David S. G. Thomas

David S. G. Thomas
University of Oxford | OX · School of Geography and the Environment

MA, DPhil, Cert. Ed.

About

283
Publications
58,116
Reads
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14,740
Citations
Additional affiliations
September 2006 - present
University of Cape Town
Description
  • Honorary Professor
June 2004 - present
University of Oxford
September 1984 - June 2004
The University of Sheffield
Description
  • Professor, Head of Department

Publications

Publications (283)
Article
Full-text available
Determining the controls on aeolian dust emissions from major sources is necessary for reliable quantification of atmospheric aerosol concentrations and fluxes. However, ground-based measurements of dust emissions at-source are rare and of generally short duration, failing to capture the annual cycle. Here, we provide new insights into dust dynamic...
Article
Full-text available
Identifying the environmental drivers of the global distribution of succulent plants using the Crassulacean acid metabolism pathway of photosynthesis has previously been investigated through ensemble-modeling of species delimiting the realized niche of the natural succulent biome. An alternative approach, which may provide further insight into the...
Article
Ocean-based photosynthesis accounts for half of global primary production. Productivity rates, driven by phytoplanktonic responses to nutrient availability, are however highly variable both spatially and temporally throughout the oceans. Intense primary production in the ocean's most productive areas, the Eastern Boundary Upwelling Systems (EBUS),...
Article
Dryland fluvial systems respond to hydroclimate changes on Quaternary timescales, yet deciphering the palaeoenvironmental histories they preserve is often complex. Whilst hydrological signals are preserved in sediment stores as variations in sediment amount, character and composition, studies in dryland settings such as Namibia that link sedimentol...
Article
The timing and extent of Late Quaternary climate and environmental changes in the Arabian Peninsula were critical for human demographic changes. High resolution palaeoclimate archives suggest that monsoon variability was a key driver of change, but these records obscure environmental heterogeneity at finer spatial scales. Recent decades have seen t...
Article
Full-text available
With one of the largest watersheds in Europe draining complex geological terrains within the Alps, Bohemian Massif, Carpathians, Dinarides, and the Balkan Mountains, the Danube River valley has long been linked to the formation of thick loess deposits, particularly within the Middle and Lower Danube basins. However, uncertainty over the provenance...
Article
In Central and Eastern Europe, research has been focused on loess associated with a plateau-setting, which preserves distinct and well-developed loess and palaeosol units linked to orbital scale changes. This has led to the view that during the last glacial period the Middle and Lower Danube predominantly experienced dry continental climates and su...
Article
Crassulacean Acid Metabolism (CAM) plants have the potential to provide future-proof biomass growth under increasingly stressed climatic conditions. Using active cultivation and anaerobic digestion, CAM plants can be grown and fermented to produce biogas or hydrolysed to extract valuable volatile fatty acids (VFAs) which can be applied to a range o...
Article
Full-text available
While there are numerous thick loess-palaeosol sequences preserved across the Carpathian Basin, well dated sites that provide terrestrial palaeoenvironmental records extending beyond last glacial-interglacial cycle are scarce. Robust chronologies are essential for correlations of loess with other long-term Quaternary records and to further understa...
Article
Full-text available
Despite numerous palaeoenvironmental investigations of loess–palaeosol sequences across the Carpathian Basin, well‐dated high‐resolution records are scarce. This paper presents a new high‐resolution chronology for the loess‐palaeosol sequence at Surduk (Serbia), based on optically stimulated luminescence (quartz) and post‐infrared infrared stimulat...
Article
Due to the scarcity of geochemical and palaeoecological proxies in drylands, dunes have often been used as geoproxies for late Quaternary palaeoenvironmental reconstruction, with chronologies commonly provided by luminescence dating. Owing to their widespread occurrence and location in a monsoonal regime, dunes in the Thar Desert in South Asia act...
Article
Asia possesses many extensive desert dune systems within the northern hemisphere subtropical belt and more northerly continental drylands. Collectively these may preserve important sedimentary records of dune system responses to climatic and environmental changes in the Quaternary period. We use the Accumulation Intensity (AI) methodology, which qu...
Article
Linear dunes are the most widespread dune type worldwide and act as important geoproxies of late Quaternary environmental change in deserts. They are less common in the Thar Desert, India than other dune types, especially parabolic forms, and to date their development history is poorly understood. Here we investigate a linear dunefield in the north...
Article
Full-text available
Understanding the historical activity of desert dune systems is important for identifying both the palaeoenvironmental drivers of change and the likelihood of future reactivation. Dating dune sediments in the Nebraska Sandhills has identified regional‐scale dune activity over centennial and millennial timescales during the Holocene, occurring at 9....
Data
Supplmentary info file for article "Using post-IR IRSL and OSL to date young (< 200 yrs) dryland aeolian dune deposits"
Article
Full-text available
Determining the most appropriate luminescence protocol, coupled with suitable data processing methods, for dating recently deposited sediments (<200 years) is important for identifying episodes of sediment movement and interpreting historical landscape dynamics. Issues of partial bleaching, dim luminescence signals and the incorrect application of...
Article
Full-text available
Land degradation and sediment remobilisation in dryland environments is considered to be a significant global environmental problem. Given the potential for currently stabilised dune systems to reactivate under climate change and increased anthropogenic pressures, identifying the role of external disturbances in driving geomorphic response is vital...
Article
Single grain OSL dating has been used to produce new chronologies for three previously investigated sites in the northern Kalahari basin in western Zambia containing both Middle and Later Stone Age material (Phillipson, 1975a, b). We find that Mode 3 (Middle Stone Age, MSA) assemblages in the Upper Zambezi Valley pre-date the Last Glacial Maximum....
Article
The Thar Desert dune system in north‐west India and eastern Pakistan provides a rich archive of past environmental, geomorphological and climatic change. Much of the knowledge about the timing of dune accumulation in the Thar stems from scattered and sporadic records, based on older luminescence dating protocols. If the Thar dune record is to be in...
Article
Sand ramps occur on a continuum of topographically-controlled landforms, ranging from purely aeolian features (climbing/falling dunes) to talus cones and alluvial fans. Sand ramps have been identified as potentially important palaeoenvironmental archives in dryland regions that possess relatively few Quaternary proxy records. Their utility however...
Article
Full-text available
Delivery of nutrients to the ocean by mineral aerosol deposition involves complex biogeochemical interactions that include atmospheric processing, dissolution and biotic uptake of available nutrients in the surface waters. Research into the fertilization potential of aeolian dust is currently constrained by a lack of understanding of the nutrient c...
Article
Full-text available
Precession-forced change in insolation has driven de-intensification of the Asian Monsoon systems during the Holocene. Set against this backdrop of a weakening monsoon, Indus Civilisation populations occupied a number of urban settlements on the Ghaggar-Hakra plains during the mid-Holocene from 4.5 ka until they were abandoned by around 3.9 ka. Reg...
Article
Research into global hot-spots of dust emission has focused on exposed fine-grained sediments in palaeo- or ephemeral dryland lake basins including Etosha (Namibia) and Makgadikgadi (Botswana) in southern Africa. Namibia's western ephemeral river valleys are also known to produce dust but have remained largely overlooked as a regionally-significant...
Article
Luminescence dating of desert dune sediments has generated many hundreds of ages, many used in reconstructions of Quaternary environmental changes, others in attempts to elucidate dune processes. Environmental and climatic interpretations of these records have proved problematic and it remains challenging to test hypotheses of the systematic respon...
Article
Western Namibia is a significant global source of atmospheric mineral dust. We investigate the relationship between dust and source sediments, assessing the sustainability of dust flux. Remote sensing studies (Vickery and Eckhardt, 2013) have highlighted specific ephemeral fluvial systems as important contributors to dust flux, including highlighti...
Article
Full-text available
Research concerning the global distribution of aeolian dust sources has principally focussed on salt/clay pan and desiccated lacustrine emission areas. In southern Africa such sources are identified as Etosha Pan in northern Namibia and Makgadikgadi Pans in northern Botswana. Dust emitting from ephemeral river valleys, however, has been largely ove...
Article
Full-text available
The Anthropocene is proposed as a new interval of geological time in which human influence on Earth and its geological record dominates over natural processes. A major challenge in demarcating the Anthropocene is that the balance between human-influenced and natural processes varies over spatial and temporal scales owing to the inherent variability...
Article
Full-text available
The INQUA Dunes Atlas project has developed a global digital database of chronological information for periods of inland or continental sand dune accumulation and stabilization. The database comprises information on the site location (including coordinates), dune type, and stratigraphic context, pertinent analytical information (e.g. luminescence p...
Article
Full-text available
Sodium accumulating playas (also termed sodic or natric playas) are typically covered by polygonal crusts with different pattern characteristics, but little is known about the short-term (hours) dynamics of these patterns or how pore water may respond to or drive changing salt crust patterning and surface roughness. It is important to understand th...
Technical Report
Full-text available
1. Ган, зуд зэрэг байгалийн гамшигт үзэгдлийн үр дагаврыг сааруулахад нүүдэл нь үр дүнтэй, өвөрмөц арга зам болохыг зарим судалгаа харуулав 2. (Тайлбар). Нүүдэл нь бэлчээрт үзүүлж буй ачааллыг багасгах (сэлгэх, нөхөн сэргээх хугацааг олгох), биологийн төрөл зүйлийг хамгаалах 3,4 , үнэ өртөг өндөр шаардагдсан нэмэлт тэжээл бэлтгэх зардлыг бууруулах...
Article
Full-text available
Environmental change poses risks to societies, including disrupting social and economic systems such as migration. At the same time, migration is an effective adaptation to environmental and other risks. We review novel science on interactions between migration, environmental risks and climate change. We highlight emergent findings, including how d...
Conference Paper
Full-text available
Playas are ephemeral, endorheic lake systems that are common arid regions which have been identified as both regionally and globally significant sources of mineral dust. Emissions of dust from large playas can therefore impact significantly on regional climate through a range of land/atmosphere interactions. Nevertheless our understanding of spatia...
Conference Paper
Playas are ephemeral, endorheic lake systems that are common arid regions which have been identified as both regionally and globally significant sources of mineral dust. Emissions of dust from large playas can therefore impact significantly on regional climate through a range of land/atmosphere interactions. Nevertheless our understanding of spatia...
Article
Full-text available
An early-to mid-Holocene humid phase has been identified in various Arabian geo-archives, although significant regional heterogeneity has been reported in the onset, duration and stability of this period. A multi-proxy lake and dune record from Wahalah in the United Arab Emirates (UAE) documents significant variations in hydrology, biological produ...
Article
Full-text available
Within the framework of the Dust Observations for Models (DO4Models) project, the performance of three commonly used dust emission schemes is investigated in this paper using a box model environment. We constrain the model with field data (surface and dust particle properties as well as meteorological parameters) obtained from a dry lake bed with a...
Article
Full-text available
Playas are common in arid environments and can be major sources of mineral dust that can influence global climate. These landforms typically form crusts that limit evaporation and dust emission, modify surface erosivity and erodibility, and can lead to over prediction or underprediction of (1) dust-emission potential and (2) water and heat fluxes i...
Article
Full-text available
The winter of 2009/2010 induced a mass loss of livestock known as dzud in Mongolia. We examine spatial heterogeneity in this livestock loss in a western Mongolian province using a semi-structured questionnaire, key informant interviews, meteorological station data, and two datasets derived from satellite imagery. We identify marked local variabilit...
Article
A series of small, shallow seasonally, or interannually, waterlogged depressions (dambos) in the upper Zambezi Valley in western Zambia hold shallow peat deposits and are bounded on their western margin by sandy lunette dunes. Using luminescence dating of sands, fossil pollen analyses and the macrocharcoal record from cored peat, the long-term stab...
Conference Paper
Full-text available
The INQUA Dunes Atlas project has developed a global digital database of chronologic information for periods of desert sand dune accumulation and stabilization. The database currently contains 3278 luminescence and 535 radiocarbon records of directly dated periods of aeolian sand deposition from 1200 inland dune locations throughout the world, most...
Chapter
Introduction Since our human lineage evolved in the open woodlands and grasslands of Africa, savanna landscape images may lie in our genetic memory and, indeed, may be subliminally familiar to us all. Certainly they are among the more wide-spread of the global zonal systems that are known as major biomes and their extent and diversity lends importa...
Article
One of the fundamental questions in the reconstruction of Quaternary dryland environmental conditions is: what do dune OSL ages mean in terms of palaeoenvironmental change? This paper investigates the relationship between dune chronological records and external environmental forcing in the southern Arabian Peninsula during the last 30 ka. Aeolian r...
Article
Full-text available
Within the framework of the Dust Observations for Models (DO4Models) project, the performance of three commonly used dust emissions schemes is investigated in this paper using a box model environment. We constrain the model with field data (surface and dust particle properties as well as meteorological parameters) obtained from a dry lake bed with...
Article
Full-text available
The Namib Sand Sea in southern Africa offers an ideal location in which to consider general questions about the evolution of sand seas, about the fluxes of sand through contemporary dune fields and about the patterns of dune form that are created. This paper aims to provide a concise account of the approaches and techniques that are currently being...
Article
Attempts to reconstruct past changes in climate-related forcing of dryland landscapes are hampered by the lack of an adequate quantitative framework for understanding the production and interpretation of dated sedimentary records. In drylands, as in other environments, information on past forcing conditions is progressively modified, degraded and r...
Article
Salinization caused by irrigation mismanagement is a major cause of desertification. Monitoring of land degradation caused by salinization and other processes has been subject to international scientific debates leading to the commitment by global decision-makers to address these threats collectively through the UNCCD. This paper discusses the expe...
Article
Full-text available
Playas are common in arid environments and can be major sources of mineral dust that can influence global climate. These landforms typically form crusts that limit evaporation and dust emission, modify surface erosivity and erodibility, and can lead to over prediction or underprediction of (1) dust-emission potential and (2) water and heat fluxes i...
Article
Full-text available
Surface roughness plays a key role in determining aerodynamic roughness length (zo) and shear velocity, both of which are fundamental for determining wind erosion threshold and potential. Whilst zo can be quantified from wind measurements, large proportions of wind erosion prone surfaces remain too remote for this to be a viable approach. Alternati...
Article
A lack of knowledge of the underlying stratigraphy is often cited as a limitation of dunefield optically stimulated luminescence (OSL) sampling campaigns. Here we examine the role of allostratigraphy in characterising aeolian structural sequences, and the implications of the relationship between visible internal structure and dune accumulation chro...
Article
The distributions of optically stimulated luminescence (OSL) ages from dunes are affected by palaeoenvironmental changes, complex dune dynamics and sampling strategy. Extracting the relative importance of these factors when interpreting discontinuous OSL chronologies from sand dunes has proven difficult, and is particularly hindered in contexts whe...
Article
Over 600 luminescence ages have to date been published from southern Africa's continental dunefields and isolated dunes, providing a rich record of aeolian system dynamics during the Late Quaternary. The majority of records come from sites within the five linear dune-dominated dunefields of the Kalahari, with lesser representation of other major du...
Article
The major driver of palaeoclimatic dynamics over the southeast Arabian region is the varying latitudinal interface between the Westerly driven shamaal winds and a northward branch of the southwesterly Indian Ocean Summer Monsoon (IOM). At present, this latter system is restricted in extent to the southern coastal regions of Yemen and Oman. Monsoona...
Article
This article examines the problems of elite capture in community-driven development (CDD). Drawing on two case studies of non-governmental organisation (NGO) intervention in rural Mozambique, the authors consider two important variables – (1) the diverse and complex contributions of local elites to CDD in different locations and (2) the roles that...
Article
Post-disaster development policies, such as resettlement, can have major impacts on communities. This paper examines how and why people's livelihoods change as a result of resettlement, and relocated people's views of such changes, in the context of natural disasters. It presents two historically-grounded, comparative case studies of post-flood res...
Article
Dust Observations for Models (DO4Models) is a project designed to gather data from source regions at a scale appropriate to climate model grid box resolution. During the southern winter of 2011 and 2012 an array of automatic weather stations and dust monitoring instruments were deployed across Sua Pan in Botswana. Surface characteristics were also...