Desertification in the Sahel Region: A Product of Climate Change or Human Activities? A Case of Desert Encroachment Monitoring in North-Eastern Nigeria Using Remote Sensing Techniques

In Nigeria, desertification has become one of the most pronounced ecological disasters, with the impacts mostly affecting eleven frontline States. This has been attributed to a range of both nat-ural and man-made factors. This study applied a remote sensing-based change detection and indicator analysis to explore land use/land cover changes and detect major conversions from ecologically active land covers to sand dunes. Results indicate that areas covered by sand dunes (a major indicator of desertification) have doubled over the 25 years under consideration (1990 to 2015). Although about 0.71 km2 of dunes have been converted to vegetation, indicative of the success of various international, national, local, and individual afforestation efforts, conversely about 10.1 km2 of vegetation were converted to sand dunes, implying around 14 times more de-forestation compared to afforestation. Juxtaposing the progression of sand dune with climate records of the study area and examining the relationship between indicators of climate change and desertification suggested a mismatch between both processes as increasing rainfall and lower temperatures observed in 1994, 2005, 2012, and 2014 did not translated into positive feedbacks for desertification in the study area. On average, our results reveal that sand dune is progressing at a mean annual rate of about 15.2 km2 in the study area. Based on this study’s land cover change, trend and conversion assessment, visual reconciliation of climate records with land cover data, statistical analysis, observations from ground-truthing, as well as previous literature, it can be inferred that desertification in Nigeria is less a function of climate change, but more a product of human activities driven by poverty, population growth and failed government policies. Further projections by this study also reveal a high probability of more farmlands being converted to sand dunes by the year 2030 and 2045 if current practices prevail.

EXPLORING THE EFFECTIVENESS AND STUDENTS’ PERCEPTIONS OF E-LEARNING IN ENGLISH AS SECOND LANGUAGE (ESL) SPEAKING CLASSES AMIDST COVID-19

The COVID-19 outbreak quickly demonstrates the importance of adopting online education in teaching and learning. It has forced education systems worldwide to find alternatives to face-to-face interactions. Language instructors have made attempts to explore and utilise e-learning tools to enrich their teaching and assist learners in improving their language learning. This paper, therefore, attempts to shed light on the effectiveness of adopting e-learning tools in ESL speaking class and their perception of it. Fifty-three pre-university students from the Foundation Programme of the Preparatory Centre for Science and Technology were involved in this study. Data analysed in this paper were derived from a threaded online discussion via Dotstorming. The structured interview questions were carefully designed based on the objectives to elicit the students’ opinions on the topic of interest. To explore the effectiveness of e-learning in developing the students’ speaking skills, scores of Individual Speaking Assessment and Group Speaking Assessment of each student were collected. These assessments were marked based on the Malaysian University English Test (MUET) Speaking Rubric – Task Fulfilment, Language, and Communicative Ability. The findings show that the adoption of technology in ESL speaking classes improves the students’ speaking abilities. The thematic analysis also shows that the use of e-learning tools in language learning received positive feedbacks from the students, suggesting it would be a promising virtual platform to improve the student's confidence, knowledge, and language.

ESD Ideas: A Global Warming Scaling Law

In this study, we highlight a component of global warming variability, a scaling law that is based purely on fundamental physical properties of the climate system. We suggest that three similarity parameters define the system response to external forcing, and an argument of physical similarity with observed climate responses in the past can be made when all three parameters are identical for the current and historical climates. We determined that the scaling law of global warming is the (𝜆 + 1 + m) – power of time, where 𝜆 is prescribed by external forcing and m is defined by climate system internal dynamics. When the climate system develops in the direction of intensified positive feedbacks, the power m changes from m = −1 (negative feedbacks dominate) to m ≥ 1 (positive feedbacks dominate). We also establish that a “hothouse” climate with dominant positive feedbacks will be preceded by a climate having a property of incomplete similarity in feedbacks similarity parameters. It implies that the same future scenario may be produced by climate feedbacks of different magnitudes as long as their positive-to-negative ratio is the same.

Socioeconomic Patterns for Global Mangrove Cover Changes with Multivariate Analyses

Socioeconomic patterns beyond the land conversions of global mangrove cover changes were few discussed. This study integrated databases of global mangrove covers, i.e., a multi-database in 1980-2016 with a combination of FAO country-survey and the global mangrove watch, and a mangrove biome cover database in 2000-2012. Annual mangrove cover change (%) of each mangrove holding country or territory was incorporated with its socioeconomic indicators in the two periods to testify possible socioeconomic patterns beyond the mangrove deforestation. The socioeconomic indicators consisted of GDP per capita and urban population percentile, and aquacultural indicators (production per capita, sales value per capita, contribution to the national GDP, and product price). Results indicated that annual mangrove cover change was interactively driven by multi-factors of national economy measures, urbanization, and aquaculture, instead of aquacultural dominance or GDP per capita alone. The multi-factor driven patterns of annual mangrove changes differed geographically among the continents. Temporal change of aquacultural product price was significantly and positively correlated to annual mangrove cover change (increase), especially in Asia and Oceania for both the periods, suggesting positive feedbacks of mangrove conservation and restoration in the two continents although the price was used to a motivator of mangrove deforestation, such as currently in Africa. These findings preliminarily bridge the knowledge gap between land conversion losses and socioeconomics of global mangrove cover changes.

Riverine nitrogen supply to the global ocean and its limited impact on global marine primary production: a feedback study using an Earth system model

A common notion is that negative feedbacks stabilize the natural marine nitrogen inventory. Recent modeling studies have shown, however, some potential for localized positive feedbacks leading to substantial nitrogen losses in regions where nitrogen fixation and denitrification occur in proximity to each other. Here we include dissolved nitrogen from river discharge in a global 3-D ocean biogeochemistry model and study the effects on near-coastal and remote-open-ocean biogeochemistry. We find that at a steady state the biogeochemical feedbacks in the marine nitrogen cycle, nitrogen input from biological N2 fixation, and nitrogen loss via denitrification mostly compensate for the imposed yearly addition of 22.8 to 45.6 Tg of riverine nitrogen and limit the impact on global marine productivity to < 2 %. Global experiments that regionally isolate river nutrient input show that the sign and strength of the feedbacks depend on the location of the river discharge and the oxygen status of the receiving marine environment. Marine productivity generally increases in proximity to the nitrogen input, but we also find a decline in productivity in the modeled Bay of Bengal and near the mouth of the Amazon River. While most of the changes are located in shelf and near-coastal oceans, nitrogen supply from the rivers can impact the open ocean, due to feedbacks or knock-on effects.

The Evaluation of AR Mobile App as a Learning Media for Children

A user evaluation stage is an integral part of designing an application. A practical evaluation can provide an overview of the problems that arise in the application and improve the user experience. The Kupuku application is an augmented reality (AR)-based game application for learning about butterflies. The Kupuku application is specifically intended for children aged 6-13 years. The user sample was selected using a purposive sampling method with the criteria for users of elementary school-age children for the child user segment and their companions as the adult user segment. This study aims to evaluate the usability of the Kupuku game application to users. User evaluation was carried out to measure the application’s usability. The evaluation process was conducted on two user segments, namely 20 child users and 16 adult users. Assessment of children employed the Fun Toolkit and usability factor-based question - Nielsen method. The obtained results showed positive feedbacks. In contrast, the assessment for adult users utilized the system usability scale (SUS) and the user experience questionnaire (UEQ). The SUS score of 76 was included in the good category, and the UEQ score produced an excellent average. The test results indicate that this application can be accepted by users, both children, and adults.

Strong pairwise ant-plant mutualism has limited spillover effects on an ant community

Pairwise mutualisms are embedded within rich communities of co-occurring species. Mutualism by definition benefits partner species and theory predicts these effects can spill over into broader communities, with consequences for abundance, diversity, and composition. Specifically, positive feedbacks between partner species may shift competitive hierarchies and drive reductions in non-partner species. We used long-term monitoring data spanning 16 years to determine the ant partner species of tree cholla cacti (Cylindriopuntia imbricata), which reward ants with extrafloral nectar in exchange for anti-herbivore defense. We coupled these long-term data with short-term characterization of the ant community via pitfall trapping, which sampled partner and non-partner species across ten plots that varied naturally in cactus density. The long-term data revealed one dominant ant partner (Liometopum apiculatum) and two other less common partners (Crematogaster opuntiae and Forelius pruinosus). In the short-term census, the dominant ant partner occupied more cacti in plots of higher cactus density, and was also found at higher occurrence within the pitfall traps in the high cactus density plots, suggesting strong positive feedbacks that promote ant occurrence where plant partners are available. Despite the consistency of L. apiculatum partnership with cacti through time and the dominance of this partnership in areas of high cactus density, spillover effects from this mutualism appear limited. Of the common ant species, a single non-partner ant species showed a modest reduction in occurrence at high cactus density, possibly in response to increased presence of L. apiculatum. Additionally, the composition and diversity of the ant community in our plots were insensitive to cactus density variation, indicating that positive effects on the dominant ant partner did not have cascading impacts on the ant community. This study provides novel evidence that pairwise mutualisms, even those with strong positive feedbacks, may be limited in the scope of their community-level effects.

Rapid fragmentation of Thwaites Eastern Ice Shelf, West Antarctica

Ice shelves play a key role in the dynamics of marine ice sheets, by buttressing grounded ice and limiting rates of ice flux to the oceans. In response to recent climatic and oceanic change, ice shelves fringing the West Antarctic Ice Sheet (WAIS) have begun to fragment and retreat, with major implications for ice sheet stability. Here, we focus on the Thwaites Eastern Ice Shelf (TEIS), the remaining pinned floating extension of Thwaites Glacier. We show that TEIS has undergone a process of fragmentation in the last five years, including brittle failure along a major shear zone, formation of tensile cracks on the main body of the shelf, and release of tabular bergs on both eastern and western flanks. Simulations with the Helsinki Discrete Element Model (HiDEM) show that this pattern of failure is associated with high backstress from a submarine pinning point at the distal edge of the shelf. We show that a significant zone of shear upstream of the main pinning point developed in response to the rapid acceleration of the shelf between 2002 and 2006, seeding damage on the shelf. Subsequently, basal melting and positive feedbacks between damage and strain rates weakened TEIS, allowing damage to accumulate. Thus, although backstress on TEIS has likely diminished through time as the pinning point has shrunk, accumulation of damage has ensured that the ice in the shear zone has remained the weakest link in the system. Experiments with the BISICLES ice sheet model indicate that additional damage to or unpinning of TEIS are unlikely to trigger significantly increased ice loss from WAIS, but the calving response to loss of TEIS remains highly uncertain. It is widely recognised that ice-shelf fragmentation and collapse can be triggered by hydrofracturing and/or unpinning from ice shelf margins or grounding points. Our results indicate a third mechanism, backstress-triggered failure, that can occur when ice ffractures in response to stresses associated with pinning points. In most circumstances, pinning points are essential for ice shelf stability, but as ice shelves thin and weaken the concentration of backstress in damaged ice upstream of a pinning point may provide the seeds of their demise.

Physical Inactivity: A Modifiable Risk Factor for Morbidity and Mortality in Kidney Transplantation

In patients with chronic kidney disease, sedentary behavior is widely recognized as a significant risk factor for cardiovascular disease, diabetes, obesity, osteoporosis, cancer, and depression. Nevertheless, the real impact of physical inactivity on the health of kidney transplant (KT) recipients remains uncertain. Over the last decade, there has been a renewed interest in exploring the effects of regular physical exercise on transplant-related outcomes. There is now mounting evidence that physical activity may reduce the burden of cardiovascular risk factors, preserve allograft function, minimize immunosuppression requirement, and ameliorate the quality of life of KT recipients. Many positive feedbacks can be detected in the early stages of the interventions and with a minimal exercise load. Despite these encouraging results, the perceived role of physical activity in the management of KT candidates and recipients is often underrated. The majority of trials on exercise training are small, relatively short, and focused on surrogate outcomes. While waiting for larger studies with longer follow-up, these statistical limitations should not discourage patients and doctors from initiating exercise and progressively increasing intensity and duration. This narrative review summarizes current knowledge about the deleterious effects of physical inactivity after KT. The benefits of regular physical exercise are also outlined.

Late Paleocene CO₂ drawdown, climatic cooling, and terrestrial denudation in the southwest Pacific

Late Paleocene deposition of an organic-rich sedimentary facies on the continental shelf and slope of New Zealand and eastern Australia has been linked to short-lived climatic cooling and terrestrial denudation following sea-level fall. Recent studies have confirmed that the organic matter in this facies, termed Waipawa organofacies, is primarily of terrestrial origin, with a minor marine component. It is also unusually enriched in δ13C. In this study we aim to determine the cause or causes of this enrichment. For Waipawa organofacies and its bounding facies in the Taylor White section, Hawkes Bay, paired palynofacies and δ13C analysis of density fractions indicate that the heaviest δ13C values are associated with degraded phytoclasts (woody plant matter) and that the 13C enrichment is partly due to lignin degradation. Compound specific δ13C analyses of samples from the Taylor White and mid-Waipara (Canterbury) sections confirms this relationship but also reveal a residual 13C enrichment of ~ 2.5 ‰ in higher plant biomarkers (n-alkanes and n-alkanoic acids) and 3–4 ‰ in the subordinate marine component, which we interpret as indicating a significant drawdown of atmospheric CO2. Refined age control for Waipawa organofacies indicates that deposition occurred between 59.2 and 58.4 Ma, which coincides with a Paleocene oxygen isotope maximum (POIM) and the onset of the Paleocene carbon isotope maximum (PCIM). This timing suggests that this depositional event was related to global cooling and carbon burial. This relationship is further supported by published TEX86-based sea surface temperatures that indicate a pronounced regional cooling during deposition. We suggest that reduced greenhouse gas emissions from volcanism and accelerated carbon burial related to several tectonic factors and positive feedbacks resulted in short-lived global cooling, growth of ephemeral ice sheets, and a global fall in sea level. Accompanying erosion and carbonate dissolution in deep sea sediment archives may have hidden the evidence of this "hypothermal" event until now.