Literatura académica sobre el tema "African Continent for fresh water collection"

Species of the genus Ceratophallus are known only from some islands in the western Indian Ocean and Africa, where they occur in Eritrea and the area extending southwards and westwards into the Western Cape of South Africa. The most recent classification recognises nine species of this genus of which only two, namely Ceratophallus natalensis (Krauss) and Ceratophallus gibbonsi (Nelson) occur in South Africa. Although partially sympatric, C. gibbonsi is largely associated with a tropical climate and perennial water-bodies while C. natalensis is fairly common in cooler areas and are often found in ephemeral rain pools. This article focuses on the geographical distribution and habitats of C. natalensis, the most widespread species of the genus, as reflected by the data on record in the National Freshwater Snail Collection (NFSC). Details pertaining to the habitats of 1 797 samples of C. natalensis as recorded at the time of collection were extracted from the database of the NFSC. In view of the finding of Brown1 that C. natalensis and C. gibbonsi are partly sympatric, but that the latter is associated with fully tropical climatic areas, samples of Ceratophallus collected in loci ( 1 / 16 th square degrees) that fall within the altitude interval ranging from 0-500 m, were selected for closer investigation. A number of 153 samples from 64 loci falling within this altitude interval was subsequently identified as C. natalensis. The number of loci in which the 1 797 collection sites were located, was distributed in intervals of mean annual air temperature and rainfall, as well as intervals of mean altitude, to illustrate the frequency of occurrence within specific intervals. A temperature index was calculated for all mollusc species in the database from their frequencies of occurrence within selected temperature intervals and the results were used to rank them in order of their association with low to high climatic temperatures. Chi-square values were calculated to evaluate the significance of the difference between the frequency of occurrence in, on, or at the different options for each variable. Additionally, an effect size value was calculated to determine the significance of the effect of all the different variables discussed in this paper on the geographical distribution of C. natalensis in South Africa. A multivariate analysis in the form of a decision tree was also constructed. This is a statistical model that enables the selection and ranking of those variables that can maximally discriminate between the frequency of occurrence of a given species under specific conditions as compared to all other mollusc species in the database.The 1 797 samples of C. natalensis of which the collection sites could be located on a 1:250 000 topo-cadastral map series of South Africa were spread over 334 loci. This species was recovered from all types of water-bodies represented in the database but the largest percentage was reported from dams (31.2%), streams (22.2%) and rivers (15.7%). The majority of samples came from habitats with perennial (60.0%), standing (62.9%), clear (63.8%) and fresh (76.7%) water, while 42.1% of the samples were recovered from habitats with a muddy substratum. More than 95% of the samples were reported from sites that fell within the temperature interval ranging from 16-20°C and the majority of samples (64.8%) came from sites falling within the rainfall interval ranging from 601–900 mm. More than 50% of the samples came from sites falling within the altitude interval ranging from 1 001–1 500 m and this differed significantly from the frequency of occurrence within all the alternative altitude intervals. The temperature index calculated for C. natalensis ranked it in the eighth position for all species in the database due to its association with low climatological temperatures. However, the effect size values calculated for this index for 18 of the other 53 species in the database did not differ significantly from the value calculated for C. natalensis. A moderate to large effect size value was calculated for temperature and altitude suggesting that these two variables played an important role in the geographical distribution of C. natalensis, a finding also substantiated by the results of the decision tree analysis. Harrison8 divided the riverine and stream invertebrates of southern Africa into two main groups – a so-called old element with Gondwanaland affinities with relatives in other southern continents and a Pan-Ethiopian (Sub-Saharan) element. Also included in this last element are some species associated with temperate climate and sometimes with mountains, that obviously related to the African fauna. According to this author this group includes the following four sub- groups: (1) widespread species found in tropical and temperate climates, (2) warm stenothermal, tropical species, (3) Highveld-temperate climate species, (4) montane, cold stenothermal species and (5) temporary mountain stream species. According to Brown9 C. natalensis could be placed in the more or less eurythermal sub-group (1). This is supported by the geographical distribution of the collection sites of the samples of C. natalensis depicted in figure 1. Presently this species is the only member of the subfamily Planorbinae reported from Lesotho and it is currently on record from nine loci in that country in our database. It is therefore not surprising that the temperature index calculated for this species ranked it under the eight species in the database most closely associated with cooler climatic conditions. It is reported in literature that this species can utilise a wide variety of habitats including ephemeral water-bodies like marshes, slow-flowing streams, natural depressions and ditches only briefly filled with water. This is supported by the results of the present investigation which indicated the presence of this species in all types of water-body on record in the database and that 26% of the samples came from temporary habitats. It is not known whether C. natalensis can serve as intermediate host for any human helminth parasite. However, Loker et al. 12 reported the shedding of 11 different trematode cercariae from naturally infected snails in Tanzania and Frandsen and Christensen13 mention at least 10 different cercariae which could be shed from species of Ceratophallus under natural conditions. To our knowledge no efforts have been made to establish the possible role of C. natalensis as intermediate host of economically important helminth parasites in South Africa. In view of its relatively wide distribution in this country and the reports that it can act as intermediate host of a variety of helminth parasites elsewhere in Africa, it is recommended that its role as potential intermediate host in South Africa should be investigated.

In West Africa, as in many other estuaries, enormous volumes of marine water are entering the continent. Fresh water discharge is very low, and it is commonly strongly linked to rainfall level. Some of these estuaries are inverse estuaries. During the Great Sahelian Drought (1968–1993), their hyperhaline feature was exacerbated. This paper aims to describe the evolution of the two main West African inverse estuaries, those of the Saloum River and the Casamance River, since the end of the drought. Water salinity measurements were carried out over three to five years according to the sites in order to document this evolution and to compare data with the historical ones collected during the long dry period at the end of 20th century. The results show that in both estuaries, the mean water salinity values have markedly decreased since the end of the drought. However, the Saloum estuary remains a totally inverse estuary, while for the Casamance River, the estuarine turbidity maximum (ETM) is the location of the salinity maximum, and it moves according to the seasons from a location 1–10 km downwards from the upstream estuary entry, during the dry season, to a location 40–70 km downwards from this point, during the rainy season. These observations fit with the functioning of the mangrove, the West African mangrove being among the few in the world that are markedly increasing since the beginning of the 1990s and the end of the dry period, as mangrove growth is favored by the relative salinity reduction. Finally, one of the inverse estuary behavior factors is the low fresh water incoming from the continent. The small area of the Casamance and Saloum basins (20,150 and 26,500 km² respectively) is to be compared with the basins of their two main neighbor basins, the Gambia River and the Senegal River, which provide significant fresh water discharge to their estuary.

Nowhere in the world is poverty more visible, more destructive and more pervasive than in Africa. Too often, Africa is associated with stories of failure and pessimism, of wars and famines, floods and unrest. Africa appears to be slipping back on many development indicators, even as other parts of the world move ahead. In 2003, however, there are prospects of achieving progress in water, sanitation and hygiene in Africa. Across the continent, there is a strong sense of the need for peace, democracy and co-operation. Through the Highly Indebted Poor Countries initiative, industrialised countries are finally proposing to write off a significant part of the debt into which the poorest countries have fallen. Many African countries have written Poverty Reduction Strategy Papers, which give clarity and direction to the development work in those countries. Within the water sector itself, the African Ministerial Conference on Water (AMCOW) has been formed to share ideas and lessons and to provide mutual support and active direction. Recent meetings, especially the World Summit on Sustainable Development (August 2002), are giving fresh political impetus to this work. This paper suggests five priorities for achieving the water and sanitation Millennium Development Goals in Africa. It relates them to practical examples of inspiring and positive initiatives in water and sanitation from across the continent. These examples have worked, or have the potential to work, at a large scale, are demonstrably sustainable, and do not benefit from too many unique local conditions. These characteristics enable the lessons from these examples to be useful for other people in, and indeed outside, Africa.

Notwithstanding the dispersed nature of the water, energy and food (WEF) nexus scholarship in the African continent, its strategic importance to the African agenda has gained widespread attention in research and planning circles. In this regard, the bibliometric science mapping and content analysis of the WEF nexus scientific publication trends, the conceptual, intellectual and social structures, as well as the inherent paradigmatic shifts in the WEF nexus body of knowledge in the African continent have been undertaken, using the nexus body of literature accessed from the Web of Science and Scopus core collection databases. The review results confirmed that, whilst the WEF nexus scholarship has expanded since 2013, there is also evidence of growth in the conceptual, intellectual and social structures of the WEF nexus in the African continent. These shifts have resulted in the emergence of hot topics (subfields) including modelling and optimization, climate variability and change, environmental ecosystem services sustainability, and sustainable development and livelihoods. The review further determined that these structures have evolved along two main perspectives of WEF nexus research development, i.e., the interdisciplinary and transdisciplinary domains. In support of the interpretation of the visual analytics of the intellectual structure and changing patterns of the WEF nexus research, the shifts in positivist, interpretivist and pragmatic paradigmatic perspectives (these are underpinned by the ontology, epistemology, and methodology and methods) are considered when explaining WEF nexus research shifts: (a) From the unconnected silo paradigms that focus on water, energy and food (security concerns) to interconnected (and sometimes interdependent or nested) linkages or systems incorporating environmental, social-economic and political drivers (also viewed as subfields) in a bid to holistically support the Sustainable Development Goals (SDGs) across the African continent; and (b) in the evaluation of the WEF nexus scholarship based on novel analytical approaches. We contend that whilst the theories of science change underpin this apparent expansion, the macro-economic theory will find use in explaining how the WEF nexus research agenda is negotiated and the Integrative Environmental Governance (IEG) is the duly suited governance theory to bridge the inherent disconnect between WEF nexus output and governance processes uncovered in the literature. Overall, operational challenges and opportunities of the WEF nexus abound, transitioning the WEF nexus research to practice in Africa, motivating the need to take advantage of the scholar–practitioner research underpinnings, as contemplated in the transdisciplinary research approach, which is characterised by the dual quest for new knowledge and considerations of use. Yet, there is need for more coordinated and collaborative research to achieve impact and transition from WEF nexus thinking to WEF nexus practice.

In December 2000 seed harvested from wheat (Triticum aestivum L.) cultivars SST 876 and SST 825 produced under sprinkler irrigation near Douglas, Northern Cape Province, South Africa, contained a substantial amount of partially bunted kernels. Kernel embryos contained black masses of teliospores, and in many instances the endosperm was partially degraded. Teliospores were brown to dark brown, densely echinulate, 25 to 45 μm in diameter with a short mycelial fragment on some of the spores. Hyaline, smooth-walled sterile cells were also present. Teliospores were soaked in sterile distilled water for 2 days, streaked on 2% water agar plates and incubated at 22°C in the dark. Teliospores germinated after 5 days, producing 50 to 250 filiform, nonconjugating, primary basidiospores and forcibly discharged allantoid, secondary basidiospores. Based on kernel appearance, a rotten fish odor in infected grain, teliospore morphology, and germination characteristics, the pathogen was identified as Tilletia indica Mitra, the cause of Karnal bunt (1). This morphological identification was confirmed at the USDA-ARS Systematic Botany and Mycology Laboratory, Beltsville, MD. Molecular verification of 12 South African isolates was provided by the Foreign Disease-Weed Science Research Unit at Fort Detrick, MD, using real-time polymerase chain reaction with the Tin3/Tin10 T. indica-specific primer set (2). Four additional isolates were confirmed as T. indica using the same primer set as well as ITS rDNA sequencing at the Beltsville laboratory. Reference specimens were deposited at the National Fungal Collection in Pretoria, South Africa (PREM 57214), and at Beltsville (BPI 748170). At present, the mode of introduction of T. indica into South Africa, as well as its precise distribution, is not known. It appears, however, that the pathogen is restricted to the Douglas production area in the Northern Cape where quarantine measures have been taken to contain and possibly eradicate the disease. References: (1) L. A. Castlebury and L. M. Carris. Mycologia 91:121, 1999. (2) R. D. Frederick et al. Phytopathology 90:951, 2000.

The objective of virtually all development initiatives in Africa is poverty reduction. The crippling challenge of poverty facing most African states is, by no means, a fresh one. However, the problem has assumed a disturbing dimension at the turn of the 21st Century, if we compare African states with emerging economies in the global south. The paper adopts functionalism as a theoretical framework due to the fact that African states have embraced the idea of integration, with African Union (AU) being a potential instrument of realising their d `evelopment aspirations. Relying on secondary sources of data collection, it sought to gain in-depth understanding of previous studies, in order to gain fresh insight and enriched perspectives. The paper examined selected continental and global development initiatives, as well as their impact towards achieving the goal of poverty reduction in Africa. While noting that political stability is a major precondition for economic growth, the paper noted that most African states are at sub-optimal level of economic performance because of high level of impunity among the political leadership, abuse of due process and failure to adhere to global best practices. The paper observed that the realities of the present interdependent world system dictate that there is no alternative to global partnership if African states are desirous to make a break from their stunted growth and vicious cycle of poverty. The paper recommends that African states need to re- tool and refine their development strategies along the Asian trajectory. It concludes that only an African consensus on the utility of an integration framework can help advance the goal of poverty reduction in the continent.

The Southern African Millennium Ecosystem Assessment (SA f MA) evaluated the relationships between ecosystem services and human well-being at multiple scales, ranging from local through to sub-continental. Trends in ecosystem services (fresh water, food, fuel-wood, cultural and biodiversity) over the period 1990–2000 were mixed across scales. Freshwater resources appear strained across the continent with large numbers of people not securing adequate supplies, especially of good quality water. This translates to high infant mortality patterns across the region. In some areas, the use of water resources for irrigated agriculture and urban–industrial expansion is taking place at considerable cost to the quality and quantity of freshwater available to ecosystems and for domestic use. Staple cereal production across the region has increased but was outstripped by population growth while protein malnutrition is on the rise. The much-anticipated wood-fuel crisis on the subcontinent has not materialized but some areas are experiencing shortages while numerous others remain vulnerable. Cultural benefits of biodiversity are considerable, though hard to quantify or track over time. Biodiversity resources remain at reasonable levels, but are declining faster than reflected in species extinction rates and appear highly sensitive to land-use decisions. The SA f MA sub-global assessment provided an opportunity to experiment with innovative ways to assess ecosystem services including the use of supply–demand surfaces, service sources and sink areas, priority areas for service provision, service ‘hotspots’ and trade-off assessments.

Sediments of two small watercourses Leskava and Troubsky Brook in the Brno city suburban area were examined for their ecotoxicity. Using a standard procedure, extracts of the sediments were prepared for diagnostic tests. These extracts were tested for acute toxicity to fresh-water organisms. The ecotoxicological tests were performed on the fresh-water algaPseudokirchneriella subcapitata, the vascular water plantLemna minor, on a representative of invertebrates – the water fleaDaphnia magnaand on theXenopus laevisfrog embryo and luminiscentVibrio fischeribacteria. Possible toxic effects were evaluated using the test determining the inhibition of the growth of white mustard rootSinapis alba. Results of ecotoxicological assessment of sediment leachates showed that their quality varied significantly during the year. Differences were found between results of sediment evaluations from different collection profiles, which may indicate effects of point source pollution. Of the ecotoxicological tests used, the most sensitive organisms included the green algaePseudokirchneriella subcapitata, bioluminiscent bacteriaVibrio fischeriand the African clawed frogXenopus laevis. The highest concentrations of arsenic were found by chemical analysis in both spring and autumn sediment leachate samples collected at Site L1 (Leskava). The highest organic pollutant concentrations were found in autumn sediment leachate samples from Site L1. In total PAH sums, phenanthrene was the dominant pollutant at all the sites investigated.

This article presents a critical analysis of the impact (influence) of the theory of liberalism on the United Nations’ (UN) and Africa Union’s (AU) approach to global peace and security. There are various and sometimes conflicting theories of international relations relating to how world politics functions, including international and regional peace and security. Which theory of international relations and peace would explain the United Nations' role in promoting worldwide peace and security, as well as the African Union's role in promoting regional peace and security within the African continent? Even though this question is difficult to answer and no single theory can fully capture the complexities surrounding the issues at hand, this article contends that the liberal peace framework has had a profound influence on the creation of the United Nations and the African Union, as well as their roles in international and regional peace and security. To this purpose, the study adopts a qualitative critical research strategy with secondary data collection and analytical approaches which comprise characterizing, thematizing, and contextualizing the topic at hand. The paper explains how liberalism influenced the essential thinking, values and norms, institutional legitimacy and mandate. It also conceptualizes and operationalizes peace and security concerns at the UN and AU. This is tied to UN-led global action which, when paired with the AU's considerable continental role, illustrates liberalism's impact in terms of laws, conventions, principles, and practices, facilitating cooperative peacebuilding efforts. Despite some critical theoretical and practical shortcomings, this paper argues that liberalism is still essential to achieving the UN’s and AU's, agenda for global peace and security.

Although agriculture remains the mainstay of the African economy, it is currently going through stress because of a multitude of factors including climate change. Thus, many countries in their efforts to transform their agricultural sectors are employing climate-smart initiatives including the provision of water harvesting technologies for irrigated crop production during the dry season. This paper examines the role of irrigation in the drive towards a transformation of smallholder agriculture in Africa. Focus group discussions, key informant interviews and individual questionnaires were employed for the data collection. The data were analyzed using the regression adjustment (RA) technique. The results indicate that irrigation has significant and positive impacts on farm incomes, employment, consumption, food security and non-farm businesses, all of which are necessary conditions for a successful transformation of smallholder agriculture in Africa. The impacts of irrigation on health and environmental sustainability are mixed—the positive being the ability of irrigators to pay for improved healthcare for their families and the negatives include the outbreak of waterborne diseases associated with irrigation water. Construction of irrigation facilities causes destruction to the environment but improves provisioning ecosystem services. It is generally concluded that access to irrigation is associated with higher farm incomes, employment, consumption, food security and engagement in non-farm business activities. The key policy implication of these findings is that African governments must formulate strategic policies that will accelerate investments in the provision of irrigation facilities to better promote the agenda to transform smallholder agriculture in the continent.

The introduction describes how this collection brings together the scholarship of leading international specialists on African and French imperial history, political science and related fields to offer fresh perspectives on this process. It is the first systematic attempt at characterizing networks and links that, for the populations of large parts of the African continent, have lost none of their importance.

According to the World Bank (2015) Africa’s urbanization rate has surpassed other parts of the world. It is believed that by 2030, over 50% of Africans will reside in Urban Centres. Kenya is among the African counties that has experienced a tremendous increase in her urban population. This is most visible in the capital, the primate city of Nairobi. The growth has led to increased pressure on basic needs like housing, transport, water, education and security. Coupled with unequal economic development and social benefits, the result has been the tremendous expansion of informal sectors across fields. To respond to some of this pressure, the central government has vowed initiate large projects in housing, transport, water and others (Republic of Kenya, 2018). Newly enacted legislation also provides for the establishment of multi-sectoral urban boards to oversee the delivery of some services. Among the major projects coming up include Affordable Housing schemes and Mass Rapid Transport investments such as Bus Rapid Transit and expanded commuter rail systems. However, experience from the past both in Nairobi and other Cities has taught us the importance of inclusion, empathy and participation in such projects. Recent times have shown that public projects tend to ignore these and other key elements leading to massive failure of investment. The paper investigates case studies from similar projects in other parts of Africa, Bus Rapid Transit Projects in Lagos, Dar es Salaam and South African Cities; past Slum Upgrading and Housing Projects in Nairobi and other parts of the continent. The research methods also involve data collection on inclusion and participation from those who are affected directly by these proposed projects as well as the impacts that previous projects have had. The results from the study show that without proper communication and participation there are several misunderstandings on liveable spaces in cities. These include misinterpretations of the challenge’s citizens face, on the intentions of proposed solutions as well as the socioeconomic decision-making process of citizens. The implication of this leaves an unhealthy competition between existing informal ‘structures’ in various sectors against the new government driven proposals. The results are that those meant to benefit end up not being the primary beneficiaries. In conclusion, the role of putting people primarily as the centre objective of planning remains critical and key. For African planners, diverting from this will increase the existing inequalities and lead to further social divisions.