Makgadikgadi Research Articles

Dynamic primary resources, not just wild prey availability, underpin lion depredation of livestock in a savanna ecosystem.

Because it can lead to retaliatory killing, livestock depredation by large carnivores is among the foremost threats to carnivore conservation, and it severely impacts human well-being worldwide. Ongoing climate change can amplify these human-wildlife conflicts, but such issues are largely unexplored, though are becoming increasingly recognized. Here, we assessed how the availability of primary resources and wild prey interact to shape large carnivore selection for livestock rather than wild prey (i.e., via prey switching or apparent competition). Specifically, we combined remotely sensed estimates of primary resources (i.e., water availability and primary productivity), wild prey movement, and 7 years (2015-2021) of reports for livestock depredation by African lions (Panthera leo) in the Makgadikgadi Pans ecosystem, Botswana. Although livestock depredation did not vary between wet versus dry seasons, analyses at finer temporal scales revealed higher incidences of livestock depredation when primary production, water availability, and wild prey availability were lower, though the effects of wild prey availability were mediated by water availability. Increased precipitation also amplified livestock depredation events despite having no influence on wild prey availability. Our results suggest that livestock depredation is influenced by the diverse responses of livestock, wild prey, and lions to primary resource availability, a driver that is largely overlooked or oversimplified in studies of human-carnivore conflict. Our findings provide insight into tailoring potential conflict mitigation strategies to fine-scale changes in resource conditions to efficiently reduce conflict and support human livelihoods.

The astrobiological potential of the Makgadikgadi Basin, Botswana: Field analogue for planetary exploration

Terrestrial analogue sites have been crucial for studying Martian geology and mineralogy, integrating the direct evidence available from Mars through remote sensing and in situ measurements carried out by the instruments on board robotic missions. Studying readily available and accessible terrestrial analogues of Martian fossil or extant environments is considered the most efficient way to answer crucial scientific questions. These analogues offer opportunities to collect a range of geological and microbiological data. The Makgadikgadi Basin (MKB) in Botswana is one of such environments hosting a system of salt pans presenting striking similarities with Mars playa deposits. The MKB presents layered mounds, relict fan deltas with inverted channels, polygonal structures and evaporitic crusts harboring communities of extremophiles. The present-day MKB is predominantly fed by groundwater and local precipitations in an overall arid to semi-arid climate, characterized by high UV radiation and salinity, deposition of evaporitic minerals and authigenic clays. The shallow subsurface of the MKB pans is covered by diagenetic features (duricrusts) including silcretes and calcretes. These pans can serve as test beds for the physical and chemical characteristics of playa deposits on Mars and help improve our understanding of the conditions that might support life outside our planet.

Aerial photography and machine learning for estimating extremely high flamingo numbers on the Makgadikgadi Pans, Botswana

Monitoring biodiversity over time and space is essential for effective conservation of habitats, processes, and dependent organisms. Estimating large abundances of individuals can be challenging (e.g. birds and mammals), demanding efficient and effective methods. The Makgadikgadi Pans in north-eastern Botswana have high concentrations of breeding and feeding flamingos (Phoenicopterus roseus and Phoeniconaias minor), among the world’s most important breeding sites. No published estimates of flamingos exist since 2009, with historical estimates providing limited details on methods. We developed a semi-supervised machine learning method for counting a large feeding concentration of flamingos (2 June 2019) in aerial photographs from northern Sua Pan of the Makgadikgadi Pans. We also analysed rainfall and flooding frequency and extent, using satellite imagery, estimating likely frequency of these flamingo concentrations. Lastly, we reviewed the site’s global importance as flamingo breeding habitat. Our analysis successfully provided an estimate of 372,172 to 689,473 flamingos, with methods producing over 97 % test accuracy. Uncertainty related primarily to data coverage and collection rather than methodology. This estimate underlined the Makgadikgadi Pans’ significance for flamingos, supported by a high frequency of flooding (>5:10 years). Sua Pan ranked in the top ten breeding sites for the lesser and greater flamingos in the world. These methods can be applied to other large concentrations of flamingos and other animals. Our techniques provide considerable promise for tracking flamingo populations to ensure their protection. We provide code, for use in Google Earth Engine.

Geomorphology of the Makgadikgadi Basin (Botswana): Insight Into the Propagation of the East African Rift System

AbstractThe Southwestern Branch of the East African Rift System propagates through the Central and Southern African plateaus and ends in the Okavango Makgadikgadi Zambezi Basin. This basin hosts the Okavango Graben and the Eiseb Graben, considered as the terminus of the Southwestern Branch of the rift. To the southeast, the Makgadikgadi Basin is affected by a series of normal faults forming the Makgadikgadi Rift Zone (MRZ) which regional geodynamic significance remains unclear. Based on fieldwork and geomorphic analysis, we revisited the geomorphological features associated with paleolakes and the fault pattern within the Makgadikgadi Basin to better constrain the dynamics of the MRZ. Fault scarps and offsets along linear dunes show normal‐dip kinematics of faults, indicating a NW‐SE extension direction in the area. Furthermore, lacustrine shorelines in the basin are undeformed, proving that they post‐date the fault activity. The previously published ages of these shorelines demonstrate that the MRZ currently has a low tectonic activity. Integrated in the geodynamic framework of the region, these results suggest that present‐day deformation shifts toward the Okavango Graben north of the MRZ. We therefore propose a “zip‐opening” model to explain the propagation of the Southwestern Branch of the East African Rift System where the tip of the system progressively progresses southwestward, driven by motions of the continental plates.

Diversity of Microbial Mats in the Makgadikgadi Salt Pans, Botswana.

The Makgadikgadi Salt Pans are the remnants of a mega paleo-lake system in the central Kalahari, Botswana. Today, the Makgadikgadi Basin is an arid to semi-arid area receiving water of meteoric origin during the short, wet season. Large microbial mats, which support primary production, are formed due to desiccation during the dry season. This study aimed to characterise the microbial diversity of the microbial mats and the underlying sediment. The focus was the Ntwetwe Pan, located west of the Makgadikgadi Basin. Metagenomic analyses demonstrated that the mats consisted of a high relative abundance of Cyanobacteriota (synonym Cyanobacteria) (20.50-41.47%), Pseudomonadota (synonym Proteobacteria) (15.71 to 32.18%), and Actinomycetota (synonym Actinobacteria) (8.53-32.56%). In the underlying sediments, Pseudomonadota, Actinomycetota, and Euryarchaeota represented over 70% of the community. Localised fluctuations in water content and pH did not significantly affect the microbial diversity of the sediment or the mats.

Using the Perseverance MEDA-RDS to identify and track dust devils and dust-lifting gust fronts

In the framework of the Europlanet 2024 Research Infrastructure Transnational Access programme, a terrestrial field campaign was conducted from 29 September to 6 October 2021 in Makgadikgadi Salt Pans (Botswana). The main goal of the campaign was to study in situ the impact of the dust devils (DDs) on the observations made by the radiometer Radiation and Dust Sensor (RDS), which is part of the Mars Environmental Dynamics Analyzer instrument, on board NASA’s Mars 2020 Perseverance rover. Several DDs and dust lifting events caused by non-vortex wind gusts were detected using the RDS, and the different impacts of these events were analyzed in the observations. DD diameter, advection velocity, and trajectory were derived from the RDS observations, and then, panoramic videos of such events were used to validate these results. The instrument signal variations produced by dust lifting (by vortices or wind gusts) in Makgadikgadi Pans are similar to those observed on Mars with the RDS, showing the potential of this location as a Martian DD analog.

Validation of the generic name Prescottiella gen. nov. (Desmidiales, Zygnematophyceae): a rare African desmid

Prescottiella sudanensis is a rare, asymmetrical desmid currently known from only a few countries in equatorial Africa. During the present study, P. sudanensis cells were found in water samples from Vogel Pan located in the far north-eastern side of Namibia, thereby expanding the known geographical distribution of the species. The location of the sampling site, which is situated in a direct line halfway between the Makgadikgadi pans and Okavango Delta towards the east (Botswana) and the Etosha pans towards the west (Namibia), suggests that migrating birds are likely vectors spreading desmids from one waterbody to another. In this paper a morphological description (including dimensions) and micrographs of P. sudanensis are presented, and the known geographical distribution of the species is discussed in relation to migration routes of birds. As the genus and species names are invalid according to ICN Art. 40.1, the names are also validated in this paper.

Structural influences on groundwater circulation in the Makgadikgadi salt pans of Botswana? Implications for martian playa environments

Across the surface of Mars, evidence of past lacustrine and evaporitic environments has been found within basins and craters, where often layered sedimentary deposits and hydrated minerals are observed. However, the intensity, duration, and precise phases of aqueous processes during their deposition remain unresolved mostly for our inability to model subsurface structures. Although several geological processes and locations on Earth have been previously proposed as examples to describe these deposits on Mars, we lack a strong visualization of what water activity might have looked like during evaporitic stages within basins and craters. Here we propose to investigate the shallow subsurface of the Makgadikgadi salt pans of Botswana as a potential analog for understanding groundwater upwelling on Mars. The pans are found within the Makgadikgadi Basin, a depression located at the southwestern end of a northeast-southwest set of graben linked with the East African Rift. The Makgadikgadi Pans are evaporitic environment rich in hydrated minerals and groundwater activity. The purpose of this work is to identify buried faults and areas of relative water saturation within the lacustrine sediment of the Makgadikgadi Basin by means of electrical resistivity surveys. This work represents the first electrical resistivity survey of the basin floor which provides a precursory investigation of the relationship between groundwater, faults, basement depth, and the lacustrine sediments. We present four electrical survey lines from different locations in the pans which reveal distinct sedimentary units. Several faults are inferred from the vertical displacement of these units and accompanying low resistivity where displacement is observed. These results provide a framework for visualizing the sedimentary sequences of infilled basins and craters on Mars, which can broaden the ongoing discussion of hydrogeological processes that were active in the planet’s past. We propose Meridiani Planum, as well as Oyama and Becquerel crater of Arabia Terra as locations to establish this framework. Since such processes are still ongoing in the Makgadikgadi Basin, imaging the subsurface of the pans helps explain the formation of layered and salty deposits on the surface of Mars, how they may have interacted with flowing water, and whether they might have hosted life.

Factors leading to sub-surface pan silcrete formation in north-central Botswana

AbstractNew evidence was sought for sub-pan silcrete formation along the southern margin of Ntwetwe Pan in the Botswana Makgadikgadi basin. This was achieved by integrating drillhole and surface sample descriptions with element and isocon analysis. The silcrete deposit which lies ~1.0 m below the pan surface, comprises Ntane sandstone fragments and detrital infill, cemented by amorphous silica. The deposit probably evolved during sequential periods of palaeo-lake infilling and drying since at least the Mid-Pleistocene. Changes in basin water pH brought about during fresher water infill interspersed with brine evapo-concentration and later evaporative pumping, induced the mobilisation and precipitation of the silica cement immediately below the pan floor.

Post-depositional disturbance and spatial organization at exposed open-air sites: Examples from the Middle Stone Age of the Makgadikgadi Basin, Botswana

The influence of natural factors such as bioturbation or sediment movement caused by wind and water is a perennial concern for Stone Age site selection and subsequent interpretation. This paper discusses the spatial artefact distribution of five recently excavated, open-air exposed Middle Stone Age (MSA) sites in Ntwetwe Pan, Botswana. The finds comprise lithic assemblages dominated by MSA points, manufactured in a variety of silcretes. The sites were examined following the assumption that archaeological sites are the product of a combination of natural and cultural factors, occurring both during and after artefacts are deposited. The results indicate that some of these exposed pan floor sites do preserve cultural artefact distribution patterns, and that the level of post-depositional disturbance varies locally. Refitting was an important tool of analysis, especially on the largest site, MAK33, where it was possible to identify working areas that focussed on different modes of lithic manufacture. In combination with a chaîne opératoire analysis of lithic production stages, it was then possible to map movement of artefacts across the site. We argue that the spatial organization of open-air sites may preserve behavioural records that are not present at caves and rock shelters, and provide a view into the short-term, single-use locations that likely formed the basis of MSA occupation patterns.

Making Points: The Middle Stone Age lithic industry of the Makgadikgadi Basin, Botswana

Studies of early human occupation of Africa over recent decades have profoundly changed how we understand our early ancestors, their inventiveness and adaptability. The spread of Homo sapiens to new environmental settings, the expansion of diet breadth, the development of more complex technology and the use of personal ornaments have all been recognized at well-documented Middle Stone Age (MSA) cave and shelter sites, particularly along the South African coast. This paper addresses two under-represented aspects of MSA research: open-air sites and the African interior. We present here recent surveys and excavations in Ntwetwe Pan, Botswana, a remote, open landscape, that formerly contained a vast palaeolake. The five excavated sites yielded assemblages composed exclusively of silcrete, a locally available raw material. The lithic industry at these sites was deposited during dry periods following palaeolake high stands dating to c.128–81 ka and c. 72–57 ka. This industry, characterized by a limited toolkit dominated by highly retouched unifacial and bifacial points, is not previously documented but shows similarities to dated MSA sites of equivalent age in north-western Botswana and Zimbabwe. Combined, these exposed open-air sites document the successful MSA adaptation to a hydrologically dynamic, interior landscape and arguably display MSA behavioural patterns that complement and balance the more well-documented perspectives from coastal cave and shelter sites.

Fault controlled geometries by inherited tectonic texture at the southern end of the East African Rift System in the Makgadikgadi Basin, northeastern Botswana

One of the three narrow rift belts that mark the southern end of the East African Rift System (EARS) intersects the Makgadikgadi Basin of northeastern Botswana. Although tectonic activity in the region is known to have influenced the evolution of these pans, the interrelationship between shoreline geometry, fault strikes, and the intersection of the underlying tectonic terranes has yet to be fully realized. We analyzed faults and subsurface structures in the region of the pans using a field investigation in combination with satellite imagery and geophysical data, to constrain the influence that the regional tectonic regime has had on the formation of the present-day pan geometry. We find that pan shorelines are controlled by the intersection of three preferred fault orientations which can be understood in the context of the “older” terranes they overlie, namely the Magondi Belt and the Limpopo Belt. We propose that the pronounced curvature of the southern Magondi Belt has influenced the eastward curvature of the rift-related faults and was likely produced by the impingement of the developing fold belt on the Zimbabwe Craton. Furthermore, limited focal mechanism solutions data from earthquakes north and south of the pans suggests a change in regional extension direction from NW-SE to NE-SW. Determining the relationship between these fault orientations and the underlying tectonic terrains is an important step in understanding the formation of the Makgadikgadi Basin, and more broadly the current tectonic regime of Botswana. The evidence of fault-controlled shorelines within an evaporitic environment may also have implications for regional groundwater activity.

Mapping Middle Stone Age human mobility in the Makgadikgadi Pans (Botswana) through multi-site geochemical provenancing of silcrete artefacts

Analyses of the distance over which lithic raw materials were transported for use in stone tool production provide important insights into early human mobility through prehistoric landscapes. This study combines the use of geochemical provenancing, chaîne opératoire analysis and geochronology to examine patterns of lithic raw material procurement at five single-use open-air Middle Stone Age (MSA) archaeological sites in Ntwetwe Pan, part of the Makgadikgadi Pans complex in north-central Botswana. Maximum ages of the five sites ranged from 106 ± 3 to 69 ± 7 ka, with site formation thought to have occurred before and after a lake high stand dated to c. 72-57 ka. Tool manufacture at all sites was largely confined to the production of MSA points, with silcrete used exclusively as the raw material. Geochemical provenancing investigations aimed to identify the specific silcrete outcrops used as lithic raw material sources. Analysis of contemporary pan floor deposits show that sediment (and hence silcrete) geochemistry in Ntwetwe is determined by the proportional sediment input into the pan from fluvial systems with different catchment geologies. Immobile trace element signatures for 46 waste manufacturing flakes were compared against equivalent data for 321 silcrete samples collected at outcrops within and beyond Ntwetwe Pan. Waste flakes were chosen to be representative of the main silcrete raw material types present within the artefact assemblage at each site. Fifteen waste flakes were shown to match specific outcrops on the basis of their geochemical signatures and petrographic properties; all matching outcrops were within Ntwetwe Pan, at distances ranging from 7 to 55 km from individual sites. Multi-site analysis of procurement patterns identifies common silcrete source areas, revealing a preference for silcrete from particular locations within Ntwetwe Pan. Given that the five archaeological sites were likely occupied at different times, this resource preference may have been a longer-term behavioural feature of MSA populations in the Ntwetwe region. The distances over which silcrete was transported in Ntwetwe Pan are smaller than identified in investigations at similar-aged MSA sites in northwest Botswana. The reasons for the different silcrete procurement ranges in the two regions are likely related to silcrete availability and/or raw material preference, but this requires further investigation.

Lacustrine geoarchaeology in the central Kalahari: Implications for Middle Stone Age behaviour and adaptation in dryland conditions

The Middle Stone Age (MSA) was a time of great human adaptation and innovation. In southern Africa, coastal locations have been viewed as key places for the development of human resource use and behaviour, with the dryness of the continental interior after c.130 ka regarded as both an obstacle to occupation and a limit on behaviour. Newly excavated MSA sites on the floor of the now-dry palaeolake Makgadikgadi basin, central Botswana, along with accompanying environmental data, have provided a significant opportunity to reassess the nature of MSA adaptation to, and behaviour under, dry conditions. Excavated sites dated to 80–72 ka and post 57 ka reveal purposeful early human use of an extensive 60,000 km2 lacustrine basin during dry, as opposed to lake-high, phases, as well as highlighting movement strategies for tool-making resource procurement. Findings have significant implications for theories of early human mobility and innovation, as well as for understanding the drivers, constraints and opportunities for the use of drylands. The deliberate selective movement of lithic raw materials within the basin for artefact manufacture evidences thoughtful adaptation to dry conditions within the lake basin. This research shows that open-air sites in the Kalahari drylands of central southern Africa can make important contributions to debates surrounding the development of human-environment relationships during the MSA, as well as challenging narratives of a hostile and largely empty landscape.

Lessons from a lakebed: unpicking hydrological change and early human landscape use in the Makgadikgadi basin, Botswana

The intersection of archaeological material with the landscape is investigated using OSL dating of landforms associated with Middle Stone Age (MSA) archaeology in the Makgadikgadi basin, Botswana. In this study, MSA archaeological sites on the Makgadikgadi pan floor date to two dry periods in the basin during the late Quaternary. Site formation at one site occurred during dry, or seasonally dry conditions that followed a period of high lake levels between 128 ± 18 ka and 81 ± 6 ka. The site was buried by sediments from a subsequent period of high lake levels dating to between 72 ± 5 ka and 57 ± 8 ka. At other investigated sites, the archaeological material was most likely deposited during a second dry period sometime after this. Overlying dunes are much younger (late Holocene) than the late Pleistocene lakebed sediments associated with the archaeological sites. Rapid burial of the archaeological sites by clayey sands has resulted in limited disturbance and weathering of archaeological material which appears to have only been exposed very recently, perhaps in the last 350 years when conditions have been particularly dry and susceptible to deflation. The spatial patterning of both sediment accumulation and deflation strongly influences archaeological visibility both within and around the Makgadikgadi basin.

Late Pleistocene–Holocene Palaeoenvironmental Evolution of the Makgadikgadi Basin, Central Kalahari, Botswana: New Evidence From Shallow Sediments and Ostracod Fauna

The Makgadikgadi Basin in Botswana hosts a system of salt lakes, which developed from the Upper Pleistocene onward due to the gradual shrinking of the giant Lake Palaeo-Makgadikgadi. Stratigraphic and palaeoclimatic studies of this area are difficult due to the influence of several factors, such as a complex history of regional tectonic activities, as well as climatic changes coupled with dryland diagenetic processes. This lake, in the central Kalahari, is the key to understanding the climatic variability in the southern part of Africa in the Quaternary and has played an important role in the evolution of numerous taxa, including our own. In this study, detailed sedimentological analyses (grain size and major elements distribution) of shallow sediments from the Makgadikgadi Pans were combined with the first comprehensive study of the encountered ostracod fauna to establish trends in the environmental changes in the area from the late Quaternary. Ostracod fossil assemblages from the cores of the Makgadikgadi Pans are dominated by theLimnocytheressp., an opportunistic taxa commonly colonizing the littoral areas of shallow evaporative, ephemeral lakes, together with the subordinate occurrences ofSarcypridopsis ochracea,Sclerocypriscf.bicornis, Candonopsisspp., andIlyocyprisspp. The sediments from the pans show fluctuations in the Cl/K and Ca/Cl ratios, often in phase with the relative abundance ofLimnocytheresuggesting a cyclicity induced by changes of salinity and alkalinity in the water. This multi-proxy study of the cores collected from the pans suggests a Late Pleistocene shallow, playa lake environment with strongly alkaline water, interrupted by a prolonged drought with sustained aeolian conditions between ∼16 and 2 ka BP. Increasing diversity of ostracod fauna in the top 20–30 cm of the cores indicates that a temporary shift toward higher humidity occurred around 2–1.5 ka BP and lasted through the Medieval Warm Period. This humid period was followed by an overall desiccation trend that started with the Little Ice Age and continues until the present day.

Effects of artificial water provision on migratory blue wildebeest and zebra in the Makgadikgadi Pans ecosystem, Botswana

In migratory tropical ecosystems governed by water availability, artificially altering water availability can affect herbivore distribution and movement. The Makgadikgadi Pans, Botswana, sustains approximately 10,000 blue wildebeest (Connochaetes taurinus) and 24,000 plains zebra (Equus quagga) migrating between a dry season range with permanent water and a rainy season range with productive grasses. Artificial water points (AWPs) have been created by pumping some natural waterholes in the rainy season range. We combined data from aerial surveys and from GPS collars on 20 and 12 zebra pre- and post-AWP installation, respectively, and on 17 wildebeest post-AWP, to test hypotheses relating to large- and small-scale movement patterns. Post-AWP, a higher proportion of wildebeest, but not zebra, were in the rainy season range during the dry season. Post-AWP zebra migration to their rainy season range occurred longer after rainfall cessation than pre-AWP, though this period was still shorter than that of wildebeest (one month compared to three). The effect of proximity to waterholes on probability of space use varied seasonally for both species and followed opposing trends, suggesting resource partitioning or competition effects. Both species visited AWPs more than natural waterholes, particularly wildebeest in the dry season. Wildebeest movement patterns were more likely to be disturbed by AWPs, which could cause the development of residency and reduce population resilience. Management interventions, such as AWPs, can affect species to different extents, so the responses of several species should be assessed to determine the level of disturbance to migratory ecosystem resilience and functioning.

Fault Controlled Geometries by Inherited Tectonic Texture at the Southern End of the East African Rift System in the Makgadikgadi Pans, Northeastern Botswana

Fault Controlled Geometries by Inherited Tectonic Texture at the Southern End of the East African Rift System in the Makgadikgadi Pans, Northeastern Botswana

Uneven surface moisture as a driver of dune formation on ephemeral lake beds under conditions similar to the present day: A model‐based assessment from the Makgadikgadi Basin, northern Botswana

AbstractAn association between salt pans or dry lake beds and distinctive crescentic lake‐floor sand mounds (1–10 m high, tens to hundreds of metres wide) is commonplace in desert systems. In the Makgadikgadi Basin of northern Botswana, a debate about the formative processes of these landforms has persisted despite numerous morphometric, sedimentary and geochronological analyses, with mound landforms variously inferred to be aeolian dunes, subaqueous dunes, spring mounds or shoreline remnants. We propose a new formative mechanism which draws on the interaction between uneven moisture distribution on the pan surface and mobile aeolian sediments. We use a numerical model (ViSTA), which couples vegetation and aeolian sand transport dynamics, together with optically stimulated luminescence (OSL) dating of a mound in the Makgadikgadi Basin to investigate the feasibility of this ‘sticky mound hypothesis’. We find that under a range of modelled environmental conditions, uneven moisture distribution on the pan surface can lead to the development and stabilization of crescentic aeolian dunes, with these dunes growing upwind from the point of initial deposition, corresponding with the chronological data gained from OSL dating of a mound feature. On removal of this moisture, the modelled dunes erode and dissipate. These findings suggest that the formative mechanism of the mounds could be dependent on the interaction between differential drying of the pan surface and the competence of the aeolian sediment transport system across the pan floor.

Complete Genome Sequence of an Antimicrobial-Producing Bacillus velezensis Sam8H1 Isolate from the Makgadikgadi Saltpans of Botswana

The global antimicrobial drug resistance crisis requires urgency in searching for more effective broad-spectrum antimicrobial drugs. Here, we present a complete circular genome sequence and a plasmid of an antimicrobial-producing isolate, Bacillus velezensis strain Sam8H1, from the Makgadikgadi saltpans in Botswana. Bioinformatic analyses revealed 12 putative secondary metabolite biosynthetic gene clusters important for genome-guided drug discovery studies.