David William Hedding

University of South Africa | unisa · Department of Geography

Highest and percentile values determined for daily, hourly and 5-min rainfall data (July 1994 to June 2021) from 64 automatic weather stations across South Africa were used to define extreme hourly and 5-min rainfall intensity. Internationally, 99.9th and 99.99th percentiles are typically considered as thresholds for hourly and sub-hourly extreme r...

Excessive tree mortality is a global concern and remains poorly understood as it is a complex phenomenon. We lack global and temporally continuous coverage on tree mortality data. Ground-based observations on tree mortality, e.g., derived from national inventories, are very sparse, not standardized and not spatially explicit. Earth observation data...

Radiocarbon dating of basal peats has been a key factor in determining minimum ages for deglaciation on sub‐Antarctic islands. On Marion Island, peat bogs dominate the landscape below 300 m a.s.l., and palynological assessments of peat cores have been used to assess the vegetation history and succession rates as well as the sensitivity of the indig...

Biodiversity patterns are shaped by the interplay between geodiversity and organismal characteristics. Superimposing genetic structure onto landscape heterogeneity (i.e., landscape genetics) can help to disentangle their interactions and better understand population dynamics. Previous studies on the sub‐Antarctic Prince Edward Islands (located midw...

Plain Language Summary Unraveling the provenance of aeolian dust deposited in the oceans is critical for understanding marine biogeochemical cycles, past climate changes, and dust transport mechanisms. Here we measured the (²³⁴U/²³⁸U) activity ratio of marine sediments in the North Pacific Ocean to understand the source and pre‐deposition time of d...

In active mountains, landslides are the primary agent of erosion that readily generates materials with high weatherability. Understanding the linkage between landslide activity, erosion, and chemical weathering is critical for assessing how tectonic uplift affects the carbon cycle and Earth's climate. However, quantifying the contribution to chemic...

To effectively reduce CO2 emissions, it’s vital to identify and quantify their sources. While the focus has been on CO2 from fossil fuel combustion, especially coal, the CO2 produced from coal’s other elements, such as sulfur, through chemical reaction, remains an ‘invisible’ carbon source. We analyzed the invisible carbon flux due to coal burning...

The aeolian loess deposits in northeastern China have substantial potential for reconstructing the paleoclimate in the East Asian monsoon boundary zone. Identifying the source of the aeolian dust is crucial to interpret the paleo-proxies recorded in the loess deposits in northeastern China; however, traditional geochemical tracers such as Nd and Sr...

Background: Editorial board members of academic journals are often considered gatekeepers of knowledge and role models for the community. Editorial boards should have sufficiently diverse backgrounds to facilitate the publication of manuscripts with a wide range of research paradigms, methods, and cultural perspectives. Objectives: This study crit...

Background: Members of editorial boards of academic journals are often considered gatekeepers of knowledge and role models for the academic community. Editorial boards should be sufficiently diverse in the background of their members to facilitate publishing manuscripts representing a wide range of research paradigms, methods, and cultural perspect...

Researchers of projects at the sub-Antarctic Prince Edward Islands are increasingly considering geospatial data as an essential component in answering scientific questions. A need exists for high-resolution geospatial data in both multi- and transdisciplinary research to better analyse fine-scale biotic–abiotic interactions of the Islands’ landscap...

Sub-Antarctic Marion Island's glacial history has acted as a control on abiotic terrestrial processes and the colonization and distribution of biotic species found on the island today. Recent chronological studies have shown an early deglaciation of the island and identified new geomorphological features associated with past ice dynamics. These per...

Extreme changes in temperature, rainfall and wind regimes have been correlated with plant species range expansion upslope on sub‐Antarctic islands. Ongoing climatic changes are expected to continue driving changes in species distributions globally, but niche specialisations may limit the capacity for range shifts. We hypothesised that non‐climatic...

Several factors may drive bird nest‐site selection, including predation risk, resource availability, weather conditions, and interaction with other individuals. Understanding the drivers affecting where birds nest is important for conservation planning, especially where environmental change may alter the distribution of suitable nest sites. This st...

Background: Editorial board members of academic journals are often considered gatekeepers of knowledge and role models for the community. Editorial boards should have sufficiently diverse backgrounds to facilitate the publication of manuscripts with a wide range of research paradigms, methods, and cultural perspectives.Objectives: This study critic...

Gully erosion can reach alarming dimensions, and in several cases contributes significantly to soil loss and sediment yield in catchments. The studied example is one of the largest known gully networks in the world (its surface area is approximately 0.5 million m ² and volume 5 million m ³ ), more than twice as large compared to the largest gullies...

Projecting future changes in effective precipitation under global warming, which requires constraints on both the precipitation and evapotranspiration, is still challenging in the semi‐arid region of East Asia. Here we present proxies, based on Sr/Ca and ⁸⁷Sr/⁸⁶Sr of soil carbonate, to reconstruct the evolution of both effective precipitation and t...

Since the discovery of glacial features on sub-Antarctic Marion Island, the character and extent of a historic glacial period have remained an important research focus for earth science investigations. Previous glacial reconstructions were limited to mostly pre-GPS field observations and pre-digital mapping through a Geographic Information System....

Questions Species distribution models have traditionally relied heavily on temperature and precipitation, often ignoring other potentially important variables. However, recent advances have shown other climatic variables, including snow cover and solar radiation, may strongly improve predictions of species occurrence. Wind has long been known to ha...

Lithium isotopes show great potential to trace Earth surface processes due to the large mass discrimination between 6Li and 7Li associated with clay uptake. However, factors controlling the Li isotopic composition (δ7Li) of river water, especially those with a water-bedrock δ7Li difference higher than that of the equilibrium fractionation associate...

Weathering plays a significant role in the Earth system through the exchange of material among the lithosphere, atmosphere, hydrosphere, and biosphere. Variation of continental weathering in deep-time, however, remains elusive. This work investigates continental weathering recorded by detrital zircon. Zircon can record the oxygen isotopic compositi...

One manifestation of the glaring lack of equality, diversity and inclusion in higher education relates to the underrepresentation of certain individuals and/or regions in the scholarly publication process. Here, we analyse the affiliations of editorial board members in 126 Geography journals. Specifically, we examine editorial board membership by r...

Background: Open access (OA) implies free and unrestricted access to and re-use of research articles. Recently, OA publishing has seen a new wave of interest, debate, and practices surrounding that mode of publishing. Obj ectives: To provide an overview of publication practices and to compare them among six countries across the world to stimulate f...

Volcanological maps of the sub-Antarctic Prince Edward Islands were first published in 1968, with a revised surface geology map of Marion Island produced in 2006. These maps have been widely used in terrestrial studies on the Prince Edward Islands but they have limitations in spatial accuracy and detail. Using high-resolution satellite imagery and...

The effects of temperature and precipitation, and the impacts of changes in these climatic conditions, on plant communities have been investigated extensively. The roles of other climatic factors are, however, comparatively poorly understood, despite potentially also strongly structuring community patterns. Wind, for example, is seldom considered w...

South Africa’s first national democratic elections in 1994 marked a turning point in the history of the country. Since democracy much of the focus of African National Congress (ANC)-led government has been on redress and transformation across all spheres of society, including higher education. This paper examines one important aspect inherent in tr...

Background. Open Access (OA) describes the free, unrestricted access to and re-use of research articles. Recently, a new wave of interest, debate, and practice surrounding OA publishing has emerged.Objectives. The paper presented here focuses on international disparities in OA publication practices of the Earth Science community. We aim to provide...

Mauritius is a Small Island Developing State (SIDS) with a high population density and increasing agricultural, urban and infrastructural demands, superimposed over limited physical resources. Soil and coastal erosion are recognized as an important environmental challenge facing the island. Here we review the studies on soil erosion over the past t...

Marion Island is a peak of a shield volcano located in the southern Indian Ocean. The island is strategically important for the collection of climatological data and marine and terrestrial research in a vast, oceanic region of the globe. This paper reviews the series of earth science programmes on Marion Island over the last 25 years, provides a sy...

Although burrow-nesting petrels are the most abundant group of seabirds in the Southern Ocean, their global populations are poorly known, because most species breed on remote islands. For example, there are no accurate estimates for Great-winged Petrel Pterodroma macroptera populations at any of its major breeding sites. Moreover, current global po...

The glaciers in the Aktru River basin of Gornyi Altai, Russia currently represent some of the fastest receding glaciers in the world. Formation of the morainic complexes closest to the contemporary glaciers in the Aktru River basin took place during the 17th - 18th centuries with recession commencing at the end of the 18th century. Coupled with thi...

Basalt-derived agricultural soil is widely distributed around the world and is extensively used as a medium to plant many kinds of crops. Weathering of basalt can release heavy metals into the soils and may cause health risks via the food chain. However, the geochemical behavior and the potential human health risks of heavy metals remain poorly und...

Short communication on international disparities in open access practices of the Earth Sciences community

Southern Hemisphere glacial chronologies can provide valuable insights into interactions between glaciation and past climate changes, but are not well constrained on most sub-Antarctic islands. We present the first cosmogenic ³⁶Cl exposure ages of deglaciated bedrock surfaces and moraine deposits from sub-Antarctic Marion Island in the southern Ind...

Concentrations of major ions in stream water from the Soft Plume River on Subantarctic Marion Island were measured. During the annual relief voyage, samples were collected daily over a 16-day period (21 April–6 May 2015) from three sites along the stream to better understand temporal and spatial variability of stream water chemistry on the island....

In a recent publication in the journal Science of the Total Environment, Sonne et al. (2020) highlight how Open Access journals and associated fees may limit the production and flow of knowledge. Sonne et al. (2020) also illustrate how the pressure to publish has accelerated the proliferation of predatory journals and has, in some cases, led to the...

The catastrophic landslide-dam outburst flood, possibly caused by the same earthquake that destroyed the well-dated Lajia archaeological site, in the upper reaches of the Yellow River in China, may provide an accurate constraint on the age of the first Chinese dynasty (Xia Dynasty), which, according to Chinese ancient documents, has been associated...

Round Island, a small (219 ha) volcanic island 22.5 km north of Mauritius, has steep slopes and thin soils. This small tropical island was previously subjected to overgrazing by goats and rabbits, which detrimentally affected ecosystem functioning. Classified as a nature reserve since 1957, Round Island houses the last remnant of palm savannah whic...

Basaltic terrains contribute a significant component to the global silicate weathering flux despite their limited areal coverage. A strong correlation between chemical weathering flux and climatic factors such as temperature in volcanically inactive basaltic fields implies that weathering of basalt might have played an important role in maintaining...

Intro • Thúfur (earth hummocks, pounus) are common in the Lesotho Highlands of southern Africa. However, many thúfa mounds exhibit signs of disintegration in this marginal periglacial environment. • This study investigated thúfur morphology in the context of disintegration with both infield measurements and the use of high resolution (2cm), droned...

We compared systematic and random survey techniques to estimate breeding population sizes of burrow-nesting petrel species on Marion Island. White-chinned ( Procellaria aequinoctialis ) and blue ( Halobaena caerulea ) petrel population sizes were estimated in systematic surveys (which attempt to count every colony) in 2009 and 2012, respectively. I...

In this paper we critically examine the research landscape in South Africa. We do this by documenting the progression and transformation of the country’s National Research Foundation (NRF)-rated researchers from 2005 to 2015. Results indicate that most NRF-rated researchers in South Africa are white and male but this trend is slowly changing with b...

If South Africa truly wants to encourage good research, it must stop paying academics by the paper, says David William Hedding. If South Africa truly wants to encourage good research, it must stop paying academics by the paper, says David William Hedding.

Feedbacks between geomorphic and vegetation dynamics create spatial patterns of vegetation, soils and landforms in biogeomorphic ecosystems and determine their structure and functioning. In glacier forelands, it was shown that these biogeomorphic feedbacks link paraglacial adjustment and vegetation succession and control landscape development and s...

The ratio between the activity of dissolved ²³⁴U and ²³⁸U in river water, (²³⁴U/²³⁸U)Riv, shows promise for tracing weathering processes. It has been suggested that preferential ²³⁴U release generates a high (²³⁴U/²³⁸U)Riv under low weathering intensity while congruent weathering, as expected for high weathering intensity, would release uranium wit...

Provenance of the silt on the Chinese Loess Plateau (CLP) is essential for the paleo-environmental interpretation of the thick eolian deposits, but is highly debated. The controversy mainly comes from the multi-interpretation of similar geochemical signatures of potential source areas (PSAs). This work applies the (²³⁴U/²³⁸U) activity ratio as a ne...

In this work, we contribute to the debate on the transformation of higher education institutions (HEIs) in post-apartheid South Africa by examining the changing demography of academic staff bodies at 25 South African HEIs from 2005 to 2015. We use empirical data to provide initial insights into the changing racial profiles of academic staff bodies...

Given the remoteness and challenging environmental conditions on sub-Antarctic Marion Island, continuous high-resolution studies of the island's natural water systems are rare. Subsequently, current understanding of the island's hydrochemistry is based entirely on manual point-based measurements. To address this research gap we analysed continuous,...

We measured the hydrogen and oxygen isotope composition (δ ² H and δ ¹⁸ O) of precipitation and stream water from the Soft Plume River at multiple spatiotemporal scales on sub-Antarctic Marion Island, Indian sector of the Southern Ocean. Monthly precipitation δ ² H and δ ¹⁸ O values ranged from -43.7‰ to -14.7‰ and from -7.0‰ to -3.3‰ ( n =13), res...

Rock glaciers are lobate or tongue-shaped landforms which consist of rock debris and have either an ice core or an ice-cemented matrix. Characteristics such as the landscape setting, morphology, material and current geomorphological state are universally used to classify rock glaciers. In Antarctica, rock glaciers have only been surveyed on the Ant...

Weather-related delays in the aviation sector will always occur; however, through effective delay management, the impact and duration of delays can be reduced. Part of delay management is thoroughly assessing adverse weather risks. A weather impact index was specifically designed for O. R. Tambo International Airport, in Kempton Park, South Africa,...

Antarctica and the Southern Ocean form a critical natural laboratory where international scientific investigation can infer the fundamental drivers of the entire earth system and of the near-earth space environment. Advancing our understanding is critical to better comprehend the region’s role in global ocean-atmospheric circulation, ecosystem adap...

Pronival ramparts are debris ridges formed at the downslope margins of perennial or semi-permanent snowbeds beneath bedrock cliffs. These landforms, also previously known as protalus ramparts, are located in periglacial environments, but the apparent simplicity of rampart formation made these landforms far less interesting than other modified forms...

Pronival ramparts are debris ridges formed at the downslope margins of perennial or semi-permanent snowbeds at the foot of bedrock cliffs. The close spatial proximity and morphological similarities of pronival ramparts to modified talus sheets and cones as well as protalus rock glaciers, moraines and landslides has led to difficulties in correctly...

South Africa has undergone transformation since the end of apartheid governance in 1994. Legislatively enforced, this transformation has permeated most sectors of society, including higher education. Questions remain, however, about the extent to which transformation has occurred in Higher Education Institutions (HEIs) in general, and across the ac...

This paper presents the first rock mass loss data for uncut clasts from continental Antarctica. A rock mass loss experiment using doleritic rock samples was conducted over a seven-year period, between 2008 and 2014, at the Vesleskarvet nunataks, Western Dronning Maud Land.The data show that approximately 10% of clasts suffered a mass loss that is a...

Sub-Antarctic Marion Island has a hyperoceanic climate, with cold and wet conditions and consistently strong wind velocities throughout the year. Recent observations recognized the increasing role of aeolian processes as a geomorphic agent, and this paper presents the first data for transport by aeolian processes on a sub-Antarctic island. Data wer...

This chapter presents and reflects on two campus greening initiatives by the Department of Geography at the University of South Africa (Unisa). The first initiative is the environmental management degree programme, which was implemented in 2000 as the first multidisciplinary, cross-faculty study programme offered at the institution. Successes and c...

Abstract A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological da...

A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets an...

This paper is the maritime and sub–Antarctic contribution to the Scientific Committee for Antarctic Research (SCAR) Past Antarctic Ice Sheet Dynamics (PAIS) community Antarctic Ice Sheet reconstruction. The overarching aim for all sectors of Antarctica was to reconstruct the Last Glacial Maximum (LGM) ice sheet extent and thickness, and map the sub...

Pronival ramparts are discrete debris accumulations found below steep rock faces at the foot of snowbeds or firn fields but they are often confused with moraines, protalus rock glaciers or rock-slope failure debris accumulations. This can be attributed to a poor understanding of the modes of rampart genesis, failure to recognise the significance of...

Summer observations of the morphology and the debris accumulation processes at an actively forming pronival rampart at Grunehogna Peaks, Western Dronning Maud Land, Antarctica demonstrate that rockfall debris accumulation is causing downslope (outward) rampart extension even though the distal slope is not at the angle of repose. Field experiments s...