Remote Arid Research Articles

EFFICIENT SCHEMES OF CLASSIFIERS FOR REMOTE SENSING SATELLITE IMAGERIES OF LAND USE PATTERN CLASSIFICATIONS

Land use pattern classification of remote sensing imagery data is imperative to research that is used in remote sensing applications. Remote sensing (RS) technologies were exploited to mine some of the significant spatially variable factors, such as land cover and land use (LCLU), from satellite images of remote arid areas in Karnataka, India. Four diverse classification techniques unsupervised, and supervised (Maximum likelihood, Mahalnobis Distance, and Minimum Distance) are applied in Bellary district in Karnataka, India for the classification of the raw satellite images. The developed maps are then visually compared with each other and accuracy evaluations make using of ground-truths are carried out. It was initiated that the Maximum likelihood technique gave the finest results and both Minimum distance and Mahalnobis distance methods overvalued agricultural land areas. In spite of missing a few insignificant features due to the low resolution of the satellite images, a high-quality accord between parameters extracted automatically from the developed maps and field observations was found. Keywords: Remote sensing (RS), land cover and land use (LCLU).

Green hydrogen production from thermoelectric condensation of ambient moist air

As the world transitions towards reducing carbon emissions, green hydrogen produced through solar-powered alkaline water electrolysis (AWE) presents a promising eco-friendly fuel option. In response to the challenges caused by global warming, including air moisture saturation leading to unbalanced rainfall, flooding, concern for freshwater depletion and the limited availability of water and energy sources in arid regions. The present study introduces a novel method of integrating thermoelectric water condenser (TEWC) and AWE for green hydrogen production in remote and arid regions where both the water and the conventional energy sources are scarce. Numerical simulations of the present study show that the impact of relative humidity, temperature, and air flow rate significantly affect water condensation, energy requirement, and hydrogen production. The TEWC and AWE models showed excellent agreement with the experimental data. TEWC model reveled that the highest water production rate of 1.50 kg/(m2h) is achieved at ambient air temperature of 308 K and relative humidity of 80%. Furthermore, increasing the moist air flow from 1 m/s to 2 m/s results in a 47.5% increase in water production rate. The AWE model showed that cell's performance improved with higher temperatures, lower electrode-separator gap, and overpotentials. The hydrogen evolution rate reached a maximum of 5.2 kg/(m2h) at current density of 1.4 A/cm2 and potential of 3.96 V. By optimizing the TEWC and AWE systems the integrated method proved to be an efficient way of converting moist air into green hydrogen using solar energy, making it a viable and sustainable setup in remote arid regions.

Using desiccation-resistant eggs to explore the ecology of giant ostracods (subfamily Mytilocypridinae) in Australian salt lakes

AbstractGiant ostracods in the subfamily Mytilocypridinae are an important component of the biota of Australian salt lakes, which are predominantly temporary, and often located in remote arid areas. Mytilocypridines produce desiccation-resistant eggs to persist in these habitats during unfavourable conditions. In this study, we used mytilocypridine eggs collected from sediments in salt lakes in Western Australia to analyse aspects of the ecology of these ostracods. We conducted two rehydration trials, where sediment was collected from dry lakes or the dry margins of lakes, rehydrated in a laboratory setting, and selected mytilocypridine species hatched and raised in cultures. The first trial found that the eggs of mytilocypridine species were unevenly distributed in a dry lake and could be hatched even after 27 months of dry storage with no discernible loss of viability. The second trial assessed the capacity of selected mytilocypridines to hatch and develop into adults under different salinity treatments. One species, Australocypris insularis, hatched and developed across a very wide salinity range (0–100 g/L). Egg/sediment samples provide a means for testing species’ tolerance to physical and chemical variables throughout their entire life cycle, as well as for surveying the mytilocypridines in remote lakes that rarely hold water.

Reconstructing monthly 0.25° terrestrial evapotranspiration data in a remote arid region using Bayesian-driven ensemble learning method

This study presents a Bayesian-driven ensemble learning framework to minimize errors in evapotranspiration (ET) data assimilation, thereby generating a continuous-scale ET estimation with improved accuracy for the data-scarce arid Central Asia (CA). Five state-of-the-art gridded ET products were extensively tested and utilized to reconstruct new long-term ET data at grid scale, including two Global Land Data Assimilation System (GLDAS)-Land Surface Models (LSM) (Catchment and NOAH), two reanalysis products (European Centre for Medium-Range Weather Forecasts Reanalysis 5 (ERA5) and Modern-Era Retrospective Analysis for Research and Applications – ver. 2 (MERRA2)), along with the Global Land Evaporation Amsterdam (GLEAM) satellite ET product ver. 3.6b. Taylor Skill Score was employed to evaluate the input gridded ET datasets, using in situ measurements across four arid biomes — cropland, shrubland, farmland, and grassland —as benchmarks. Bayes-Markov Chain Monte Carlo (Bayes-MCMC)-derived logarithmically transformed predictors from the posterior ensemble anomalies were standardized to resolve the mismatches in the cumulative distribution functions of ET data relating to the in situ observations. We found that the constrained residual errors were more profound between 45th and 95th percentiles for the rescaled total ET anomalies across all the input ET datasets at 95 % confidence interval. Moreover, the weighted ensemble estimates derived from the Bayes-MCMC were instrumental in correcting ET anomalies, leading to the robust reconstruction of a more reliable ensemble mean ET data for Central Asia (CAETens) at monthly temporal and 0.25° spatial resolutions, spanning from 2003 to 2020. Overall, CAETens exhibited superior performance, achieving the highest averaged Kling-Gupta Efficiency of 0.75 and registering the lowest Root Mean Square Error of 6.85 mm/m compared to the standalone gridded ET products. Comparisons of spatial distributions of fine-scale features, and evaluations using standard metrics revealed that all ET products varied significantly (p < 0.05) by biome types. Remarkably, only CAETens exhibited a reasonable low positive bias and pronounced ability to resolve the complex spatiotemporal patterns associated with the input gridded ET products. The study bridges the gap in continuous ET monitoring for sustainable water resources management in CA.

Non-systematic surveys reveal increases in areas occupied by endangered and data-deficient Nubian bustard

A large proportion of endangered species lack good-quality data for assessing population trends. Obtaining these data is especially challenging in remote arid ecosystems, in part because these desert environments have historically attracted less scientific attention and funding than more mesic areas. The Sahara-Sahel biome in northern Africa is home to over 1000 species of terrestrial vertebrates, of which 79 have been classified as threatened or near-threatened by the IUCN Red List. This includes the Nubian bustard (Neotis nuba), a species with deficient ecological information and unknown population trends. In this study we used non-systematic data collected over a 10-year period (2008–2017) across the Termit and Tin-Toumma National Nature Reserve in Niger to i) study the temporal trend in the proportion of areas occupied, ii) map occurrence, and iii) assess how vegetation productivity, elevation, and surface roughness affect species occupancy. We implemented a single-species, multi-year site-occupancy model with an intrinsic conditional autoregressive structure to account for detection probability and the spatial autocorrelation nature of the non-systematic patrolling dataset. Our results showed that birds were imperfectly detected, and detection probability increased for longer transects. Occupancy probability was higher in higher elevated areas and in smoother terrain. Contrary to expected, occupancy probability decreased with increasing vegetation productivity. However, all parameters presented high uncertainty. We found a small positive trend in the proportion of areas occupied by Nubian bustards across the study area and mapped the spatial distribution after accounting for the spatial autocorrelation. Our study provides a better understanding of the population status of Nubian bustards across the ecosystem and will serve as a guide to target and improve surveys for future conservation efforts. Systematic data collection is always advisable for monitoring biodiversity. However, our analysis demonstrates that combining advanced modeling with observations from non-systematic patrolling activities in protected areas can be used for assessing population trends of other endangered and data-deficient species across remote areas.

A spatiotemporal monitoring model of TSM and TDS in arid region lakes utilizing Sentinel-2 imagery

The assessment of lake water quality is crucial for protecting and managing natural resources. Total suspended matter (TSM) and total dissolved solids (TDS) are significant parameters in evaluating lake water quality, and their concentration levels provide useful information about the health of the ecosystem. However, measuring TSM and TDS concentrations in remote arid areas can be challenging, necessitating the development of a simple, efficient, and cost-effective monitoring system. In this study, the aim was to retrieve TDS and TSM concentrations in the arid region using an empirical and physics-based method simultaneously. Measured data and remote sensing images for Chah-Nimeh Reservoirs (CNRs), Iran, were used to establish the TSM and TDS concentration model. Twenty-seven Sentinel-2 multispectral instrument (MSI) data acquired from 2018 to 2021 were employed to determine the spatiotemporal distribution of TDS and TSM concentrations. The results indicate that Sentinel-2 MSI data is a productive tool for retrieving TSM concentration using the Case-2 Regional/Coastal Color (C2RCC) processor, with a high level of performance in the dry ecosystem of CNRs (R2 = 0.92). Furthermore, the Bayesian regularization artificial neural network (BRANN) algorithm was used to evaluate TDS concentration, and the results demonstrated that the BRANN algorithm outperforms other models, with a high level of performance (R2 = 0.89). It is noteworthy that evaluating TDS concentration is generally more challenging than TSM. The study provides a valuable model for monitoring TSM and TDS concentrations in remote arid areas using Sentinel-2 MSI data. The proposed approach can facilitate effective spatiotemporal monitoring of TSM and TDS concentrations and aid in the evaluation of lake water quality, specifically in regions where in-situ measurements are not feasible. The findings have significant implications for the management and conservation of natural resources in arid and remote regions.

Estimating water fluxes in the critical zone using water stable isotope approaches in the Groundnut and Ferlo basins of Senegal

AbstractSustainable water management in semi‐arid agriculture practices requires quantitative knowledge of water fluxes within the soil‐vegetation‐atmosphere system. Therefore, we used stable‐isotope approaches to evaluate evaporation (Ea), transpiration (Ta), and groundwater recharge (R) at sites in Senegal's Groundnut basin and Ferlo Valley pasture region during the pre‐monsoon, monsoon, and post‐monsoon seasons of 2021. The approaches were based upon (i) the isothermal evaporation model (for quantifying Ea); (ii) water and isotope mass balances (to partition Ea and Ta for groundnut and pasture); and (iii) the piston displacement method (for estimating R). Ea losses derived from the isothermal evaporation model corresponded primarily to Stage II evaporation, and ranged from 0.02 to 0.09 mm d−1 in the Groundnut basin, versus 0.02–0.11 mm d−1 in Ferlo. At the groundnut site, Ea rates ranged from 0.01 to 0.69 mm d−1; Ta was in the range 0.55–2.29 mm d−1; and the Ta/ETa ratio was 74%–90%. At the pasture site, the ranges were 0.02–0.39 mm d−1 for Ea; 0.9–1.69 mm d−1 for Ta; and 62–90% for Ta/ETa. The ETa value derived for the groundnut site via the isotope approach was similar to those from eddy covariance measurements, and also to the results from the previous validated HYDRUS‐1D model. However, the HYDRUS‐1D model gave a lower Ta/ETa ratio (23.2%). The computed groundwater recharge for the groundnut site amounted to less than 2% of the local annual precipitation. Recommendations are made regarding protocols for preventing changes to isotopic compositions of water in samples that are collected in remote arid regions, but must be analysed days later. The article ends with suggestions for studies to follow up on evidence that local aquifers are being recharged via preferential pathways.

Development of a graphical resilience framework to understand a coupled human-natural system in a remote arid highland of Baja California Sur.

Hydrological systems are important to society as water resources and effective management requires an understanding of how water and humans influence each other. To describe human-water connections it is necessary to bridge social and natural sciences. To this end, we construct an interdisciplinary graphical framework for evaluating potential human-water system resilience, which is a tool to show the spatial and temporal response to system change of both human and natural systems. This helps to identify the ways that human responses to change relate to changing water resources and identifies important thresholds and potential disconnects that would create vulnerability. We further use this tool to describe a dynamic, coupled human-water system present in the arid Sierra de la Giganta region of Baja California Sur, Mexico. In this remote mountain range, there is a community (self-identifying as Choyeros) who rely on spring water for ranching and subsistence. Using mixed methods of hydrogeochemistry and anthropology, we describe spatial connectivity and temporal changes of both hydrologic and social systems. We use these observations to examine the Choyero response to system changes and explore the topology of the various approaches that the community employs to adapt to changing water availability. The framework guides dialogue to constrain the types of policies, strategies, and responses that help to promote the sustainability of water resources. This framework can be used to compare systems across spatio-temporal scales to produce more generalizable and communicable insights of coupled human-natural systems.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11625-022-01101-6.

Estimation of health risk associated with consumption of groundwater of apscheronia propinqua at a Prielton region

In modern conditions, health risk assessment activities have become the leading direction in the analysis of potential threats to the health of the population living on the territory of a certain hydrogeochemical province. Based on the analysis of the reporting documentation of state reports in the field of consumer protection and human well-being, as well as ecology and natural resources of the Volgograd region, a priority list of pollutants was selected, due to the chemical nature of the aquifers of the Volgograd Trans-Volga region. The health risk assessment was carried out on the basis of 19 samples taken from non-centralized water supply sources in the Elton rural settlement using the methodology presented in P 2.1.10.1920-04. In this study, for the first time for groundwater in the Volgograd region, a risk-based approach was applied to assess the effect of dissolved toxicants on the health status of the population. The greatest contribution to the formation of a non-carcinogenic risk to the health of adults and children is made by oral exposure to sodium and nitrates. The cardiovascular system is the main critical system that is jointly affected by these toxicants. The total risk of non-carcinogenic hazard (HI) was HI = 0.5262 for adults and 1.2366 for children (taking into account standard exposure factors). The excess of the maximum permissible concentrations of the most significant in the formation of an unfavorable sanitary and ecological situation is primarily due to the geochemical nature of sodium-chloride-sulfate underground waters in the southeast of the Volgograd region, as well as irrational agriculture and the lack of zones of sanitary protection of water sources. The identified risks should be taken into account when exploring new groundwater resources and organizing water supply systems on the territory of the Elton rural settlement. The data obtained are planned to be used in the development of recommendations for the procedure for organizing water treatment in remote arid regions of the Volgograd region in the context of determining priority treatment facilities for sources of non-centralized water supply. Prospects for further research are related to the determination of carcinogenic risks formed by natural heavy metals and agricultural toxins associated with irrational agriculture.

Structure and projected decline of a Karoo dwarf tortoise population

AbstractInconspicuous, secretive, or sparsely distributed species receive relatively little research attention, potentially leading to uncertainty about their status and lack of efforts to conserve them. Karoo dwarf tortoises (Chersobius boulengeri) are endemic to South Africa, spend most of the time in retreats at remote arid locations, and are seldom seen. We conducted a 3‐year (2018–2020) mark‐recapture study to investigate the size and structure of the only Karoo dwarf tortoise population currently known to exist. The population in the 16‐ha core of our study site consisted primarily of adult males and females, at a density of 3.3 individuals/ha. Many individuals had severely worn shells and appeared old. Small individuals (straight carapace length &lt;65 mm) represented just 8% of the population and were mostly recent hatchlings. Overall, tortoises had high estimated survival rates (0.77–0.95; lower 95% confidence limit for the smallest tortoises was 0.16), despite a 15‐month drought. The lack of small individuals may reflect low levels of recruitment and population decline. Predation by corvids was an obvious threat to all size classes. We estimated that the local population across the 250‐ha study area was 800–900 males and females, and recommend precautionary conservation measures focused on reducing human‐subsidized avian predation.

Light-weight oxygen supply for portable biological nitrogen removal from urine and sweat

The weight or availability of potable water often limits foot travel into remote arid regions for recreational, or government-sponsored activities. To address this limitation, a portable bioprocessing unit, intended to be one treatment stage in the continuous regeneration of drinking water from urine and sweat was prototyped. Biological treatment of urine requires oxygen, and the goal of this work was to determine the oxygen supply option that is the least weight to carry for safe and sustained treatment. Four oxygen supply options were modeled; battery powered aeration, battery powered electrolysis, diffused oxygen gas generated from hydrogen peroxide (H2O2), and platinum catalyzed liquid phase oxygen supply (PtLPOS) from H2O2. Modeling focused on a small reactor (<0.3 L) operating at 3 mg O2L − 1, using hydrogel immobilized bacteria. The results indicated PtLPOS adds the least amount of weight per additional day of travel at 123 g d − 1 compared to 290, 572, 654 g d − 1, for aeration, electrolysis, and oxygen gas via H2O2, respectively. PtLPOS was prototyped for urine treatment using a hydrogel immobilized culture seeded with urease positive Nitrospira inopinata (comammox) and an enrichment of Ca. Brocadia sinica (anammox), which were chosen because prior work showed the co-culture is capable of producing nitrate free effluent. The prototype provided oxygen efficiently, achieving 86% of the maximum nitrogen removal per H2O2 consumed via a theoretical comammox-anammox partnership. This work demonstrated for the first time that Pt catalyzed LPOS has the potential to enhance the portability of bioprocessing technologies and specifically works with autotrophic nitrogen removal in the treatment of natural urine.

Climate Change is Likely to Alter Sheep and Goat Distributions in Mainland China

Climate change endangers food security worldwide, especially in developing countries. Livestock husbandry is one of the essential livelihoods for farmers and herders in remote arid and semiarid regions. However, it remains unclear how climate change will impact livestock husbandry in the future. This study collected sheep and goat distributions from the “gridded livestock of the world” (GLW) dataset for 1943 counties in Mainland China. Current climate data include precipitation and temperature from the National Meteorological Information Center (NMIC). We disentangled the effects of precipitation and temperature on current distributions of sheep and goats with the Bayesian Hierarchical Model by Integrated Nest Laplace Approximation (INLA). Further, we forecasted the potential sheep and goat distributions in 2030 and 2050 under Coupled Model Intercomparison Project (CMIP) scenarios. Our result showed that sheep distribution is significantly correlated with elevation, slope, market density, and highway distance, with absolute correlation coefficients ranging from 0.019 to 0.411. In addition to elevation, slope, and market density, goat distribution is also affected by gain production, with a correlation coefficient of 0.055. There is a dynamic correlation of temperature and precipitation with sheep and goat density. The sheep density distribution is predicted to increase in Northwest China, while the goat density distribution might increase in farming areas under climate change. Finally, this study suggests for the sheep and goat breeding industry to respond to climate change.

A neglected transport of plastic debris to cities from farmland in remote arid regions

Although microplastics have been investigated in terrestrial environments, the occurrence and transport of microplastics in semiarid regions with serious wind erosion are still limited. We investigated plastic debris, including macroplastics (>5 mm) and microplastics (50 μm to 5 mm), from twenty semiarid farmlands and then developed a mass flux model to calculate the quantities of plastic debris transport by wind erosion. Finally, the spatial extent of microplastic deposition was estimated. The average abundance of macroplastics increased with duration of mulching film use, whereas the abundance of microplastics did not change significantly (p > 0.05). Moreover, the highest abundance of microplastics among samples was from the farmland using greenhouse, which suggests that wind erosion played an essential role in retention of plastic debris. Besides, the enrichment ratio (ER) which depends on the shape of microplastics is identified to be a key indicator of the mass flux model. The results showed that 6.91–38.11 kg/ha of plastic debris was released by wind in the 25th year after film application, with 6.14 n/m2 of microplastics settling in February in Xi'an, which is 690 km away from the source.

AN INVESTIGATION OF GREYWATER ONSITE REUSE POTENTIAL IN AN ARID ENVIRONMENT

Wastewater originating from bathtubs, showers, hand basins, kitchen sinks, dishwashers and laundry machines is usually not as heavily polluted as toilet water and is thus given the name greywater. Greywater separation for onsite reuse has often been voiced as a viable option, particularly for areas suffering from water scarcity. Such areas include remote arid areas, such as desert cities and arid coastal zones. However, issues related to consistency in the quality and quantity of generated greywater were listed as challenges hindering the adoption of greywater reuse. Thus, the objective of this study was to characterize the different greywater sources for variations in the quality and quantity of greywater in households in the city of Al Ain, UAE over a period of 3 months. Samples were collected from 10 Households and tested for the typical water quality parameters (pH, turbidity, COD, and TDS). In addition, a questionnaire was designed to get an estimate of the greywater flow in the different households. Results indicate that the average daily greywater production was around 88 L per person per day. Even though the results of the water quality analysis for light greywater sources (laundry, showers, and hand basins) exhibited high variability, it was still suitable for direct irrigation. The quantification of greywater flow and potential water savings indicated that greywater could be sufficient for onsite reuse in non-crop irrigation in some of the households.

MIL-160 as an Adsorbent for Atmospheric Water Harvesting

Nowadays, the rapidly growing population, climate change, and environment pollution put heavy pressure on fresh water resources. The atmosphere is the immense worldwide and available water source. The Adsorptive Water Harvesting from the Atmosphere (AWHA) method is considered a promising alternative to desalination technologies for remote arid regions. The development of novel adsorbents with advanced water-adsorption properties is a prerequisite for practical realization of this method. Metal–organic frameworks (MOFs) are a novel class of porous crystalline solids that bring a great potential for AWHA due to their extremely high specific surface area, porosity, and tailored adsorption properties. This work addresses MIL-160 as a water adsorbent for AWHA. The water-adsorption equilibrium of MIL-160 was studied by volumetric method, the isosteric heat of adsorption was calculated, and finally, the potential of MIL-160 for AWHA was evaluated for climatic conditions of the deserts of Saudi Arabia, Mongolia, the Sahara, Atacama, and Mojave as reference arid regions. MIL-160 was shown to ensure a maximum specific water productivity of 0.31–0.33 gH2O/gads per cycle. High fractions of water extracted (0.90–0.98) and collected (0.48–0.97) could be achieved at a regeneration temperature of 80 °C with natural cooling of the condenser by ambient air. The specific energy consumption for water production varied from 3.5 to 6.8 kJ/g, which is acceptable if solar heat is used to drive the desorption. The AWHA method employing MIL-160 is a promising way to achieve a fresh water supply in remote arid areas.

Regional Mapping of Groundwater Potential in Ar Rub Al Khali, Arabian Peninsula Using the Classification and Regression Trees Model

Mapping of groundwater potential in remote arid and semi-arid regions underneath sand sheets over a very regional scale is a challenge and requires an accurate classifier. The Classification and Regression Trees (CART) model is a robust machine learning classifier used in groundwater potential mapping over a very regional scale. Ten essential groundwater conditioning factors (GWCFs) were constructed using remote sensing data. The spatial relationship between these conditioning factors and the observed groundwater wells locations was optimized and identified by using the chi-square method. A total of 185 groundwater well locations were randomly divided into 129 (70%) for training the model and 56 (30%) for validation. The model was applied for groundwater potential mapping by using optimal parameters values for additive trees were 186, the value for the learning rate was 0.1, and the maximum size of the tree was five. The validation result demonstrated that the area under the curve (AUC) of the CART was 0.920, which represents a predictive accuracy of 92%. The resulting map demonstrated that the depressions of Mondafan, Khujaymah and Wajid Mutaridah depression and the southern gulf salt basin (SGSB) near Saudi Arabia, Oman and the United Arab Emirates (UAE) borders reserve fresh fossil groundwater as indicated from the observed lakes and recovered paleolakes. The proposed model and the new maps are effective at enhancing the mapping of groundwater potential over a very regional scale obtained using machine learning algorithms, which are used rarely in the literature and can be applied to the Sahara and the Kalahari Desert.

A small neighborhood well-organized: seasonal and daily activity patterns of the community of large and mid-sized mammals around waterholes in the Gobi Desert, Mongolia

BackgroundAnimal communities have complex patterns of ecological segregation at different levels according to food resources, habitats, behavior, and activity patterns. Understanding these patterns among the community is essential for the conservation of the whole ecosystem. However, these networks are difficult to study nowadays, due to anthropic disturbances and local extinctions, making it difficult to conclude if segregation patterns are natural or human-induced. We studied ecological segregation in a community of large and mid-sized mammals in the Great Gobi Desert, a remote arid area free from recent extinctions and human disturbances. Activity patterns of 10 sympatric mammal species were monitored around 6 waterholes through camera-trapping over a two-year period, and analyzed them primarily through circular statistics.ResultsComplex patterns of spatial, seasonal, and daily segregation were found. Overlap in seasonal activity was detected in only 3 of the 45 possible pairs of species. Four species used the waterholes all-year-round, while others peaked their activity during different periods. The Bactrian camel showed continuous daily activity, the grey wolf had bimodal activity, and the argali and Siberian ibex were diurnal, while the others had nocturnal peaks during different hours. Daily and spatial overlap were both detected in only 6 of the 45 pairs. Only one species pair (snow leopard and Eurasian lynx) showed an overlap at two levels: seasonal and daily. Climate and moon phase significantly affected the activity of certain species.ConclusionsAltogether, the results showed complex patterns of ecological segregation at different levels in the use of the key resource in arid environments: waterholes. These results are important for understanding the biology of these species under natural conditions, as well as potential changes in altered ecosystems, and may help to design conservation strategies.

Differences in Fatty Acid Composition between Orb-Weaver Spiders Inhabiting a Riparian Zone and a Steppe Are Associated with the Consumption of Different Chironomid Taxa.

Amphibiotic insects, chironomids of the genera Glyptotendipes and Chironomus, which emerged from saline Lake Shira, differed in composition and content of fatty acids, including the essential eicosapentaenoic acid (20:5n-3, EPA), and upon flying out they were concentrated in different territories, the riparian zone and remote arid steppe zone, respectively. Potential consumers of chironomids adults, the orb-weaver spiders Larinoides suspicax, which inhabited both zones, also differed in fatty acid composition. The main difference in their biochemical composition was a significantly higher level of EPA in spiders from the riparian zone that likely to be explained by consumption of the Glyptotendipes adults enriched in this fatty acid and concentrated only within this zone. The higher level of EPA, which is deficient in terrestrial ecosystems, in orb-weaver spiders from the riparian zone of the saline lake may potentially promote a successful survival of the consumers in the arid landscape.

Activity patterns of leopards (Panthera pardus) and temporal overlap with their prey in an arid depredation hotspot of southern Africa

The ecology of wildlife in remote arid regions with free-range livestock farming activities remains largely unexplored. We studied the temporal activity patterns of African leopards (Panthera pardus) in relation to prey in Namaqualand, South Africa, a semi-desert ecosystem with extensive livestock farming and a protected area. Camera trapping in winter and summer 2014–2015 (n = 95 stations) showed that leopards had high temporal overlap with aardvark (Orycteropus afer) and lagomorphs, and partial overlap with red hartebeest (Alcelaphus buselaphus), the only reintroduced ungulate present in leopard diet (n = 82 scats). Goats (Capra hircus) had the lowest temporal overlap with leopard but comprised most biomass in leopard scat. Sheep (Ovis aries) and cattle (Bos sp.) also had generally low temporal overlap with leopards, with cattle contributing less biomass to leopard diet than sheep. Leopards were active primarily at night across seasons (n = 103 photos). These results suggest that leopards hunted at night when prey were resting and presumably less vigilant, or that they effectively predated some species during daylight. We recommend research on leopard hunting behaviour and habitat selection, and broad-scale implementation of livestock management such as guardian dogs, herders, and protective enclosures to minimize livestock-carnivore interactions and facilitate coexistence.

Thermal-hydraulic performance analysis of a novel parabolic trough receiver with double tube for solar cascade heat collection

The utilization of solar energy is of great significance to alleviate energy shortage and environmental problems. In view of the different thermal grade requirements of electricity production and water desalination in remote arid areas as well as to improve the performance of the parabolic trough receiver (PTR), a novel solar cascade heat collection system based on a PTR with double tube and two heat transfer fluids (HTF) is proposed in this paper. A three-dimensional model is developed to simulate and investigate the temperature distribution, heat transfer and flow characteristics and heat collecting performance of the novel system. Moreover, the effects of the operating parameters on the performance are studied in details. The temperatures of the absorber tube are significantly reduced over the plain PTR, and the heat transfer coefficient on the absorber inner surface is enhanced about 50% with 2.5–6.8 times increment in total pumping work. In addition, the heat loss reduced up to 43.1%, thus, the maximum improvement of the total thermal efficiency reaches up to 1.5%. Within the parameters considered in this study, the proportions of the high and low temperature heat gains are ranged in 39.01–62.92% and 28.37–8.86% of the incident solar energy, respectively.