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.

Development of Desertification Indicators for Desertification Monitoring from Landsat Images Using Python Programming

Nowadays, desertification is one of the most serious environment socioeconomic issues and sand dune advances are a major threat that causes desertification. Wadi El-Rayan is one of the areas facing severe dune migration. Therefore, it's important to monitor desertification and study sand dune migration in this area. Image differencing for the years 2000 (Landsat ETM+) and 2019 (OLI images) and Bi-temporal layer stacking was performed. It was found that image differencing is a superior method to get changes of the study area compared to the visual method (Bi-temporal layer stacking). This research develops a quantitative technique for desertification assessment by developing indicators using Landsat images. Spatial distribution of the movement of sand dunes using some spectral indices (NDVI, BSI, LDI, and LST) was studied and a Python script was developed to calculate these indices. The results show that NDVI and BSI indices are the best indices in the identification and detection of vegetation. It was found that mobile sand dunes on the southern side of the lower Wadi El-Rayan Lake caused filling up of large part of the lower lake. The indices results show that sand movement decreased the size of the lower Wadi El-Rayan Lake and there are reclamation activities in the west of the lower lake. The results show that a good result could be achieved from the developed codes compared to ready-made software (ENVI 5).

Numerical evidence of persisting surface roughness when deposition stops

Do evolving surfaces become flat or not with time evolving when material deposition stops? As one qualitative exploration of this interesting issue, modified stochastic models for persisting roughness have been proposed by Schwartz and Edwards (2004 Phys. Rev. E 70 061602). In this work, we perform numerical simulations on the modified versions of Edwards–Wilkinson (EW) and Kardar–Parisi–Zhang (KPZ) systems when the angle of repose is introduced. Our results show that the evolving surface always presents persisting roughness during the flattening process, and sand dune-like morphology could gradually appear, even when the angle of repose is very small. Nontrivial scaling properties and differences of evolving surfaces between the modified EW and KPZ systems are also discussed.

Proposed Strategy for the Development of a Local Geopark at Mui Ne Red Sand Dunes, Phan Thiet, Vietnam - based on Tourist Perceptions and Experience from Taiwan

Vietnam attracts many tourists owing to its unique and diverse geological landscapes. The Vietnam tourism development strategy until 2030 sets a target to make tourism a more sustainable economic sector, in which the advantages of natural resources and development of a variety of tourism products are promoted. Binh Thuan province in central-south Vietnam, hosts many high potential geosites including Mui Ne Red Dunes. Although this is a popular tourist destination, there is no clear tourism strategy for this site and local communities now regulate tourism in an unsustainable way. Online comments from review databases (TripAdvisor and Google reviews) are analysed to find themes in tourism perceptions after a visit to the Red Sand Dunes. Main themes are found that negatively affect tourist perceptions, such as the extended pollution of the dunes, theft reports and disturbance by jeeps, ATV’s and motorbikes. Many tourists recommend that this site should be better managed. To conserve this area in the future, the development of an all-inclusive local geopark is suggested, based on the tourism perceptions and previous studies assessing this landscape. This strategy is adapted from the UNESCO geopark framework and an example of a recently established local sand dune geopark in Taiwan is discussed. Implementing a local geopark, following the steps described in this study, can be beneficial for sustainable development and local communities in this area, while also promoting environmental education and enhancing disaster risk reduction.

Lessons Learnt Reprocessing a Noisy Onshore 3D Seismic Survey

An 1,100 km2 400-fold seismic survey was acquired over some of the largest sand dunes in UAE in 2007. Large sand dunes generate many challenges for seismic processing due to the irregular data acquisition, large statics caused by the significant difference between the sand and sabkha velocities, and a massive amount of reverberation noise that hides the signal in the data. Occidental and ADNOC Sour Gas reprocessed this survey from January 2019 to August 2020 to overcome the challenges of the strong sand dune noise. For the first time, it was processed through prestack depth migration (PSDM). The primary objectives of the reprocessing project were to get an accurate PSDM volume that tied all of the available well control data; and to derive as accurate seismic amplitudes as possible over the target reservoir interval from near to far offsets to enable elastic inversion for reservoir porosity and net-thickness prediction. Whilst the reprocessing project achieved the project objectives and generated good subsurface images, it did not run as smoothly as hoped, despite being processed by one of the premier multinational processing companies. The extremely large sand dunes, which are present across most of the survey area, created major imaging problems. Key technical lessons learnt during reprocessing included: (1) CRS errors occurred sporadically during acquisition, requiring correction; (2) the sand curve (Liner, 2008) worked well for sand dune static corrections for this data set; (3) near surface statics changed whilst the survey was acquired by up to 6 ms - each shot station needed to be corrected for these statics changes because the shot stations were acquired twice with a symmetric split recording spread; and (4) the contractor's standard post-migration processing sequence (gather flattening, radon, noise attenuation, stack) did not work well for this very noisy data set. Next time we work with similar data and require a high quality result, we know to double the estimated project timeline as every step in the processing sequence takes much longer than expected when the signal-to-noise ratio of the data is very low. The novelty of this work was that we obtained large improvements in the seismic stack by applying offline gather conditioning before calculating trim statics to optimally flatten the very noisy migrated offset vector tile (OVT) gathers, prior to running the final noise attenuation and stacking workflows. Without this offline gather conditioning, the trim statics workflow mostly aligned the noise and damaged the stack.

Devosia litorisediminis sp. nov., isolated from a sand dune

A Gram-negative, aerobic, non-motile, and rod-shaped bacterial strain, designated BSSL-BM10T, was isolated from a sand dune that was collected from the Yellow Sea, Republic of Korea. It was subjected to a polyphasic taxonomic study. 16S rRNA gene sequence analysis showed that strain BSSL-BM10T fell phylogenetically within the radiation comprising type strains of Devosia species. The 16S rRNA gene sequence of strain BSSL-BM10T shared sequence similarities of 98.2% with the type strain of D. naphthalenivorans and 93.5-97.7% with type strains of other Devosia species. ANI and dDDH values between strain BSSL-BM10T and type strains of 18 Devosia species were 71.0-78.4% and 18.8-21.5%, respectively. The DNA G+C content of strain BSSL-BM10T was 60.9% based on its genomic sequence data. Strain BSSL-BM10T contained Q-10 as the predominant ubiquinone and 11-methyl C18:1 ω7c, C18:1 ω7c, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), and C16:0 as its major fatty acids. Major polar lipids of strain BSSL-BM10T were phosphatidylglycerol and two unidentified glycolipids. Strain BSSL-BM10T showed distinguished phenotypic properties with its phylogenetic and genetic distinctiveness separated from recognized Devosia species. Based on data presented in this study, strain BSSL-BM10T should be placed in the genus Devosia. The name Devosia litorisediminis sp. nov. is proposed for strain BSSL-BM10T (= KACC 21633T = NBRC 115152T).

Sand Dune Restoration in New Zealand: Methods, Motives, and Monitoring

<p>Sand dunes are critically endangered ecosystems, supporting a wide variety of specialist native flora and fauna. They have declined significantly in the past century, due to coastal development, exotic invasions, and stabilization using marram grass (Ammophilia arenaria). An increasing number of restoration groups have carried out small scale rehabilitations of using native sand binding plants spinifex (Spinifex sericeus) and pingao (Desmoschoenus spiralis). However like many other restoration ventures, efforts are not formally monitored, despite the potential for conservation of species in decline. This thesis seeks to investigate the social and ecological aspects of sand dune restoration in New Zealand. Firstly, the status of restoration in New Zealand was examined using web based surveys of dune restoration groups, identifying motivations, methods, and the use of monitoring in the restoration process. Secondly, the ecology of restored and marram dominated sand dunes was assessed. Vegetation surveys were conducted using transects of the width and length of dunes, measuring community composition. Invertebrates were caught using pitfall traps and sweep netting, sorted to order, and spiders, beetles and ants identified down to Recognizable Taxonomic Units (RTUs) or species where possible. Lizards were caught in pitfall traps, and tracking tunnels tracked the presence of small mammals in the dunes. Analysis of each variable involved the comparison of biodiversity data between restored and marram dominated dunes, at six sites across the Wellington region. The survey of dune restoration practitioners confirmed that restoration was generally based on the motivation of erosion protection and foreshore stabilization, however an increasing number of groups were interested in the conservation of flora. Conservation of fauna was a priority for only one of the respondents. Informal monitoring of restoration attempts was carried out by the majority of groups, but specific biodiversity monitoring or monitoring using systematic scientific methods was carried by only a small proportion of groups. Re-vegetation of dunes commonly used a small suite of native sand binding species mostly pingao and spinifex. Species in decline such as sand tussock (Austrofestuca littoralis) and sand daphne (Pimelia arenaria) were only planted at a small proportion of sites. Restoration of dune ecosystems has the potential to not only enhance erosion protection and sand stabilization mechanisms, but to benefit native flora and fauna endemic to sand dunes. Identifying biological change and carrying out biodiversity monitoring may be beneficial in maximizing the ecological effectiveness of restoration attempts. Marram dunes contained higher foliage cover, vegetation height and vegetation species diversity than restored dunes. Abundance and diversity of beetle, spider, and ant families were higher in marram dominated dunes. Estimated population size of common skink (O. nigraplantare polychroma) and mouse population density was also higher in marram dunes. These results were positively correlated with the percentage of vegetation foliage cover and vegetation species diversity, suggesting that the habitat conditions created by marram grass were favored by fauna. These results suggest that for maximum biodiversity gains, future dune restoration attempts should increase vegetation cover, and include a wider range of plant species. Species in decline known to be important for fauna, such as pohuehue (Muehlenbeckia spp.), sand pimelia, and sand coprosma (Coprosma acerosa) should also be included for reciprocal benefits for conservation of flora and fauna. Marram grass could also be incorporated into restoration, as its mass removal may have considerable consequences for fauna using it as a refuge, and it appears to provide desirable habitat for fauna.</p>

Sand Dune Restoration in New Zealand: Methods, Motives, and Monitoring

<p>Sand dunes are critically endangered ecosystems, supporting a wide variety of specialist native flora and fauna. They have declined significantly in the past century, due to coastal development, exotic invasions, and stabilization using marram grass (Ammophilia arenaria). An increasing number of restoration groups have carried out small scale rehabilitations of using native sand binding plants spinifex (Spinifex sericeus) and pingao (Desmoschoenus spiralis). However like many other restoration ventures, efforts are not formally monitored, despite the potential for conservation of species in decline. This thesis seeks to investigate the social and ecological aspects of sand dune restoration in New Zealand. Firstly, the status of restoration in New Zealand was examined using web based surveys of dune restoration groups, identifying motivations, methods, and the use of monitoring in the restoration process. Secondly, the ecology of restored and marram dominated sand dunes was assessed. Vegetation surveys were conducted using transects of the width and length of dunes, measuring community composition. Invertebrates were caught using pitfall traps and sweep netting, sorted to order, and spiders, beetles and ants identified down to Recognizable Taxonomic Units (RTUs) or species where possible. Lizards were caught in pitfall traps, and tracking tunnels tracked the presence of small mammals in the dunes. Analysis of each variable involved the comparison of biodiversity data between restored and marram dominated dunes, at six sites across the Wellington region. The survey of dune restoration practitioners confirmed that restoration was generally based on the motivation of erosion protection and foreshore stabilization, however an increasing number of groups were interested in the conservation of flora. Conservation of fauna was a priority for only one of the respondents. Informal monitoring of restoration attempts was carried out by the majority of groups, but specific biodiversity monitoring or monitoring using systematic scientific methods was carried by only a small proportion of groups. Re-vegetation of dunes commonly used a small suite of native sand binding species mostly pingao and spinifex. Species in decline such as sand tussock (Austrofestuca littoralis) and sand daphne (Pimelia arenaria) were only planted at a small proportion of sites. Restoration of dune ecosystems has the potential to not only enhance erosion protection and sand stabilization mechanisms, but to benefit native flora and fauna endemic to sand dunes. Identifying biological change and carrying out biodiversity monitoring may be beneficial in maximizing the ecological effectiveness of restoration attempts. Marram dunes contained higher foliage cover, vegetation height and vegetation species diversity than restored dunes. Abundance and diversity of beetle, spider, and ant families were higher in marram dominated dunes. Estimated population size of common skink (O. nigraplantare polychroma) and mouse population density was also higher in marram dunes. These results were positively correlated with the percentage of vegetation foliage cover and vegetation species diversity, suggesting that the habitat conditions created by marram grass were favored by fauna. These results suggest that for maximum biodiversity gains, future dune restoration attempts should increase vegetation cover, and include a wider range of plant species. Species in decline known to be important for fauna, such as pohuehue (Muehlenbeckia spp.), sand pimelia, and sand coprosma (Coprosma acerosa) should also be included for reciprocal benefits for conservation of flora and fauna. Marram grass could also be incorporated into restoration, as its mass removal may have considerable consequences for fauna using it as a refuge, and it appears to provide desirable habitat for fauna.</p>