Search Results (6)

Oases in arid regions are critical ecosystems, providing essential ecological, agricultural, and socio-economic functions. However, urbanization and climate change increasingly threaten their sustainability. This study examines land cover (LULC) and land surface temperature (LST) dynamics in four representative North African oases: Tolga (Algeria), Nefta (Tunisia), Ghadames (Libya), and Siwa (Egypt) over the period 2000–2023, using Landsat satellite imagery. A three-step analysis was employed: calculation of NDVI (Normalized Difference Vegetation Index), NDBI (Normalized Difference Built-up Index), and LST, followed by supervised land cover classification and statistical tests to examine the relationships between the studied variables. The results reveal substantial reductions in bare soil (e.g., 48.10% in Siwa) and notable urban expansion (e.g., 136.01% in Siwa and 48.46% in Ghadames). Vegetation exhibited varied trends, with a slight decline in Tolga (0.26%) and a significant increase in Siwa (+27.17%). LST trends strongly correlated with land cover changes, demonstrating increased temperatures in urbanized areas and moderated temperatures in vegetated zones. Notably, this study highlights that traditional urban designs integrated with dense palm groves significantly mitigate thermal stress, achieving lower LST compared to modern urban expansions characterized by sparse, heat-absorbing surfaces. In contrast, areas dominated by fragmented vegetation or seasonal crops exhibited reduced cooling capacity, underscoring the critical role of vegetation type, spatial arrangement, and urban morphology in regulating oasis microclimates. Preserving palm groves, which are increasingly vulnerable to heat-driven pests, diseases and the introduction of exotic species grown for profit, together with a revival of the traditional compact urban fabric that provides shade and has been empirically confirmed by other oasis studies to moderate the microclimate more effectively than recent low-density extensions, will maintain the crucial synergy between buildings and vegetation, enhance the cooling capacity of these settlements, and safeguard their tangible and intangible cultural heritage. Full article

This work explores issues related to traditional heritage, its evolution, and its transmission within construction practices. It focuses on a case study concerning the reintroduction in Tamentit, an oasis in southwestern Algeria, of a nearly forgotten construction technique: the use of a local stone known as “Agharf”, composed of saline pebbles, bound or assembled with a clay mortar enriched with salt, allowing the construction of robust structures adapted to their environment. Traditionally used in certain specific areas of the Sahara, it was notably employed in isolated regions such as Siwa in Egypt. After a long period of disuse, this technique is experiencing a renewed interest and appears to be gradually reintegrating into the local practices of artisans. This raises several questions: What justifies the return of this technique? What role does contemporary society assign to it, and what actions are being taken to ensure its sustainability? Fieldwork, consisting of on-site observations and semi-structured interviews with artisans and master artisans, the ma‘alem, was conducted to analyze their perception of this heritage, to understand the tangible and intangible aspects of the construction process, and to explore the challenges related to its transmission. The interviews reveal that, despite the challenges and reservations expressed by the community, the Agharf remains for the artisans a symbol of identity and craftsmanship, far from being a lost intangible heritage. The conditions and benefits of its use are also discussed. Full article

Detecting and monitoring changes in soil salinity through remote sensing provides an opportunity for field assessment in regions where on-site measurements are limited. This research, conducted in Siwa Oasis, Egypt, aimed to assess the effectiveness of remote sensing techniques in detecting and monitoring changes in soil salinity. Using Landsat 5 and Landsat 7 satellite images, the researchers evaluated various soil salinity indices based on 56 on-site ground measurements. The study aimed to improve the correlation between electrical conductivity (EC) and index values and explore the relationship between salinity and changes in land cover. Eleven spectral indices were calculated for nine scenes captured in different months. Different approaches were employed, including stacking the data, categorizing EC measurements into salinity levels, analyzing data temporally, and conducting spatial correlation analysis. The initial approach revealed a weak correlation, due to substantial variation in EC values. However, the salinity index SI demonstrated the highest correlation coefficient of 0.38. In the second scenario, the salinity index 2 S2 index exhibited the highest correlation of 0.96 for moderate salinity samples. The third scenario showed that the salinity index 1S1 achieved the highest correlation value of 0.99 for moderately saline areas. In the fourth scenario, the SI index exhibited the strongest correlation among all four ponds, with correlation coefficients of 0.23, 0.23, 0.18, and 0.61. Notably, the correlations observed in the second and third scenarios demonstrated higher correlation coefficients than those of both the first and fourth scenarios. Additionally, remote sensing methods detected a 48% increase in total vegetated area over 17 years, showing the potential of remote sensing techniques in salinity monitoring for expanding agriculture and improving land management. Full article

Microfacies studies were carried out on the Middle Miocene Marmarica Formation exposed at the Gabal Western Bahi El-Din and Gabal El-Najdeen, the Siwa Oasis, northwestern Desert (Egypt). It was distinguished into the lower, middle, and upper members. Eleven microfacies types were recognized, which include skeletal lime-mudstone, dolomitic lime-mudstone, intraclastic wackestone, bryozoan wackestone, foraminiferal wackestone, foraminiferal bryozoan packstone, glauconitic molluscan packstone, molluscan intraclastic packstone, pelletal peloidal skeletal packstone, dolostones, and claystone microfacies. This formation includes several types of emergence- meter-scale cycles (shallowing-upward). Field observations and petrographic analyses revealed that these cycles consist of pure carbonates and mixed siliciclastic carbonates. These cycles consist of four types of gradual cycles and six types of non-gradual cycles. The gradual emergence cycles indicate a balance between the rate of subsidence, sea level oscillations, and sedimentation rate. The non-gradual cycles indicate an irregular balance between sedimentation rate and subsidence rate. The non-gradual cycles denote high-frequency sea level variation and/or short-term sea level oscillations, which are associated with high carbonate formation. The depositional environments of the Marmarica Formation are restricted to lagoonal at the base, followed upward to open marine conditions. Both environments most probably characterize the platform setting. Full article

Environmental degradation is reducing crop productivity in many regions of Egypt. Moreover, unsustainable surface water drainage contributes to salinized soil conditions, which negatively impact crops. Egypt is seeking solutions to mitigate the problem of surface water drawdown and its consequences by exploring renewable and sustainable sources of energy. Geothermal energy and the desalination of saline water represent the only solutions to overcoming the fresh water shortage in agricultural industry and to providing sustainable fresh water and electricity to villages and the Bedouin livelihood. In Egypt, the Siwa Oasis contains a cluster of thermal springs, making the area an ideal location for geothermal exploration. Some of these thermal springs are characterized by high surface temperatures reaching 20 °C to 40 °C, and the bottom-hole temperatures (BHT) range from 21 °C to 121.7 °C. Pre-Cambrian basement rocks are usually more than 440 m deep, ranging from 440 m to 4724.4 m deep. It is this feature that makes the Siwa Oasis locality sufficient for geothermal power production and industrial processes. This study utilized both the Horner and the Gulf of Mexico correction methods to determine the formation temperatures from BHT data acquired from 27 deep oil wells. The present study revealed a geothermal gradient ranging from 18 to 42 °C/km, a heat flux of 24.7–111.3 mW/m², and a thermal conductivity of 1.3–2.65 W/m/k. The derived geothermal, geophysical, and geological layers were combined together with space data and the topographic layer to map relevant physiographic variables including land surface elevation, depth to basement, lineament density, land surface temperature, and geologic rock units. The ten produced variables were integrated in GIS to model the geothermal potential map (GTP) for the Siwa Oasis region. According to the model, both the eastern side and north and northeastern portions of the study region contain high and very high geothermal potential energy. Combining bottom-hole temperature measurements with satellite remote sensing and geospatial analysis can considerably enhance geothermal prospecting in Egypt and other East African areas that have geologically and tectonically similar settings. In addition to identifying sustainable resources needed for food production, this research has implications for renewable energy resources as well. Full article

The objective of the current work is to study the genetic differentiation between Acacia species growing in Egypt as plant genetic resources based on morphological, biochemical, and molecular markers. The 20 replicates of Acacia tree collected from four localities from Egypt were A. tortilis ssp. raddiana and A. farnesiana (Siwa Oasis and Borg El-Arab City), A. stenophylla, A. sclerosperma (Marsa Matroh City), and A. saligna (Abis Station Farm, Alexandria). The results based on the previous markers indicated highly significant differences between Acacia species, confirming the hypothesis of the possibility of using morphological, biochemical, and molecular parameters in species identification. Qualitative characteristics results indicated some similarities and differences that are taxonomically important for comparing taxonomical grouping with morphological data for the genetic description of Acacia species. The activities of antioxidant enzymes have been studied intensively and the results provide strong similarities between the Acacia species (69%), between A. raddiana (Siwa and Borg Al-Arab) and A. saligna, followed by all Acacia species (50%). Finally, the molecular studies showed that a total of 563 amplification fragments, 190 fragments were monomorphic, and 373 fragments were polymorphic. The highest number of amplification fragments (21) was detected with OPB-20 primer, while OPA-20 showed seven amplification fragments; the average number was 13.09. The results indicated that Acacia species exhibit high genetic differentiation, helpful in the future for genetic improvement programs. The novelty of the current study is highlighting the importance of plant genetic resources in Egypt and using different techniques to measure the differentiation between these species. Full article