70 research outputs found

    Mapping of the Prosopis-Juliflora (Mesquite) invasion and its effects on pastoralist livelihoods in the Red Sea State, Sudan – a remote sensing approach

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    Land cover management policies and land use changes are among the risks facing pastoral lands in eastern Sudan. Land use/land cover (LULC) changes play a major role in the study of global change. LULC and human/natural modifications have largely resulted in deforestation, biodiversity loss, global warming, and an increase in natural disaster flooding. This thesis’s investigates vegetation change with a focus on the expansion of Prosopis-Juliflora (Mesquite) and its impact on pastoralist livelihoods in Red Sea State in Sudan. The current study was conducted in three areas of Red Sea State (Sinkat and Jubayt, Ashat, and Salum). Remote sensing and Geographical Information systems (GIS) were used to monitor and map changes in land cover and land use (LULC). Multi-temporal Landsat satellite data from 1984-2020, were used to identify LULC change and study the dynamics of change, the effects of the expansion of the P. juliflora on the livelihoods of pastoralists in the Red Sea region (Sudan), and the identification of possible adaptations therein were studied using interviews. Socioeconomic data were correlated with remote sensing data to analyze the causes and effects of change in LULC and land degradation.Master's Thesis in GeographyGEO350MASV-PHYGMPGEOGRMASV-GEOGMASV-MEH

    Mapping Prosopis glandulosa (mesquite) invasion in the arid environment of South African using remote sensing techniques

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    A dissertation submitted to the School of Geography, Archaeology and Environmental Studies, Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science in Environmental Sciences. Johannesburg, March 2016.Mapping Prosopis glandulosa (mesquite) invasion in the arid environment of South Africa using remote sensing techniques Mureriwa, Nyasha Abstract Decades after the first introduction of the Prosopis spp. (mesquite) to South Africa in the late 1800s for its benefits, the invasive nature of the species became apparent as its spread in regions of South Africa resulting in devastating effects to biodiversity, ecosystems and the socio-economic wellbeing of affected regions. Various control and management practices that include biological, physical, chemical and integrated methods have been tested with minimal success as compared to the rapid spread of the species. From previous studies, it has been noted that one of the reasons for the low success rates in mesquite control and management is a lack of sufficient information on the species invasion dynamic in relation to its very similar co-existing species. In order to bridge this gap in knowledge, vegetation species mapping techniques that use remote sensing methods need to be tested for the monitoring, detection and mapping of the species spread. Unlike traditional field survey methods, remote sensing techniques are better at monitoring vegetation as they can cover very large areas and are time-effective and cost-effective. Thus, the aim of this research was to examine the possibility of mapping and spectrally discriminating Prosopis glandulosa from its native co-existing species in semi-arid parts of South Africa using remote sensing methods. The specific objectives of the study were to investigate the spectral separability between Prosopis glandulosa and its co-existing species using field spectral data as well as to upscale the results to different satellites resolutions. Two machine learning algorithms (Random Forest (RF) and Support Vector Machines (SVM)) were also tested in the mapping processes. The first chapter of the study evaluated the spectral discrimination of Prosopis glandulosa from three other species (Acacia karoo, Acacia mellifera and Ziziphus mucronata) in the study area using in-situ spectroscopy in conjunction with the newly developed guided regularized random forest (GRRF) algorithm in identifying key wavelengths for multiclass classification. The GRRF algorithm was used as a method of reducing the problem of high dimensionality associated with hyperspectral data. Results showed that there was an increase in the accuracy of discrimination between the four species when the full set of 1825 wavelengths was used in classification (79.19%) as compared to the classification used by the 11 key wavelengths identified by GRRF (88.59%). Results obtained from the second chapter showed that it is possible to spatially discriminate mesquite from its co-existing acacia species and other general land-cover types at a 2 m resolution with overall accuracies of 86.59% for RF classification and 85.98% for SVM classification. The last part of the study tested the use of the more cost effective SPOT-6 imagery and the RF and SVM algorithms in mapping Prosopis glandulosa invasion and its co-existing indigenous species. The 6 m resolution analysis obtained accuracies of 78.46% for RF and 77.62% for SVM. Overall it was concluded that spatial and spectral discrimination of Prosopis glandulosa from its native co-existing species in semi-arid South Africa was possible with high accuracies through the use of (i) two high resolution, new generation sensors namely, WorldView-2 and SPOT-6; (ii) two robust classification algorithms specifically, RF and SVM and (iii) the newly developed GRRF algorithm for variable selection and reducing the high dimensionality problem associated with hyperspectral data. Some recommendations for future studies include the replication of this study on a larger scale in different invaded areas across the country as well as testing the robustness of the RF and SVM classifiers by making use of other machine learning algorithms and classification methods in species discrimination. Keywords: Prosopis glandulosa, field spectroscopy, cost effectiveness, Guided Regularised Random Forest, Support Vector Machines, Worldview-2, Spot-

    Temporal relationship between climate variability, Prosopis juliflora invasion and livestock numbers in the drylands of Magadi, Kenya

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    A study was conducted to determine the association of climate variability, Prosopis juliflora spread, and other vegetation trends with livestock population dynamics in Kajiado County, Kenya. Monthly rainfall, mean monthly temperatures, cattle, sheep and goats populations from January 2000 to December 2014, were analyzed to determine time series trends. Normalized Difference Vegetation Index (NDVI) data derived from moderate resolution imaging spectroradiometer (MODIS) 250 m satellite imageries for 2000 to 2014 were used to determine the temporal dynamics of P. juliflora invasion in the study area. Both temperature and rainfall trends showed marked variability over the period under study. The mean monthly temperatures during the long dry season increased erratically from 33°C in 2000 to 37°C in 2014. Moreover, the rainfall during the wettest season was 600 mm in 2000 and 250 mm in 2014. During the study period, divergence from the long term mean rainfall (450 mm) decreased from 585 to 403 mm. At the same time cattle population decreased, sheep and goats populations remained static. P. juliflora invasion correlated positively (r=0.2; P<0.05) with mean monthly temperature and negatively (r=-0.4; P<0.05) with rainfall and other vegetation cover in drier parts, but not in the higher altitude and wetter parts of the study area. It also correlated negatively with cattle populations (r=-0.4; P<0.05). In the 1980’s, bushlands and woodlands constituted 95 and 5% of the land cover, while in 2008, herbaceous vegetation, shrublands, and open trees together with bare areas constituted 50, 30, and 22%, respectively; out of which 70% had been taken over by Prosopis in 2014. This study demonstrated that even though the trends showed that cattle population decreased as climate variability and Prosopis invasion increased, there was no significant correlation among the attributes, over the period under study.Key words: Climate, drylands, livestock, Prosopis juliflora, variability vegetation, trends, mesquite

    Distribution and economic analysis of Prosopis juliflora in Ethiopia

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    Includes bibliographical references.2015 Fall.Invasive species are one of the drivers of biological and socio-economic changes around the world. Over the past 30-40 years, the non-native Prosopis juliflora plant has emerged as a major invader of the arid and semi-arid regions of Ethiopia. Information on its distribution, impact, use and management is highly needed to contain and prevent the spread of this highly invasive plant. In the first study, I used a correlative modeling framework to track and map the current and potential distribution of P. juliflora in Afar, north-eastern Ethiopia. Specifically, I used time-series of Moderate Resolution Imaging Specrtoradiometer (MODIS) satellite imagery, 143 species-occurrence records and the Maxent modeling technique to map its current distribution. I then used topo-climatic predictors, species-occurrence records and the Maxent software to map its forecasted distribution. I found that the current extent of P. juliflora invasion in the Afar region is approximately 3,605 Km2, while its predicted distribution is approximately 5,024 Km2. My findings demonstrates that MODIS vegetation indices and species-occurrence points can be used with Maxent modeling software to map the current distribution of P. juliflora, while topo-climatic variables are good predictors of its potential habitat in Ethiopia. In the second study, I used a participatory research framework to map P. juliflora over a fine geographic scale, and to identify the major resource related problems in the region. I learned about the introduction history, spread, impacts, uses and traditional management practices of P. juliflora in Afar by interviewing 108 pastoralists and agro-pastoralists. Additionally, I detected the land-cover categories most affected by P. juliflora invasion by superimposing community produced maps on ancillary land-cover layers, and performing overlay analysis. Prosopis juliflora has highly invaded grasslands and open areas in Afar. The species displaces useful native grass and forage species, which are important for sustaining the region's wildlife and livestock resources. In addition to threats from invasive species, Afar people face conflicts from neighboring Issa ethnic groups, and land-grabs from the central government and foreign investors. The findings demonstrates that participatory mapping methods are suitable for mapping species distribution, detecting land-cover changes, and managing invasive plants. High invasive species control costs have swayed most developing countries to adopt cost effective P. juliflora eradication and utilization practices. However, the effectiveness and economic viability of these new approaches have not been thoroughly tested. In the third study, I used an economic analysis framework to assess the economic feasibility of selected P. juliflora eradication and utilization methods that are practiced in southern Afar. The dominant P. juliflora eradication option was to convert infested lands into irrigated farms, while the preferred utilization options were to make animal fodder from P. juliflora seed pods, and to produce charcoal from P. juliflora wood. I interviewed 19 enterprise owners (i.e., farmers, flour producers and charcoal makers) and collected primary data on prices, yields, costs and revenues. I assessed the economic feasibility of the selected methods by performing enterprise, profitability, sensitivity and risk analyses over 10 years and an interest rate of 10% per year. Converting P. juliflora infested lands into irrigated agriculture is a profitable and risky P. juliflora eradication approach. Charcoal making is a moderately profitable and less risky utilization approach, while flour production is a risky and an un-profitable utilization approach. Introducing new changes in the production and management steps of flour production may be needed to make flour enterprises profitable. My overall economic analysis suggests that control through utilization may be one of the effective and economically viable P. juliflora management strategies currently accessible to Ethiopia. I generated reliable information on the distribution and impacts of P. juliflora in Afar by employing a wide variety of scientific approaches. My results can guide local level P. juliflora utilization and control efforts in Afar, while my methodologies can be replicated for managing invasive plants in other developing countries

    Mapping Spatial and Temporal Distributions of P. juliflora (Sw.) Dc in Afar Region, Ethiopia

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    In Ethiopia, Invasive Alien Species (IAS) and their related impacts on biodiversity are increasing. The expansion rate of P. juliflora (Mesquite) brought economic, social and ecological problems in Afar region. The intension of the present study is to map the spatial and temporal distributions of P. juliflora in Afar region, Ethiopia. Mapping the temporal and spatial distributions and quantifying the invaded areas was carried out using geospatial techniques. The results showed that during the period 1985 to 2016, P. juliflora expands by 136 km2 Year-1annually. Its trend involves lag phase, astonishing recover after disturbance, and high infestation rate. The results of the study are helpful in making and/or implementing policies and strategies of environmental and biodiversity managements. The study suggests future studies to include ecological triggers of IAS

    The Great Green Forest is here and expanding all on its own: A call for action

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    Prosopis juliflora is recognized as one of the most invasive tree species worldwide. Following widespread introductions throughout arid and semi-arid regions of Africa and throughout the world, it has spread rapidly, threatening natural ecosystems and livelihoods. Control through utilization as a resource is now accepted as the way forward in developing countries, but efforts have so far been uncoordinated, with only isolated impacts. This paper reports on the global state of knowledge and recent advances, but focuses on prosopis-related research and innovations from IGAD member countries; the successes, failures, challenges and opportunities. It underlines the need to build and apply scientific knowledge to scale up new, resilient, drought-proof livelihood options in the Greater Horn of Africa and elsewhere where introduced, from value-added prosopis wood and non wood products. The authors estimate that there are at least five million hectares of prosopis forest across the region of the perhaps ten million throughout Africa, and growing significantly in extent every year. Experiences from the native range such as in Peru are well documented, where community associations sustainably manage and make a living from fuel, fodder, food, honey and timber from their prosopis forests. Efforts in Ethiopia, Djibouti and Kenya have had mixed results, but milling the sweet protein-rich pods into animal feed is becoming increasingly popular with the introduction of appropriate small scale technologies. Its use as a human food ingredient has also been promoted, though with little uptake, but there is sharp rise in the use of prosopis charcoal in the region, and the possibility of electricity generation using wood chips (bioenergy), with the transfer of experiences from India where there are at least 15 power stations fueled entirely by prosopis. But much more can be done by applying scientific knowledge and innovation to enhance the role of prosopis in improving food security, climate change mitigation and adaptation, and building resilience for millions of the poorest rural and urban people in the Greater Horn of Africa, with great potential for exchange and scaling up in other arid areas in Africa, Asia and the Americas. This paper is a call to the African Union, national governments, IGAD, IFAD, FAO, the Arab League and other international, regional and bilateral donors, to come together and support a regional research and development programme to push the frontiers on prosopis management and utilization and develop a transnational strategy, as the impacts are potentially enormous and immediate. The initial objectives are to take stock of existing knowledge and practices, assess prosopis forest areas throughout the region, estimate wood and pod volumes and production rates, document prosopis management and utilization experiences, enhance South-South knowledge sharing, and rapidly and effectively scale up the successes

    Ecological impacts of Prosopis invasion in Riverine forests of Kenya

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    Drylands occupy over 41% of the global land surface, with Africa and Asia accounting for 32% of the global total each. Because of poor resource management, resource overexploitation and periodic droughts, drylands have experienced severe land degradation. Land degradation is manifested in vegetation loss or deterioration, soil erosion and salinization of soil and water. In Kenya, drylands occupy over 87% of the land surface, and support about 30% of the national population, over 70% of national livestock and the bulk of wildlife that support the tourist sector. Following the prolonged sahelian droughts of the 1970’s Kenya’s drylands were seriously degraded through extensive loss of ground vegetation cover; thus threatening the survival of local populations, livestock production and sustenance of tourism sector. Subsequently, exotic trees and shrubs were introduced for land rehabilitation and fodder supply. Trees from from Prosopis genus emerged as the most adapted and were widely planted. Since introduction, Prosopis species have spread from target rehabilitation sites and invaded riverine and wetlands ecosystems but invasion mechanisms and impacts are not yet well understood. In this study we combined geographical information systems techniques; field, greenhouse and laboratory studies, to evaluate riverine habitat invasibility, invasion impacts, invasiveness of Prosopis species and the composition of invasive Prosopis species in Kenya. The following questions were addressed: 1) What abiotic factors make riverine forests vulnerable to Prosopis invasion?, 2) What are the ecological implications of Prosopis invasion in riverine forests?, 3) What mechanisms underlie inhibition of A. tortilis regeneration by Prosopis species invasion?, 4) What are the species composition in Prosopis invaded areas of Kenya, and 5) What are the implications of our results? The present study revealed indiscriminate Prosopis invasion in all land cover and land use types identified through satellite image analysis, field surveys and historical site information provided by local informants. As a result of this trend, we found a contrasting occurrence increase of Prosopis species and decrease of Acacia tortilis between 1998 and 2007. Accordingly, the study has demonstrated that Prosopis species invasion in the Turkwel Riverine forest is invoked more by species invasiveness rather than habitat susceptibility. Consequently, we investigated the invasiveness of Prosopis species by studying invasion impacts and the underpinning mechanisms Our study has shown reduction of herbaceous species ground vegetation cover and herbaceous species diversity, and termination of A. tortilis regeneration by Prosopis invasion. The negative regression coefficients found between herbaceous species ground cover or between herbaceous species diversity and Prosopis canopy dummy, clarifies the partial direct negative effect of Prosopis on herbaceous species. We corroborate this finding by greenhouse studies that show stronger inhibition A. tortilis and Prosopis seed germination by increasing the concentration of fresh Prosopis litter than by increasing the concentration A. tortilis litter in the soil. Indeed, our study demonstrates potential of seed germination termination at 50% fresh Prosopis litter concentration in the soil. After one month of watering of soil-litter mixture, we found no litter effect on seed germination. Since water leaching decreased the concentration of soluble phenols and leached litter had no effect on seed germination, our study has clarified that the inhibition of A. tortilis regeneration by Prosopis canopy was partially the result of allelopathic effect of Prosopis litter on A. tortilis seed germination. There has been great confusion on Prosopis species identity in Prosopis invaded areas of Kenya, because of similar morphology and introduction of several species within sites. Species misidentification may hamper invasion management. In this study we used Random Amplified DNA markers to differentiate species according to sites. Our study shows that only one species or a hybrid is adapted to any one site, despite the number of species that were introduced to any site. We have further clarified that P. juliflora and its hybrid are the most invasive germplasm in Kenya. However, P. juliflora and the hybrid trees tended to have similar tree characteristics in riverine forests and wetlands as we could predict tree volumes in wetlands from equations developed from a distant riverine site. Our study demonstrates potential for perpetual replacement of A. tortilis by Prosopis species in riverine ecosystems. A notable consequence is reduction of both herbaceous species productivity and diversity. Since both A. tortilis and herbaceous species are used for fodder; invasion may have severe consequences on the pastoral economy but this can be reversed by intensified utilization of Prosopis biomass for fuelwood and pods for fodder.   </p

    Invasive Alien Weed Species Distribution, Impacts on Agriculture, Challenge and Reaction in Ethiopia: A Review

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    Invasive Alien Species are of a great concern in Ethiopia, posing particular problems on agricultural lands, range lands, biodiversity of the country, national parks, water ways, rivers, power dams, roadsides and urban green spaces with great economic and ecological consequences. In Ethiopia, there are about 35 invasive alien species were identified. Foremost among these are Parthenium hysterophorus L., Eichhornia crassipes (Mart.) Solms, Prosopis juliflora (Sw.) DC., Lantana camara L., Argemone ochroleuca Sweet, Xanthium strumarium L., Ageratum conyzoides L., Datura stramonium L., Nicotiana glauca Graham, Senna didymobotrya (Fresen.) Irwin &amp; Barneby and Senna occidentalis (L.) Link. They have been identified as a threat to Agriculture land, biodiversity of the country and economic well-being of its people. Their high seed production capacity and spread, adaptation to wide climatic and soil conditions, spread by animal movement and their association with pastoralists way of life and overgrazing are challenges to their management in Ethiopia. Parthenium exert strong allelopathic effect and reduce the growth and reproductively of associated crops. Labor-intensive control of parthenium resulted in some of them developing skin allergies, itching, fever, and asthma. Eichhornia crassipes restrict proper water flow, water loss through excessive evapo-transpiration, interference with fishing, grazing and crop production activities, effect on power generation, increase siltation, flooding, and increase cost of production. Prosopis form impenetrable thicket that prohibits free movement of people and animals and its thorns damage eyes and hooves of animals. Current costs of Prosopis invasion in Ethiopia was estimated 2.2 billion Birr. More resources have to be invested to tackle the IAS problem as the estimated loss is disproportionate to the cost of investment on IAS research and development activities. This paper attempts to review the available research information on IAS, i.e, distribution and spread, impacts, control measures and suggest the future prospects on research and management. Keywords: Alien Invasive Species, Ecological distribution, Ethiopia, Impac

    The biogeography of South African terrestrial plant invasions

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    Thousands of plant species have been introduced, intentionally and accidentally, to South Africa from many parts of the world. Alien plants are now conspicuous features of many South African landscapes and hundreds of species have naturalised (i.e. reproduce regularly without human intervention), many of which are also invasive (i.e. have spread over long distances). There is no comprehensive inventory of alien, naturalised, and invasive plants for South Africa, but 327 plant taxa, most of which are invasive, are listed in national legislation. We collated records of 759 plant taxa in 126 families and 418 genera that have naturalised in natural and semi-natural ecosystems. Over half of these naturalised taxa are trees or shrubs, just under a tenth are in the families Fabaceae (73 taxa) and Asteraceae (64); genera with the most species are Eucalyptus,Acacia, and Opuntia. The southern African Plant Invaders Atlas (SAPIA) provides the best data for assessing the extent of invasions at the national scale. SAPIA data show that naturalised plants occur in 83% of quarter-degree grid cells in the country. While SAPIA data highlight general distribution patterns (high alien plant species richness in areas with high native plant species richness and around the main human settlements), an accurate, repeatable method for estimating the area invaded by plants is lacking. Introductions and dissemination of alien plants over more than three centuries, and invasions over at least 120 years (and especially in the last 50 years) have shaped the distribution of alien plants in South Africa. Distribution patterns of naturalised and invasive plants define four ecologically-meaningful clusters or “alien plant species assemblage zones”, each with signature alien plant taxa for which trait-environment interactions can be postulated as strong determinants of success. Some widespread invasive taxa occur in high frequencies across multiple zones; these taxa occur mainly in riparian zones and other azonal habitats,or depend on human-mediated disturbance, which weakens or overcomes the factors that determine specificity to any biogeographical region
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