SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Desertification

6

Educational attainment for women of reproductive age is linked to reduced child and maternal mortality, lower fertility and improved reproductive health. Comparable analyses of attainment exist only at the national level, potentially obscuring patterns in subnational inequality. Evidence suggests that wide disparities between urban and rural populations exist, raising questions about where the majority of progress towards the education targets of the Sustainable Development Goals is occurring in African countries. Here we explore within-country inequalities by predicting years of schooling across five by five kilometre grids, generating estimates of average educational attainment by age and sex at subnational levels. Despite marked progress in attainment from 2000 to 2015 across Africa, substantial differences persist between locations and sexes. These differences have widened in many countries, particularly across the Sahel. These high-resolution, comparable estimates improve the ability of decision-makers to plan the precisely targeted interventions that will be necessary to deliver progress during the era of the Sustainable Development Goals.

Concepts: Africa, Sahara, Demography, Population, Millennium Development Goals, Sustainable development, Sahel, Desertification

4

Performance of migrating birds can be affected by a number of intrinsic and extrinsic factors like morphology, meteorological conditions and migration strategies. We compared travel speeds of four raptor species during their crossing of the Sahara desert. Focusing the analyses on this region allows us to compare different species under equivalent conditions in order to disentangle which factors affect migratory performance.

Concepts: Species, Sahara, Motivation, Desertification

3

Summer rainfall in the Sahel region of Africa exhibits one of the largest signals of climatic variability and with a population reliant on agricultural productivity, the Sahel is particularly vulnerable to major droughts such as occurred in the 1970s and 1980s. Rainfall levels have subsequently recovered, but future projections remain uncertain. Here we show that Sahel rainfall is skilfully predicted on inter-annual and multi-year (that is, >5 years) timescales and use these predictions to better understand the driving mechanisms. Moisture budget analysis indicates that on multi-year timescales, a warmer north Atlantic and Mediterranean enhance Sahel rainfall through increased meridional convergence of low-level, externally sourced moisture. In contrast, year-to-year rainfall levels are largely determined by the recycling rate of local moisture, regulated by planetary circulation patterns associated with the El Niño-Southern Oscillation. Our findings aid improved understanding and forecasting of Sahel drought, paramount for successful adaptation strategies in a changing climate.

Concepts: Africa, Prediction, Futurology, Future, Niger, Forecasting, Desertification, Droughts

3

Synoptic-scale African easterly waves (AEWs) impact weather throughout the greater Atlantic basin. Over the African continent, AEWs are instrumental in initiating and organizing precipitation in the drought-vulnerable Sahel region. AEWs also serve as the precursors to the most intense Atlantic hurricanes, and contribute to the global transport of Saharan dust. Given the relevance of AEWs for the climate of the greater Atlantic basin, we investigate the response of AEWs to increasing greenhouse gas concentrations. Using an ensemble of general circulation models, we find a robust increase in the strength of the winds associated with AEWs along the Intertropical Front in West Africa by the late 21st century of the representative concentration pathway 8.5. AEW energy increases directly due to an increase in baroclinicity associated with an enhanced meridional temperature gradient between the Sahara and Guinea Coast. Further, the pattern of low-level warming supports AEW development by enhancing monsoon flow, resulting in greater convergence and uplift along the Intertropical Front. These changes in energetics result in robust increases in the occurrence of conditions that currently produce AEWs. Given relationships observed in the current climate, such changes in the location of AEW tracks and the magnitude of AEW winds carry implications for the relationship between AEWs and precipitation in the Sahel, the mobilization of Saharan dust, and the likelihood of cyclogenesis in the Atlantic. Our results therefore suggest that changes in AEW characteristics could play a critical role in shaping the response of Atlantic basin climate to future increases in greenhouse gas concentrations.

Concepts: Africa, Sub-Saharan Africa, Sahara, West Africa, Tropical cyclone, Monsoon, Sahel, Desertification

2

The Namib Desert in southwest Africa is hyperarid and composed of distinct microbial communities affected by a longitudinal aridity gradient. Here, we report four soil metaviromes from the Namib Desert, assessed using deep sequencing of metavirome libraries prepared from DNA extracted from gravel plain surface soils.

Concepts: Desertification, Namib Desert, Namib-Naukluft National Park

2

Microbes in hot desert soil partake in core ecosystem processes e.g., biogeochemical cycling of carbon. Nevertheless, there is still a fundamental lack of insights regarding short-term (i.e., over a 24-hour [diel] cycle) microbial responses to highly fluctuating microenvironmental parameters like temperature and humidity. To address this, we employed T-RFLP fingerprinting and 454 pyrosequencing of 16S rRNA-derived cDNA to characterize potentially active bacteria in Namib Desert soil over multiple diel cycles. Strikingly, we found that significant shifts in active bacterial groups could occur over a single 24-hour period. For instance, members of the predominant Actinobacteria phyla exhibited a significant reduction in relative activity from morning to night, whereas many Proteobacterial groups displayed an opposite trend. Contrary to our leading hypothesis, environmental parameters could only account for 10.5% of the recorded total variation. Potential biotic associations shown through co-occurrence networks indicated that non-random inter- and intra-phyla associations were ‘time-of-day-dependent’ which may constitute a key feature of this system. Notably, many cyanobacterial groups were positioned outside and/or between highly interconnected bacterial associations (modules); possibly acting as inter-module ‘hubs’ orchestrating interactions between important functional consortia. Overall, these results provide empirical evidence that bacterial communities in hot desert soils exhibit complex and diel-dependent inter-community associations.

Concepts: DNA, Archaea, Bacteria, Precipitation, Ecosystem, Microorganism, Desert, Desertification

2

Hundreds of millions of Afro-Palaearctic migrants winter in the Sahel, a semi-arid belt south of the Sahara desert, where they experience deteriorating ecological conditions during their overwintering stay and have to prepare for spring migration when conditions are worst. This well-known phenomenon was first described by R.E. Moreau and is known ever since as Moreau’s Paradox. However, empirical evidence of the deteriorating seasonal ecological conditions is limited and little is known on how birds respond. Montagu’s Harriers Circus pygargus spend 6 months of the year in their wintering areas in the Sahel. Within the wintering season, birds move gradually to the south, visiting several distinct sites to which they are site-faithful in consecutive years. At the last wintering site, birds find themselves at the southern edge of the Sahelian zone and have no other options than facing deteriorating conditions. We tracked 36 Montagu’s Harriers with GPS trackers to study their habitat use and behaviour during winter and collected data on the abundance of their main prey, grasshoppers, in Senegal. Since grasshopper abundance was positively related to vegetation greenness (measured as normalized difference vegetation index, NDVI), we used NDVI values as a proxy for prey abundance in areas where no field data were collected. Prey abundance (grasshopper counts and vegetation greenness) at wintering sites of Montagu’s Harriers decreased during the wintering period. Montagu’s Harriers responded to decreasing food availability by increasing their flight time during the second half of the winter. Individuals increased flight time more in areas with stronger declines in NDVI values, suggesting that lower food abundance required more intense foraging to achieve energy requirements. The apparent consequence was that Montagu’s Harriers departed later in spring when their final wintering site had lower NDVI values and presumably lower food abundance and consequently arrived later at their breeding site. Our results confirmed the suggestions Moreau made 40 years ago: the late wintering period might be a bottleneck during the annual cycle with possible carry-over effects to the breeding season. Ongoing climate change with less rainfall in the Sahel region paired with increased human pressure on natural and agricultural habitats resulting in degradation and desertification is likely to make this period more demanding, which may negatively impact populations of migratory birds using the Sahel.

Concepts: Africa, Sahara, Burkina Faso, Niger, Chad, Senegal, Sahel, Desertification

2

Soils are among the most valuable non-renewable resources on the Earth. They support natural vegetation and human agro-ecosystems, represent the largest terrestrial organic carbon stock, and act as stores and filters for water. Mankind has impacted on soils from its early days in many different ways, with burning being the first human perturbation at landscape scales. Fire has long been used as a tool to fertilize soils and control plant growth, but it can also substantially change vegetation, enhance soil erosion and even cause desertification of previously productive areas. Indeed fire is now regarded by some as the seventh soil-forming factor. Here we explore the effects of fire on soils as influenced by human interference. Human-induced fires have shaped our landscape for thousands of years and they are currently the most common fires in many parts of the world. We first give an overview of fire effect on soils and then focus specifically on (i) how traditional land-use practices involving fire, such as slash-and-burn or vegetation clearing, have affected and still are affecting soils; (ii) the effects of more modern uses of fire, such as fuel reduction or ecological burns, on soils; and (iii) the ongoing and potential future effects on soils of the complex interactions between human-induced land cover changes, climate warming and fire dynamics.This article is part of the themed issue ‘The interaction of fire and mankind’.

Concepts: Effect, Soil, Affect, Erosion, Surface runoff, Geomorphology, Deforestation, Desertification

2

Recently, there has been increasing concern about adverse health effects of exposure to desert dust events. However, the association between dust and the incidence of ischemic heart diseases is unknown. The aim of the present study was to elucidate whether Asian dust (AD), a windblown sand dust originating from mineral soil in China and Mongolia, is associated with the incidence of acute myocardial infarction (AMI).

Concepts: Epidemiology, Myocardial infarction, Heart, Stroke, People's Republic of China, Necrosis, Ischaemic heart disease, Desertification

1

Maps of abiotic stresses for rice can be useful for (1) prioritizing research and (2) identifying stress hotspots, for directing technologies and varieties to those areas where they are most needed. Large-scale maps of stresses are not available for Africa. This paper considers four abiotic stresses relevant for rice in Africa (drought, cold, iron toxicity and salinity/sodicity). Maps showing hotspots of the stresses, the countries most affected and total potentially affected area are presented. In terms of relative importance, the study identified drought as the most important stress (33% of rice area potentially affected), followed by iron toxicity (12%) and then cold (7%) and salinity/sodicity (2%). Hotspots for iron toxicity, cold and salinity are identified. For drought, local variation along the hydromorphic zone was a stronger determinant than larger-scale climatic variation, therefore mapping of drought based on climatic zones has only limited value. Uncertainties in the mappings are discussed.

Concepts: Malnutrition, Map, Madagascar, Kenya, Sudan, World War II, Prehistory, Desertification