Western Sahel Research Articles

Content of lipid nutrients in the milk of Fulani women.

Little is known about the nutrition of the infants of the Fulani, migratory nomads of the western Sahel of Africa. Milk was collected from 18 Fulani women 10 to 30 days postpartum and the fatty acid compositions of the triacylglycerol and phospholipid fractions were determined by capillary gas-liquid chromatography. De novo fatty acids (10:0-14:0) comprised 36.3 +/- 12.7% of fatty acids of the triacylglycerols. Compared to the milk of various populations worldwide, the milk of the Fulani women contained adequate proportions of alpha-linolenic acid (0.50 +/- 0.16%) and arachidonic acid (0.42 +/- 0.22%), but relatively low amounts of linoleic acid (9.95 +/- 2.13%) and docosahexaenoic acid (DHA) (0.15 +/- 0.08%). In addition, the milk of the Fulani women contained adequate concentrations of beta-carotene (1.58 +/- 0.69 micrograms/dl) and vitamin A (42.7 +/- 40.3 micrograms/dl), but very low levels of vitamin E (0.11 +/- 0.10 mg/dl). These data indicate that exclusively breasted infants of Fulani women were receiving relatively low amounts of critical fatty acids and vitamin E.

Does grasshopper control create grasshopper problems? -Monitoring side-effects of fenitrothion applications in the western Sahel

The effects of grasshopper control on the density and the natural mortality of grasshopper egg-pods was monitored in Senegal. Twenty-six operational treatments with fenitrothion was carried out during the rainy seasons of 1991 and 1992, and grasshopper egg-pod surveys were conducted both in treated plots and paired untreated control plots in the following dry season. Control operations generally were targeted at Oedaleus senegalensis, the Senegalese grasshopper, although the majority of egg-pods found in the surveys were those of Kraussaria angulifera. Egg-pod densities in treated plots were not different from controls in 1991, but were 140% higher in 1992. Damage to egg-pods due to natural enemies was on average 9% higher in treated plots. Most of this damage appeared to be caused by larvae of tenebrionid beetles. It is suggested that the increase in natural mortality may be due to insecticide impact on hyper-predators or hyper-parasitoids. Increased egg-pod densities might also arise from reduced activity of natural enemies of the post-embryonic stages of late hatching or immigrating grasshopper species such as K. angulifera. The net outcome of these processes is that control with broad-spectrum insecticides of grasshoppers that hatch early in the rainy season may augment populations of late hatching species the following year.

El Niño/La Niña and Sahel precipitation during the Middle Holocene

Simulations with a synchronously coupled atmosphere‐land‐ocean‐sea ice model indicate El Niño/La Niña‐like events in the eastern tropical Pacific Ocean during the middle Holocene (6 ka) with similar intensities and frequencies as at present (0 ka). July‐August‐September Sahel precipitation shifts northward as expected from proxy data. For present‐day, interannual‐decadal variability of western Sahel precipitation is correlated with both Pacific El Niño/La Niña sea surface temperature (SST) anomalies and the Atlantic dipole. Teleconnections at 6 ka between Sahel precipitation and El Niño/La Niña SST anomalies are absent with tropical Atlantic SSTs asserting a dominant influence. These results illustrate potential problems with using present‐day teleconnection patterns in interpreting past climate variability from proxy data.

RESEARCH IN SAHARAN HISTORY

Desert Frontier: Ecological and Economic Change along the Western Sahel, 1600–1850. By JAMES L. A. WEBB JR. Madison and London: University of Wisconsin Press, 1995. Pp. xxvi+227. £40.95 (ISBN 0-299-14330-9); £17.95, paperback (ISBN 0-299-14334-1).In contrast to the desert itself, the Sahara as subject of historical (re)construction is currently displaying signs of health and vitality. It is enticing historians into a range of theoretical and methodological domains deriving from other disciplines, and simultaneously attracting scholars from other disciplines to play out their own explorations around its contours. For a space which seems to have no difficulty occupying well-delineated and identified areas in every genre of cartographical representation, the Sahara is surprisingly difficult to ‘locate’ in academic discourse. Its identity, in current parlance, is a popular focus of speculation and debate, challenging conventional notions of its location, both in time and in space. One of these challenges is engagingly articulated in the recent publication of economic historian James Webb Jr. His Desert Frontier: Ecological and Economic Change along the Western Sahel, 1600–1850, invites wider participation in this ‘search for the Sahara’ and in so doing, encourages broader understanding of just where ‘Saharan studies’ and in particular Saharan history and Saharan society stand in these so-called post-colonial times.

Nutrient Content of Two Indigenous Plant Foods of the Western Sahel:Balanites aegyptiacaandMaerua crassifolia

Populations of the western Sahel consume many different indigenous plant foods, and during times of food scarcity, this dependency increases. In early 1997, the Famine Early Warning System reported that, due to a drought, jiga (Maerua crassifolia) and aduwa (Balanites aegyptiaca) were contributing increasingly to the diets of people living in Chad, Mauritania, and Niger. At present, there are no comprehensive reports published on the nutrient content of these two plant foods. Herein we report the lipid, fatty acid, amino acid, total protein, and mineral contents ofB. aegyptiacamesocarp andM. crassifolialeaves.M. crassifolialeaves contain more protein (39.4%) than the mesocarp ofB. aegyptiaca(7.10%), as well as proportions of the essential amino acids that compare favorably to a World Health Organization protein standard.M. crassifolialeaves can also provide significant amounts of calcium (17 mg/g dry wt), linoleic acid (1.26 mg/g dry wt), and α-linolenic acid (9.29 mg/g dry wt). In summary,M. crassifolialeaves can contribute significantly to the nutrition of populations inhabiting the Sahel.

Use of the trolox assay to estimate the antioxidant content of seventeen edible wild plants of niger

Although wild edible plants of the western Sahel and other parts of sub-Saharan Africa are consumed to some extent at all times of the year, greater amounts are consumed when cereal harvests are insufficient to support the populations living in these areas. The purpose of this study was to use a recently reported Trolox-based assay to measure the total antioxidant capacity of aqueous extracts of 17 plants that we gathered from southern Niger. The antioxidant contents of the aqueous extracts were compared to those of spinach and potato. Of the 17 plants, 11 had a greater antioxidant content than spinach and 14 had a greater antioxidant content than potato. The leaves of Tapinanthus globiferus had the greatest antioxidant content, and the fruit of Parinari macrophylla had the lowest. In general, leaves contained more antioxidants than either fruits or seeds. The total antioxidant capacity of the aqueous extracts was relatively high, indicating that the wild plants of the western Sahel may contain substantial amounts of water-soluble flavonoid glycosides, which are potent antioxidants and have been shown to have anticancer properties.

Analysis of nutritional components of eight famine foods of the Republic of Niger.

In the western Sahel, indigenous plants become important staples when cereal harvests are inadequate to support populations inhabiting that region of Africa. The purpose of this study was to assess the nutrient content of several of these edible wild plants. The leaves of the following seven plant foods were analyzed: Ziziphus mauritiana, Cerathotheca sesamoides, Moringa oleifera, Leptadenia hastata, Hibiscus sabdarifa, Amaranthus viridis, and Adansonia digitata. The fatty acid, vitamin E, carotenoid, selected mineral and amino acid contents of these plant foods were determined. These same analyses were performed on the fruit of the Adanisonia digitata. In quantitative and qualitative terms, Amaranthus viridis was found to be an excellent source of protein. Its amino acid composition compared favorably to that of a World Health Organization (WHO) protein standard. It also contained considerable amounts of the two fatty acids that are essential in humans (linoleic and alpha-linolenic) and a number of minerals including iron, magnesium. calcium and zinc. The leaves of Hibiscus sabdarifa contained an appreciable quantity of protein the composition of which was comparable to the WHO standard. The mineral content of the leaves of this plant was also exceptionally high; noteworthy was its high zinc content. H. sabdarifa also contained significant quantities of the two essential fatty acids. Ziziphus mauritiana was an excellent source of the essential fatty acid linoleic acid and several of the metals including iron, calcium, magnesium and zinc. Its content of other essential nutrients, however, was rather low. In general, Adansonia digitata leaves were nutritionally superior to the fruit of the tree; however, the fruit did contain useful quantities of potassium, phosphorus, zinc and alpha-linolenic acid. The Leptadenia hastata leaves were an especially good source of lutein and beta-carotene. These data should be useful to the people who inhabit the western Sahel in helping them devise healthy diets during times when cereal staples are in short supply.

Nutrient content of the edible leaves of seven wild plants from Niger.

Wild plants play an important role in the diet of the inhabitants of Niger. These plants tend to be drought-resistant and are gathered both in times of plenty as well as times of need. Used in everyday cooking, famine foods may be an important source of nutrients. The goal of this study was to investigate the nutritional role of wild plants in the nigérien diet. To this end, leaves of seven plants species were analyzed for their mineral, amino acid and fatty acid contents: Ximenia americana, Amaranthus viridus, Corchorus tridens, Hibiscus sabdarifa, Maerua crassifolia, Moringa oleifera, and Leptadenia hastata. Ximenia americana contained large amounts of calcium. Large quantities of iron were present in Amaranthus viridus. All seven plants contained significant amounts of selenium and phosphorus. Corchorus tridens contained the most protein (19-25% dry weight), and its composition compared favorably to the World Health Organization's standard for essential amino acids. Moringa oleifera contained 17% protein and compared favorably with the WHO standard. Corchorus tridens contained the largest amounts of the two essential fatty acids linoleic and alpha-linolenic acids. These results reinforce the growing awareness that wild edible plants of the Western Sahel can contribute useful amounts of essential nutrients, including amino acids, fatty acids and trace minerals, to human diets.

Amino Acid, Fatty Acid, and Mineral Composition of 24 Indigenous Plants of Burkina Faso

The leaves, seeds, flowers, and fruit of many indigenous plants are staples of populations who inhabit the Sahel region of Africa. They serve to supplement the nutrients provided by cereals such as millet and sorghum. However, there is a lack of comprehensive compositional data regarding the nutrient content of these indigenous plants. In this report, we present nutritional data for 24 plant materials collected in Burkina Faso, including their content of amino acids, fatty acids, and minerals. Three plants contained 20 to 37% protein (on a dry weight basis):Vigna sp., Hibiscus esculentus,andParkiia biglobosa.Relative to a WHO protein standard, three plants scored relatively high:Voadzeiia subterranea, Pennisetum americanum,andBixa orellana.Plants which contained large amounts of the essential fatty acids linoleic or α-linolenic acid wereVigna sp., Hibiscus esculentusseeds,Parkiia biglobosaseeds, andVitex donianafruit. Three plants were rich in iron:Adansonia digitata, Bixa orellana,andXylopia sp.The fruit and seeds ofHibiscus esculentuswere an excellent source of zinc. The plant foods with the highest calcium content wereAdansonia digitataleaves,Hibiscus sp.,andBombax costatum.These data show that in terms of both quality and quantity there are numerous spontaneous desert plants that can serve as significant sources of essential amino acids, essential fatty acids and trace minerals for populations living in the western Sahel.

The Diurnal and Seasonal Cycles of Wind-Borne Dust over Africa North of the Equator

This article presents a study of the diurnal and seasonal cycles of dust over North Africa, using surface visibility as an indicator of dust. The diurnal cycle shows a reduction of visibility during the daytime hours in the areas where dust is generated, a consequence of the elimination of the nocturnal inversion. The annual cycle reveals that, at latitudes from 5° to 16°N, there is a latitudinal increase in the duration of the presence of aerosols over the course of the year. The presence of aerosols dimishes in the latitudes from 20° to 35°N, indicating that the aerosol content of the Saharan air is lower than that over the semiarid sub-Saharan zones, such as the Sahel. A comparison of three periods, 1957–61, 1970–74, and 1983–87, shows a continually increasing presence of dust, particularly in the western Sahel. The interannual variability of the dust and its annual cycles in these three periods throughout North Africa bear a strong relationship to rainfall fluctuations in the Sahel. Overall, the results indicate that over the last few decades the Sahel region has replaced the central Sahara as the source of atmospheric aerosols over most of North Africa.

The Nutritional Composition of Seeds fromBoscia senegalensis(Dilo) from the Republic of Niger

The seeds ofBoscia senegalensisare used as a staple food during periods of famine in the Sahel zone of West Africa. Seeds collected in the Republic of Niger were extracted exhaustively with water to remove bitter components and possible toxic substances and then analyzed for their content of various nutrients. The processed seeds, calleddiloby the Hausa-speaking people of the western Sahel, contained 21% (dry wt) protein whose quality is inferior to that of an “ideal” WHO protein standard. Whilediloprotein contains a considerable quantity of tryptophan (4%) and extraordinarily large amounts of arginine (15.8%), it is deficient in lysine (3%) and threonine (3%). Lipid accounted for 3.68% of the dry weight ofdilo.Three-fourths of the fatty acids in the crude lipid extract were contributed by saturated fatty acids: palmitic acid (690 mg/100 g dry wt) and stearic acid (130 mg/100 g dry wt).Dilocontains 70 mg/100 g dry wt of the essential fatty acid linoleic acid, but undetectable levels of α-linolenic acid. In terms of mineral content,dilocontained relatively little calcium (29 mg/100 g dry wt) and magnesium (4.2 mg/100 g dry wt), and only traces of copper, selenium, and manganese. Zinc and iron, however, were present at relatively high levels, 6.0 and 5.3 mg/100 g dry wt, respectively. These data indicate that whiledilodoes not provide a complete food source in terms of essential nutrients, it does contain substantial quantities of arginine, tryptophan, and other essential amino acids, one of the essential fatty acids (linoleic acid), and zinc and iron. The chemical composition ofdiloharvested in Niger differs significantly from that ofB. senegalensisseeds grown in Sudan.

Rainfall in the Sahel during 1994

This paper evaluates the rainfall conditions of 1994 in the West African Sahel. This analysis confirms that the year was relatively wet in the Sahel. The strongest positive anomalies occurred in the central Sahel and during the months of August, September, and October. Conditions in the western Sahel were, as a whole, relatively dry. This year was the wettest for the region as a whole since 1969. Nevertheless, rainfall barely exceeded the long-term mean and was still slightly subnormal in the southern Sahel (i.e., the Soudan zone).

Physical Mechanisms for the Association of El Niño and West African Rainfall with Atlantic Major Hurricane Activity

Abstract Physical mechanisms responsible for the contemporaneous association, shown in earlier studies, of North Atlantic basin major hurricane (MH) activity with western Sahelian monsoon rainfall and an equatorial eastern Pacific sea surface temperature index of El Nino are examined, using correlations with 200- and 700-mb level wind data for the period 1968–92. The use of partial correlations isolates some of the relationships associated with the various parameters. The results support previous suggestions that the upper- and lower-level winds over the region in the basin between ∼10° and 20°N where most MHs begin developing are critical determinants of the MH activity in each hurricane season. In particular, interannual fluctuations in the winds that produce changes in the magnitude of vertical shear are one of the most important factors, with reduced shear being associated with increased activity and stronger shear with decreased activity. The results show that most of these critical wind fluctuations...

Response of a stably stratified atmosphere to large‐scale diabatic forcing with applications to wind patters in Brazil and the Sahel

The response of a stably stratified atmospheric flow to large‐scale elevated and low‐level thermal forcing on a β plane at several latitudes are investigated using a simple nonlinear numerical model. The formation of a westerly jet at the equator, a pair of low‐pressure and cyclonic circulation regions, and the decoupling of the westerly jet and the heating center are explained by the β effect. It is found that the vertical motion in the case with heating centered at the equator is much larger than that with heating centered at higher latitudes. This is explained by the trapping of more wave energy in equatorial regions when the heating is centered at the equator. On the other hand, the pressure perturbation is much stronger for cases with heating located at a higher latitude due to vortex stretching. It is found that there exists a vertical phase tilt which is explained by the upward propagating Kelvin waves near the equator and mixed Rossby gravity waves at higher latitudes. The vertical wavelength of the disturbance increases as the heating center is located at a higher latitude. In addition, we find that this type of flow is not sensitive to the existence of the stratosphere. One interesting feature is that the maximum vertical velocity for the case with heating centered at the equator is significantly larger than that with heating centered at 30°N. Comparing both linear and nonlinear cases with surface heating or cooling, we find (1) the nonlinearity suppresses (enhances) the disturbance induced by cooling (heating), (2) the differences between the nonlinear and linear responses are larger when the forcing is located at lower latitudes, and (3) the disturbed areas are much wider in the zonal direction for cooling cases than for cases with heating. The nonlinear effects are studied by inspecting individual terms. To explore the relationships between Atlantic sea surface temperature anomaly (SSTA) and rainfall anomalies in the Sahel and northeastern Brazil, the SSTA is represented by low‐level diabatic forcing in the numerical model. With a coupled warm SSTA in the South Atlantic and cold SSTA in the North Atlantic, model results indicate a combination of offshore flow and downward motion in the Sahel, while there exists an upward motion and an offshore flow in northeastern Brazil. When the SSTA pattern is reversed, then there exists an onshore flow and an upward motion in the western Sahel, while there exists a strong onshore flow and a downward motion in northeastern Brazil.

Premigratory diet of trans-Saharan migrant passerines in the western Sahel

Faecal analysis was used to investigate the relative contribution of arthropods and fruit to the premigratory diet of the Redstart and 4 European Sylvia warblers in Senegal in March. The warblers showed greater premigratory fattening and higher fruit consumption than the Redstart. Berries of the shrub Salvadora persica¸ were exploited by all species with berries over 5 mm diameter being selected.

Abrupt post-glacial climate events in West Asia and North Africa monsoon domains

Regions beyond the present or past penetration of the Indian and African monsoons have experienced several large and abrupt climatic fluctuations over the past 13 14C kyr. Pollen and lake records from West Asia (Western Tibet and Rajasthan), East Africa (Ethiopia) and West Africa (Western Sahara, Sahel and subequatorial Africa) were selected on the basis of chronological control, sensitivity of both site and environmental indicators to climate change, the continuity of the record, and interdisciplinary control of the palaeoclimatic interpretation. Conditions wetter than those of today prevailed during the early-mid-Holocene period, but major dry spells are recorded at all sites during the intervals ∼ 11.0–9.5 kyr BP, ∼ 8–7 kyr BP and 3–4 kyr BP. Several records also suggest dry events of minor amplitude around 6 kyr BP. Potential boundary forcings of insolation and sea surface and tropical land surface conditions are discussed. The solar radiation accounts for the general envelop of the post-glacial monsoon fluctuations, but explains neither the timing nor the amplitude of the short-term changes. In spite of apparent covariation between fluctuations in sea surface conditions in the North Atlantic and the monsoon record, no direct mechanism could be found relating the intensity of the oceanic thermohaline conveyor belt to the monsoon strength. Changes in tropical land surface conditions (soil moisture negative feedback, and changes in CH 4 production from wetlands) provide a more satisfactory hypothesis for explaining abrupt reversal events.

The Global Climate of June–August 1992: Warm ENSO Episode Decays and Colder Than Normal Conditions Dominate the Northern Hemisphere

The June-August 1992 (JJA 1992) season featured a weakening of the 1991-1992 El Nino-Southern Oscillation (ENSO) warm episode and a return toward normal conditions in the tropical Pacific. The sea surface temperature anomalies (SSTA) in the central and eastern equatorial Pacific decreased rapidly through the season. SSTA less than -1[degrees] were found in the eastern equatorial Pacific in August. The depth of the oceanic thermocline, which continued to decreased from April on, became shallower in the eastern Pacific (120[degrees]W-80[degrees]W) during the JJA season. The outgoing longwave radiation (OLR) index, Southern Oscillation index (SOI), and equatorial wind indices all indicate near-normal oceanic and atmospheric circulations in the tropical Pacific. However, positive SSTA remained in the central Pacific Nino 4 area. In the Northern Hemisphere, below-normal temperatures dominated the landmass regions in midlatitudes except in Europe where above-normal temperatures persisted throughout the season. The unusual coolness during this season may have been related to the June 1991 eruption of Mount Pinatubo in the Philippines. The United States experienced its third coldest and third wettest summer in 77 years according to the National Climate Data Center (NCDC) climate records. The Indian monsoon season started in mid-June, which was later than usual, but overallmore » it was a normal rainfall year, while the drought in the western Sahel continued. Tropical features are reviewed in section 2. The extratropics are discussed in section 3. The Indian summer monsoon and related circulation features are reviewed in section 4. 13 refs., 21 figs., 1 tab.« less

New Evidence of Desertification from Case Studies in Northern Burkina Faso

Case studies on desertification in northern Burkina Faso, in the Western Sahel, using satellite-aided ground navigation technology, have shown that a noticeable environmental degradation took place...

Epidémiologie de la trypanosomose à <em>T. evansi</em> chez le dromadaire au Mali : résultats d'enquêtes parasitologiques et cliniques

An epidemiological study of trypanosomiasis was conducted in the rearing areas of dromedary camels in Mali. According to the parasitological and clinical surveys performed, the overall infection rates were 9.5% (29/305) in Western Sahel (region I) and 4.5% (28/627) in the areas of Tombouctou and Gao (region II). The proportion of contaminated herds was 55% in region I and 68% in region II and in some herds the infection rate exceeded 50%. The surveys showed a trend for increasing parasitological prevalence with age. While it was almost nonexistent in young camels less than one year old, it increased with age and reached a maximum in 2 to 5-year old camels. The authors showed that the infection has a significantly negative effect on PCV and on the overall status of the animals, confirming the pathogenicity of Trypanosoma evansi in dromedary camels. This trypanosome is almost the only species detected in the dromedary camel in Mali and it does not seem to cause infections in other animals reared in the same environment.

New Evidence of Desertification from Case Studies in Northern Burkina Faso

Case studies on desertification in northern Burkina Faso, in the Western Sahel, using satellite-aided ground navigation technology, have shown that a noticeable environmental degradation took place from the late 1960s to 1990. Analyses of aerial photographs and satellite images indicate that the most severe land degradation occurred during the first of a series of droughts, which started in the late 1960s, when large areas with bare ground developed. Despite increased rainfall since 1985, the areas with bare ground have not recovered. The main cause is to be found in a combination of human impact and of repeated droughts.