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"NEL, WERNER"
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Global rainfall erosivity assessment based on high-temporal resolution rainfall records
The exposure of the Earth’s surface to the energetic input of rainfall is one of the key factors controlling water erosion. While water erosion is identified as the most serious cause of soil degradation globally, global patterns of rainfall erosivity remain poorly quantified and estimates are typically associated with large uncertainties. This hampers the implementation of effective soil degradation mitigation and restoration strategies. Quantifying rainfall erosivity is challenging as it requires high temporal resolution (<30min) and high fidelity rainfall recordings over long periods of time (>10 years). Here, we present the results of an extensive global data collection effort whereby we estimated rainfall erosivity for 3,625 stations covering 63 countries. This first ever Global Rainfall Erosivity Database was used to develop a global erosivity map at 30 arc-seconds (~1 km) based on a Gaussian Process Regression (GPR). Globally, the mean rainfall erosivity was estimated to be 2,190 MJ mm ha-1 h-1 yr-1, with the highest values (>5,200 MJ mm ha-1 h-1 yr-1) in major parts of South America and the Caribbean countries, Central east Africa and South east Asia. The lowest values (< 200 MJ mm ha-1 h-1 yr-1) are mainly found in Canada, the Russian Federation, Northern Europe, Northern Africa and the Middle East. The tropical climate zone has by far the highest mean rainfall erosivity (7,104 MJ mm ha-1 h-1 yr-1) followed by the temperate (3,729 MJ mm ha-1 h-1 yr-1), whereas the lowest mean (493 MJ mm ha-1 h-1 yr-1) was estimated in the cold climate zone.
Publication
COVID-19 and the academe in South Africa : not business as usual
The famous R.E.M. song laments ‘It’s the end of the world as we know it, I had some time alone, I feel fine…’. Many South Africans would agree that COVID-19 signals the end of the world (or business) as we know it, and through the lockdown we have certainly had some time alone. But contrary to the lyrics, all may not be fine, especially for South Africa’s scientific community.
Journal Article
An open access geospatial database for the sub-Antarctic Prince Edward Islands
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’ landscape and ecosystems within the context of climate change and the impacts of invasive species. However, much of the geospatial data that currently exist have limitations in spatial coverage and/or resolution, are outdated, or are not readily available. To address these issues, we present an online geospatial database for the Prince Edward Islands (both islands) produced from a high-resolution digital surface model and satellite imagery. This database contains vector files, raster data sets, and maps of topographical and hydrological parameters. It is freely available to download from Figshare – an open access data repository. We encourage the South African polar science community to make use of similar platforms for improved data sharing practices. SIGNIFICANCE : • A topographical and hydrological geospatial database – produced from a 1 m x 1 m digital surface model of the Prince Edward Islands – is provided. • These fine-scale geospatial data allow for a more comprehensive assessment of biotic–abiotic interactions at an island scale. • Also included are locality maps specifying place names and established long-term marine mammal monitoring beaches and coastal zones for improved cross-referencing. • The dataset is downloadable from an open access data repository and intended to promote open science and data sharing practices.
Journal Article
The glacial geomorphology of sub-Antarctic Marion Island
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. With the aid of GPS field mapping, high-resolution satellite imagery and a digital surface model with a 1 × 1 m cell resolution, this paper provides a comprehensive, geo-rectified spatial geodatabase and map of Marion Island's glacial geomorphology. The geodatabase includes an inventory of glacial erosional (e.g. striations) and depositional (e.g. moraines) features compiled from existing records as well as new features mapped from recent field observations. The final map and the geodatabase, which is downloadable as ESRI layer-package files, will aid future field investigations and modelling applications to understand Marion Island's Quaternary landscape evolution and post-glacial ecological succession.
Journal Article
Temporal and spatial variability of stream water chemistry on Subantarctic Marion Island
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. The chemical composition of the stream is dominated by the sea salts Na+ and Cl−. Mean solute concentrations for Na+ and Cl− are 7 ± 0.58 and 12.5 ± 0.84 mg/L, respectively. The mean molar Na:Cl ratio for all samples is 0.86 ± 0.05, with a range from 0.71 to 0.99 (n = 47), and there is a strong, significant positive correlation between Na+ and Cl− concentrations (r = 0.80; p < 0.001). These values are consistent with previous studies from Marion Island and other Subantarctic islands. Temporal variation in ion concentrations was small. The largest detected change was a decrease in most solute concentrations that coincided with two precipitation events. This decrease was largest at the highest altitude and the shallowest site, suggesting that there was more rainfall at this location. These findings confirm the dominance of the surrounding ocean as the main source of the island’s stream water chemistry and illustrate spatiotemporal patterns that provide an insight into mechanisms affecting their composition on Subantarctic Marion Island.
Journal Article
The intervention of Rural Enterprise Development Hub Project on Maize Production in Mqanduli: The Implication on Food Security Status of Maize Farmers
The research analyzed the impact of the Rural Enterprise Development Hub Project (RED Hub Project) on food security of maize farmers. The data were analyzed using both inferential and descriptive statistics. Values were considered to be significant statistically where the P-value was less than 0.05. The study reveals a significant average increase in annual yield from 39.52 bags (50kg) to 87.02 bags (50kg) with a percentage increase of 120.19% per maize farm (t-statistics of 32.7 t-value and p-value of <0.05). Also, none of the maize farmers were food secure before the RED Hub project, 1 (0.5%) were mildly food insecure, 97 (48.5%) were averagely food insecure, and 102 (51%) were critically food insecure. After the RED Hub project intervention, 3.5% (7) are food secure, 104 (52%) are mildly food insecure, 76 (38%) are averagely food insecure and 13 (6.5%) critically food insecure. There was also more access and affordability of other food to meet maize farmers’ nutritional needs after the project intervention. An average of 72.5 (29.2%) beneficiaries and 99.3 (47.6%) beneficiaries respectively had access to other foods to meet their nutritional needs before and after the project intervention.
Journal Article
Rock glaciers in the Jutulsessen, Dronning Maud Land, East Antarctica
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 Antarctic Peninsula, Ellsworth Mountains and in Victoria Land. This paper presents the first data on the identification and description of rock glaciers in the Jutulsessen nunataks, Dronning Maud Land, East Antarctica. The rock glaciers in the Jutulsessen exhibit a variety of morphologies and states. Our data suggests that the rock glaciers in Brugdedalen and Jutuldalen are active, while the features at Vassdalen and Grjotlia are considered inactive, and a feature at Grjotøyra is considered relict. The described rock glaciers do not fit into existing classification systems and appear to be different to alpine, Arctic and Andean rock glaciers. They further present examples that fit both the ‘glaciogenic’ and ‘permafrost’ development theories.
Journal Article
Aspect-controlled weathering observed on a blockfield in dronning maud land, antarctica
Investigations of openwork block deposits have the potential to improve understanding of the production of substrates for biological colonisation, the control of geological structure and the impacts of climate change on landforms. As part of research into the morphology and characterisation of a blockfield located on the orthern uttress of the esleskarvet unataks, estern ronning aud and, ntarctica (2°, 71°), this paper investigates the influence that aspect has on weathering for a blockfield using data collected during the 2009-2012 ustral summer seasons. Proxy data recorded for weathering included rock hardness rebound values as well as visual evidence of flaking, pitting, surface roughness and lichen presence. Aspect was found to affect weathering of blockfield samples across the study site, with the south-facing sides being the least weathered of the directional aspects. This paper argues that a higher radiation budget associated with slope aspect and angle could drive thermal regimes and subsequent weathering of clast faces. Furthermore, in the absence of abundant precipitation, ice and snow cover become the primary source of moisture in this high-latitude ntarctic environment.
Journal Article
