Decrease In Vegetation Cover Research Articles

Dynamic monitoring of vegetation coverage in weibei dry plateau based on remote sensing

Taking Fu County, a typical area of Weibei dry plateau, as the research object, the normalized difference vegetation index ( NDVI ) was calculated by using Landsat 8 OLI remote sensing image. On this basis, the vegetation coverage in the study area was estimated and graded according to the binary pixel model, and the dynamic changes of vegetation coverage in the study area from 2013 to 2017 were quantitatively analyzed. Results showed that the overall NDVI value in the study area increased from 2013 to 2017. The vegetation cover in the study area is dominated by extremely high vegetation cover. The coverage area of low, medium and high vegetation cover decreases, and the coverage area of extremely high and extremely low vegetation cover increases. The coverage area of high vegetation and extremely high vegetation cover accounts for more than 75% of the study area. The study area showed a transfer trend of extremely low vegetation→low vegetation→medium vegetation→high vegetation coverage. The vegetation coverage generally developed to a good trend, but there was also a transfer of high vegetation coverage to medium vegetation coverage. The areas with the greatest changes in the study area are mainly concentrated in the northwest and near the southern Damagou, and the high NDVI area of Ziwuling National Nature Reserve has moved eastward and narrowed. Accuracy assessment indicates that the dynamic monitoring using the fused image time series produces results with relatively high accuracy. Bangladesh J. Bot. 52(2): 479-486, 2023 (June) Special

Assessment of the environmental impacts of gold mining activities at Gankombol (Adamawa-Cameroon) using Leopold matrix, Fecteau grid and remote sensing approach

In the present study, the environmental impacts of gold mining activities at Gankombol (Adamawa Cameroon) are assessed over four-year period. The Leopold matrix and the Fecteau grid are used to identify the environmental impacts and to determine their absolute importance. The spatio-temporal variation of spectral indices and land degradation are assessed using remote sensing analysis. The approach adopted is based on the calculation of spectral indices and spatio-temporal analysis. For this purpose, from Sentinel-2 satellite images, spectral indices such as the normalized difference vegetation index (NDVI), the brightness index (BRI), the normalized difference water index (NDWI), the bare soil index (BSI) and the dry bare soil index (DBSI) are computed during four years (2016, 2019, 2020 and 2021). The environmental degradation maps are generated by using supervised Random Forests (RF) algorithm and field observations. Finally, the confusion matrix and the kappa coefficient are used to check the performance and the accuracy of the classification maps. The environmental impact assessment by the Leopold matrix and the Fecteau grid reveal that the environmental impacts of mining activities are mainly negative and manifested by deforestation, degradation of water and soil quality, and high risks to human health. These impacts have a major absolute importance. The analysis of the spectral indices suggest a clear difference between the values obtained for each year due to the evolution of the mining activity over time. The environmental degradation maps which made it possible to discriminate water bodies, exploited area, vegetation and barren soils show that the values of water bodies decrease from 16.33 to 11.69 km2 between 2016 and 2020, then increase to 13.46 km2 in 2021. The exploited area increases from 0.00 to 13.75 km2 between 2016 and 2021. Vegetation cover decreases from 24.49 to 15.25 km2 between 2016 and 2021, while barren soils increase from 19.65 to 21.53 km2 between 2019 and 2021. These results reveal significant environmental degradation in the study area due to mining activities.

Spatial and Temporal Variation in Vegetation Cover and Its Response to Topography in the Selinco Region of the Qinghai-Tibet Plateau

In recent years, the vegetation cover in the Selinco region of the Qinghai-Tibet Plateau has undergone significant changes due to the influence of global warming and intensified human activity. Consequently, comprehending the distribution and change patterns of vegetation in this area has become a crucial scientific concern. To address this concern, the present study employed MODIS-NDVI and elevation data, integrating methodologies such as trend analysis, Hurst exponent analysis, and sequential cluster analysis to explore vegetation cover changes over the past 21 years and predict future trends, while examining their correlation with topographic factors. The study findings indicate a fluctuating upward trend in vegetation cover, with a notable decrease in 2015. Spatially, the overall fractional vegetation cover (FVC) in the study area showed a basic stability with a percentage of 78%. The analysis of future trends in vegetation cover revealed that the majority of areas (68.26%) exhibited an uncertain trend, followed by stable regions at 15.78%. The proportion of areas showing an increase and decrease in vegetation cover accounted for only 9.63% and 5.61%, respectively. Elevation and slope significantly influence vegetation cover, with a trend of decreasing vegetation cover as elevation increases, followed by an increase, and then another decrease. Likewise, as the slope increases, initially, there is a rise in vegetation cover, followed by a subsequent decline. Notably, significant abrupt changes in vegetation cover are observed within the 4800 m elevation band and the 4° slope band in the Selinco region. Moreover, aspect has no significant effect on vegetation cover. These findings offer comprehensive insights into the spatial and temporal variations of vegetation cover in the Selinco region and their association with topographic factors, thus serving as a crucial reference for future research.

Distress Characteristics in Embankment-Bridge Transition Section of the Qinghai-Tibet Railway in Permafrost Regions

The Qinghai-Tibet Railway has been operating safely for 16 years in the permafrost zone and the railroad subgrade is generally stable by adopting the cooling roadbed techniques. However, settlement caused by the degradation of subgrade permafrost in the embankment-bridge transition sections (EBTS) is one of the most representative and severe distresses. A field survey on 440 bridges (including 880 EBTSs) was carried out employing terrestrial laser scanning and ground-penetrating radar for comprehensively assessing all EBTSs in the permafrost zone. The results show that the types of distresses of EBTSs were differential settlement, upheaval mounds of the protection-cone slopes, subsidence of the protection-cone slopes, surface cracks of the protection cones and longitudinal and transverse dislocation of the wing walls. The occurrence rates of these distresses were 78.93, 3.47, 11.56, 3.36, 21.18 and 4.56%, respectively. The most serious problem was differential settlement, and the average differential settlement amount (ADSA) was 15.3 cm. Furthermore, the relationships between differential settlement and 11 influencing factors were examined. The results indicate that ADSA is greater on the northern side of a bridge than on the southern side and on the sunny slope than on the shady slope. It is also greater in the high-temperature permafrost region than in the low-temperature permafrost region and in the high-ice content area than in the low-ice content area. The EBTSs are more influenced by ice content than by ground temperature. The ADSA increases when the embankment height increases, the particle size of subgrade soil decreases and the surface vegetation cover decreases.

Study of the Deterioration in the Vegetation Cover of Al-Amiriya Region in Baghdad Province by using PCA equation on the Satellite Image

This paper examines the decrease in vegetation cover in Al-Amiriya from 2007 to 2020. Using two Landsat satellite multispectral images and Principal Components Analysis (PCA) with a classification technique, the overall vegetation cover in the city was determined. Results show a decrease in overall green land when comparing the two images. The ArcMap-GIS program was used to conduct the study, and the results showed that the overall vegetation cover ratio had decreased from 32.53% in 2007 to 31.29% in 2020. This means that there has been a decrease in vegetation cover over the past 13 years. It is important to note that this could be a sign of environmental degradation and increased human development in the area, and should be taken into consideration when developing strategies to protect the environment.

Analysis of sediment from an irrigation dam in an agricultural valley impacted by the mega-drought in central Chile

Central Chile has been affected since 2010 by an increasing mega-drought accompanied by a historically low precipitation rate, as a probable consequence of climate change. Additionally, the increasing pressure exerted by the withdrawals of human activities, such as agriculture and metal mining, promotes conditions of hydric scarcity. Despite this intensive use of the watersheds and the sustained and increasing aridity, it has not been explored whether an artificial sedimentary record can trace these changes in the agricultural valleys of the region. To unravel and evaluate the recent environmental/climatic variability, the effects of the mega-drought that has pertained since 2010, extractivist pressures on a Mediterranean valley in central Chile, and sediment records were obtained from an irrigation dam and studied through a multi-proxy analysis. The dam was built and has been in operation since 1975 and is located in the Aconcagua River Valley, Valparaíso, Chile. Magnetic properties, carbon content, mineral composition, and metal content were analyzed from sediments of a 120 cm long core. Changes in vegetation cover from 1990 to 2020 were analyzed through NDVI filters. Horizons associated with drier conditions were observed in the upper zone of the core, which corresponded from the year 2001 to the present, assuming a constant sedimentation rate of 2.72 cm·yr−1. Additionally, the characteristic alternation of dry–wet conditions was observed in the deep horizon of the dam sediments. The concentrations of Cu, Pb, Al, and As have increased over the years, while the concentration of Mo has decreased. Some of these elements are associated with copper mining, existing in the valley. Analysis of Landsat images from the year 2000 to the present has identified a significant decrease in vegetation cover associated with dry/wet periods, which may be related to cycles of El Niño/La Niña events. Although not all the proxies analyzed were sensitive enough to detect changes at the desired resolution, since the dam is very recent, the results shed light on the effects of the interaction between industrial activities and the decrease of water availability in multiple-use watersheds, suggesting variations in metals concentrations and changes in water availability, probably promoted by anthropic activities, climatic events, and increasing aridity in the Aconcagua River Valley.

Beyond "greening" and "browning": Trends in grassland ground cover fractions across Eurasia that account for spatial and temporal autocorrelation.

Grassland ecosystems cover up to 40% of the global land area and provide many ecosystem services directly supporting the livelihoods of over 1 billion people. Monitoring long-term changes in grasslands is crucial for food security, biodiversity conservation, achieving Land Degradation Neutrality goals, and modeling the global carbon budget. Although long-term grassland monitoring using remote sensing is extensive, it is typically based on a single vegetation index and does not account for temporal and spatial autocorrelation, which means that some trends are falsely identified while others are missed. Our goal was to analyze trends in grasslands in Eurasia, the largest continuous grassland ecosystems on Earth. To do so, we calculated Cumulative Endmember Fractions (annual sums of monthly ground cover fractions) derived from MODIS 2002-2020 time series, and applied a new statistical approach PARTS that explicitly accounts for temporal and spatial autocorrelation in trends. We examined trends in green vegetation, non-photosynthetic vegetation, and soil ground cover fractions considering their independent change trajectories and relations among fractions over time. We derived temporally uncorrelated pixel-based trend maps and statistically tested whether observed trends could be explained by elevation, land cover, SPEI3, climate, country, and their combinations, all while accounting for spatial autocorrelation. We found no statistical evidence for a decrease in vegetation cover in grasslands in Eurasia. Instead, there was a significant map-level increase in non-photosynthetic vegetation across the region and local increases in green vegetation with a concomitant decrease in soil fraction. Independent environmental variables affected trends significantly, but effects varied by region. Overall, our analyses show in a statistically robust manner that Eurasian grasslands have changed considerably over the past two decades. Our approach enhances remote sensing-based monitoring of trends in grasslands so that underlying processes can be discerned.

98 Environmental impacts and daily voluntary movement of horses housed in pasture tracks as compared to conventional pasture housing

Pasture tracks are a recent trend in equine management. Tracks are a way to increase movement by theoretically mimicking patterns of wild horses, though this has not been proven. To test movement patterns of horses housed in pasture tracks as compared with conventional pastures, a track (3.5m in width) was created around the perimeter of a rectangular 2.0 ha pasture with feeding troughs placed roughly equidistant around the track. Eight horses were paired and rotated between 3 treatment locations: the track (T), the small 2 ha pasture housed within the track (SP), and a larger 12 ha pasture on the same farm (LP). Movement was tracked using a GPS watch (Amazfit Bip U by Zepp Health) attached to the crown of a halter. Testing occurred over a 10-week period in which horses were randomly rotated in pairs to each location with testing in each location occurring simultaneously. Horses were acclimated to each location for 3 d and then tested over a 4-d period during which one horse in each pair would wear the GPS monitor for 2 d followed by the second horse. At the conclusion of the 10-week study, 4 horses on 2 additional farms with existing track systems were monitored for a one-week period to compare their movement patterns to those collected in the test location as controls. Environmental impact of the pasture tracksystem was evaluated by comparing erosion measurements of the track to the small pasture. Erosion was evaluated via quantification of vegetative cover (as measured by standing biomass) and sediment relocation (as measured using an adapted mesh-bag technique). Data was collected on days −7, 14, 33, 67, and 86 of horses being placed on the track. GPS data was analyzed using Minitab v.21 (State College, PA, USA) with housing as a treatment effect. Erosion measurements were run as a repeated-measures over time with location as the treatment effect. Results indicate no differences in daily distance traveled between T and SP (5.7 vs 5.4 km, P = 0.60) or between T and LP (5.7 vs 6.2 km, P = 0.36). Though not comparable, horses on the private farm tracks walked a similar daily distance of 6.1 ± 0.2 km/d avg. There was a decrease in vegetative cover on the track (P < 0.001) from beginning to end of the study, which resulted in sediment relocation (P = 0.013). Collectively, this data does not support the use of pasture tracks as a beneficial management practice to increase movement, and potential environmental impacts of the use of tracks should be considered.

The Impact of Breeding Yellow-Legged Gulls on Vegetation Cover and Plant Composition of Grey Dune Habitats

The establishment of large populations of yellow-legged gull Larus michahellis in coastal and urban areas can lead to strong changes in vegetation cover and composition through creating physical disturbance in the vegetation and impacting the soil quality through defecation. In this study, we evaluated the effects of breeding yellow-legged gull populations on tall and short vegetation cover and plant species composition in old (occupied for 13 years) and new (occupied for 3 years) colony sites in grey dunes of the Algarve, southern Portugal. In each site, sampling plots were used to measure the percentage of vegetation cover in areas with and without breeding gulls. In the old colony site, the cover by tall vegetation was substantially reduced and the cover by short vegetation substantially increased in the areas where gulls are breeding in comparison with the adjacent areas. In the new colony sites, there were only minor differences. The increase in cover of short vegetation in the breeding area of the old colony site was mostly by nitrophilous species (Paronychia argentea and Malcolmia littorea) and should be explained by the decrease in vegetation cover of tall plant species and by feces deposition. Tall and slow-growing species Suaeda maritima and Helichrysum italicum covers were negatively affected. Our results showed that yellow-legged gulls affected vegetation cover and composition of grey dunes after 3 years of consecutive breeding, and this should be considered in the management of these habitats where breeding yellow-legged gulls are increasing.

Detecting land-use landcover changes in a protected area conservancy using geospatial technology

This paper analyses the present and future changes in land-use landcover of the Midlands Rhino Conservancy which is a protected area with mining activities. A GIS and Remote Sensing approach was used for detecting change in the protected area. A thirty-year time of 1980-2020 shows a major land use change, with agricultural activities increasing within the protected area. The projected results help to detect the future changes that might occur under the same case scenario in the protected area. Agricultural activities increased with 20%., Alternatively, there is a decrease in vegetation cover from 60% to 15%, built up increased from 0.03% to 0,08%. The reasons for the change detection such as (for monitoring habitat disturbance among others) have been discussed.

Monitoring of forest ecosystems (on the example of the Kabardino-Balkarian Republic)

The forest is one of the complex terrestrial ecosystems with landscape-geographic variability. The problem of anthropogenic influence on the environment in general and forest ecosystems in particular is steadily growing. The cause of pollution of all environments with the products of technogenesis, a decrease in biodiversity, a decrease in vegetation cover is most often human activity. The increasing anthropogenic impact on forest ecosystems over the years causes a decrease in their biological resistance and can lead to degradation and even complete destruction. The work studies forest ecosystems of the Kabardino-Balkarian Republic. The main forestforming rocks of the republic were identified. The age structure of the main forest-forming species has been determined. An analysis of the dynamics of the forest area by completeness, bonite classes was carried out.

The Growth of Urban Heat Island Effect Monitored in a Rapidly Developing City of Lombok Island

The study aims to monitor urban development around Mataram City and the correlation between Urban Heat Island. Also, analyze the vegetation and built-up changes surrounding Mataram City with Land Surface Temperature (LST) growth. The boundary of the study location is a 25-kilometer radius from the Mataram City centroid. The data used in this research is Landsat 8 Surface Reflectance for the period June-September in 2013, 2019 and 2023 obtained from Google Earth Engine. The Random Forest method is used to obtain land use classification with urban, rice fields, dry land, water bodies, and vegetation. NDBI values are processed from Shortwave infrared (SWIR) and Near-infrared (NIR), NDVI from Near-infrared (NIR) and Red, and LST from thermal bands. The data processing results indicate that Mataram City and its neighboring areas are showing growth, marked by rising NDBI and LST values. This growth is characterized by an expansion of built-up areas to the north, east, and south especially rings 4 and 5, simultaneously by higher NDBI values. Additionally, there is a decrease in vegetation cover, particularly in lowland areas within these rings, leading to a decline in NDVI values. Areas with increased NDBI values also show an increase in LST.

Spatio-temporal Analysis of Changes in Land Use-Land Cover for Conservation Efficacy of Urban Forest Reserve: The Case of Rau Forest Reserve, Tanzania

Changes in land use and land cover in different places around the globe have a significant impact on ecological structure and functions as well. Analysis of the changes in land use and land cover is useful in management activities, especially forest reserves as it reflects the interaction between adjacent communities and natural resources. Due to the rapid sprawl in urbanisation, there has been a rapid change in the human-land relationship. Rau Forest is situated in Moshi Municipality of Kilimanjaro Region in Tanzania. There have been several claims of a decrease in vegetation cover in this important forest reserve, although there is no documentation on such claims. It is on the basis of this background this study was conducted to explore the changes in land use and land cover in the Rau Forest reserve to show the management status of this ecosystem which is also located in an urban area where management activities have been a challenge. The land use and cover (LULC) Spatio-temporal changes in the Rau Forest were classified as Densely Vegetation, Slightly Vegetation, Grassland, Bare land, Built-up, and Waterbodies to evaluate qualitative and quantitative changes in this reserve through the use of GIS techniques and tools over time (1990, 2000 and 2019). Forest encroachment has driven changes in land use and land cover and transformed parts of the Rau Forest reserve into the urban settlement, and grazing lands which has ultimately led to gradual forest degradation. Landsat imageries for the year were used to identify the Spatio-temporal changes in vegetation in the area. This study shows the downward trend for the densely vegetated part of the reserve at the expense of expansion in the built-up area. The results demonstrate the urgent need for strong and more severe regulations concerning the protection of Rau Forest and other urban situated forest reserves against land use and land cover changes for the benefit of the present and future generations.

Climate change impact on water resources of Iraq (a review of literature)

Maintaining natural processes and supporting social and economic growth depend heavily on water supplies. However, Future climate is predicted to bring higher temperatures, which will increase evapotranspiration; lower precipitation totals; and changes in the seasonal pattern of precipitation. Iraq is more vulnerable to climate change than other nations due to the underdeveloped and fragile water management systems there, as well as the country’s desert and warmer environment and increasing sensitivity to extreme weather events. The present work aims to analyse the literature dealing with climate change’s effects on water resources in Iraq. The Scopus database was searched using the keywords (Iraq, models of climate change, and water resources). Most models study the effect of high temperatures and evaporation on water resources using different tools, the most important of which are SWAT, LARS-WG, and HEC-HM. The analysis of previous studies shows that the results of all the literature concordant that Iraq is on the verge of severe water scarcity due to high temperatures and the resulting decrease in rainfall, increase in evaporation, decrease in vegetation cover and increase in desertification.

Geospatial modeling to assess the past and future land use-land cover changes in the Brahmaputra Valley, NE India, for sustainable land resource management.

Satellite remote sensing and geographic information system (GIS) have revolutionalized the mapping, quantifying, and assessing the land surface processes, particularly analyzing the past and future land use-land cover (LULC) change patterns. Worldwide river basins have observed enormous changes in the land system dynamics as a result of anthropogenic factors such as population, urbanization, development, and agriculture. As is the scenario of various other river basins, the Brahmaputra basin, which falls in China, Bhutan, India, and Bangladesh, is also witnessing the same environmental issues. The present study has been conducted on the Brahmaputra Valley in Assam, India (a sub-basin of the larger Brahmaputra basin) and assessed its LULC changes using a maximum likelihood classification algorithm. The study also simulated the changing LULC pattern for the years 2030, 2040, and 2050 using the GIS-based cellular automata Markov model (CA-Markov) to understand the implications of the ongoing trends in the LULC change for future land system dynamics. The current rate of change of the LULC in the region was assessed using the 48years of earth observation satellite data from 1973 to 2021. It was observed that from 1973 to 2021, the area under vegetation cover and water body decreased by 19.48 and 47.13%, respectively. In contrast, cultivated land, barren land, and built-up area increased by 7.60, 20.28, and 384.99%, respectively. It was found that the area covered by vegetation and water body has largely been transitioned to cultivated land and built-up classes. The research predicted that, by the end of 2050, the area covered by vegetation, cultivated land, and water would remain at 39.75, 32.31, and 4.91%, respectively, while the area covered by built-up areas will increase by up to 18.09%. Using the kappa index (ki) as an accuracy indicator of the simulated future LULCs, the predicted LULC of 2021 was validated against the observed LULC of 2021, and the very high ki observed validated the generated simulation LULC products. The research concludes that significant LULC changes are taking place in the study area with a decrease in vegetation cover and water body and an increase of area under built-up. Such trends will continue in the future and shall have disastrous environmental consequences unless necessary land resource management strategies are not implemented. The main factors responsible for the changing dynamics of LULC in the study area are urbanization, population growth, climate change, river bank erosion and sedimentation, and intensive agriculture. This study is aimed at providing the policy and decision-makers of the region with the necessary what-if scenarios for better decision-making. It shall also be useful in other countries of the Brahmaputra basin for transboundary integrated river basin management of the whole region.

LST variability and population growth in district of Rawalpindi, Pakistan during 1993–2018: A regional climate model based bias correction approach for LST

Variability of satellite-based land surface temperature (LST) due to variations in vegetation cover is analyzed using the Landsat Thematic Mapper/Enhanced Thematic Mapper Plus satellite data in district of Rawalpindi, Pakistan during the period of 1993–2018. Analysis was performed over two Tehsils (sub-districts) of district Rawalpindi: Taxila and Rawalpindi. Trends and variability in LST are examined using the probability density functions (PDFs). The 10th and 90th percentile (P10 and P90) of PDFs were computed to assess the lower and upper LST percentile differences for both Tehsils. It is noted that ΔP90(2018–1993) > ΔP10(2018–1993), implying more warming in higher temperatures as compared to that in lower temperatures during the study period for Tehsil Taxila only. The applicability of a regional climate model (RCM) for bias correction of LST is discussed. A mean and variance-based bias correction was performed by using a RCM Providing REgional Climates for Impacts Studies (PRECIS). Before correction, the LST overestimation approaches to −6.48 °C for all years for district Rawalpindi except for the year 1993, however bias corrected overestimation reduces to −4.40 °C. Relationship of census data with LST over Tehsil Rawalpindi is somewhat stronger using PRECIS based bias correction. The correlation between LST and Green Vegetation Fraction (GVF) is −0.55; the negative sign indicates a decrease in vegetation cover resulting in an increase of LST.

Impact of Land System Changes and Extreme Precipitation on Peak Flood Discharge and Sediment Yield in the Upper Jhelum Basin, Kashmir Himalaya

The Kashmir valley is prone to flooding due to its peculiar geomorphic setup compounded by the rapid anthropogenic land system changes and climate change. The scarcity of observations is one of the major challenges for understanding various land surface processes in the mountainous and mostly ungauged terrain. The study assesses the impact of land use and land cover (LULC) changes between 1980 and 2020 and extreme rainfall on peak discharge and sediment yield in the Upper Jhelum Basin (UJB), Kashmir Himalaya, India using KINEROS2 model. Analysis of LULC change revealed a notable shift from natural LULC to more intensive human-modified LULC, including a decrease in vegetative cover, deforestation, urbanization, and improper farming practices. The findings revealed a strong influence of the LULC changes on peak discharge, and sediment yield relative to the 2014 timeframe, which coincided with the catastrophic September 2014 flood event. The model predicted a peak discharge of 115,101 cubic feet per second (cfs) and a sediment yield of 56.59 tons/ha during the September 2014 flooding, which is very close to the observed peak discharge of 115,218 cfs indicating that the model is reliable for discharge prediction. The model predicted a peak discharge of 98,965 cfs and a sediment yield of 49.11 tons/ha in 1980, which increased to 118,366 cfs and, 58.92 tons/ha, respectively, in 2020, showing an increase in basin’s flood risk over time. In the future, it is anticipated that the ongoing LULC changes will make flood vulnerability worse, which could lead to another major flooding in the event of an extreme rainfall as predicted under climate change and, in turn, compromise achievement of sustainable development goals (SDG). Therefore, regulating LULC in order to modulate various hydrological and land surface processes would ensure stability of runoff and reduction in sediment yield in the UJB, which is critical for achieving many SDGs.

Detecting land surface water changes in the Upper Mzingwane sub-catchment using remotely sensed data

Abstract Globally, water is acknowledged as indispensable. It is essential for both human life and environmental needs. However, surface water resources are threatened by human and climatic influences, which may result in changes in size and density. This study aimed to evaluate the effectiveness of the normalised difference water index (NDWI), modified normalised difference water index (MNDWI) and automated water extraction index (AWEI) in detecting land surface water changes using Landsat satellite data. The results showed that the AWEI performed considerably better than the MNDWI and NDWI for extracting water surface area in the Upper Mzingwane sub-catchment, with an overall accuracy of 0.93 and a kappa coefficient of 0.82. The MNDWI and NDWI had overall accuracy/kappa values of 0.88/0.74 and 0.89/0.73, respectively. The AWEI can enhance surface water features while effectively suppressing or eliminating pollution and noise from surrounding vegetation and muddy soil. NDWI/MDWI water information is often mixed with pollution noise, vegetation and muddy soil, overestimating the area of water. All the applied indices indicate a progressive loss in the surface area of the water bodies in the sub-catchment. The decrease in water surface area could be a result of degradation, as it coincided with a decrease in vegetation cover and an increase in degraded areas. Future research needs to investigate the hydrological response of the sub-catchment to the potential influence of climate, variability, change, and land use land cover (LULC) changes.

Spatial evolution of land use and land cover for the Tatu-Bola Wildlife Refuge - Pernambuco, using orbital images

This article aims the analyze NDVI (Normalized Difference Vegetation Index), NDWI (Normalized Difference Water Index), and NDBI (Normalized Difference Built-up Index) radiometric indices for TM and OLI sensor scenes aboard the LANDSAT satellite. The study area is the Tatu-Bola Wildlife Refuge, created in March 2015 through State Decree number 41,546, and its surroundings. The study aimed to monitor the spatial and temporal evolution of land use and land cover in a period before and after the implementation of the Armadillo-Bola Wildlife Refuge, using indices of vegetation (NDVI), moisture (NDWI), and exposed soil (NDBI) and its relationship with the surroundings. TM and OLI images (orbit and point 217-066) were used on board the LANDSAT satellite 5 (23-05-1987, 15-05-1996, and 01-02-2005) and 8 (28-01-2015 and 17- 03-2021), radiometrically and geometrically corrected and obtained by accessing EarthExplorer, with the calculation of radiance and reflectance being performed, and the indices applied. In order to better identify the area with vegetation and exposed soil, the RGB composition was performed, with NDBI, NDVI, and NDWI indices for Landsat images and fusion of multispectral and panchromatic bands in WPM sensor images from the CBERS-4A satellite from 23- 08-2020 (orbit and point 198-124) and 18-09-2020 (199-124). Digital numbers of cloud and shadow pixels were excluded through supervised classification. Between 1987 and 2021, it was possible to observe a decrease in vegetation cover, especially around the RVS Armadillo-balla, and an increase in area, with NDVI values lower than 0.40. The Refuge area in Petrolina has the largest amount of deforested area. The use of RGB composition of the indices and the merged images from the CBERS-4A satellite, with a spatial resolution of 2 m, present a significant improvement in identifying areas of exposed soil and dry vegetation.

Assessment of Runoff and Soil Loss Under Natural Vegetation Cover and Rainfall in a Semi-Arid Catchment, West Pokot County, Kenya

Soil erosion has become a major cause of land degradation with regrettable economic losses. It has affected livelihoods of many agro-pastoral communities in Arid and Semi-arid Lands (ASALs). There is need for continuous assessment of soil erosion in these areas in order to provide sufficient data on soil loss for soil resource management, conservation, and land use planning. The purpose of this study was to determine the rate of soil loss by water for soil conservation planning in West Pokot County, Kenya. Two adjacent fields with variable vegetation cover density were identified in a semi-arid catchment for runoff plot research. Vegetation cover on the fields was measured using the transect line-intercept survey method. Field 1 had 25–50% vegetation cover while field 2 had 50–75% vegetation cover. On each field, three identical erosion plots with dimensions 20 m along the slope and 10 m wide were constructed. Runoff and sediment from the plots were measured for fifteen rainfall-runoff events during the long rains season. Data was analysed using correlation analysis and linear regression methods. The results show that runoff production varied from 1.03% to 1.44% of total rain water. Soil loss from the plots was 120.3–155.5 g/ . Runoff-rainfall correlation analysis showed a significant positive relationship (r =0.9609, P&lt;0.05%) with 92.33% variance in runoff production. Soil loss had significant positive relationship with runoff (r =0.9840, P&lt;0.05%) with 96.83% variance in soil loss. The study found that runoff production and soil loss was slow in the field with dense vegetation cover. Studies project an increase in human and livestock populations in semi-arid areas. This points at possible decrease in vegetation cover and increase in the rate of soil loss by water. The study recommends development of a soil conservation and management strategy in the study area.