Central Sahara Research Articles

The Saharan heat low and moisture transport pathways in the central Sahara—Multiaircraft observations and Africa‐LAM evaluation

AbstractWe present a characterization of the Saharan heat low (SHL) based on dropsonde observations made on 22 June 2011 by two simultaneously flying aircraft during the Fennec project. The observations are used to identify moisture transport pathways and to validate the UK Met Office limited area model for northern Africa (Africa‐LAM). The observations capture the SHL, harmattan, and monsoon surge. The SHL has a northeast‐southwest orientated elongated shape centered over northern Mauritania. The SHL core is associated with a 950 hPa temperature minimum (36.4°C) in the morning caused by the monsoon surge and a maximum (42.6°C) in the afternoon. The monsoon surge east of the SHL core splits into two transport pathways: (a) curving around the SHL core in the north, especially pronounced in a morning near‐surface layer, and (b) northeastward transport within the ~2 km deep monsoon surge (afternoon observations only). In the morning the model forecasts the harmattan, monsoon surge, and the SHL geographic location and northeast‐southwest orientation well but the model represents the SHL flatter and more spatially extended and overestimates the convective boundary layer (CBL) by up to ~0.3 km. The simulated afternoon SHL location appears shifted westward by up to ~1°. The model overestimates the shallow afternoon monsoon surge CBL depth of ~1.8 km by >2 km resulting in southwestward transport of vertically mixed moisture above ~2.5 km contrasting observed northeastward‐only transport at lower levels. This moisture distribution model error is likely to have consequences for simulations of Saharan thermodynamics and dust emissions caused by convection‐driven cold pools.

Lithic landscapes: early human impact from stone tool production on the central Saharan environment.

Humans have had a major impact on the environment. This has been particularly intense in the last millennium but has been noticeable since the development of food production and the associated higher population densities in the last 10,000 years. The use of fire and over-exploitation of large mammals has also been recognized as having an effect on the world’s ecology, going back perhaps 100,000 years or more. Here we report on an earlier anthropogenic environmental change. The use of stone tools, which dates back over 2.5 million years, and the subsequent evolution of a technologically-dependent lineage required the exploitation of very large quantities of rock. However, measures of the impact of hominin stone exploitation are rare and inherently difficult. The Messak Settafet, a sandstone massif in the Central Sahara (Libya), is littered with Pleistocene stone tools on an unprecedented scale and is, in effect, a man-made landscape. Surveys showed that parts of the Messak Settafet have as much as 75 lithics per square metre and that this fractured debris is a dominant element of the environment. The type of stone tools—Acheulean and Middle Stone Age—indicates that extensive stone tool manufacture occurred over the last half million years or more. The lithic-strewn pavement created by this ancient stone tool manufacture possibly represents the earliest human environmental impact at a landscape scale and is an example of anthropogenic change. The nature of the lithics and inferred age may suggest that hominins other than modern humans were capable of unintentionally modifying their environment. The scale of debris also indicates the significance of stone as a critical resource for hominins and so provides insights into a novel evolutionary ecology.

Colour in context. Pigments and other coloured residues from the Early-Middle Holocene site of Takarkori (SW Libya)

We present the multidisciplinary investigation of pigments and artefacts with traces of colour from the Early-Middle Holocene site of Takarkori, located in the Tadrart Acacus Mountains (central Sahara, SW Libya). Here, geological, archaeological, taphonomic and chemical studies (Raman, Fourier-transform infrared, X-ray powder diffraction, gas chromatography–mass spectrometry) are used to examine a vast range of artefacts (raw materials, grinding stones, painted items, as well as lithic, bone, wooden and ceramic tools) equally distributed from Late Acacus contexts related to hunter-gatherers (ca. 8900–7400 uncal years bp) to pastoral groups (ca. 7400–4500 uncal years bp). The exploited minerals (goethite, hematite, kaolinite and jarosite, among others) are locally procured and processed using quartzarenite grinding stones of different shapes and sizes. Thermal treatment of the minerals is also suggested by X-ray powder diffraction (XRD) and Raman studies. Gas chromatography–mass spectrometry (GC-MS) analyses show the addition of a lipid binder to small lumps of pigments in order to obtain a sticky product. Their fatty acid distribution differs from the residues on grinding stones, pointing to a specific use of these lumps. The grinding stones have also been used to crush and pulverize the pigments and as base for colour preparation. A sample of colour from a fallen painted slab referable to late pastoral phases shows the presence of a binder, chemically identified as casein. Taken together, the evidence collected at Takarkori conveys to suggest an articulated chaine operatoire, not only directed towards the preparation of pigments for the parietal rock art but also to other non-utilitarian functions, such as body care and ornamentation and decoration of artefacts.

Dust detection from ground‐based observations in the summer global dust maximum: Results from Fennec 2011 and 2012 and implications for modeling and field observations

AbstractIn boreal summer, the central Sahara is the dustiest place on Earth. Fennec supersite 1 is located within the dust maximum. With two field seasons completed, June 2011 (intensive observation period (IOP) 1) and June 2012 (IOP2), we now have an initial measure of their representativeness. Although the number of dust event hours in IOP2 is up to 169 h (60%) more than in IOP1, the relative importance of the different dust mechanisms is the same. In both years, emission by cold pool outflows from deep convection causes most dust, followed by dust advection, monsoon surges, low‐level jet emission and lastly dry convective plumes. Given the dominance of cold pools, it is very important that they be incorporated in dust modeling efforts over the region. Because cold pools frequently occur at night and are associated with cloud cover, instruments that can monitor in these conditions are particularly valuable in this region. Sun photometer aerosol optical depth retrievals, for example, are only available for 23% (41%) of the time cold pool emission occurs at the supersite in IOP1 (IOP2). Deployment of instrumentation in remote regions being difficult and expensive, choosing the optimal instrument payload pays dividends. With this motivation, we evaluate the different dust detection instrumentation deployed at the supersite and develop an approach which can identify and characterize individual dust emission mechanisms with a high degree of success purely from routine meteorological observations and remote sensing. This identification is, however, much more challenging in the case of dust advection.

The origins and development of Zuwīla, Libyan Sahara: an archaeological and historical overview of an ancient oasis town and caravan centre

Zuwīla in southwestern Libya (Fazzān) was one of the most important early Islamic centres in the Central Sahara, but the archaeological correlates of the written sources for it have been little explored. This paper brings together for the first time a detailed consideration of the relevant historical and archaeological data, together with new AMS radiocarbon dates from several key monuments. The origins of the settlement at Zuwīla were pre-Islamic, but the town gained greater prominence in the early centuries of Arab rule of the Maghrib, culminating with the establishment of an Ibāḍī state ruled by the dynasty of the Banū Khaṭṭāb, with Zuwīla its capital. The historical sources and the accounts of early European travellers are discussed and archaeological work at Zuwīla is described (including the new radiocarbon dates). A short gazetteer of archaeological monuments is provided as an appendix. Comparisons and contrasts are also drawn between Zuwīla and other oases of the ash-Sharqiyāt region of Fazzān. The final section of the paper presents a series of models based on the available evidence, tracing the evolution and decline of this remarkable site.

The daytime cycle in dust aerosol direct radiative effects observed in the central Sahara during the Fennec campaign in June 2011

AbstractThe direct clear‐sky radiative effect (DRE) of atmospheric mineral dust is diagnosed over the Bordj Badji Mokhtar (BBM) supersite in the central Sahara during the Fennec campaign in June 2011. During this period, thick dust events were observed, with aerosol optical depth values peaking at 3.5. Satellite observations from Meteosat‐9 are combined with ground‐based radiative flux measurements to obtain estimates of DRE at the surface, top‐of‐atmosphere (TOA), and within the atmosphere. At TOA, there is a distinct daytime cycle in net DRE. Both shortwave (SW) and longwave (LW) DRE peak around noon and induce a warming of the Earth‐atmosphere system. Toward dusk and dawn, the LW DRE reduces while the SW effect can switch sign triggering net radiative cooling. The net TOA DRE mean values range from −9 Wm−2 in the morning to heating of +59 Wm−2 near midday. At the surface, the SW dust impact is larger than at TOA: SW scattering and absorption by dust results in a mean surface radiative cooling of 145Wm−2. The corresponding mean surface heating caused by increased downward LW emission from the dust layer is a factor of 6 smaller. The dust impact on the magnitude and variability of the atmospheric radiative divergence is dominated by the SW cooling of the surface, modified by the smaller SW and LW effects at TOA. Consequently, dust has a mean daytime net radiative warming effect on the atmosphere of 153Wm−2.

Changing Places: Rock Art and Holocene Landscapes in the Wadi al-Ajal, South-West Libya

This article examines the relationship between rock art and landscape use by pastoral groups and early settled communities in the central Sahara from around 6000 BC to 1000 AD. During this period the region experienced significant climatic and environmental fluctuations. Using new results from a systematic survey in the Wadi al-Ajal, south-west Libya, our research combines data from over 2000 engraved rock art panels with local archaeological and palaeoenvironmental evidence within a GIS model. Spatial analysis of these data indicates a correspondence between the frequency of rock art sites and human settlement over time. However, while changes in settlement location were guided primarily by the constraints on accessibility imposed by surface water, the distribution of rock art relates to the availability of pasture and patterns of movement through the landscape. Although the reasons for these movements undoubtedly altered over time, natural routes that connected the Wadi al-Ajal and areas to the south continued to be a focus for carvings over several thousand years.

Geomorphological Map of the Tadrart Acacus Massif and the Erg Uan Kasa (Libyan Central Sahara)

Here we present a geomorphological map of the Tadrart Acacus Massif and Erg Uan Kasa (SW Libya, central Sahara). The geomorphological mapping of the area was carried out by means of satellite imagery analysis followed by detailed control of units in the field. The Tadrart Acacus is a sandstone massif delimited to the West by a high scarp and cut by a dendritic fossil drainage network of W-E-oriented wadis. The massif has been shaped since the Tertiary by etchplanation and solutional processes; the latter is demonstrated by the ruiniform landscape and the high number of caves and rock shelters that dot the vertical cliffs of the wadis. To the East, the Tadrart Acacus merges below a complex system of sand ridges that form the Erg Uan Kasa. The large interdune corridors of the sand sea are dotted by lake sediments, which formed during the Pleistocene interglacials and the African Humid Period of the Holocene, when piezometric lakes were sustained by intense monsoonal rainfall. Geomorphological investigation demonstrates that the extant landscape originated thanks to the overlap of surface processes triggered by divergent (humid/arid) environmental conditions.

Sandstone Geomorphology of South-West Jordan, Middle East

Abstract In the desert environment of south-west Jordan thick sequences of continental sandstones of Cambrian-Ordovician age support spectacular scenery, comparable with that of the Colorado Plateau of south-west USA or the central Sahara and similar in many aspects to the Danxia landform of southern China. Dissection of a sandstone tableland has given rise to numerous inselbergs and large mesas, rising from the sand-covered desert floor. The height of the hills varies from a few tens to 500-700 m in the Wadi Rum area, whereas their slope shapes are controlled by lithological properties of particular sandstone units. Rock walls of the sandstone inselbergs are subject to frequent rock falls and rock slides and host an impressive array of tafoni and honeycombs due to selective weathering, as well as a number of rock arches. Lithological differences within the sandstone sequence are crucial controls on the shape and evolution of rock slopes, exerting the influence via contrasting patterns of weathering and slope failures. The presence of ferruginous layers in the Umm ‘Ishrin Sandstone is of major importance and explains the fundamental morphological differences between the otherwise similar Umm ‘Ishrin and Disi sandstone units

Project provides new look at Saharan low‐level jet streams

Hot, dusty Saharan winds are known to influence atmospheric processes in the greater Atlantic region, but the desert's harsh environment makes meteorological observations of weather patterns originating in the Sahara nearly impossible. In the last few years, with the help of the multinational terrestrial, satellite, and modeling endeavor called the Fennec project, scientists have begun to quantify atmospheric phenomena over the remote central Sahara.

Combining image analysis and modular neural networks for classification of mineral inclusions and pores in archaeological potsherds

The approach combining image analysis techniques and artificial neural networks is proposed here for automatic classification of mineral inclusions and pores in archaeological potsherds using optical digital images. Particularly, the automatic identification of quartz, calcareous aggregates and secondary porosity is considered. A collection of both plane and cross polarised light images acquired via a digital camera connected to optical microscopy in transmitted light is used. Images concern Holocene potsherds (8900–4200 years BP) from Takarkori rock shelter archaeological site (SW Libya, Central Sahara).The adopted methodology involves different phases. Firstly, image segmentation is carried out to isolate regions corresponding to the interested mineral inclusions and pores. A segmentation procedure based on mathematical operators is customized for each type of inclusions and for pores. Secondly, numerical features are extracted from each segmented region, thus collecting data to perform automatic classification. A modular classifier is considered for classification, which is based on a combination of three two-layer feed-forward neural networks that are trained separately to recognise each class.Experimental results show that the created modular classifier provides high classification accuracy for both inclusions and pores. The classifier was finally applied absent the image analysis phase on new samples to show the effectiveness of the proposed methodology.

Takarkori rock shelter (SW Libya): an archive of Holocene climate and environmental changes in the central Sahara

Rock shelters in the central Saharan massifs preserve anthropogenic stratigraphic sequences that represent both a precious archive for the prehistory of the region and a powerful proxy data for Holocene palaeoenvironments. The geoarchaeological (micromorphology) and archaeobotanical (pollen analysis) approaches were integrated to investigate the anthropogenic sedimentary sequence preserved within the Takarkori rock shelter, a Holocene archaeological site located in the Libyan central Sahara (southern Tadrart Acacus massif). The site was occupied throughout the Early and Middle Holocene (African Humid Period) by groups of hunter–gatherers before and by pastoral communities later. The investigation on the inner part of the sequence allows to recognize the anthropogenic contribution to sedimentation process, and to reconstruct the major changes in the Holocene climate. At the bottom of the stratigraphic sequence, evidence for the earliest frequentation of the site by hunters and gatherers has been recognized; it is dated to c. 10,170 cal yr BP and is characterized by high availability of water, freshwater habitats and sparsely wooded savannah vegetation. A second Early Holocene occupation ended at c. 8180 cal yr BP; this phase is marked by increased aridity: sediments progressively richer in organics, testifying to a more intense occupation of the site, and pollen spectra indicating a decrease of grassland and the spreading of cattails, which followed a general lowering of lake level or widening of shallow-water marginal habitats near the site. After this period, a new occupational phase is dated between c. 8180 and 5610 cal yr BP; this period saw the beginning of the frequentation of pastoral groups and is marked by an important change in the forming processes of the sequence. Sediments and pollen spectra confirm a new increase in water availability, which led to a change in the landscape surrounding the Takarkori rock shelter with the spreading of water bodies. The upper part of the sequence, dating between c. 5700 and 4650 cal yr BP records a significant environmental instability towards dryer climatic conditions, consistent with the end of the African Humid Period. Though some freshwater habitats were still present, increasing aridity pushed the expansion of the dry savannah. The final transition to arid conditions is indicated by the preservation of ovicaprines dung layers at the top of the sequence together with sandstone blocks collapsed from the shelter's vault. On the contrary, the outer part of the sequence preserves a significantly different palaeoenvironmental signal; in fact, the surface was exposed to rainfall and a complex pedogenetic evolution of the sequence occurred, encompassing the formation of an argillic laminar horizon at the topsoil, the evolution of a desert pavement, and the deposition of Mn-rich rock varnish on stones. These processes are an effect of the general environmental instability that occurred in the central Sahara since the Middle Holocene transition. Finally, the local palaeoclimatic significance of the sequence fits well with Holocene regional and continental environmental changes recorded by many palaeohydrological records from North Africa. This highlights the potential of geoarchaeological and archaeobotanical investigations in interpreting the palaeoenvironmental significance of anthropogenic cave sediments in arid lands.

Patina and Environment in the Wadi al-Hayat: Towards a Chronology for the Rock Art of the Central Sahara

This paper proposes a broad chronological framework for the engravings of the Wadi al-Hayat that is based on environmental parameters rather than stylistic observations. During the Holocene, the climate of the central Sahara changed from savanna to desert. This environmental background informed the experience of the engravers and underpinned the weathering of rock surfaces. To establish a link between images and climatic sequence, 2,466 individual animal engravings were analyzed with regard to the depicted species, patina and the location of the panel in relation to the dated shorelines of the al-Hayat palaeolake. Based on their patina, engravings are grouped into a broad, four-stage chronological sequence. The chronological relevance of this framework is tested in three different ways. The dates and sequence of the introduction of domestic animals match their depiction across the four engraving groups. The habitats of the depicted wild animals reflect a dramatic change from savanna to desert that is consistent with climatic records and the physical process of the patina formation. In addition, Early and Middle Pastoral engravings are shown to be in locations that correspond to the high lake levels of the African Humid period. Late Pastoral and Garamantian engravings are also recorded in areas that only became accessible once the palaeolake had dried up. Although the proposed methodology cannot provide precise dates for individual engravings, it can be used to establish a broad chronological framework that allows us to place the rock art within its archaeological context.

Quantifying particle size and turbulent scale dependence of dust flux in the Sahara using aircraft measurements

The first size-resolved airborne measurements of dust fluxes and the first dust flux measurements from the central Sahara are presented and compared with a parameterization by Kok (2011a). High-frequency measurements of dust size distribution were obtained from 0.16 to 300 µm diameter, and eddy covariance fluxes were derived. This is more than an order of magnitude larger size range than previous flux estimates. Links to surface emission are provided by analysis of particle drift velocities. Number flux is described by a −2 power law between 1 and 144 µm diameter, significantly larger than the 12 µm upper limit suggested by Kok (2011a). For small particles, the deviation from a power law varies with terrain type and the large size cutoff is correlated with atmospheric vertical turbulent kinetic energy, suggesting control by vertical transport rather than emission processes. The measured mass flux mode is in the range 30–100 µm. The turbulent scales important for dust flux are from 0.1 km to 1–10 km. The upper scale increases during the morning as boundary layer depth and eddy size increase. All locations where large dust fluxes were measured had large topographical variations. These features are often linked with highly erodible surface features, such as wadis or dunes. We also hypothesize that upslope flow and flow separation over such features enhance the dust flux by transporting large particles out of the saltation layer. The tendency to locate surface flux measurements in open, flat terrain means these favored dust sources have been neglected in previous studies.

Animal engravings in the central Sahara: A proxy of a proxy

The rock art of the central Sahara was created out of the beliefs, traditions and experiences of the engravers and painters. The animal engravings of the Wadi al-Ajal in south-western Libya are used to isolate some of the environmental and cultural/symbolic components that make up the pictorial record. A comparison between the depicted animals and the faunal remains recovered in the area identifies a number of characteristics. The engraving repertoire is dominated by a small number of frequently depicted animals that were of symbolic or economic importance to the engravers. Rare and singular depicted species extend this record to a diverse species spectrum. Although a preferential depiction of herbivores is evident in the data, there is a close match between faunal record and engravings which shows that all larger animals (over ca. 10 kg) that were present in the area were also depicted. The selection of animals in the rock art appears to reflect their visibility in the landscape while also providing a record of changing climatic conditions from savanna to desert habitats. The rock art therefore provides an indirect record of the local environment while also capturing the engravers' perception of animals and landscape.

The low-level jet dust emission mechanism in the central Sahara: Observations from Bordj-Badji Mokhtar during the June 2011 Fennec Intensive Observation Period

This paper presents the first detailed analysis of low-level jets (LLJs) in the central Sahara from ground-based observations at Bordj-Badji Mokhtar, Algeria, and addresses their operation as a dust emission mechanism. On LLJ mornings, composite wind speeds in the core (300 m aboveground level) reach 13.5 m s−1 at 0400. Surface temperatures increase from 0545 (30 min after sunrise), and jet decay begins around 0600. Ten meter winds lag those in the core by 5 h; peak 10 m wind speed, 7.5 m s−1, occurs at 0900. Only the deepest and strongest LLJs lead to dust emission. At 0600, these five LLJs have core wind speeds ≥16 m s−1, below-core wind shear ≥ 0.6 m s−1/30 m, and wind shear between the core and 500 m above the core ≤−1.8 m s−1. On these occasions, momentum mixes down from the LLJ after surface heating, leading to emission. On nondusty LLJ mornings, the convective boundary layer is 100 m shallower, and the LLJ is too weak to provide enough momentum to be mixed down for emission. LLJs are most frequently embedded in the monsoon flow or in the Harmattan; there is a clear association with the Saharan Heat Low. ERA-Interim reanalysis underestimates both Harmattan and monsoon LLJ core winds (by 4 m s−1 and 6 m s−1, respectively). The Met Office Africa Limited Area Model underestimates Harmattan LLJ core winds by only 0.2 m s−1. Monsoon LLJ core winds, however, are underestimated by 8.5 m s−1. Surface winds at 0900 are underestimated in both cases by up to 6 m s−1.

The formation of a large summertime Saharan dust plume: Convective and synoptic-scale analysis

Haboobs are dust storms produced by the spreading of evaporatively cooled air from thunderstorms over dusty surfaces and are a major dust uplift process in the Sahara. In this study observations, reanalysis, and a high-resolution simulation using the Weather Research and Forecasting model are used to analyze the multiscale dynamics which produced a long-lived (over 2 days) Saharan mesoscale convective system (MCS) and an unusually large haboob in June 2010. An upper level trough and wave on the subtropical jet 5 days prior to MCS initiation produce a precipitating tropical cloud plume associated with a disruption of the Saharan heat low and moistening of the central Sahara. The restrengthening Saharan heat low and a Mediterranean cold surge produce a convergent region over the Hoggar and Aïr Mountains, where small convective systems help further increase boundary layer moisture. Emerging from this region the MCS has intermittent triggering of new cells, but later favorable deep layer shear produces a mesoscale convective complex. The unusually large size of the resulting dust plume (over 1000 km long) is linked to the longevity and vigor of the MCS, an enhanced pressure gradient due to lee cyclogenesis near the Atlas Mountains, and shallow precipitating clouds along the northern edge of the cold pool. Dust uplift processes identified are (1) strong winds near the cold pool front, (2) enhanced nocturnal low-level jet within the aged cold pool, and (3) a bore formed by the cold pool front on the nocturnal boundary layer.

Amulets and talismans of the Central Sahara – Tuareg art in context of magical and mystical beliefs

Amulets and talismans of the Central Sahara – Tuareg art in context of magical and mystical beliefs

Health and sanitary status in 1970 of Tubu nomads dwelling in Northeastern Niger.

BackgroundThe Tubu are nomadic people who live in remote parts of the central Sahara, primarily in the Tibesti massif (Chad), and in both Northeastern Niger and Southern Libya. No data about the Tubu’s health and sanitary status are currently available.MethodsIn 1970, the “Mission Anthropologique Belge au Niger” (MABN) investigated a Tubu tribe named Broaya that lived on the northeastern rim of the Tenere desert. One hundred and fifty-one adult volunteers were investigated. The environmental fauna of medical importance was also studied.ResultsAlbeit 43 year-old, these results have not been previously published. The estimated age of death for fathers was approximately 56 years, and that for mothers was 60 years. The overall perinatal mortality rate was 232%, the overall infant mortality rate was 153%, and the overall child mortality rate was 99%. The physical examination found 6 cases of blindness (4.0%). Five subjects presented with an elevated blood pressure (3.3%), and 5 (3.3%) displayed an abnormal thoracic auscultation evocative of tuberculosis or of an acute lung infection. In the field, no blood-fluke eggs were found in the urine samples. The blood thin films and stool samples were preserved then subsequently examined in Toulouse. The search for blood parasites was negative. Three subjects (2%) passed E. histolytica/E. dispar cysts in stools, 16 (10.6%) were parasitized with Giardia sp. and 4 (2.65%) were parasitized with Hymenolepis nana. Two specimens of scorpions captured in the camp were subsequently identified as belonging to the harmful genus Androctonus or Leiurus. An investigation into the freshwater fauna was conducted in the marshy ponds surrounding the ghost city of Djado, and no intermediate snail hosts for schistosomiasis haematobium were found. Larvae and nymphs, of Anopheles hispaniola and of An. multicolor, which are not efficient vectors for malaria, were collected.ConclusionsInfection-related blindness and trachoma, along with acute pulmonary infections and probably tuberculosis were the major health burden in this tribe. The harsh dry and hot climate may explain the low prevalence of soil-transmitted protozoan diseases or helminthiases.

Burning without slashing. Cultural and environmental implications of a traditional charcoal making technology in the central Sahara

We describe in this paper a traditional charcoal making technology occasionally adopted by Tuareg people in the hyper-arid central Sahara (SW Libya). This methodology (called esed) has been identified thanks to ethnobotanic and ethnographic interviews with people living in the Tadrart Acacus massif (the kel Tadrart Tuareg) and confirmed by macroscopic and micromorphological analyses of residual field evidence. Esed consisted of burning in situ trunks of dead Acacia tortilis (Forssk.) Hayne; subsequently, small portions of collapsed and still-burning wood were buried with sand in an attempt to ensure combustion under anoxic conditions. Our interviews elucidated that the esed technology is well known by people living in the region and has possibly been practiced for a long time. Surprisingly, local informants highlighted that esed was employed to made charcoal only during years marked by abrupt reduction of precipitation and consequently of natural resources. The last employment of esed dates to the dry phase of the mid-1970s, when charcoal was used as an exchangeable good. The discovery of this charcoal making technology shed new light on the capability of Tuareg to manage the few natural resources available in marginal environments and to cope with rapid climate changes.