124 research outputs found
A QUICK SEASONAL DETECTION AND ASSESSMENT OF INTERNATIONAL SHADEGAN WETLAND WATER BODY EXTENT USING GOOGLE EARTH ENGINE CLOUD PLATFORM
Understanding the variation of Water Extent (WE) can provide insights into Wetland conservation and management. In this study, and-inter inner-annual variations of WE were analyzed during 2019â2021 to understand the spatiotemporal changes of the International Shadegan Wetland, Iran. We utilized a thresholding process on Modified Normalized Difference Water Index (MNDWI) to extract the WE quickly and accurately using the Google Earth Engine (GEE) platform. The water surface analysis showed that: (1) WE had a downward trend from 2019 to 2021, with the overall average WE being 1405.23 km2; (2) the water area reached its peak due to the water supply to International Shadegan Wetland through the Jarahi River and upstream reservoirs at the end of 2019 and the beginning of 2020, and the largest water body appeared in Winter 2019, reaching 1953.31 km2. In contrast, the smallest water body appeared in Autumn 2021, reaching 563.56 km2; (3) The WE of the wetland showed predictable seasonal characteristics. The water area in Winter was the largest, with an average value of 1829.1 km2, while it was the smallest in Summer, with an average value of 1100.3 km2; (4) The average water area in 2019 was 1490.5 km2 whereas in 2020 and 2021 decreased by 9% and 25%, respectively, and reached 968.6 km2 and 811.9 km2. Finally, to evaluate the proposed model, its results were compared with the Random Forest (RF) classification results. Accordingly, Histogram Analysis (HA) classification achieved 94.6% of the average overall accuracy and the average Kappa coefficient of 0.93, but the RF method obtained 95.38% of the average overall accuracy and an average Kappa coefficient of 0.94
Potential impact of climate change and water resources development on the epidemiology of schistosomiasis in China
Schistosomiasis japonica, caused by the blood fluke Schistosoma japonicum, has been
endemic in China since ancient times. An estimated 11 million people were infected in the
mid-1950s. Recognizing the huge public health significance and the economic impact of the
disease, the central government of China implemented a large-scale control programme, which
has been sustained and constantly adapted over the past half century. Today, the endemic areas
are mainly confined to the lake and marshland regions along the Yangtze River in five
provinces, namely Jiangsu, Anhui, Jiangxi, Hunan and Hubei. It is estimated that currently
about 800,000 people are infected and that 40 million people are at risk of infection.
Historically, the northern geographical limit where schistosomiasis transmission occurred was
around the 33°15â N latitude (e.g. in Baoying county, Jiangsu province), governed by low
temperature thresholds.
Based on various climate models, the Intergovernmental Panel of Climate Change (IPCC)
recently concluded that the Earth has warmed by approximately 0.6°C over the past 100 years.
This unusual warming has been particularly pronounced during the last three decades. There is
growing consensus that the global trend of climate warming will continue in the 21st century. It
has been suggested that climate change could impact on the distribution of the intermediate
host snail of S. japonicum, i.e. Oncomelania hupensis.
The frequency and transmission dynamics of schistosomiasis can also be affected by waterresource
development and management. Among others, the South-to-North Water Transfer
(SNWT) projectâ is currently under construction in China, which intends to divert water from
South (the snail-infested Yangtze River) to North (Beijing and Tianjing) via the lakes of
Gaoyou, Hongze and others. The implementation and operation of this project could further
amplify the negative effects of climate change and facilitate the northward spread of
O. hupensis.
The main objective of this PhD thesis was to explore the potential impact of climate change
and the SNWT project on the future distribution of schistosomiasis japonica, particularly in
eastern China. The techniques used were geographic information system (GIS) and remote
sensing (RS), coupled with Bayesian spatial statistics, which have become key tools for disease
mapping and prediction.
First, we reviewed the application of GIS/RS techniques for the epidemiology and control
of schistosomiasis in China. The applications included mapping prevalence and intensity data
of S. japonicum at a large scale, and identifying and predicting suitable habitats for O. hupensis
at a small scale. Other prominent applications were the prediction of infection risk due to
ecological transformations, particularly those induced by floods and water-resource
development projects, and the potential impact of climate change. We discussed the limitations
of the previous work, and outlined potential new applications of GIS/RS techniques, namely
quantitative GIS, WebGIS and the utilization of emerging satellite-derived data, as they hold
promise to further enhance infection risk mapping and disease prediction. We also stressed
current research needs to overcome some of the remaining challenges of GIS/RS applications
for schistosomiasis, so that further and sustained progress can be made towards the ultimate
goal to eliminate the disease from China.
Second, recognizing the advantages of combining GIS/RS techniques with advanced spatial
statistical approaches, we developed Bayesian spatio-temporal models to analyze the
relationship between key climatic factors and the risk of schistosomiasis infection. We used
parasitological data collected annually from 1990 to 1998 by means of cross-sectional surveys
carried out in 47 counties of Jiangsu province. Climatic factors, namely land surface
temperature (LST) and normalized difference vegetation index (NDVI), were obtained from
satellite sensors. Our analysis suggested a negative association between NDVI and the risk of
S. japonicum infection, whereas an increase in LST contributed to a significant increase in
S. japonicum infection prevalence.
Third, in order to better understand the changes in the frequency and transmission
dynamics of schistosomiasis in a warmer future China, a series of laboratory experiments were
conducted to assess the effect of temperature on the parasite-intermediate host snail interaction.
We found a positive linear relationship between the development of. S. japonicum larvae
harboured in O. hupensis and temperature. In snails kept at 15.3°C, S. japonicum larvae tend to
halt their development, while peak development occurs at 30°C. The temperature at which half
of the snails were in hibernation is 6.4°C. A statistically significant positive association was
observed between temperature and oxygen intake of O. hupensis at temperatures below 13.0°C.
We also detected a logistic relationship between snailsâ oxygen intake and their hibernation
rate. Our results underscored the important role temperature plays both for the activity of
O. hupensis and the development of S. japonicum larvae harboured in the intermediate host
snail.
Fourth, to substantiate the claim that global warming might alter the frequency and
transmission dynamics of S. japonicum in China, we conducted a time-series analysis from
1972-2002, using temperature data from 39 counties of Jiangsu province. Using annual
growing degree days (AGDDs) with a temperature threshold of 15.3°C, we forecasted changes
in S. japonicum transmission. The final model included a temporal and a spatial component.
The temporal trend consisted of second order polynomials in time plus a seasonality
component, while the spatial trend was formed by second order polynomials of the coordinates
plus the thin plate smoothing splines. The AGDDs of S. japonicum in 2003 and 2006 and their
difference were calculated. The temperatures at the 39 locations showed an increasing temporal
trend and seasonality with periodicities of 12, 6 and 3 months. The predicted AGDDs increased
gradually from north to south in both 2003 and 2006. The increase in AGDD was particularly
pronounced in the southern part of the study area. Our results suggest that alterations in the
transmission intensity of S. japonicum in south Jiangsu will be more pronounced than in the
northern part of the province.
Fifth, we further assessed the potential impact of climate change on the distribution of
O.hupensis via a spatially-explicit analytical approach. We employed two 30-year composite
datasets comprising average monthly temperatures collected at 623 meteorological stations
throughout China, spanning the periods 1961-1990 and 1971-2000. Temperature changes were
assessed spatially between the 1960s and the 1990s for January, as this is the critical month for
survival of O. hupensis. Our results show that the mean January temperatures increased at 590
stations (94.7%), and that Chinaâs average January temperature in the 1990s was 0.96°C higher
than 30 years earlier. The historical 0-1°C January isotherm, which has been considered the
approximate northern limit of S. japonicum transmission, has shifted from 33°15â N to 33°41â
N, expanding the potential transmission area by 41,335 km2. This translates to an estimated
additional 21 million people at risk of schistosomiasis. Two lakes that form part of the SNWT
project are located in this new potential transmission area, namely Hongze and Baima.
Finally, we applied GIS/RS techniques to predict potentially new snail habitats around
the lakes of Hongze and Baima, as well as Gaoyou lake, which is considered as a habitat where
O. hupensis could re-emerge. A model based on flooding areas, NDVI and a wetness index
extracted from Landsat images was developed to predict the snail habitats at a small scale. A
total of 163.6 km2 of potential O. hupensis habitats were predicted around the three study lakes.
In conclusion, our work suggests that global warming and a major water-resource
development project could impact on the distribution of S. japonicum and its intermediate host
snail in China and demonstrates that the combination of GIS, RS and Bayesian spatial
statistical methods is a powerful approach in estimating their extent. The predictions can serve
as a basis for health policy makers and disease control managers, and can be of use in the
establishment and running of schistosomiasis surveillance systems. It is further suggested that
an efficient early warning system should be set up in potential new endemic areas to monitor
subtle changes in snail habitats due to climate change and major ecological transformations,
and to assure the early detection of emerging and re-emerging schistosomiasis
Remote Sensing of Surface Water Dynamics in the Context of Global Change - A Review
Inland surface water is often the most accessible freshwater source. As opposed to groundwater, surface water is replenished in a comparatively quick cycle, which makes this vital resourceâif not overexploitedâsustainable. From a global perspective, freshwater is plentiful. Still, depending on the region, surface water availability is severely limited. Additionally, climate change and human interventions act as large-scale drivers and cause dramatic changes in established surface water dynamics. Actions have to be taken to secure sustainable water availability and usage. This requires informed decision making based on reliable environmental data. Monitoring inland surface water dynamics is therefore more important than ever. Remote sensing is able to delineate surface water in a number of ways by using optical as well as active and passive microwave sensors. In this review, we look at the proceedings within this discipline by reviewing 233 scientific works. We provide an extensive overview of used sensors, the spatial and temporal resolution of studies, their thematic foci, and their spatial distribution. We observe that a wide array of available sensors and datasets, along with increasing computing capacities, have shaped the field over the last years. Multiple global analysis-ready products are available for investigating surface water area dynamics, but so far none offer high spatial and temporal resolution
Remotely sensed mid-channel bar dynamics in downstream of the Three Gorges Dam, China
The downstream reach of the Three Gorges Dam (TGD) along the Yangtze River (1560 km) hosts numerous mid-channel bars (MCBs). MCBs dynamics are crucial to the riverâs hydrological processes and local ecological function. However, a systematic understanding of such dynamics and their linkage to TGD remains largely unknown. Using Landsat-image-extracted MCBs and several spatial-temporal analysis methods, this study presents a comprehensive understanding of MCB dynamics in terms of number, area, and shape, over downstream of TGD during the period 1985â2018. On average, a total of 140 MCBs were detected and grouped into four types representing small ( 2 km2), middle (2 km2 â 7 km2), large (7 km2 â 33 km2) and extra-large size (>33 km2) MCBs, respectively. MCBs number decreased after TGD closure but most of these happened in the lower reach. The area of total MCBs experienced an increasing trend (2.77 km2/yr, p-value 0.01) over the last three decades. The extra-large MCBs gained the largest area increasing rate than the other sizes of MCBs. Small MCBs tended to become relatively round, whereas the others became elongate in shape after TGD operation. Impacts of TGD operation generally diminished in the longitudinal direction from TGD to Hankou and from TGD to Jiujiang for shape and area dynamics, respectively. The quantified longitudinal and temporal dynamics of MCBs across the entire Yangtze River downstream of TGD provides a crucial monitoring basis for continuous investigation of the changing mechanisms affecting the morphology of the Yangtze River system
How would big data support societal development and environmental sustainability? Insights and practices
The theme of this Special Volume (SV) focuses on improving natural resource management and human health to ensure sustainable societal development. Natural resources have been exploited unduly regardless of the consequences, which has resulted in inappropriate management natural resources and has caused severe environmental degradation. Contributions in this SV addressed improved environmental management, utilization, and allocation of natural resources; evaluation of sustainable natural resource management; pollution prevention and treatment; and evaluation and suggestions for improved natural resource-related policies. The authors presented an inspiring panorama of the initiatives that have been developed throughout the world for sustainable natural resource management and improve societal development. Theoretically, new approaches to bridge the gaps between the economic development and environmental protection were increasingly dominant. Empirically, many of the papers provided case studies of regions in China and other regions. The authorship reflected growing collaboration between researchers from many different countries or universities. While the great diversity of contributions on the topic reflected the wealth of insights generated on the topic in recent years, there is much more that must be done to achieve societal sustainability in natural resource management.No Full Tex
Assessment Of Spatio-Temporal Changes Of Wetlands Using GIS And RS Techniques In Dawa Chefa Area In The Northern Central Ethiopian Highlands
Wetland resources play an important role in sustaining human, plant and animal life. They
balance climatic and hydrology cycle to our environment. However, wetlands have been
decreased both in time and space. This in turn narrowed the opportunities of wetland services.
Thus, the study focused on assessment of the spatio-temporal change of wetlands and its socioeconomic
effect in Northern Central Ethiopian highlands. Four sets of Landsat satellite
imageries for the years of 1984, 1993, 2000 and 2013 were used to produce land cover maps and
quantify the land use and land cover dynamics. Moreover; practical observation, structured
questionnaire and focus group discussions were used to supplement remotely sensed satellite
data. The qualitative data were then narrated. Unlike built up area expansion, grassland and
farmland, the land use and land cover analysis showed that wetlands are reduced from the year
1984 to 2013. Overgrazing, water diversion for irrigated farm, waste dumping, and rapid
population growth are the key driving forces of wetlands changes. Moreover, the study shows
that wetland change brought social effect in the study area. In this regard, the shrinkage of the
wetlands caused prevailing conflict between nomads and local farmers as both of them need
wetland for different purposes. As they are more dependent on the wetland resources, the
nomads were more resistant to the strategies of the government. The study also showed that
wetland loss has controversial effects. In this respect when wetland loss increases swampy plants
and animals also decreased and even later disappeared. Economically very important mangrove
species started declining which directly affected the lives of nomads. Conversely, when wetland
decreases, farmers encroach the wetlands for agricultural and grazing land due to the fact that it
is very fertile and suitable for the application of modern irrigation. This is, however, at the
expense of wetland loss. In conclusion, the study highlights that the wetland size has been
decreased and brought ecological and socio-economic effect in the study area. Therefore, the
government and other stakeholders should intervene by providing appropriate water
management practices, awareness creation and family planning education to enhance
sustainable land management and to meet the national and international interest linked to the
Millennium Development Goals
Monitoring wetlands and water bodies in semi-arid Sub-Saharan regions
Surface water in wetlands is a critical resource in semi-arid West-African regions that are frequently exposed to droughts. Wetlands are of utmost importance for the population as well as the environment, and are subject to rapidly changing seasonal fluctuations. Dynamics of wetlands in the study area are still poorly understood, and the potential of remote sensing-derived information as a large-scale, multi-temporal, comparable and independent measurement source is not exploited. This work shows successful wetland monitoring with remote sensing in savannah and Sahel regions in Burkina Faso, focusing on the main study site Lac Bam (Lake Bam). Long-term optical time series from MODIS with medium spatial resolution (MR), and short-term synthetic aperture radar (SAR) time series from TerraSAR-X and RADARSAT-2 with high spatial resolution (HR) successfully demonstrate the classification and dynamic monitoring of relevant wetland features, e.g. open water, flooded vegetation and irrigated cultivation. Methodological highlights are time series analysis, e.g. spatio-temporal dynamics or multitemporal-classification, as well as polarimetric SAR (polSAR) processing, i.e. the Kennaugh elements, enabling physical interpretation of SAR scattering mechanisms for dual-polarized data. A multi-sensor and multi-frequency SAR data combination provides added value, and reveals that dual-co-pol SAR data is most recommended for monitoring wetlands of this type. The interpretation of environmental or man-made processes such as water areas spreading out further but retreating or evaporating faster, co-occurrence of droughts with surface water and vegetation anomalies, expansion of irrigated agriculture or new dam building, can be detected with MR optical and HR SAR time series. To capture long-term impacts of water extraction, sedimentation and climate change on wetlands, remote sensing solutions are available, and would have great potential to contribute to water management in Africa
Geospatial analysis of shoreline changes in the Oman coastal region (2000-2022) using GIS and remote sensing techniques
This research introduces an innovative method employing the Canny edge detector for automatic and precise coastline extraction, aiming to analyze spatial and temporal variations in the Oman coastline from 2000 to 2022 using GIS and remote sensing (RS) techniques. Focusing on both multi-decadal and short-term periods, the study aims to detect accretion and erosion rates through the observation and interpretation of coastal changes. Utilizing the Digital Shoreline Analysis System and LANDSAT imageries, Shoreline changes have been quantitatively evaluated using three distinct approaches: Linear Regression Rate (LRR), End Point Rate (EPR), and Net Shoreline Movement (NSM). The dynamic nature of the Oman coastal region necessitates a comprehensive understanding of its evolving coastline. Our investigation applies digital shoreline analysis to discern shifts in the coastlineâs position, employing a multiple regression approach for quantifying the rate of coastal change. To facilitate automatic shoreline extraction, various methods were experimented with, ultimately determining the Canny Edge algorithmâs superiority in yielding precise results. The paper outlines the monitoring procedures for the coastal area and analyzes coastline changes using geospatial techniques. This analysis provides valuable insights for the planning and management of the Oman shore. Furthermore, the proposed modelâs applicability is rigorously tested against other generic edge detection algorithms, including Sobel, Prewitt, and Robertâs techniques. The conclusive findings demonstrate that our model outperforms these alternatives, particularly excelling in the accurate detection of the coastline. This research contributes to a deeper understanding of coastal dynamics and offers a robust methodology for coastal monitoring, with implications for effective planning and management strategies in the Oman shore region
- âŠ