Browsing by Subject "demography"

Now showing 1 - 6 of 6
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    Citizen Science - Mammal Map
    (2014-09-12) Hoffman, Tali; Neary, Tim
    In this radio broadcast, Tali Hoffman explains the purpose and scope of MammalMAP - an online platform which aims to update the distribution records of all African mammal species - and how citizens all over Africa can contribute by sending in photos of animals in conjunction with their location. Tali discusses capacity and services offered by the platform, the ways in which this information is being used, and the ethical considerations required and the measures taken to prevent abuse of such a resource, such as poaching. Image provided courtesy of Johan Taljaard under a Creative Commons Attribution Non-Commercial Share-Alike 3.0 Unported license.
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    Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography
    (2016) White, J D M; Jack, S L; Hoffman, M T; Puttick, J; Bonora, D; Visser, V; February, E C
    BACKGROUND: Conifer populations appear disproportionately threatened by global change. Most examples are, however, drawn from the northern hemisphere and long-term rates of population decline are not well documented as historical data are often lacking. We use a large and long-term (1931-2013) repeat photography dataset together with environmental data and fire records to account for the decline of the critically endangered Widdringtonia cedarbergensis. Eighty-seven historical and repeat photo-pairs were analysed to establish 20th century changes in W. cedarbergensis demography. A generalized linear mixed-effects model was fitted to determine the relative importance of environmental factors and fire-return interval on mortality for the species. RESULTS: From an initial total of 1313 live trees in historical photographs, 74% had died and only 44 (3.4%) had recruited in the repeat photographs, leaving 387 live individuals. Juveniles (mature adults) had decreased (increased) from 27% (73%) to 8% (92%) over the intervening period. Our model demonstrates that mortality is related to greater fire frequency, higher temperatures, lower elevations, less rocky habitats and aspect (i.e. east-facing slopes had the least mortality). CONCLUSIONS: Our results show that W. cedarbergensis populations have declined significantly over the recorded period, with a pronounced decline in the last 30 years. Individuals that established in open habitats at lower, hotter elevations and experienced a greater fire frequency appear to be more vulnerable to mortality than individuals growing within protected, rocky environments at higher, cooler locations with less frequent fires. Climate models predict increasing temperatures for our study area (and likely increases in wildfires). If these predictions are realised, further declines in the species can be expected. Urgent management interventions, including seedling out-planting in fire-protected high elevation sites, reducing fire frequency in higher elevation populations, and assisted migration, should be considered.
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    Emergence of a peak in early infant mortality due to HIV/AIDS in South Africa
    (2009) Bourne, David E; Thompson, MaryLou; Brodya, Linnea L; Cotton, Mark; Draper, Beverly; Laubscher, Ria; Abdullah, M Fareed; Myers, Jonny E
    Objectives: South Africa has among the highest levels of HIV prevalence in the world. Our objectives are to describe the distribution of South African infant and child mortality by age at fine resolution, to identify any trends over recent time and to examine these trends for HIV-associated and non HIV-associated causes of mortality. Methods: A retrospective review of vital registration data was conducted. All registered postneonatal deaths under 1 year of age in South Africa for the period 1997–2002 were analysed by age in months using a generalized linear model with a log link and Poisson family. Results: Postneonatal mortality increased each year over the period 1997–2002. A peak in HIV-related deaths was observed, centred at 2–3 months of age, rising monotonically over time. Conclusion: We interpret the peak in mortality at 2–3 months as an indicator for paediatric AIDS in a South African population with high HIV prevalence and where other causes of death are not sufficiently high to mask HIV effects. Intrauterine and intrapartum infection may contribute to this peak. It is potentially a useful surveillance tool, not requiring an exact cause of death. The findings also illustrate the need for early treatment of mother and child in settings with very high HIV prevalence.
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    Projecting fertility by educational attainment: proof of concept of a new approach
    (2018) Ncube, Presley; Moultrie, Thomas
    The United Nations Population Division publishes fertility projections for all countries in the World Population Prospects (WPP). These are the most widely used projections for planning and policy implementation. Despite a substantial body of literature that suggests education has a significant impact on fertility, these projections do not incorporate changes in the composition of the population by level of education. We therefore propose and implement a method that incorporates education composition change in projecting fertility. We investigate fertility differentials by level of education, then evaluate how education influences fertility independently; and finally, a model is fitted to project fertility rates by education levels. In both cases, the fertility rates by education level are then weighted by the IIASA educational attainment distributions to get the national fertility rates. These national fertility rates are in turn validated against the WPP fertility rates to evaluate how good the proposed method works. Fertility is high among the less educated relative to educated women. Education proves to be an important driver of fertility decline in Southern Africa. The proposed model is a good fit for countries with sufficient DHS data. However, there are other sources of data that are available, for example, the census data but we could not rely on them since they only give summary information. Validation was done to evaluate how good the model is working. This exercise produced consistent results with the observed fertility estimates. The percentage difference between the projected and WPP fertility estimates varied from 1 to 5 percent in Lesotho, Namibia and Zimbabwe. In conclusion, the model can also be used for other countries. Furthermore, education composition change should be considered when projecting fertility since it has proven to be a significant driver of fertility change. Data quality and availability issues were a major limitation to our study and in future should be improved.
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    The National Food Consumption Survey (NFCS): South Africa, 1999
    (2005) Labadarios, D; Steyn, NP; Maunder, E; MacIntryre, U; Gericke, G; Swart, R; Huskisson, J; Dannhauser, A; Vorster, HH; Nesmvuni, AE; Nel, J H
    Bournemouth University Website, Bournemouth, England, UK
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    Weaver Birds
    (2014-09-12) Oschadleus, Dieter; Neary, Tim
    In this radio broadcast, Dieter Oschadleus discusses weavers, from nest-building patterns to the different kinds of weavers (masked weaver, widow and bishop birds, and sparrow weavers, scaly-feathered finch, etc.) and their respective habitats. Weaver nest sites also attract a variety of predators (snakes, birds of prey) and obligate nesters such as the pygmy falcon who do not create their own nests, and thus weaver sites create their own ecologies through provision of shade and concentration of droppings. Citizen scientists can get involved by photographs of weaver sites which are then used to build up a database of weaver sites which provide demographic information very useful to avian zoologists. Image provided courtesy of Snowmanradio under a Creative Commons Attribution Share-Alike 2.0 Generic license.