest countries in area per continent store 75%of the global SOC stock.However,the poorest countries face rapid organic matter degradation.We indicate an interconnection between societal growth and spatially explicit mapping of soil properties.This soil-human nexus establishes a geographically based link between soil health and human development.It underscores the importance of soil management in enhancing agricultural productivity and promotes sustainable-land-use planning.展开更多
The Arctic sea-ice extent has shown a declining trend over the past 30 years. Ice coverage reached historic minima in 2007 and again in 2012. This trend has recently been assessed to be unique over at least the last 1...The Arctic sea-ice extent has shown a declining trend over the past 30 years. Ice coverage reached historic minima in 2007 and again in 2012. This trend has recently been assessed to be unique over at least the last 1450 years. In the summer of 2010, a very low sea-ice concentration(SIC) appeared at high Arctic latitudes—even lower than that of surrounding pack ice at lower latitudes. This striking low ice concentration—referred to here as a record low ice concentration in the central Arctic(CARLIC)—is unique in our analysis period of 2003–15, and has not been previously reported in the literature. The CARLIC was not the result of ice melt, because sea ice was still quite thick based on in-situ ice thickness measurements.Instead, divergent ice drift appears to have been responsible for the CARLIC. A high correlation between SIC and wind stress curl suggests that the sea ice drift during the summer of 2010 responded strongly to the regional wind forcing. The drift trajectories of ice buoys exhibited a transpolar drift in the Atlantic sector and an eastward drift in the Pacific sector,which appeared to benefit the CARLIC in 2010. Under these conditions, more solar energy can penetrate into the open water,increasing melt through increased heat flux to the ocean. We speculate that this divergence of sea ice could occur more often in the coming decades, and impact on hemispheric SIC and feed back to the climate.展开更多
Despite many studies on land degradation in the Highlands of Northern Ethiopia, quantitative information regarding long-term changes in land use/cover(LUC) is rare. Hence, this study aims to investigate the LUC change...Despite many studies on land degradation in the Highlands of Northern Ethiopia, quantitative information regarding long-term changes in land use/cover(LUC) is rare. Hence, this study aims to investigate the LUC changes in the Geba catchment(5142 km2), Northern Ethiopia, over 80 years(1935–2014). Aerial photographs(APs) of the 1930 s and Google Earth(GE) images(2014) were used. The point-count technique was utilized by overlaying a grid on APs and GE images. The occurrence of cropland, forest, grassland, shrubland, bare land, built-up areas and water body was counted to compute their fractions. A multivariate adaptive regression spline was applied to identify the explanatory factors of LUC and to create fractional maps of LUC. The results indicate significant changes of most types, except for forest and cropland. In the 1930 s, shrubland(48%) was dominant, followed by cropland(39%). The fraction of cropland in 2014(42%) remained approximately the same as in the 1930 s, while shrubland significantly dropped to 37%. Forests shrank further from a meagre 6.3% in the 1930 s to 2.3% in 2014. High overall accuracies(93% and 83%) and strong Kappa coefficients(89% and 72%) for point counts and fractional maps respectively indicate the validity of the techniques used for LUC mapping.展开更多
The 1st Chinese carbon dioxide(CO2)monitoring satellite mission,TanSat,was launched in 2016.The 1st TanSat global map of CO2 dry-air mixing ratio(XCO2)measurements over land was released as version 1 data product with...The 1st Chinese carbon dioxide(CO2)monitoring satellite mission,TanSat,was launched in 2016.The 1st TanSat global map of CO2 dry-air mixing ratio(XCO2)measurements over land was released as version 1 data product with an accuracy of 2.11 ppmv(parts per million by volume).In this paper,we introduce a new(version 2)TanSat global XCO2 product that is approached by the Institute of Atmospheric Physics Carbon dioxide retrieval Algorithm for Satellite remote sensing(IAPCAS),and the European Space Agency(ESA)Climate Change Initiative plus(CCI+)TanSat XCO2 product by University of Leicester Full Physics(UoL-FP)retrieval algorithm.The correction of the measurement spectrum improves the accuracy(−0.08 ppmv)and precision(1.47 ppmv)of the new retrieval,which provides opportunity for further application in global carbon flux studies in the future.Inter-comparison between the two retrievals indicates a good agreement,with a standard deviation of 1.28 ppmv and a bias of−0.35 ppmv.展开更多
Several factors may contribute to on-going challenges for spatial planning and policy in megacities such as Rome, including rapid population shifts, poorly organized areas, and lack of data through which monitoring ur...Several factors may contribute to on-going challenges for spatial planning and policy in megacities such as Rome, including rapid population shifts, poorly organized areas, and lack of data through which monitoring urban growth and land use change. This research was conducted to examine past and current effects of the urbanization process, occurred over the large Roman urban system, on the basis of multi-source and multi-temporal optical remote sensing (RS) data, collected between 1990 and 2013. These changes were then validated via Geographic Information System (GIS) techniques, in a particular procedure applied to urban land/agricultural transformations. The proposed approach, based on geo-statistical methods, was used to calculate the index of innovative space (AP Index), useful for the monitoring of the urban sprawl phenomenon. Strong evidence of urban expansion over the north-eastern quarter of the city, accompanied by environmental degradation and loss of biodiversity, is provided. Urban infill developments are expected to emerge in the south-eastern areas too, and these might increase urban pressure as well. In conclusion, RS and GIS technologies together with ancillary data can be used to assist decision makers in preparing future plans to find out appropriate solutions to urbanization encroachment.展开更多
Soil dissolved organic matter(DOM)plays an essential role in the Three Gorges Reservoir(TGR)as a linkage between terrestrial and aquatic systems.In particular,the reducing capacities of soil DOM influence the geochemi...Soil dissolved organic matter(DOM)plays an essential role in the Three Gorges Reservoir(TGR)as a linkage between terrestrial and aquatic systems.In particular,the reducing capacities of soil DOM influence the geochemistry of contaminants such as mercury(Hg).However,few studies have investigated the molecular information of soil DOM and its relationship with relevant geochemic al reactivities,including redox properties.We collected samples from eight sites in the TGR areas and studied the link between the molecular characteristics of DOM and their electron donation capacities(EDCs)toward Hg(II).The average kinetic rate and EDC of soil DOM in TGR areas were(0.004±0.001)hr-1 and(2.88±1.39)nmol e-/mg DOMbulk,respectively.Results suggest that higher EDCs and relatively rapid kinetics were related to the greater electron donating components of ligninderived and perhaps pyrogenic DOM,which are the aromatic constituents that influenced the reducing capacities of DOM in the present study.Molecular details revealed that even the typical autochthonous markers are important for the EDCs of DOM as well,in contrast to what is generally assumed.More studies identifying specific DOM molecular components involved in the abiotic reduction of Hg(II)are required to further understand the relations between DOM sources and their redox roles in the environmental fate of contaminants.展开更多
Accurate boundaries of smallholder farm fields are important and indispensable geo-information that benefits farmers,managers,and policymakers in terms of better managing and utilizing their agricultural resources.Due...Accurate boundaries of smallholder farm fields are important and indispensable geo-information that benefits farmers,managers,and policymakers in terms of better managing and utilizing their agricultural resources.Due to their small size,irregular shape,and the use of mixed-cropping techniques,the farm fields of smallholder can be difficult to delineate automatically.In recent years,numerous studies on field contour extraction using a deep Convolutional Neural Network(CNN)have been proposed.However,there is a relative shortage of labeled data for filed boundaries,thus affecting the training effect of CNN.Traditional methods mostly use image flipping,and random rotation for data augmentation.In this paper,we propose to apply Generative Adversarial Network(GAN)for the data augmentation of farm fields label to increase the diversity of samples.Specifically,we propose an automated method featured by Fully Convolutional Neural networks(FCN)in combination with GAN to improve the delineation accuracy of smallholder farms from Very High Resolution(VHR)images.We first investigate four State-Of-The-Art(SOTA)FCN architectures,i.e.,U-Net,PSPNet,SegNet and OCRNet,to find the optimal architecture in the contour detection task of smallholder farm fields.Second,we apply the identified optimal FCN architecture in combination with Contour GAN and pixel2pixel GAN to improve the accuracy of contour detection.We test our method on the study area in the Sudano-Sahelian savanna region of northern Nigeria.The best combination achieved F1 scores of 0.686 on Test Set 1(TS1),0.684 on Test Set 2(TS2),and 0.691 on Test Set 3(TS3).Results indicate that our architecture adapts to a variety of advanced networks and proves its effectiveness in this task.The conceptual,theoretical,and experimental knowledge from this study is expected to seed many GAN-based farm delineation methods in the future.展开更多
The urban land-use allocation problem is a spatial optimization problem that allocates optimum land-uses to specific land units in urban areas.This problem is an NP(nondeterministic polynomial time)-hard problem becau...The urban land-use allocation problem is a spatial optimization problem that allocates optimum land-uses to specific land units in urban areas.This problem is an NP(nondeterministic polynomial time)-hard problem because of involving many objective functions,many constraints,and complex search space.Moreover,this subject is an important issue in smart cities and newly developed areas of cities to achieve a sustainable arrangement of land-uses.Different types ofMulti-Objective Optimization Algorithms(MOOAs)based on Artificial Intelligence(AI)have been frequently employed,but their ability and performance have not been evaluated and compared properly.This paper aims to employ and compare three commonly used MOOAs i.e.NSGA-II,MOPSO,and MOEA/D in urban land-use allocation problems.Selected algorithms belong to different categories of MOOAs family to investigate their advantage and disadvantages.The objective functions of this study are compatibility,dependency,suitability,and compactness of land-uses and the constraint is compensating of Per-Capita demand in the urban environment.Evaluation of results is based on the dispersion of the solutions,diversity of the solutions’space,and comparing the number of dominant solutions in Pareto-Fronts.The results showed that all three algorithms improved the objective functions related to the current arrangement of the land-uses.However,the run time of NSGA-II is the worst,related to the Diversity Metric(DM)which represents the regularity of the distance between solutions at the highest degree.Moreover,MOPSO provides the best Scattering Diversity Metric(SDM)which shows the diversity of solutions in the solution space.Furthermore,In terms of algorithm execution time,MOEA/D performed better than the other two.So,Decision-makers should consider different aspects in choosing the appropriate MOOA for land-use management problems.展开更多
Situations of heavy and congested traffic in urban areas have been analysed by using a statistical approach based on both the identification of specific locations that attract drivers in a multipoint-to-multipoint tra...Situations of heavy and congested traffic in urban areas have been analysed by using a statistical approach based on both the identification of specific locations that attract drivers in a multipoint-to-multipoint traffic structure and their classification (attractor’s value) as a function of the number of people visiting them by car in different time ranges. By using a Kernel Density Estimation (KDE) function, attractors’ distribution density values have been estimated and then integrated with nodal and critical traffic points and traffic density in a “congestion” map. Finally, cross-comparing congestion values with the location of buildings, the road network and the Corine Land Use/Land Cover environmental classification, a “Quality of Life” map has been generated. The authors use this term because the congestion of traffic flows, with all the problems that it entails (such as long travel time, air and acoustic pollution, and so on) is a good indicator of the quality of life, especially in small towns. Results show that this type of “off-line” analysis would allow administrators to identify, quickly and at low cost, areas where citizens’ quality of life is most affected by traffic noise and jumps and, hence, to focus costly ground measurements and interventions primarily there.展开更多
The transformation of mercury(Hg) in the environment plays a vital role in the cycling of Hg and its risk to the ecosystem and human health. Of particular importance are Hg oxidation/reduction and methylation/demethyl...The transformation of mercury(Hg) in the environment plays a vital role in the cycling of Hg and its risk to the ecosystem and human health. Of particular importance are Hg oxidation/reduction and methylation/demethylation processes driven or mediated by the dynamics of light, microorganisms, and organic carbon, among others. Advances in understanding those Hg transformation processes determine our capacity of projecting and mitigating Hg risk. Here, we provide a critical analysis of major knowledge gaps in our understanding of Hg transformation in nature, with perspectives on approaches moving forward. Our analysis focuses on Hg transformation processes in the environment, as well as emerging methodology in exploring these processes. Future avenues for improving the understanding of Hg transformation processes to protect ecosystem and human health are also explored.展开更多
The attenuation of lateral propagating light （LPL） in sea ice was measured using an artificial light source in the Canadian Arctic during the 2007/2008 winter. The apparent attenuation coefficientμ（λ）for lateral...The attenuation of lateral propagating light （LPL） in sea ice was measured using an artificial light source in the Canadian Arctic during the 2007/2008 winter. The apparent attenuation coefficientμ（λ）for lateral prop-agating light was obtained from the measured logarithmic relative variation rate. In this study an analytical solution based on the strict optical theories is developed to validate the measured result. There is a good consistency between theoretical solution and measured data, by which a quite simple but very rigorous relationship among the light source, measurement geometry, and measured irradiance is established. The attenuation coefficients acquired by measurement and theory are the diffusion attenuation as an apparent optical property of ice, independent of the light source and shining condition. The attenuation ability of sea ice should be caused by the microstructure of sea ice, such as crystal size, ice density, brine volume, air inclusion, etc. It also includes the leak from both interfaces by directional scattering. It is verified that the measuring approach is operational and accurate to measure the attenuation of the LPL. The solution from this study did not tell the connection among the extinction and the inclusions of sea ice theoretically be-cause of insufficient understanding.展开更多
Traffic flows form a complex system, especially in the context of urban sprawl. Direct estimation of traffic flows requires significant efforts and knowing in advance where to focus the study and where to place tools ...Traffic flows form a complex system, especially in the context of urban sprawl. Direct estimation of traffic flows requires significant efforts and knowing in advance where to focus the study and where to place tools to directly measure traffic flows, and consequently traffic congestion could lead to significant savings in time and money. In the case of Rome municipality, we have monitored a situation in which a very high rate of urban fragmentation has occurred in the last 30 years, making the direct estimation of traffic difficult. The work described here can help to solve the problem of estimating traffic flows and in particular the congestion phenomenon through a very cheap approach by using remote sensing and geographical information system technology. This method is based on the identification of attractor points that draw traffic flows such as malls, schools, offices, shops, etc. that is to say, points in a territory that attract a certain number of people with vehicles (estimated with a scale) in specific periods of the day. The identification of those points and the calculation of the urban density through the satellite image processing have allowed the creation of a congestion map for the study area. Then the road network and the buildings have been classified according to the congestion values. The results highlight the most critical and congested areas that affect the traffic flows and impact the quality of life.展开更多
Based on the continuation of our past study, the present analysis is conducted to examine recent effects of the urbanization process occurring over the entire district of Rome. Overlays of ALOS AVNIR-2 and SENTINEL-2A...Based on the continuation of our past study, the present analysis is conducted to examine recent effects of the urbanization process occurring over the entire district of Rome. Overlays of ALOS AVNIR-2 and SENTINEL-2A satellite images, collected over a 6 years period, were validated via Geographic Information System (GIS) techniques, in a particular procedure applied to urban land and agricultural transformations. The use of Copernicus SENTINEL-2A imagery has improved the previous results on urban processes, by reducing the uncertainty of the discrimination of land cover classes and facilitating the photo-interpretation. Statistical analysis was performed via the Urban Area Profile index in order to quantify the sprawl phenomenon, by defining several landscape metrics. This work, to be enriched in the future by means of complementary information available from Copernicus radar sensors, like the one onboard Sentinel-1, completes the series of observations on land use published by the Italian National Institute for Environmental Protection and Research, which stopped back in 2008.展开更多
The science that underpins our knowledge and understanding of Isotope-Based Hydrograph separation (IHS) has gained grounds, over the last few decades, in the identification of streamflow sources. However, challenges s...The science that underpins our knowledge and understanding of Isotope-Based Hydrograph separation (IHS) has gained grounds, over the last few decades, in the identification of streamflow sources. However, challenges still exist in identifying appropriate tracers and the right combination of end-members for the IHS process. In a two-component IHS analysis, the application of the dual isotopes tracers, δ18O and (or) δ2H, is regarded as the simplest method. We undertook an IHS study within a nested system of eight Prairie watersheds located in South central Manitoba, Canada. The work evaluated about 17,000 results emanating from the application of a combination of two potential tracers (δ18O and δ2H) and eight each of potential “old” and “new” water end-members in a two-component IHS process. The outcome showed occurrences of many mathematically possible but hydrologically unacceptable IHS results. The observation was particularly predominant within relatively larger perennial sub-catchments of the watershed. It is also shown that inter-site sub-catchment isotopic end-member transferability is possible within watersheds of similar physio-hydrographic characteristics. We suggest that a careful evaluation of the physio-hydrographic characteristics of catchments be considered in IHS studies in addition to the recommended guidelines in the selection of tracers and end-members.展开更多
The Digital Earth concept as originally proposed by former US Vice president Al Gore is now well established and widely adopted internationally.Similarly,many researchers world-wide are studying the causes,effects and...The Digital Earth concept as originally proposed by former US Vice president Al Gore is now well established and widely adopted internationally.Similarly,many researchers world-wide are studying the causes,effects and impacts of Global Change.The authors commence by describing a five-step approach to the development of Digital Earth technologies.This is followed by a detailed account of Digital Earth research and developments in China.The authors then present the research results of Global Change studies carried out in China,based on the Digital Earth approach.These research results are based on a classification of global change regions.This covers the following global change situations:Forest and grassland fires in Northern China,temperate region desertification and dust storms,underground coal fires,deforestation and carbon sequestration,protection and utilisation of wetlands,Avian Influenza and the spread of diseases,Tibet Plateau uplift and sub-tropical monsoon climate region,and sea-level rise.The research results show that the environment does not behave in a way easily understood by the traditional disciplinary approach.Although man is clearly a contributing factor to certain Global Change aspects,such as underground coal fires,desertification,land use changes etc.,many of the aspects of Global Change are naturally occurring phenomena which have been changing over centuries,and will continue to do so,no matter what actions we undertake to reverse these processes.Hence,in their conclusions,the authors propose that the communities involved in Digital Earth modelling and in Global Change research co-operate closer to overcome the limitations inherent in the current‘conventional’scientific approach,where scientists have very much stayed within their respective scientific boundaries.Such an integrated approach will enable us to build the next level of scientific infrastructure required to understand and predict naturally occurring environmental changes,as well as that of coupled humanenvironmental systems.展开更多
The concept of Digital Earth(DE)was formalized by Al Gore in 1998.At that time the technologies needed for its implementation were in an embryonic stage and the concept was quite visionary.Since then digital technolog...The concept of Digital Earth(DE)was formalized by Al Gore in 1998.At that time the technologies needed for its implementation were in an embryonic stage and the concept was quite visionary.Since then digital technologies have progressed significantly and their speed and pervasiveness have generated and are still causing the digital transformation of our society.This creates new opportunities and challenges for the realization of DE.‘What is DE today?’,‘What could DE be in the future?’,and‘What is needed to make DE a reality?’.To answer these questions it is necessary to examine DE considering all the technological,scientific,social,and economic aspects,but also bearing in mind the principles that inspired its formulation.By understanding the lessons learned from the past,it becomes possible to identify the remaining scientific and technological challenges,and the actions needed to achieve the ultimate goal of a‘Digital Earth for all’.This article reviews the evolution of the DE vision and its multiple definitions,illustrates what has been achieved so far,explains the impact of digital transformation,illustrates the new vision,and concludes with possible future scenarios and recommended actions to facilitate full DE implementation.展开更多
Almost all causative factors of diseases depend on location.The Digital Earth approach is suitable for studying diseases globally.Geospatial information systems integrated with statistical models can be used to model ...Almost all causative factors of diseases depend on location.The Digital Earth approach is suitable for studying diseases globally.Geospatial information systems integrated with statistical models can be used to model the relationship between a disease and its causative factors.Through modelling,the most important causative factors can be extracted and the epidemiology of the disease can be observed.In this paper,skin cancer(the most common type of cancer)has been modelled based on its causative factors,including climate factors,people’s occupations,nutrition habits,socio-economic factors,and usage of chemical fertiliser.To fit the model,a data framework was first designed,and then data were gathered and processed.Finally,the disease was modelled using Generalised Linear Models(GLM),a statistical model based on the location of the factors.The results of this study identify the most important causative factors together with their relative priority.Furthermore,a model was used to predict the change in skin cancer occurrences caused by a change in one of its causative factors.This work illustrates the ability of the model to predict disease occurrence.Thus,by using this Digital Earth approach,skincancer can be studied in all the key countries around the world.展开更多
Mercury is one of the primary contaminants of global concern.As anthropogenic emissions of mercury are gradually placed under control,evidence is emerging that biotic mercury levels in many aquatic ecosystems are incr...Mercury is one of the primary contaminants of global concern.As anthropogenic emissions of mercury are gradually placed under control,evidence is emerging that biotic mercury levels in many aquatic ecosystems are increasingly driven by internal biogeochemical processes,especially in ecosystems that have been undergoing dramatic environmental changes.Here we review the unique properties of mercury that are responsible for the exceptional sensitivity of its biogeochemical cycles to changes in climatic,geochemical,biological and ecological processes.We show that,due to rapid climate warming,a shift from sources-driven to processes-driven mercury bioaccumulation is already happening in the Arctic marine ecosystem.We further suggest that such a shift might also be operating in the Three Gorges Reservoir due to changes in these biogeochemical processes induced by the damming.As a result,the effectiveness of mercury emission control is expected to be followed by long delays before ensuing reduction is seen in food-web levels,making it all the more pressing to control and reduce mercury emissions to the reservoir.Long-term monitoring and targeted studies are urgently needed to understand how biotic mercury levels in the reservoir are responding to changes in mercury emissions and in biogeochemical processes.展开更多
by Q.Weng,CRC Press,Taylor&Francis Group,Boca Raton,USA,2011,556 pp.,(hardback),ISBN 978-1-4200-9175-5 This volume is part of the Taylor&Francis Series in Remote Sensing Applications.So far,some seven books ha...by Q.Weng,CRC Press,Taylor&Francis Group,Boca Raton,USA,2011,556 pp.,(hardback),ISBN 978-1-4200-9175-5 This volume is part of the Taylor&Francis Series in Remote Sensing Applications.So far,some seven books have been published in this series,on topics such as:Remote Sensing of Coastal Environments,Remote Sensing of Global Croplands for Food Security,Global Mapping of Human Settlement,Hyperspectral Remote Sensing,etc.展开更多
The Belt and Road initiative has a significant focus on infrastructure,trade,and economic development across a vast region,and it also provides significant opportunities for sustainable development.The combined pressu...The Belt and Road initiative has a significant focus on infrastructure,trade,and economic development across a vast region,and it also provides significant opportunities for sustainable development.The combined pressure of climate variability,intensified use of resources,and the fragility of ecosystems make it very challenging,however,to achieve future sustainability.To develop the path in a sustainable way,it is important to have a comprehensive understanding of these issues across nations and evaluate them in a scientific and well-informed approach.In this context,the Digital Belt and Road(DBAR)program was initiated as an international venture to share expertise,knowledge,technologies,and data to demonstrate the role of Earth observation science and technology and big Earth data applications to support large-scale development.In this paper,we identify pressing challenges,present the research priorities and foci of the DBAR program,and propose solutions where big Earth data can make significant contributions.This paper calls for further joint actions and collaboration to build a digital silk road in support of sustainable development at national,regional and global levels.展开更多
基金supported by the São Paulo Research Foundation(FAPESP)under grants 2014-22262-0 and 2021/05129-8the from the Center for Carbon Research in Tropical Agriculture(CCARBON)at the University of São Paulo,under grant 2021/10573-4+1 种基金the support of the MII Project of the Russian Federation(reg.123030300031-6)CNPq for research scholarship(307190-2021-8).
文摘Soil has garnered global attention for its role in food security and climate change.Fine-scale soil-mapping techniques are urgently needed to support food,water,and biodiversity services.A global soil dataset integrated into an Earth observation system and supported by cloud computing enabled the development of the first global soil grid of six key properties at a 90-m spatial resolution.Assessing them from environmental and socioeconomic perspectives,we demonstrated that 64%of the world’s topsoils are primarily sandy,with low fertility and high susceptibility to degradation.These conditions limit crop productivity and highlight potential risks to food security.Results reveal that approximately 900 Gt of soil organic carbon(SOC)is stored up to 20 cm deep.Arid biomes store three times more SOC than mangroves based on total areas.SOC content in agricultural soils is reduced by at least 60%compared to soils under natural vegetation.Most agricultural areas are being fertilized while simultaneously experiencing a depletion of the carbon pool.By integrating soil capacity with economic and social factors,we highlight the critical role of soil in supporting societal prosperity.The top 10 largest countries in area per continent store 75%of the global SOC stock.However,the poorest countries face rapid organic matter degradation.We indicate an interconnection between societal growth and spatially explicit mapping of soil properties.This soil-human nexus establishes a geographically based link between soil health and human development.It underscores the importance of soil management in enhancing agricultural productivity and promotes sustainable-land-use planning.
基金funded by the Global Change Research Program of China(Grant No.2015CB953900)the Key Program of the National Natural Science Foundation of China(Grant Nos.41330960 and 41406208)+1 种基金the Canada Research Chairs Program,NSERCCanadian Federal IPY Program Office
文摘The Arctic sea-ice extent has shown a declining trend over the past 30 years. Ice coverage reached historic minima in 2007 and again in 2012. This trend has recently been assessed to be unique over at least the last 1450 years. In the summer of 2010, a very low sea-ice concentration(SIC) appeared at high Arctic latitudes—even lower than that of surrounding pack ice at lower latitudes. This striking low ice concentration—referred to here as a record low ice concentration in the central Arctic(CARLIC)—is unique in our analysis period of 2003–15, and has not been previously reported in the literature. The CARLIC was not the result of ice melt, because sea ice was still quite thick based on in-situ ice thickness measurements.Instead, divergent ice drift appears to have been responsible for the CARLIC. A high correlation between SIC and wind stress curl suggests that the sea ice drift during the summer of 2010 responded strongly to the regional wind forcing. The drift trajectories of ice buoys exhibited a transpolar drift in the Atlantic sector and an eastward drift in the Pacific sector,which appeared to benefit the CARLIC in 2010. Under these conditions, more solar energy can penetrate into the open water,increasing melt through increased heat flux to the ocean. We speculate that this divergence of sea ice could occur more often in the coming decades, and impact on hemispheric SIC and feed back to the climate.
基金a scholarship of the Special Research Fund (BOF) obtained from Ghent University, Belgiumpartially covered by the RIP-MU (VLIR, Belgium) project
文摘Despite many studies on land degradation in the Highlands of Northern Ethiopia, quantitative information regarding long-term changes in land use/cover(LUC) is rare. Hence, this study aims to investigate the LUC changes in the Geba catchment(5142 km2), Northern Ethiopia, over 80 years(1935–2014). Aerial photographs(APs) of the 1930 s and Google Earth(GE) images(2014) were used. The point-count technique was utilized by overlaying a grid on APs and GE images. The occurrence of cropland, forest, grassland, shrubland, bare land, built-up areas and water body was counted to compute their fractions. A multivariate adaptive regression spline was applied to identify the explanatory factors of LUC and to create fractional maps of LUC. The results indicate significant changes of most types, except for forest and cropland. In the 1930 s, shrubland(48%) was dominant, followed by cropland(39%). The fraction of cropland in 2014(42%) remained approximately the same as in the 1930 s, while shrubland significantly dropped to 37%. Forests shrank further from a meagre 6.3% in the 1930 s to 2.3% in 2014. High overall accuracies(93% and 83%) and strong Kappa coefficients(89% and 72%) for point counts and fractional maps respectively indicate the validity of the techniques used for LUC mapping.
基金This work was supported by the National Key R&D Program of China(Grant No.2016YFA0600203)the Key Research Program of the Chinese Academy of Sciences(Grant No.ZDRW-ZS-2019-1)+4 种基金the International Partnership Program of the Chinese Academy of Sciences(Grant No.GJHZ201903)the National Natural Science Foundation of China(Grant No.41905029)ESA Climate Change Initiative CCI+(GhG theme),Earthnet Data Assessment Pilot(EDAP)project and ESA-MOST Dragon-4 programme(ID 32301)supported by the UK NERC National Centre for Earth Observation(NCEO)(Grant Nos.nceo020005 and NE/N018079/1)The TanSat L1B data service is provided by IRCSD and CASA(131211KYSB20180002).
文摘The 1st Chinese carbon dioxide(CO2)monitoring satellite mission,TanSat,was launched in 2016.The 1st TanSat global map of CO2 dry-air mixing ratio(XCO2)measurements over land was released as version 1 data product with an accuracy of 2.11 ppmv(parts per million by volume).In this paper,we introduce a new(version 2)TanSat global XCO2 product that is approached by the Institute of Atmospheric Physics Carbon dioxide retrieval Algorithm for Satellite remote sensing(IAPCAS),and the European Space Agency(ESA)Climate Change Initiative plus(CCI+)TanSat XCO2 product by University of Leicester Full Physics(UoL-FP)retrieval algorithm.The correction of the measurement spectrum improves the accuracy(−0.08 ppmv)and precision(1.47 ppmv)of the new retrieval,which provides opportunity for further application in global carbon flux studies in the future.Inter-comparison between the two retrievals indicates a good agreement,with a standard deviation of 1.28 ppmv and a bias of−0.35 ppmv.
文摘Several factors may contribute to on-going challenges for spatial planning and policy in megacities such as Rome, including rapid population shifts, poorly organized areas, and lack of data through which monitoring urban growth and land use change. This research was conducted to examine past and current effects of the urbanization process, occurred over the large Roman urban system, on the basis of multi-source and multi-temporal optical remote sensing (RS) data, collected between 1990 and 2013. These changes were then validated via Geographic Information System (GIS) techniques, in a particular procedure applied to urban land/agricultural transformations. The proposed approach, based on geo-statistical methods, was used to calculate the index of innovative space (AP Index), useful for the monitoring of the urban sprawl phenomenon. Strong evidence of urban expansion over the north-eastern quarter of the city, accompanied by environmental degradation and loss of biodiversity, is provided. Urban infill developments are expected to emerge in the south-eastern areas too, and these might increase urban pressure as well. In conclusion, RS and GIS technologies together with ancillary data can be used to assist decision makers in preparing future plans to find out appropriate solutions to urbanization encroachment.
基金supported by the National Science Foundation of China(Nos.41977275 and 41877384)the Internal Funding for Early Careers from the Department of Forest Ecology and Management(FEM)of the Swedish University of Agricultural Science(SLU)+1 种基金the funding of the Sino-Swedish Mercury Management Research Framework(SMaRef)from the Swedish Research Council(VR)(No.D697801)supporting his researcher position at the Swedish University of Agricultural Sciences(SLU)
文摘Soil dissolved organic matter(DOM)plays an essential role in the Three Gorges Reservoir(TGR)as a linkage between terrestrial and aquatic systems.In particular,the reducing capacities of soil DOM influence the geochemistry of contaminants such as mercury(Hg).However,few studies have investigated the molecular information of soil DOM and its relationship with relevant geochemic al reactivities,including redox properties.We collected samples from eight sites in the TGR areas and studied the link between the molecular characteristics of DOM and their electron donation capacities(EDCs)toward Hg(II).The average kinetic rate and EDC of soil DOM in TGR areas were(0.004±0.001)hr-1 and(2.88±1.39)nmol e-/mg DOMbulk,respectively.Results suggest that higher EDCs and relatively rapid kinetics were related to the greater electron donating components of ligninderived and perhaps pyrogenic DOM,which are the aromatic constituents that influenced the reducing capacities of DOM in the present study.Molecular details revealed that even the typical autochthonous markers are important for the EDCs of DOM as well,in contrast to what is generally assumed.More studies identifying specific DOM molecular components involved in the abiotic reduction of Hg(II)are required to further understand the relations between DOM sources and their redox roles in the environmental fate of contaminants.
基金Foundation of Anhui Province Key Laboratory of Physical Geographic Environment(No.2022PGE012)
文摘Accurate boundaries of smallholder farm fields are important and indispensable geo-information that benefits farmers,managers,and policymakers in terms of better managing and utilizing their agricultural resources.Due to their small size,irregular shape,and the use of mixed-cropping techniques,the farm fields of smallholder can be difficult to delineate automatically.In recent years,numerous studies on field contour extraction using a deep Convolutional Neural Network(CNN)have been proposed.However,there is a relative shortage of labeled data for filed boundaries,thus affecting the training effect of CNN.Traditional methods mostly use image flipping,and random rotation for data augmentation.In this paper,we propose to apply Generative Adversarial Network(GAN)for the data augmentation of farm fields label to increase the diversity of samples.Specifically,we propose an automated method featured by Fully Convolutional Neural networks(FCN)in combination with GAN to improve the delineation accuracy of smallholder farms from Very High Resolution(VHR)images.We first investigate four State-Of-The-Art(SOTA)FCN architectures,i.e.,U-Net,PSPNet,SegNet and OCRNet,to find the optimal architecture in the contour detection task of smallholder farm fields.Second,we apply the identified optimal FCN architecture in combination with Contour GAN and pixel2pixel GAN to improve the accuracy of contour detection.We test our method on the study area in the Sudano-Sahelian savanna region of northern Nigeria.The best combination achieved F1 scores of 0.686 on Test Set 1(TS1),0.684 on Test Set 2(TS2),and 0.691 on Test Set 3(TS3).Results indicate that our architecture adapts to a variety of advanced networks and proves its effectiveness in this task.The conceptual,theoretical,and experimental knowledge from this study is expected to seed many GAN-based farm delineation methods in the future.
文摘The urban land-use allocation problem is a spatial optimization problem that allocates optimum land-uses to specific land units in urban areas.This problem is an NP(nondeterministic polynomial time)-hard problem because of involving many objective functions,many constraints,and complex search space.Moreover,this subject is an important issue in smart cities and newly developed areas of cities to achieve a sustainable arrangement of land-uses.Different types ofMulti-Objective Optimization Algorithms(MOOAs)based on Artificial Intelligence(AI)have been frequently employed,but their ability and performance have not been evaluated and compared properly.This paper aims to employ and compare three commonly used MOOAs i.e.NSGA-II,MOPSO,and MOEA/D in urban land-use allocation problems.Selected algorithms belong to different categories of MOOAs family to investigate their advantage and disadvantages.The objective functions of this study are compatibility,dependency,suitability,and compactness of land-uses and the constraint is compensating of Per-Capita demand in the urban environment.Evaluation of results is based on the dispersion of the solutions,diversity of the solutions’space,and comparing the number of dominant solutions in Pareto-Fronts.The results showed that all three algorithms improved the objective functions related to the current arrangement of the land-uses.However,the run time of NSGA-II is the worst,related to the Diversity Metric(DM)which represents the regularity of the distance between solutions at the highest degree.Moreover,MOPSO provides the best Scattering Diversity Metric(SDM)which shows the diversity of solutions in the solution space.Furthermore,In terms of algorithm execution time,MOEA/D performed better than the other two.So,Decision-makers should consider different aspects in choosing the appropriate MOOA for land-use management problems.
文摘Situations of heavy and congested traffic in urban areas have been analysed by using a statistical approach based on both the identification of specific locations that attract drivers in a multipoint-to-multipoint traffic structure and their classification (attractor’s value) as a function of the number of people visiting them by car in different time ranges. By using a Kernel Density Estimation (KDE) function, attractors’ distribution density values have been estimated and then integrated with nodal and critical traffic points and traffic density in a “congestion” map. Finally, cross-comparing congestion values with the location of buildings, the road network and the Corine Land Use/Land Cover environmental classification, a “Quality of Life” map has been generated. The authors use this term because the congestion of traffic flows, with all the problems that it entails (such as long travel time, air and acoustic pollution, and so on) is a good indicator of the quality of life, especially in small towns. Results show that this type of “off-line” analysis would allow administrators to identify, quickly and at low cost, areas where citizens’ quality of life is most affected by traffic noise and jumps and, hence, to focus costly ground measurements and interventions primarily there.
基金supported by the National Natural Science Foundation of China (Nos. U2032201 and 21976193 )the Canada Research Chairs Program。
文摘The transformation of mercury(Hg) in the environment plays a vital role in the cycling of Hg and its risk to the ecosystem and human health. Of particular importance are Hg oxidation/reduction and methylation/demethylation processes driven or mediated by the dynamics of light, microorganisms, and organic carbon, among others. Advances in understanding those Hg transformation processes determine our capacity of projecting and mitigating Hg risk. Here, we provide a critical analysis of major knowledge gaps in our understanding of Hg transformation in nature, with perspectives on approaches moving forward. Our analysis focuses on Hg transformation processes in the environment, as well as emerging methodology in exploring these processes. Future avenues for improving the understanding of Hg transformation processes to protect ecosystem and human health are also explored.
基金The Global Change Research Program of China under contract No.2015CB953900the Key Program of National Natural Science Foundation of China under contract No.41330960
文摘The attenuation of lateral propagating light （LPL） in sea ice was measured using an artificial light source in the Canadian Arctic during the 2007/2008 winter. The apparent attenuation coefficientμ（λ）for lateral prop-agating light was obtained from the measured logarithmic relative variation rate. In this study an analytical solution based on the strict optical theories is developed to validate the measured result. There is a good consistency between theoretical solution and measured data, by which a quite simple but very rigorous relationship among the light source, measurement geometry, and measured irradiance is established. The attenuation coefficients acquired by measurement and theory are the diffusion attenuation as an apparent optical property of ice, independent of the light source and shining condition. The attenuation ability of sea ice should be caused by the microstructure of sea ice, such as crystal size, ice density, brine volume, air inclusion, etc. It also includes the leak from both interfaces by directional scattering. It is verified that the measuring approach is operational and accurate to measure the attenuation of the LPL. The solution from this study did not tell the connection among the extinction and the inclusions of sea ice theoretically be-cause of insufficient understanding.
文摘Traffic flows form a complex system, especially in the context of urban sprawl. Direct estimation of traffic flows requires significant efforts and knowing in advance where to focus the study and where to place tools to directly measure traffic flows, and consequently traffic congestion could lead to significant savings in time and money. In the case of Rome municipality, we have monitored a situation in which a very high rate of urban fragmentation has occurred in the last 30 years, making the direct estimation of traffic difficult. The work described here can help to solve the problem of estimating traffic flows and in particular the congestion phenomenon through a very cheap approach by using remote sensing and geographical information system technology. This method is based on the identification of attractor points that draw traffic flows such as malls, schools, offices, shops, etc. that is to say, points in a territory that attract a certain number of people with vehicles (estimated with a scale) in specific periods of the day. The identification of those points and the calculation of the urban density through the satellite image processing have allowed the creation of a congestion map for the study area. Then the road network and the buildings have been classified according to the congestion values. The results highlight the most critical and congested areas that affect the traffic flows and impact the quality of life.
文摘Based on the continuation of our past study, the present analysis is conducted to examine recent effects of the urbanization process occurring over the entire district of Rome. Overlays of ALOS AVNIR-2 and SENTINEL-2A satellite images, collected over a 6 years period, were validated via Geographic Information System (GIS) techniques, in a particular procedure applied to urban land and agricultural transformations. The use of Copernicus SENTINEL-2A imagery has improved the previous results on urban processes, by reducing the uncertainty of the discrimination of land cover classes and facilitating the photo-interpretation. Statistical analysis was performed via the Urban Area Profile index in order to quantify the sprawl phenomenon, by defining several landscape metrics. This work, to be enriched in the future by means of complementary information available from Copernicus radar sensors, like the one onboard Sentinel-1, completes the series of observations on land use published by the Italian National Institute for Environmental Protection and Research, which stopped back in 2008.
文摘The science that underpins our knowledge and understanding of Isotope-Based Hydrograph separation (IHS) has gained grounds, over the last few decades, in the identification of streamflow sources. However, challenges still exist in identifying appropriate tracers and the right combination of end-members for the IHS process. In a two-component IHS analysis, the application of the dual isotopes tracers, δ18O and (or) δ2H, is regarded as the simplest method. We undertook an IHS study within a nested system of eight Prairie watersheds located in South central Manitoba, Canada. The work evaluated about 17,000 results emanating from the application of a combination of two potential tracers (δ18O and δ2H) and eight each of potential “old” and “new” water end-members in a two-component IHS process. The outcome showed occurrences of many mathematically possible but hydrologically unacceptable IHS results. The observation was particularly predominant within relatively larger perennial sub-catchments of the watershed. It is also shown that inter-site sub-catchment isotopic end-member transferability is possible within watersheds of similar physio-hydrographic characteristics. We suggest that a careful evaluation of the physio-hydrographic characteristics of catchments be considered in IHS studies in addition to the recommended guidelines in the selection of tracers and end-members.
基金The authors also gratefully acknowledge the support of the Centre for Earth Observation and Digital Earth in Beijing,which kindly provided many of the satellite images used to illustrate the global change aspects
文摘The Digital Earth concept as originally proposed by former US Vice president Al Gore is now well established and widely adopted internationally.Similarly,many researchers world-wide are studying the causes,effects and impacts of Global Change.The authors commence by describing a five-step approach to the development of Digital Earth technologies.This is followed by a detailed account of Digital Earth research and developments in China.The authors then present the research results of Global Change studies carried out in China,based on the Digital Earth approach.These research results are based on a classification of global change regions.This covers the following global change situations:Forest and grassland fires in Northern China,temperate region desertification and dust storms,underground coal fires,deforestation and carbon sequestration,protection and utilisation of wetlands,Avian Influenza and the spread of diseases,Tibet Plateau uplift and sub-tropical monsoon climate region,and sea-level rise.The research results show that the environment does not behave in a way easily understood by the traditional disciplinary approach.Although man is clearly a contributing factor to certain Global Change aspects,such as underground coal fires,desertification,land use changes etc.,many of the aspects of Global Change are naturally occurring phenomena which have been changing over centuries,and will continue to do so,no matter what actions we undertake to reverse these processes.Hence,in their conclusions,the authors propose that the communities involved in Digital Earth modelling and in Global Change research co-operate closer to overcome the limitations inherent in the current‘conventional’scientific approach,where scientists have very much stayed within their respective scientific boundaries.Such an integrated approach will enable us to build the next level of scientific infrastructure required to understand and predict naturally occurring environmental changes,as well as that of coupled humanenvironmental systems.
文摘The concept of Digital Earth(DE)was formalized by Al Gore in 1998.At that time the technologies needed for its implementation were in an embryonic stage and the concept was quite visionary.Since then digital technologies have progressed significantly and their speed and pervasiveness have generated and are still causing the digital transformation of our society.This creates new opportunities and challenges for the realization of DE.‘What is DE today?’,‘What could DE be in the future?’,and‘What is needed to make DE a reality?’.To answer these questions it is necessary to examine DE considering all the technological,scientific,social,and economic aspects,but also bearing in mind the principles that inspired its formulation.By understanding the lessons learned from the past,it becomes possible to identify the remaining scientific and technological challenges,and the actions needed to achieve the ultimate goal of a‘Digital Earth for all’.This article reviews the evolution of the DE vision and its multiple definitions,illustrates what has been achieved so far,explains the impact of digital transformation,illustrates the new vision,and concludes with possible future scenarios and recommended actions to facilitate full DE implementation.
文摘Almost all causative factors of diseases depend on location.The Digital Earth approach is suitable for studying diseases globally.Geospatial information systems integrated with statistical models can be used to model the relationship between a disease and its causative factors.Through modelling,the most important causative factors can be extracted and the epidemiology of the disease can be observed.In this paper,skin cancer(the most common type of cancer)has been modelled based on its causative factors,including climate factors,people’s occupations,nutrition habits,socio-economic factors,and usage of chemical fertiliser.To fit the model,a data framework was first designed,and then data were gathered and processed.Finally,the disease was modelled using Generalised Linear Models(GLM),a statistical model based on the location of the factors.The results of this study identify the most important causative factors together with their relative priority.Furthermore,a model was used to predict the change in skin cancer occurrences caused by a change in one of its causative factors.This work illustrates the ability of the model to predict disease occurrence.Thus,by using this Digital Earth approach,skincancer can be studied in all the key countries around the world.
基金supported by the Natural Science and Engineering Council(NSERC) of Canada (F.W.)the National High Technology Research and Development Program of China (2012AA101405)
文摘Mercury is one of the primary contaminants of global concern.As anthropogenic emissions of mercury are gradually placed under control,evidence is emerging that biotic mercury levels in many aquatic ecosystems are increasingly driven by internal biogeochemical processes,especially in ecosystems that have been undergoing dramatic environmental changes.Here we review the unique properties of mercury that are responsible for the exceptional sensitivity of its biogeochemical cycles to changes in climatic,geochemical,biological and ecological processes.We show that,due to rapid climate warming,a shift from sources-driven to processes-driven mercury bioaccumulation is already happening in the Arctic marine ecosystem.We further suggest that such a shift might also be operating in the Three Gorges Reservoir due to changes in these biogeochemical processes induced by the damming.As a result,the effectiveness of mercury emission control is expected to be followed by long delays before ensuing reduction is seen in food-web levels,making it all the more pressing to control and reduce mercury emissions to the reservoir.Long-term monitoring and targeted studies are urgently needed to understand how biotic mercury levels in the reservoir are responding to changes in mercury emissions and in biogeochemical processes.
文摘by Q.Weng,CRC Press,Taylor&Francis Group,Boca Raton,USA,2011,556 pp.,(hardback),ISBN 978-1-4200-9175-5 This volume is part of the Taylor&Francis Series in Remote Sensing Applications.So far,some seven books have been published in this series,on topics such as:Remote Sensing of Coastal Environments,Remote Sensing of Global Croplands for Food Security,Global Mapping of Human Settlement,Hyperspectral Remote Sensing,etc.
基金the Strategic Priority Research Program of Chinese Academy of Sciences,Project title:CASEarth[XDA19000000]Digital Belt and Road[XDA19030000].
文摘The Belt and Road initiative has a significant focus on infrastructure,trade,and economic development across a vast region,and it also provides significant opportunities for sustainable development.The combined pressure of climate variability,intensified use of resources,and the fragility of ecosystems make it very challenging,however,to achieve future sustainability.To develop the path in a sustainable way,it is important to have a comprehensive understanding of these issues across nations and evaluate them in a scientific and well-informed approach.In this context,the Digital Belt and Road(DBAR)program was initiated as an international venture to share expertise,knowledge,technologies,and data to demonstrate the role of Earth observation science and technology and big Earth data applications to support large-scale development.In this paper,we identify pressing challenges,present the research priorities and foci of the DBAR program,and propose solutions where big Earth data can make significant contributions.This paper calls for further joint actions and collaboration to build a digital silk road in support of sustainable development at national,regional and global levels.
