Spatial and Temporal Variation of the Near-Surface Wind Environment in the Sahara Desert, North Africa

The Sahara Desert is the largest source of dust on Earth, and has a significant impact on global atmospheric changes. Wind is the main dynamic factor controlling the transport and intensity of dust in the Sahara Desert. This study comprehensively analyzed the spatial and temporal variation in the wind regime of the Sahara Desert from 1980 to 2019 using data from 17 meteorological stations to improve awareness of global atmospheric changes and the intensity of regional aeolian activities. All wind speed parameters decreased from northwest to southeast. While there were significant differences in the trends of temporal variation in wind speed among the different regions, there was an overall decreasing trend across the Sahara Desert, with an average wind speed of 0.09 m s−1 10 a−1. This decrease was closely related to wind frequency. The easterly, westerly, and northerly winds dominated, with more complex wind direction in the northern region. Seasonal differences in wind direction were observed in all regions. The wind direction frequency of wind speeds >6 m s−1 exceeded those with wind speeds <6 m s−1 in the western and northern regions, whereas other regions showed an opposite pattern. The highest drift potential (DP) and resultant drift potential (RDP) were found in the western and northern regions, and during spring and winter. There was a trend of decreasing annual variation in DP and RDP in all regions. The directional variability (RDP/DP) indicated mostly intermediate and high variability in wind direction. Resultant drift direction (RDD) indicated that a mainly southwest wind direction. No apparent trends in temporal variation in RDD and RDP/DP were observed. Total DP was strongly influenced by DP and the magnitude and frequency of strong winds in the prevailing wind direction. No strong correlation between wind regimes and dune types was observed in this desert, indicating the complexity of factors affecting dune morphology.

High prevalence of urinary schistosomiasis in a desert population: results from an exploratory study around the Ounianga lakes in Chad

Background Researching a water-borne disease in the middle of the Sahara desert might not seem the most relevant concern. However, nomadic Sahelian pastoralists health concerns regarding their livestock and anecdotal reports about trematode infections of Fasciola spp. and Schistosoma spp. in desert-raised animals justified an exploratory study focusing on the lakes of Ounianga in Northern Chad. The aim was to test whether trematode parasites such as Schistosoma spp. occur in human populations living around the Sahara desert lakes of Ounianga Kebir and Ounianga Serir in northern Chad. Methods The study was carried out in January 2019 and comprised of three components. First, a cross sectional survey based on a random sample drawn from the population to detect infections with S. haematobium and S. mansoni; second, focus group discussions exploring disease priorities, access to health and health seeking behaviour; and third, surveying water contact sites for intermediate host snails. Samples of trematode parasites and snails were confirmed on species level by molecular genetic methods. For parasitological and malacological surveys descriptive statistics were performed. Qualitative data analysis included the full review of all transcripts, followed by a descriptive and explorative thematic analysis. Results Among 258 participants, the overall S. haematobium prevalence using urine filtration was 39.2% [95% confidence interval (CI): 33.5–45.1%], with 51.5% of the infected suffering from heavy infection. The intermediate host snail of S. haematobium (Bulinus truncatus) occurred at water contact sites near both study villages, revealing the potential for local transmission. Although a positive S. mansoni point-of-care circulating cathodic antigen (POC-CCA) test result was obtained from 8.6% (95% CI 5.7–12.8%) of the samples, no intermediate host snails of S. mansoni were found, and the relevance of S. mansoni remains uncertain. Qualitative findings underline the importance of morbidity caused by urinary schistosomiasis, and the lack of access to diagnostics and treatment as a major health concern. Conclusions This research revealed a high prevalence of urinary schistosomiasis in the population living around the lakes of Ounianga in the Sahara, a United Nations Educational, Scientific and Cultural Organization (UNESCO) world heritage site in Chad. Despite the high public health importance of the associated morbidity expressed by the population, there is no access to diagnostics and treatment. Further work is needed to develop and test a context-adapted intervention. Graphical Abstract

Nicholas Said

The two versions of the autobiography that Nicholas Said published offer insight into 19th-century conditions in five continents as well as insight into life as a child, slave, manservant, and teacher. As a child in the 1830s, Said was enslaved in Borno, marched across the Sahara Desert, and passed from hand to hand in North Africa and the Middle East. After serving as a slave in various societies, Said was freed by a Russian aristocrat in the late 1850s after accompanying the aristocrat in question to various parts of Europe. In the 1850s, Said also traveled as a manservant for a European traveler to South and North America. Ultimately he settled in the United States, where he authored two versions of his autobiography, served as a teacher and soldier, got married, and disappeared from sight. This article compares the two versions of the autobiography that Said published, provides an overview of Said’s life, charts the development of scholarly works on Said, and draws attention to the primary sources related to the study of Said and his autobiography.

The Saharo-Canarian Circle: The forgotten Prehistory of Euro African Atlantic façade and its lack of eastern demic diffusion evidences

Canarians, North Africans and Iberians show a close genetic relatedness. Greeks have a Sub-Saharan gene input according to HLA and other autosomic markers. Also, there is a genetic kinship between both Atlantic Euro Africans and North African/Arabic people. This is concordant with a drying humid Sahara Desert, which may have occurred about 6,000 years BC, and the subsequent northwards emigration of Saharan people may have also happened in Pharaonic times. This genetic input into Atlantic and Mediterranean Europe/Africa is also supported with Lineal Megalithic Scripts in Canary Islands (as well as in Iberia) together with simple Iberian semi-syllabary rock inscriptions both at Canary Islands and Ti-m Missaou (Algeria, Central southern Sahara). Lineal African/European scripts are found in certain languages scripts like Berber/Tuareg, Iberian, Runes, Etruscan, Bulgarian (Sitovo and Gradeshnitza, 6,000 years BP), Italian Old Scripts (Lepontic, Venetic, Raetic), Minoan Lineal A and Vinca scripts (Romania, Serbia, Greece, Bulgaria, about 4,000 years BP). The possibility that Megalithic Lineal Scripts have given rise to these languages lineal writing is feasible because admixture of languages rock scripts and Megalithic Lineal Scripts have been found. Thus, resistance of Canarian aborigines (Guanches) to Carthage, Rome and Arabs left a bulk of Canarian-Saharan information which is used to study both Saharan and Canarian Prehistory, and also Atlantic and Mediterranean beginning of European and other civilizations: this preserved prehistoric inheritance may be named the “Saharo-Canarian Circle” of prehistoric knowledge. Also, linguistics-epigraphy, physical anthropology, archaeology, and domesticated cattle shows a close North Africa-Iberia Mesolithic/Neolithic relationship and demonstrates that the demic diffusion model does not exist in Iberia. Also, Tassili Sahara paintings of domesticated cattle appear 1,000 years before those agricultural practices started at Middle East. Finally, it is also inferred that circum-Mediterranean contacts during thousand years between ice and desert constructed Mediterranean cultures from Canary Islands to Ancient Great Persia and this is the origin of Classical Mediterranean cultures that was later exclusively attributed to Rome and Greece.

Birds with multiple homes. The annual cycle of the pallid swift (Apus pallidus brehmorum)

We tracked pallid swifts (Apus pallidus brehmorum) from a single breeding colony in Gibraltar over two years. Our results show movement of birds between specific regions within the non-breeding geographical area at specific times of the year. The tracking of a single individual showed remarkable fidelity to the areas visited between years. Furthermore, two pallid swifts tracked over the entire eight-month non-breeding period, while in Africa, gave no indication of coming to land, supporting previous findings of an airborne existence in swifts outside the breeding season. In addition, the crossing of the Sahara Desert to and from breeding grounds is remarkably fast, with one individual crossing it in just over a day. We discuss our findings in the context of bird migration evolutionary strategies.

High Prevalence of Urinary Schistosomiasis in a Desert Population: Results from an Exploratory Study Around the Ounianga Lakes in Chad

Background: Researching a water-borne disease in the middle of the Sahara desert might not seem the most relevant concern. However, nomadic Sahelian pastoralist’s health concerns regarding their livestock and anecdotal reports about trematode infections of Fasciola spp and Schistosoma spp in desert-raised animals justified an exploratory study focusing on the lakes of Ounianga in Northern Chad. The aim was to test whether trematode parasites such as Schistosoma spp occur in human populations living around the Sahara desert lakes of Ounianga Kebir and Ounianga Saker in northern Chad. Methods: The study comprised of three components. First, a cross sectional survey based on a random sample drawn from the population to detect infections with S. haematobium and S. mansoni ; second, focus group discussions exploring disease priorities, access to health and health seeking behaviour; and third, searching water contact sites for intermediate host snails. Samples of trematode parasites and snails were confirmed on species level by molecular genetics methods. Results: Among 258 participants, the overall S. haematobium prevalence using urine filtration was 39.1% (95% CI 33.2% – 45.1%), with 51.5% of the infected suffering from heavy infection. The intermediate host snail of S. haematobium ( Bulinus truncatus ) occurred at water sites near both study villages, revealing the potential for local transmission. Although a positive S. mansoni POC-CCA test result was obtained from 15.2% (10.6%-19.7%) of the samples no intermediate host snails of S. mansoni were found, and the relevance of S. mansoni remains uncertain. Qualitative findings underline the importance of morbidity caused by urinary schistosomiasis, and the lack of access to diagnostics and treatment as a major health concern. Conclusion: This research revealed a high prevalence of urinary schistosomiasis in the population living around the lakes of Ounianga in the Sahara, a UNESCO world heritage site in Chad. Despite the high public health importance of the associated morbidity expressed by the population there is no access to diagnostics and treatment. Further research is needed to develop and test a context adapted intervention.

The relative contributions of weathering and aeolian inputs to postglacial formation of Mediterranean alpine loess

Between the southern margin of the European loess belt and Sahara Desert, thin and irregularly distributed loess deposits occur in Mediterranean mountains. During the most recent deglaciation, along the Pleistocene-Holocene boundary, the deposition of glacial, periglacial and outwash sediments, was the main local source of Mediterranean alpine loess, whereas proximal alluvial planes comprised a secondary source. The mid-Holocene termination of African Humid Period and subsequent aridification of Sahara Desert occurred simultaneously with a change of the regional climate from Atlantic to Mediterranean-dominated, characterized by frequent episodes of southerly winds. This resulted to a change of the loess source, as deflation of quartz rich silts enriched in Zr during intense episodes of Sahara dust transport became more dominant. Here, a 32cm loess profile from the Plateau of Muses (PM), below the summit of Mount Olympus, Greece, is investigated on the basis of grain size, mineralogy, environmental magnetism and geochemistry. Comparisons of loess samples with glacial and periglacial deposits, enables us to differentiate relative contributions of local sources and allochthonous aeolian inputs. Calcite sand rich in feldspars makes up the glacial and periglacial clast free matrix. In contrast, PM loess is composed by clay and fine silt fractions with minor calcite sand contributions. The mineralogical matrix of loess contains quartz, phyllosilicates and mixed layer clays, while its geochemical composition contains high amounts of detrital Fe-Ti oxides and aeolian transported Al and Zr. Based on the multi-proxy approach applied here, the loess profile is partitioned in three layers. Holocene average deposition rates (~2.5 cm/ka) broadly agree with modern Sahara dust deposition (~2.0 cm/ka) and long-term postglacial Mediterranean mountain denudation rates (~0.5 cm/ka). Such low rates provided ample time for post depositional modifications, such as decalcification, deferrification and removal of K, evident from the trends of chemical weathering proxies Ca/Sr, Fe/Ti and K/Rb, respectively.