Agriculture

Permanent URI for this collection

http://196.216.167.205/handle/10628/945

Browse

Now showing 1 - 20 of 27

An analysis of the risks collisions between aircraft and vultures in Namibia
(Namibian Journal of Environment, 2020-05) Hauptfleisch, ML; Knox, Nichola; Aschenborn, O; MacKenzie, ML; Heita, P
Collisions between aircraft and birds and other animals occur frequently and are known in the aviation industry as wildlife strikes. They are considered to be one of the most serious safety and financial risks to the global aviation industry. The International Civil Aviation Organisation, a United Nations specialised Agency, requires that the appropriate authority shall take action to eliminate or to prevent the establishment of any source which may attract wildlife to the aerodrome, or its vicinity, unless an appropriate wildlife assessment indicates that they are unlikely to create conditions conducive to a wildlife hazard problem. Namibian airports reduce the wildlife strike risk by managing the airport habitat and actively chasing birds and other hazardous animals away. The bird strike risk in airspace between airports is not managed or assessed in Namibia. Following one White-Backed Vulture strike and several reports of near-misses with vultures by pilots of small aircraft, this study investigated possible collision hotspot areas considering small commercial aircraft flight paths and vulture movement areas. The study used spatial proximity analysis and temporal overlap to compare telemetry and nesting location data for the three most commonly encountered vulture species to flight paths and times of small commercial aircraft. Collision risk hotspots were identified over three national parks: Etosha, Waterberg and the Pro-Namib portion of the Namib-Naukluft. Ascending from, or approaching, Hosea Kutako International Airport from the east was identified as a particular risk for White-backed Vulture conflict, while risk of Lappet-faced vulture strikes was high to the east of Walvis Bay airport. Flight times of vultures and aircraft corresponded greatly, increasing the collision risk. The recommendations of this work are that pilots of small commercial aircraft should be made aware of particular risk areas, and that landing at Hosea Kutako from the east, or taking off in an easterly direction should be minimised when wind conditions allow, to reduce vulture collision risk.
Assessment of farmers' perceptions and the economic impact of climate change in Namibia: Case study on small scale irrigation farmers (SSIFs) of Ndonga Linena Irrigation Project.
(JDAE, 2014) Montle, B. P.; Teweldemedhin, Mogos Y.
This paper examines perceptions of small-scale irrigation farmers (SSIFs) with regard to climate change and their adaptation strategies in terms of its effects. The The Multinomial Logit (MNL) and the Trade-Off Analysis models were applied. Farm-level data was collected from the entire population of 30 SSIFs at the Ndonga Linena Irrigation Project in February 2014. Results from the MNL reveal that the gender, age and farming experience and extension services, yield and mean rainfall shift, are significant and positively related to the level of the farmers' diversification strategies. Trade-off analysis for multi-dimensional impact assessment (TOA_MD) model results project that climate change will have a negative economic effect on farmers, with 17.5, 25.95, 41.15 and 3.76% of farmers set to gain from climate change across 20, 30, 40 and 50% physical yield reduction scenarios respectively. Farm net return and per capita income are also expected to decline across all scenarios in future, while the poverty level is expected to rise. This study will have certain policy implications in terms of safeguarding the farmers' limited productive assets. Policy should target diversification.
Bush encroachment in the Auas-Oanob Conservancy, Namibia.
(2009) Zimmermann, Ibo
Case study of adaptive rangeland management by an innovative Kalahari farmer.
(2008) Zimmermann, Ibo; Joubert, David F.; Smit, G.N.
Scientists can learn a great deal from innovative farmers who apply adaptive management principles based on experience gained over decades. This paper records 31 observations that a farmer, Jan Labuschagne, made on his farm to the south of Gobabis. The observations relate to aspects such as animal behaviour and performance, animal trampling, and applications of grazing and fire. They are tabulated together with their possible explanations and their management applications. The conceptual model the farmer has built to aid his understanding and decision making is also shown as a diagram and explained. Of critical importance is the strategic timing of management interventions on different parts of the farm in relation to rainfall events, texture and organic content of the soil and maturity of the vegetation. Data are presented to support some of the observations
A crude quantification of wood that is and can be harvested from bush thickening species in Namibia.
(Namibia, Ministry of Environment and Tourism, 2002) Zimmermann, Ibo; Joubert, David F.
The increasing rate at which thickening bushes are being harvested in Namibia requires better information on the availability and sustainability of the resource, in order to improve management. Two sources of data from the literature were combined to give a rough approximation of the standing biomass of wood of appropriate size for charcoal production, in each of nine bush-thickened zones. The overall estimate came to roughly 135 million tons of dry wood in about 260 000 square kilometres of Namibia, or an average of just over 5 t/ha. The legal commercial harvest for the 1999/2000 financial year came to the equivalent of just under 0.2 million tons of dry wood. Interviews with ten charcoal producers, and field data gathered at one site, suggest that harvesting could take place at intervals of roughly 20 years, provided that harvesting is selective and leaves sufficient bushes of different size classes for regeneration. However, it is likely that subsequent harvests would be lower and more difficult to obtain. Previously chopped bushes could then only be re-harvested on every third or fourth cycle, preferably after being pruned to maintain a more appropriate growth form, which is easier to harvest and more conducive to grass growth.
Degradation gradient as a basis for monitoring the ephemeral Omatako floodplains of central Namibia.
(Global Wetlands, 2003) Zimmermann, Ibo
A group of Herero cattle farmers initiated a community grazing trial within a floodplain of the ephemeral Omatako River in central Namibia. A degradation model was constructed from measurements of various characteristics, for determining changes in wetland condition. Species data for Canonical Correspondence Analysis (CANOCO) came from the nearest perennial grass, if present within 5m of the sample point, otherwise from the nearest annual grass. The first ordination axis indicates a degradation gradient, with perennial grass species towards one extreme and annual grasses towards the other. The second axis appears to reflect a moisture gradient, although it was not measured.
The effect of a prescribed burn, followed up with browsing pressure, on rangeland condition in the mountain savanna and karstveld of Namibia.
(DINTERIA, 2002) Zimmermann, Ibo; Mwazi, Fidelis N.
Measurements were taken before and after the application of a prescribed burn, aimed at controlling bush thickening, on a commercial farm in the Mountain savanna and Karstveld of Namibia. The high fuel load, due to high rainfall during the previous season, resulted in an intense fire that caused considerable top kill of bushes. However, the bushes, dominated by Dichrostachys cinerea, resprouted at varying time intervals after the fire, mostly from the ground level. The occasional goat browsing pressure that was subsequently applied was insufficient to keep the majority of bushes under control. Hence browsing pressure would need to be applied more frequently and over a longer time period after a fire, in order to keep more of the bush regrowth under control. The goats also grazed significantly on the regrowth from perennial grasses. Therefore the browsing pressure should not be excessive, as the goats also threaten the perennial grasses.
Evaluating grazing response strategies in winter annuals: A multi-trait approach
(Wiley, 2021) Kurze, Susanne., Bilton, Mark C., Álvarez-Cansino, Leonor., Bangerter, Sara., Prasse, Rüdiger., Tielbörger, Katja., Engelbrecht, Bettina M. J.
Plants minimize fitness losses through grazing by three fundamental strategies: tolerance, avoidance and escape. Annual species have been traditionally assumed to escape grazing through their short life cycle and seed dormancy; however, their grazing response strategies remain almost unexplored. How traits and their coordination affect species' grazing responses, and whether the generalized grazing model, which posits convergent filtering by grazing and drought, is applicable to this ecologically and economically important species group thus remain unclear. 2. We used a trait-based approach to evaluate grazing response strategies of winter annuals from the Middle East. Across 23 species, we examined the coordination of 16 traits hypothesized to be relevant for grazing responses, and linked them to species' fecundity responses, as proxy for fitness responses, to simulated grazing in controlled conditions, to species' abundance responses to grazing in the field and to species' distribution along a large-scale rainfall gradient. 3. Winter annuals exhibited both grazing escape and to a lesser extent tolerance indicated by (a) independent coordination of escape and tolerance traits, and (b) maintenance of higher fecundity in species with more pronounced escape or tolerance traits under simulated grazing. In the natural habitat, species with a more pronounced escape but not tolerance strategy maintained higher abundance under grazing in dry habitats, indicating convergent favouring of escape by both grazing and drought. However, this finding at the local scale was not mirrored by a strategy shift along a large-scale rainfall gradient. 4. Synthesis. The convergent favouring of escape traits by grazing and drought in annuals is consistent with the generalized grazing model. This model, which has been developed for perennials based on the avoidance strategy, can thus be extended to annuals based on escape, a finding that should facilitate projecting consequences of global change in drylands dominated by annuals.
Experimental simulation of environmental warming selects against pigmented morphs of land snails
(WILEY, 2020) Köhler, Heinz-R; Capowiez, Yvan; Mazzia, Christophe; Eckstein, Helene; Kaczmarek, Nils; Bilton, Mark C; Burmester, Janne K. Y; Capowiez, Line; Chueca, Luis J; Favilli, Leonardo; Gomila, Josep Florit; Manganelli, Giuseppe; Mazzuca, Silvia; Moreno-Rueda, Gregorio; Peschke, Katharina; Piro, Amalia; Cardona, Josep Quintana; Sawallich, Lilith; Staikou, Alexandra E; Thomassen, Henri A; Triebskorn, Rita
In terrestrial snails, thermal selection acts on shell coloration. However, the biological relevance of small differences in the intensity of shell pigmentation and the associated thermodynamic, physiological, and evolutionary consequences for snail diversity within the course of environmental warming are still insufficiently understood. To relate temperature-driven internal heating, protein and membrane integrity impairment, escape behavior, place of residence selection, water loss, and mortality, we used experimentally warmed open-top chambers and field observations with a total of >11,000 naturally or experimentally colored individuals of the highly polymorphic species Theba pisana (O.F. MÜLLER, 1774). We show that solar radiation in their natural Mediterranean habitat in Southern France poses intensifying thermal stress on increasingly pigmented snails that cannot be compensated for by behavioral responses. Individuals of all morphs acted neither jointly nor actively competed in climbing behavior, but acted similarly regardless of neighbor pigmentation intensity. Consequently, dark morphs progressively suffered from high internal temperatures, oxidative stress, and a breakdown of the chaperone system. Concomitant with increasing water loss, mortality increased with more intense pigmentation under simulated global warming conditions. In parallel with an increase in mean ambient temperature of 1.34°C over the past 30 years, the mortality rate of pigmented individuals in the field is, currently, about 50% higher than that of white morphs. A further increase of 1.12°C, as experimentally simulated in our study, would elevate this rate by another 26%. For 34 T. pisana populations from locations that are up to 2.7°C warmer than our experimental site, we show that both the frequency of pigmented morphs and overall pigmentation intensity decrease with an increase in average summer temperatures. We therefore predict a continuing strong decline in the frequency of pigmented morphs and a decrease in overall pigmentation intensity with ongoing global change in areas with strong solar radiation.
Field experiments underestimate aboveground biomass response to drought
(Nature Ecology & Evolution, 2022) Kröel-Dulay, György., Mojzes, Andrea., Szitár, Katalin., Bahn, Michael., Batáry, Péter., Beier, Claus., Bilton, Mark., De Boeck, Hans J. , Dukes, Jeffrey. S., Estiarte, Marc ., Holub, Petr., Jentsch, Anke., Schmidt, Inger Kappel., Kreyling, Juergen., Reinsch, Sabine., Larsen, Klaus Steenberg., Sternberg, Marcelo ., Tielbörger, Katja., Tietema, Albert ., Vicca, Sara & Peñuelas, Josep.
Researchers use both experiments and observations to study the impacts of climate change on ecosystems, but results from these contrasting approaches have not been systematically compared for droughts. Using a meta-analysis and accounting for potential confounding factors, we demonstrate that aboveground biomass responded only about half as much to experimentally imposed drought events as to natural droughts. Our findings indicate that experimental results may underestimate climate change impacts and highlight the need to integrate results across approaches.
The fish industry in Eritrea: From comparative to competitive advantage.
(2008) Teweldemedhin, Mogos Y.
The paper examines the main constrains in stimulating extent of production driven supply chains, that could able to transform into market driven supply chain management.; Questionnaires, were developed and administered to marketing agents using purposive sampling, with the application of Porter’s diamond of national competitive advantage. Red sea being underexploited resource; and it is unique opportunity for the development of the country (MOF, 1997). However, this comparative advantage has never been converted to competitive advantage. Comparing to the percentage of fish population with in 100km from the coastal, Eritrea has the larger fish resource concentration in the region (73%). However, the sector has never made significant contribution to the country food security. The study confirms that all the role payers in the fish market chain and policy makers need to take a strategic approach, in identifying target markets, and ways to build strong and sustainable production. Moreover, all stack holder in the sector needs to formulate how to move up to: the value chain; niche marketing opportunity; converting comparative into competitive advantage; specifically focus on the services revolution; and overcoming technical and structural barriers.
The impact of trade liberalisation on South African agricultural productivity.
(Academic Journals, 2010) Teweldemedhin, Mogos Y.; Van Schalkwyk, H. D.
This study attempts to examine the empirical relationship between trade and Total Factor Producitvity (TFP) in the agricultural sector using both cross -sectional (across nine agricultural commodities) and time -series analysis. The Error Correction Model of Ordinary Least Square (OLS) results from the cross-sectional analysis confirm that export shares and capital formation were significant and postivly related; whereas, import shares and real exchange rate were found to be negatively related. However, the net effect of export and import shares was positive implies that trade liberalisation causes productivity gains, The findings from the time -series analysis followed in the same direction as the cross -sectional results, indicating a robust relationship between a TFP, degree of openness, and capital formation. Debt was found to be inversely related, this implies that agricultural industries/ farmers lack debt management skills.
The international trade prospective of agriculture sector in Southern African.
(Academic Journals, 2010) Teweldemedhin, Mogos Y.; Van Schalkwyk, H. D.
The objective of this paper is to analyse the international trade performance of the South African agricultural industry in aggregate and by product group categories. A useful tool in this regard is the Gini and intra-industrial trade coefficient (IIT), which is used to examine the international trade balance of South Africa. Moreover, Ordinary Least Squares (OLS) is also used to identify factors that may be necessary to achieve high IIT. The IIT coefficient, after 1994, achieved more than 85 percent, which is a record level even for industrialised countries. This high IIT performance reveals trade liberalisation between the Southern Africa Customs Union (SACU) and the European Union (EU), opening South Africa’s market to the world. It also reveals that South Africa is able to increase its specialisation and flexibility to gain market access, and has shown a greater ability to compete in a changing trade environment. The results of the econometric analysis of IIT determinants give a greater magnitude to the coefficients export to Gross Domestic Product (GDP) and export -to -import ratios. These results imply that if South Africa’s industries take measures to increase trade liberalisation, diversity, and the level of industrial specialisation, the IIT level would be higher, and significant economic gain might be achieved by minimising costs.
Investigating the environmental and anthropogenic spatio-temporal patterns of plant health of Welwitschia mirabilis in the central Namib Desert
(2016-09) Shuuya, Titus
Environmental and anthropogenic patterns are the major factors that determine plant persistence across the landscape over a long-term period. The spatio-temporal patterns of vegetation distribution in the Namib Desert biome is attributed to the climatic conditions, geomorphology and edaphic features. Landscape patterns in the environmental conditions (e.g. rainfall and fog) of the Namib Desert have been described as a complex gradient that has a major influence on vegetation over time. Welwitschia mirabilis Hook. fil (Gnetales: Welwitschiaceae), commonly known as Welwitschia, is one of the Namib Desert endemic species. Many surveys have reported that desert plants, such as Welwitschia are well adjusted to environmental stressors. Nevertheless, cumulative impacts (potential impacts include interference with the water supply and deposition of dust) resulting from developments in the central Namib such as uranium mines might significantly affect the Welwitschia plants’ survival. These impacts and the changing baseline conditions might affect their physiological processes, thus their growth and reproduction. In this study, we measured chlorophyll a fluorescence (as an indicator of photosynthetic efficiency), leaf growth rate and cone dimensions to determine whether there are spatial and temporal differences among Welwitschia plants across catchments over time. The study showed a clear effect of topography, climatic conditions and anthropogenic effects, with plants in different catchments being clearly healthier than others during some months. We observed an increase in the photosynthetic efficiency and leaf growth rate accelerated by the episodic rainfall that occurred during January and April months across all catchments. Anthropogenic effects such as browsing by domestic animals probably caused the reduction in photosynthetic efficiency of plants located at the Welwitschia Wash catchment in December. Plants that were located at Welwitschia campsite catchment had the lowest photosynthetic efficiency and leaf growth rate throughout our investigation when compared to plants in other catchments. We have established a baseline study that can be used to develop a protocol to monitor the plant physiological status of Welwitschia. In this way, the results from the study will feed into a management strategy for this Welwitschia population. Apart from that, the findings may also aid restoration as well as rehabilitation measures such as transplantation and reintroduction of this unique plant by understanding its current functional health status across the landscape and over time.
Joint action research at Kwandu Conservancy between community members and students of the Agriculture Diploma program.
(NUST, School of Natural Resources and Tourism., 2006) Zimmermann, Ibo
Joint action research at Queen Sofia Resettlement Project between community members and students of the Agriculture Diploma Program.
(NUST, School of Natural Resources and Tourism., 2003) Zimmermann, Ibo; Mbai, Salomo; Kafidi, Lucia; Meroro, Alex
Joint action research at Vasdraai Farm between resettled farmers and students of the Agriculture program.
(Department of Agriculture; NUST, 2010) Zimmermann, Ibo; Shiimi, Theofilus; Zaire, Helga; Kafidi, Lucia; Mbai, Salomo
Links across ecological scales: Plant biomass responses to elevated CO2
(2022) Maschler, Julia., Bialic-Murphy, Lalasia., Wan, Joe., Andresen, Louise C., Zohner, Constantin M., Reich, Peter B., Lüscher, Andreas., Schneider, Manuel K., Müller, Christoph., Moser, Gerald., Dukes, Jeffrey S., Schmidt, Inger Kappel., Bilton, Mark C., Zhu, Kai., Crowther, Thomas W.
The degree to which elevated CO2 concentrations (e[CO2]) increase the amount of carbon (C) assimilated by vegetation plays a key role in climate change. However, due to the short-term nature of CO2 enrichment experiments and the lack of reconciliation between different ecological scales, the effect of e[CO2] on plant biomass stocks remains a major uncertainty in future climate projections. Here, we review the effect of e[CO2] on plant biomass across multiple levels of ecological organization, scaling from physiological responses to changes in population-, community-, ecosystem-, and global-scale dynamics. We find that evidence for a sustained biomass response to e[CO2] varies across ecological scales, leading to diverging conclusions about the responses of individuals, populations, communities, and ecosystems. While the distinct focus of every scale reveals new mechanisms driving biomass accumulation under e[CO2], none of them provides a full picture of all relevant processes. For example, while physiological evidence suggests a possible long-term basis for increased biomass accumulation under e[CO2] through sustained photosynthetic stimulation, population-scale evidence indicates that a possible e[CO2]-induced increase in mortality rates might potentially outweigh the effect of increases in plant growth rates on biomass levels. Evidence at the global scale may indicate that e[CO2] has contributed to increased biomass cover over recent decades, but due to the difficulty to disentangle the effect of e[CO2] from a variety of climatic and land-use- related drivers of plant biomass stocks, it remains unclear whether nutrient limitations or other ecological mechanisms operating at finer scales will dampen the e[CO2] effect over time. By exploring these discrepancies, we identify key research gaps in our understanding of the effect of e[CO2] on plant biomass and highlight the need to integrate knowledge across scales of ecological organization so that large-scale modeling can represent the finer-scale mechanisms needed to constrain our understanding of future terrestrial C storage.
Overview of a variety of trials on agricultural applications of effective microorganisms (EM).
(2008) Zimmermann, Ibo; Kamukuenjandje, Richard
Effective Microorganisms (EM) is a commercially available liquid containing a variety of lactic acid bacteria, yeasts and phototrophic bacteria. These organisms create conditions which favour mutual support and enable them to outcompete harmful pathogens, while producing useful substances such as vitamins, enzymes, hormones, amino acids and anti-oxidants that create a reducing environment. Various EM agricultural application trials were run, mostly in partnership with farmers. The diverse applications included the following: improving soil conditions for better plant growth, treating waste water, controlling pests and diseases, improving animal growth, enhancing compost production and extending the shelf life of harvested crops. Generally EM appears to give the best results in situations where the natural balance of microorganisms has been severely disrupted or where agricultural inputs are in short supply. In situations where natural microorganism populations are reasonably intact, or where a balanced supply of inputs is available, the addition of EM does not seem to make a significant difference.
A problem tree to diagnose problem bush.
(2008) Zimmermann, Ibo; Joubert, David F.; Smit, G.N.
The term “problem tree” refers to a conceptual model used as a diagnostic tool to analyse a sequence of events that leads to a problem (such as bush encroachment in rangelands). A problem tree is useful because the consequences of different interventions can be visualised and understood more easily in diagrammatic form, thereby guiding management decisions regarding the problem. A problem tree was constructed to show multiple causes of bush encroachment. It was generalised by considering many possible causes, and not only those applying to particular areas of encroachment or specific species of bush. If the problem tree is to be useful in decision-making, one needs to determine which of the multiple pathways are of greater significance in any particular situation. Management decisions are bound to be more effective in the long run if they address causes higher up in the tree and closer to the root causes, than the proximate causes or symptoms at the bottom of the tree.

Browse

Browsing Agriculture by Title

Results Per Page

Sort Options