Communities In Arid Regions Research Articles

Predicting seawater intrusion in coastal areas using machine learning: A case study of arid coastal aquifers, Saudi Arabia

Groundwater is a vital resource for communities in arid regions, such as Saudi Arabia, where seawater intrusion poses a significant threat. To determine groundwater quality with traditional methods is time-consuming and costly process. In this study, we developed a machine learning method as a tool for predicting seawater intrusion in coastal areas using groundwater chemical parameters. We analysed 99 water sample data from the Red Sea and 42 from eastern coast of Saudi Arabia for 13 chemical parameters and conducted two experiments with and without chloride parameter. Unlike previous studies that developed complex machine learning methods, we focus on lightweight machine learning algorithms to model seawater intrusion for possibility of sensor deployment in future. The machine learning algorithms assessed and compared are namely decision trees, ensemble machine learning methods (Random Forest and Gradient Boosting), support vector machines, multilayer perceptrons, and ridge regression. With the chloride parameter included, ridge regression emerged as the best model, with an R2 of 99.8% and the lowest Akaike and Bayesian information criteria values. Without chloride data, multilayer perceptron achieved a marginally higher R2 of 98.7% but required longer training times. Notably, a high accuracy was maintained without chloride parameter, demonstrating the capacity of machine learning for augment monitoring. This research underscores the effectiveness of ridge regression and neural networks in predicting seawater intrusion, enabling the accurate mapping of vulnerable areas to inform adaptive management strategies for groundwater preservation. The regional scope of this study offers valuable insights for other arid coastal regions that rely on groundwater and threatened by seawater intrusion.

Precise ecological restoration under water diversions-groundwater-ecosystem interactions in drylands

Ecological Water Diversion Projects (EWDPs) have been employed worldwide to restore degraded ecosystems in drylands, but precise restoration locations and planting species under EWDP remain unknown, even if it has changed ecohydrological dynamics. Therefore, this study proposed a water diversions-groundwater-vegetation coupling framework based on Machine Learning for deciding where to restore in drylands. The Shapley Additive Explanation method was used to interpret the framework and disentangle the role of the local environment in defining vegetation patterns from a data-driven perspective. This approach was tested in a mega EWDP in the lower Tarim River Basin (TRB), Northwest China, in present and future restoration locations, and planting species were quantitatively estimated. The results showed that the terrain and groundwater table critically impact the vegetation communities in arid regions. Currently, 4.3% of the existing land should be trees and grass, while they account for 0.1% of the lower TRB in total. Within the next decade, the potential reforestation of areas with steadily growing natural vegetation would decrease by 5.3% and 12.6% if the yearly watering volume of EWPD decreased by 28.6% under climate change scenarios SSP245 and SSP585, respectively. Our results confirm the substantial variability in restoration areas under varying diversion volumes and underscore the importance of incorporating EWDP into future restoration management. The proposed approach can form a scientific basis for dryland precision restoration to facilitate water conservation and maximize ecological benefit.

Characterizing Crustose Lichen Communities—DNA Metabarcoding Reveals More than Meets the Eye

Biodiversity inventories are important for informing land management strategies, conservation efforts, and for biomonitoring studies. For many organismal groups, including lichens, comprehensive, accurate inventories are challenging due to the necessity of taxonomic expertise, limitations in sampling protocols, and the commonplace occurrence of morphologically cryptic species and other undescribed species. Lichen communities in arid regions are often dominated by crustose lichens, which have been particularly difficult to incorporate into biodiversity inventories. Here, we explore the utility of DNA metabarcoding for characterizing the diversity of lichen-forming fungi at a typical crustose lichen-dominated site on the Colorado Plateau in the southwestern USA. We assessed the consistency of independent sampling efforts to comprehensively document lichen diversity, evaluated the capability of minimally trained technicians to effectively sample the lichen communities, and provide a metagenomic-based inventory of lichen diversity, including representative sequence data, for a diverse, crustose-dominate lichen community on the Colorado Plateau. Our results revealed that crustose lichen communities in the southwestern USA are more diverse than traditionally thought, and community metabarcoding is a promising strategy for characterizing the lichen-forming fungal diversity more thoroughly than other methods. However, consistently sampling the diversity of crustose lichen communities, even at small spatial scales, remains difficult. Interpreting these results within a traditional taxonomic context remains challenging without the use of vouchers.

Ecologies of Development: Ecophilosophies and Indigenous Action on the Tana River

AbstractThis article argues for a reorientation of African environmental history that incorporates localized ecophilosophies, racial ecologies, and environmental justice, and posits that doing so allows us to challenge the sociocultural and ecological implications of colonial and postcolonial environmental development more rigorously in East Africa. Focusing on Kenya, I argue that environmental justice-oriented histories of economic development elevate the subjectivities, cosmologies, and experiences of rural Kenyan populations rather than reducing the environment and its resources to their instrumental qualities On the Tana River, pastoral and riverine groups such as the Pokomo and Orma suffered and challenged the exigencies of water extraction in specific ways tied to their existing relationships with the local environment. By looking at the ways rural communities in arid regions framed their environmental relationships, we can begin to appreciate the specific modalities and cosmologies through which they resisted the imposition of cash crop agriculture and water development. The article demonstrates an interdisciplinary approach utilizing Black ecologies and environmental justice frameworks that restores vitality to the rural experience of imperialism and offers more rigorous critiques of global development dogmas under racial capitalism, particularly surrounding the omnipresent threat of ecocide driven by dispossession, resource extraction, toxicity, and climate change.

Effect of snow cover on water content, carbon and nutrient availability, and microbial biomass in complexes of biological soil crusts and subcrust soil in the desert

Winter snowfall is an important water resource for organisms in desert ecosystems. Changing snow depth is expected to exert a potential influence on growth and ecological functions of biological soil crusts (BSCs), which are known as a dominant functional vegetation unit of desert ecosystems. However, limited attention has been paid to this potential effect on BSCs. A field simulation experiment was conducted to measure the water content, nutrient concentrations (organic carbon; total nitrogen; available nitrogen; available phosphorus; available potassium; ammonium nitrate; and nitrate nitrogen), and microbial biomass (carbon, nitrogen, and phosphorus) in samples (cyanobacterial and lichen crusts and subcrust soil) under snow cover of different depths after a four year experiment (from October 2013 to April 2017) in the Gurbantunggut Desert. The results showed that water content increased with increasing snow depth (P < 0.05). Snow removal and snow cover reduction decreased nutrient and microbial biomass concentrations in both biocrust types (P < 0.05). The concentrations of most measured nutrients and microbial biomass decreased significantly when snow depth was increased to twice ambient conditions (P < 0.05). Moreover, the concentrations of nutrients and microbial biomass were significantly influenced by snow depth (P < 0.05), crust type (P < 0.001), and their interaction (P < 0.05). The results demonstrated that variation in snow depth adversely affect the carbon and nutrient availability and microbial biomass in BSCs. Such changes might lead to a cascading effect in species composition and function of BSC communities in arid regions.

Pearl Millet: A Climate-Resilient Nutricereal for Mitigating Hidden Hunger and Provide Nutritional Security.

Pearl millet [Pennisetum glaucum (L.) R. Br.] is the sixth most important cereal crop after rice, wheat, maize, barley and sorghum. It is widely grown on 30 million ha in the arid and semi-arid tropical regions of Asia and Africa, accounting for almost half of the global millet production. Climate change affects crop production by directly influencing biophysical factors such as plant and animal growth along with the various areas associated with food processing and distribution. Assessment of the effects of global climate changes on agriculture can be helpful to anticipate and adapt farming to maximize the agricultural production more effectively. Pearl millet being a climate-resilient crop is important to minimize the adverse effects of climate change and has the potential to increase income and food security of farming communities in arid regions. Pearl millet has a deep root system and can survive in a wide range of ecological conditions under water scarcity. It has high photosynthetic efficiency with an excellent productivity and growth in low nutrient soil conditions and is less reliant on chemical fertilizers. These attributes have made it a crop of choice for cultivation in arid and semi-arid regions of the world; however, fewer efforts have been made to study the climate-resilient features of pearl millet in comparison to the other major cereals. Several hybrids and varieties of pearl millet were developed during the past 50 years in India by both the public and private sectors. Pearl millet is also nutritionally superior and rich in micronutrients such as iron and zinc and can mitigate malnutrition and hidden hunger. Inclusion of minimum standards for micronutrients—grain iron and zinc content in the cultivar release policy—is the first of its kind step taken in pearl millet anywhere in the world, which can lead toward enhanced food and nutritional security. The availability of high-quality whole-genome sequencing and re-sequencing information of several lines may aid genomic dissection of stress tolerance and provide a good opportunity to further exploit the nutritional and climate-resilient attributes of pearl millet. Hence, more efforts should be put into its genetic enhancement and improvement in inheritance to exploit it in a better way. Thus, pearl millet is the next-generation crop holding the potential of nutritional richness and the climate resilience and efforts must be targeted to develop nutritionally dense hybrids/varieties tolerant to drought using different omics approaches.

Rapid Microbial Dynamics in Response to an Induced Wetting Event in Antarctic Dry Valley Soils.

The cold deserts of the McMurdo Dry Valleys (MDV), Antarctica, host a high level of microbial diversity. Microbial composition and biomass in arid vs. ephemerally wetted regions are distinctly different, with wetted communities representing hot spots of microbial activity that are important zones for biogeochemical cycling. While climatic change is likely to cause wetting in areas not historically subject to wetting events, the responses of microorganisms inhabiting arid soils to water addition is unknown. The purpose of this study was to observe how an associated, yet non-wetted microbial community responds to an extended addition of water. Water from a stream was diverted to an adjacent area of arid soil with changes in microbial composition and activities monitored via molecular and biochemical methods over 7 weeks. The frequency of genetic signatures related to both prokaryotic and eukaryotic organisms adapted to MDV aquatic conditions increased during the limited 7 week period, indicating that the soil community was transitioning into a typical “high-productivity” MDV community. This work is consistent with current predictions that MDV microbial communities in arid regions are highly sensitive to climate change, and further supports the notion that changes in community structure and associated biogeochemical cycling may occur much more rapidly than predicted.

Soil Properties under Major Halophytic Vegetation Communities in Arid Regions

Soil physical, chemical, and biological properties of seven desert halophytes (Kalidium foliatum, Achnatherum splendens, Leymus secalinus, Phragmites australis, Karelinia caspia, Tamarix ramosissima, Atriplex tatarica) were investigated in saline-sodic badlands of the Hexi Corridor, Gansu Province, China. The results showed that sampled soils were generally infertile and characterized by low levels of organic matter, available nitrogen, phosphorus, copper, manganese, and zinc as well as microbial communities with dominant bacteria supporting native desert halophytes. Available potassium and iron were sufficient in the study sites. With increasing soil layer depth, the concentrations of organic matter, available nitrogen, potassium, manganese, copper, bacteria, and actinomyces in the soil decreased significantly (P<0.05), while the concentrations of moisture, available iron, and zinc in the soil increased significantly (P<0.05). The contents of moisture, total salt, organic matter, available nitrogen, potassium, iron, manganese, zinc, copper, bacteria, and actinomyces showed significant seasonal variations (P<0.05). All these variables except bacteria and actinomyces were the greatest in summer and the lowest in spring. The redundancy analysis revealed that total salt, organic matter, available potassium, and copper were positively correlated with vegetation coverage. K. foliatum community was the constructive or dominant species in the desert community for the biological control of soil salinization.

A comprehensive status, phylogenetic, and anatomical review of Stagnicola caperata (Say, 1829) in the south‐west United States

Abstract Freshwater gastropods are a major component of aquatic communities in arid regions. The isolation of aquatic habitats and poor dispersal abilities of organisms has resulted in the evolution of endemic species with small ranges. Human demands for water threaten the integrity of desert spring systems and as a result many freshwater snails from these regions are of conservation concern. One widespread lymnaeid species in North America, Stagnicola caperata (Say, ), exhibits distinct shell morphologies among populations in the south‐west United States. Because S. caperata is listed as endangered by the State of New Mexico owing to degradation of wetland habitats, accurate taxonomic assessment among populations is required in order to understand threats to the survival of this taxon. A holistic approach (morphometrics, phylogenetics, and reproductive anatomy) was used to investigate the taxonomic affinities of S. caperata in the south‐west United States by comparing these populations with topotypes. Morphometric analyses revealed similar levels of variation among populations, with large overlaps in shell morphologies. Both phylogenetic analysis and reproductive anatomy revealed the presence of two Stagnicola species in these populations: all populations except the Big Costilla Peak (BCP) population were referable to the nomen S. caperata, while BCP was Stagnicola cf. elodes. A total‐evidence approach that combines genetic and morphological data facilitates assessment of taxonomic affinities. The results provide conservation agencies with information necessary to detect species boundaries and then develop effective conservation and recovery plans for imperilled species.

The consequences of replacing wildlife with livestock in Africa

The extirpation of native wildlife species and widespread establishment of livestock farming has dramatically distorted large mammal herbivore communities across the globe. Ecological theory suggests that these shifts in the form and the intensity of herbivory have had substantial impacts on a range of ecosystem processes, but for most ecosystems it is impossible to quantify these changes accurately. We address these challenges using species-level biomass data from sub-Saharan Africa for both present day and reconstructed historical herbivore communities. Our analyses reveal pronounced herbivore biomass losses in wetter areas and substantial biomass increases and functional type turnover in arid regions. Fire prevalence is likely to have been altered over vast areas where grazer biomass has transitioned to above or below the threshold at which grass fuel reduction can suppress fire. Overall, shifts in the functional composition of herbivore communities promote an expansion of woody cover. Total herbivore methane emissions have more than doubled, but lateral nutrient diffusion capacity is below 5% of past levels. The release of fundamental ecological constraints on herbivore communities in arid regions appears to pose greater threats to ecosystem function than do biomass losses in mesic regions, where fire remains the major consumer.

A potential role for overland dispersal in shaping aquatic invertebrate communities in arid regions

Summary Traditionally, dispersal of aquatic invertebrates has been thought to be very closely associated with river network structure, despite many species being capable of active or passive dispersal across the terrestrial matrix. However, recent studies of both population genetics and community structure from dryland regions indicate that aquatic species commonly disperse across catchments, implying that movement away from streams is more common than originally thought. This study investigated how aquatic invertebrate metacommunity structure in central Australia is influenced by interactions between species’ dispersal traits, dispersal routes and local environmental conditions. We sampled community composition in 16 perennial and long‐term inundated freshwater habitats in central Australia. Aquatic invertebrate taxa were allocated to one of four dispersal trait groups: obligate aquatic, passive aerial, weak flying and strong flying. We then used Mantel tests to examine correlations between trait group community dissimilarities, and four isolation models representing (i) local environmental conditions, (ii) geographical distances, (iii) landscape resistances restricted to river networks and (iv) landscape resistances incorporating overland dispersal ‘conduits’. We found that the community composition of aquatic invertebrates in three of four dispersal trait groups, and all traits combined, was influenced primarily by topographic connectivity via overland dispersal conduits. Our results suggest that rainfall events and their effect on the landscape as a whole, rather than river flow during these events, shape aquatic invertebrate metacommunity structure in central Australia. This study provides further support for the importance of overland dispersal conduits to aquatic invertebrates, particularly in arid environments with irregular rainfall.

Conventional and Microwave-Assisted Extraction of Mucilage from Opuntia ficus-indica Cladodes: Physico-Chemical and Rheological Properties

Cactus pear cladodes processing has potential value for mainstream industries and is equally important for marginal rural communities in arid regions. This work is focused on physico-chemical and rheological properties of Opuntia ficus-indica (OFI) peeled cladodes extracted by conventional method “CE” and using microwave-assisted extraction “MAE.” MAE gave the highest yield extraction (8.13 %, w/w) within the lowest extraction time (500 W/7 min) and provided more protein (×1.03) and carbohydrates (×1.51) than CE. The monosaccharides detected by gas chromatography were arabinose, galactose, rhamnose, xylose, and galacturonic acid. The dialyzed mucilage solution characterized by SEC/MALS/VD/DRI (size-exclusion chromatography coupled with online multi-angle light scattering, viscometer detectors, and differential refractive index) revealed fractions with molecular weight (M w ) ranging from 15.3–15.7 × 106 g mol−1 for the CE extracts and about 16.7–17.5 × 106 g mol−1 for the MAE extracts. Dynamic oscillatory testing has been used to study the rheological properties of mucilage solution within the concentration of 0.50–3.00 % (w/v) at 25 °C. The rheological profiles of CE and MAE showed similar behavior. At low frequency and low mucilage concentration ( G"). If safely controlled, alternative energies like microwaves could extract soluble polymers with comparable properties to commercial ones, conventionally extracted.

Irrigation System Using Photovoltaics and Lithium Ion Batteries for Energy Storage

Typically, energy consuming systems are run off the traditional grid. However, there are remote areas of the United States that don’t have access to the traditional grid and in those places, there is a need for photovoltaic generation to supply those electricity needs [1].The use of photovoltaics along with lithium batteries for storing excess energy has increased due to the need for renewable energy as a viable source of electricity. Such energy storage systems (ESS) are useful for complex irrigation systems that assist in the cultivating of the United States food supply [2]. Without the ESS systems, maintaining a stable economy may be difficult in extreme cases. The object of this research will be to construct a virtual photovoltaic generation system that is capable of powering an irrigation system, and it will also be used in tandem with a lithium-ion battery storage system. The focus of this irrigation system will be to water a tomato farm in the Florida climate. The work will be performed in a virtual environment using a modular approach to a system-level design that simulates the behavior of the photovoltaic system and the degradation of the lithium-ion battery pack. Ultimately, these results suggest the necessary components for a real photovoltaic and battery operated system require the optimally sized photovoltaic panel and inverter connected to a watering pump. The PV panels convert solar energy to electrical energy with DC current and the inverter converts DC current to AC current required to run the pump. In addition, Additional information from hygrometer readings and weather profile also would be needed with a optimizing algorithm to ensure efficient irrigation operation. Acknowledgment This work was supported by the FREEDM ERC program of the National Science Foundation under award number EEC-08212121. References Louy Qoaider, Dieter Steinbrecht, Photovoltaic systems: A cost competitive option to supply energy to off-grid agricultural communities in arid regions, Applied Energy, Volume 87, Issue 2, February 2010, Pages 427-435, ISSN 0306-2619 M. Arifujjaman, A comprehensive power loss, efficiency, reliability and cost calculation of a 1 MW/500 kWh battery based energy storage system for frequency regulation application, Figure 1

Removing an invader: evidence for forces reassembling a Chihuahuan Desert ecosystem

Community reassembly is an important concept in community ecology, but in most circumstances cannot be observed and is hypothetical. Reassembly of communities is an observable process that can be examined effectively following species invasions. Our study system in southeastern Arizona has declined in diversity and abundance of native winter annual plants coincident with a sustained irruption of a nonnative invasive Eurasian species, Erodium cicutarium, and a major reassembly of the winter annual plant community. To understand the role of E. cicutarium in the reassembly process, we initiated a multiyear E. cicutarium removal experiment that varied the timing of removal. Species richness was higher as a result of removal, although this effect was variable over time. Surprisingly, the abundance of native species collectively was decreased by E. cicutarium removal. However, previously rare Astragalus nuttallianus appears to be facilitated by E. cicutarium, as demonstrated by higher density and relative abundance in the presence of E. cicutarium, and is now codominant. Excluding A. nuttallianus abundance, the remaining native species are collectively increased by removal of E. cicutarium. Although our results showed strong effects of removal, the timing of removal never significantly affected any plant variables. Our experiment implicates a major role for E. cicutarium in the reassembly of the native plant community. Our work suggests a broadening of perspective on processes structuring annual plant communities in arid regions, and calls for an integrated approach beyond the recent popular focus on the interaction between competition and the physical environment.

Aquatic Invertebrate Communities of Perennial Pans in Mpumalanga, South Africa: A Diversity and Functional Approach

Perennial pans are a common feature of the Mpumalanga Highveld in South Africa and are increasingly under threat from mining and agricultural activities. Pans are endorheic wetlands that can be perennial or ephemeral in nature. They are widespread in arid and semi-arid regions throughout the world. Although phyllopod crustaceans dominate pan communities in arid regions, the invertebrate communities of perenni al pans have not been well studied. The aim of the current research was to characterise the invertebrate com munities of several pans (both natural and impaired). A combination of taxonomic and functional approaches was followed to study these communities. The macroinvertebrate species diversity of the pans was comparable to similar ecosystems in southern Africa and other parts of the world. Results indicate large spatial and temporal variations in diversity. This variation became less obvious when the analysis was based on biological traits. It was also evident that both coal mining and agricultural activities had an impact on the aquatic invertebrate community structures. These changes were apparent in both the diversity and the biological traits of the invertebrate communities of adjacent pans.

Importance of geochemical factors in determining distribution patterns of aquatic invertebrates in mountain streams south of the Atacama Desert, Chile

The ecology of macroinvertebrate communities in arid regions is still poorly understood. Here we examined how the community structure varied at spatial and temporal scales in streams and tributaries of the Huasco River in semi-arid region of Northern Chile. We expected that macroinvertebrate distribution may be responding to natural processes of mineralization described for Chilean semiarid basins. The relationships among biotic and abiotic variables were assessed through multivariate techniques (principal component analysis, non-metric multidimensional scaling, canonical correspondence analysis), and a two-way analysis of similarity was used to evaluate differences between basins and years (2007, 2008, and 2009). Significant differences in community structure and physical–chemical variables between basins (Del Carmen and Del Transito) were found, but not between years. Altitude, Mn, Al, Ca, Na, HCO3, and dissolved oxygen were the variables that best accounted for the communities distribution. In particular, high metals concentration in El Transito basin should determine low density and diversity of macroinvertebrates. Chironomidae, Ephydridae, and Glossiphoniidae were associated to waters with high metals content and acidic pH, whereas Baetidae, Hydroptilidae, and Blephariceridae were associated to sites with more favorable physical–chemical conditions. These results contribute to understand the ecological patterns of macroinvertebrates in arid regions and should lead to conservation and monitoring plans for this remote place.

Photovoltaic systems: A cost competitive option to supply energy to off-grid agricultural communities in arid regions

The main objective of this work is to investigate the economic feasibility of photovoltaic technology to supply the entire energy demands to off-grid irrigated-farming-based communities in the arid regions. This aims at helping these communities to find practical solutions to cope with the rapid rising electricity generation costs, mainly by diesel generators (gensets). The genset electricity costs are typically affected by the high fossil fuel prices, the fuel transport costs and the intensive operation and maintenance (O&M) requirements. The work was conducted on a representative site from which conclusions could be drawn for similar regions. The case study was performed in the New Kalabsha Village in the Lake Nasser Region (LNR) in southern Egypt. The work involved the technical design and the calculation of the life cycle costs (LCC) of a PV system, which is able to supply the village with its entire energy demand. The PV generator was sized in such a way to daily pump 111 000 m 3 of lake water to irrigate 1260 ha acreage plots and to electrify the adjacent village’s households. The required pumps were designed to pump the fluctuating lake’s water for a maximum differential head of 17 m in four different locations. Consequently, water from the four pumping stations flows freely by gravity forces to the different plots through overhead open canals. The electricity generation costs and the performance of the designed PV generator were compared with those of an equivalent diesel generator (genset) in order to prove its competitiveness. With this regard, the real market value of the diesel fuel of 86.55 c€ l −1 was considered for calculating the costs of genset generated electricity. The results showed that the genset electricity unit costs 39 c€ kW h −1 while a unit of PV electricity costs only 13 c€ kW h −1 for the equivalent system size and project lifetime. Furthermore, the subsidised genset electricity cost was calculated to be 12 c€ kW h −1, which is insignificantly cheaper than that of solar electricity.

Performance evaluation of hybrid RO/MEE systems powered by a WTE plant

The solid waste management is, in different contexts, a very critical issue. The use of landfills can no longer be considered a satisfactory environmental solution, therefore new methods have to be chosen and waste-to-energy (WTE) plants would provide an answer. Today's WTE plants are a far cry from their polluting predecessors. Using modern combustion and pollution control technology, WTE plants are able to retrieve considerable amounts of energy from waste combustion while minimizing emissions. As we know, is possible to recover thermal energy by combusting municipal solid waste (MSW) for electricity generation and district heating. However, with everincreasing population and rapid growth of industrialization, there is a great demand for fresh water. So, many communities in arid regions could use thermal energy inherent in MSW to desalinate seawater. This paper makes an initial assessment of this concept and concludes that useful quantities of fresh water can be so produced by linking the two processes with significant saving in fuel consumption, determining relevant economic benefits.

Dung-insect community composition in arid zones of south-eastern Spain

Dung-insect community composition was studied at three sites for 1 year, and for a further 8 months at one site, in an arid region of Spain. The insect community was dominated by ants, dung flies and beetles. Ants were abundant and flies relatively scarce at all three sites, whereas beetle diversity and abundance differed among sites and between years. Community composition varied along the year in species richness, abundance and biomass. Although dung-insect communities of arid Spain share some traits with dung-insect assemblages in other deserts, diversity and trophic structure of these communities are highly variable, a common but underappreciated feature of communities in arid regions.

Application of the ‘waste to water’ concept to Sharm El Sheikh through a CFD simulation

Many communities in arid regions have both waste disposal and water shortage problems suggesting the use of the thermal energy inherent in municipal waste to desalinate sea and brackish waters. The technology requires to be demonstrated in an appropriate pilot study effected on a complex having the scale of an hotel or appartment block. Particularly suitable candidate sites are available in the prosperous Egyptian resorts on the Red Sea and similar complexes throughout the arid regions of the Middle East. Solid waste disposal creates a nuisance condition in relation to the tourist industry for which these resorts were conceived. This paper presents the results of a prior theoretical study of two hotels in Sharm El Sheikh. The one is a five-star hotel comprising 800 rooms (Pyramisa hotel), the other is a four-star establishment of 100 rooms (Days Inn Gafy). Data have been collected for both of these complexes in order to demonstrate the validity of the ‘waste to water’ (W2W) concept. Further support for the concept is provided via a mathematical simulation of the waste thermal treatment unit (WTTU). Thermal vapour compression distillation technology has been selected as the most suitable for direct coupling to the WTTU. It is concluded that the two hotels could be self sufficient in fresh water supply through environmentally clean thermal treatment of their waste streams. It is foreseen that the technology, once demonstrated, will be replicated in the many resorts of the Gulf region and elsewhere. It will also enable the creation of environmentally acceptable and self-sufficient new small communities in arid regions providing new habitat and employment possibilities. However, the concept is not restricted to arid rural regions, it is also perfectly suited to urban areas subject to water shortages.