Showing items related by title, author, creator and subject.

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  West African Monsoon Variability from a High-Resolution Paleolimnological Record (Lake Bosumtwi, Ghana)

  Overpeck, Jonathan T.; Shanahan, Timothy Michael; Overpeck, Jonathan T.; Overpeck, Jonathan T.; Cole, Julia; Beck, J. Warren (The University of Arizona., 2006)

  Instrumental and observational records of climate in West Africa suggest that this region may be susceptible to abrupt, decades-long drought events, with potentially catastrophic impacts for the people living in this region. However, because of the dearth of long, continuous and high quality climate records from sub-Saharan Africa, little is known about the long-term frequency and persistence of drought events in this region. It is also unclear whether observed 20th century droughts are natural or due to human impacts. In the present study, we use several complementary approaches to develop a high-resolution record of paleoclimatic changes in West Africa from the geological record preserved at Lake Bosumtwi, Ghana.Our results suggest that West Africa has undergone significant hydrologic variations over the last ca. 10,000 years. The dominant influence on hydrologic changes over this interval was changes in northern hemisphere summer insolation and the associated feedback processes acting in the oceans and on land. This led to a more northerly position of the Intertropical Convergence Zone (ITCZ) and increased precipitation during the early to mid-Holocene. In the late Holocene, a second increase in precipitation occurred along the Guinea coast as a result of the southward migration of the ITCZ from its northern position. This maximum was followed by an abrupt decrease in precipitation at ca. 2.5-3 kyr.The West African monsoon also varies on timescales from millennia to decades. Millennial and century-scale variations appear to be partly paced by changes in solar irradiance, either directly or indirectly. On decadal timescales, variability appears to be dominated by changes in Atlantic sea surface temperatures. The dominant mode is a ca. 40 year oscillation, which in strongly coherent and in phase with the Atlantic Multidecadal Oscillation (AMO). It is unclear from this study, however, if drought conditions over the last century are related to this multidecadal oscillation, or if they are forced by anthropogenic changes.
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  Reported bed net ownership and use in social contacts is associated with uptake of bed nets for malaria prevention in pregnant women in Ghana

  Ernst, Kacey C.; Erly, Steven; Adusei, Charity; Bell, Melanie L.; Kessie, David Komla; Biritwum-Nyarko, Alberta; Ehiri, John; Univ Arizona, Dept Epidemiol & Biostat, Mel & Enid Zuckerman Coll Publ Hlth (BIOMED CENTRAL LTD, 2017-01-04)

  Background: Despite progress made in the last decades, malaria persists as a pressing health issue in sub-Saharan Africa. Pregnant women are particularly vulnerable to infection and serious health outcomes for themselves and their unborn child. Risk can be mitigated through appropriate use of control measures such as insecticide-treated bed nets. Although social networks can influence uptake of preventive strategies, the role of social influence on bed net ownership has not been explored. During an evaluation of a bed net distribution programme, the influence of non-health care advisors on ownership and use of bed nets by pregnant women in Kumasi, Ghana was examined. Methods: Data were collected through in-person interviews with 300 pregnant women seeking antenatal care in an urban hospital in Kumasi, Ghana. Participants were asked about their bed net ownership, bed net use, and information about three personal contacts that they go to for pregnancy advice. Information about these advisors was combined into an influence score. Logistic regression models were used to determine the association between the score and bed net ownership. Those who owned a bed net were further assessed to determine if interpersonal influence was associated with self-reported sleeping under the bed net the previous night. Results: Of the 294 women in the analysis, 229 (78%) reported owning bed nets. Of these bed net owners, 139 (61%) reported using a bed net the previous night. A dose response relationship was observed between the interpersonal influence score and bed net ownership and use. Compared to the lowest influence score, those with the highest influence score (> 1 SD above the mean) were marginally more likely to own a bed net [OR = 2.37, 95% CI (0.87, 6.39)] and much more likely to use their bed net [5.38, 95% CI (1.89, 15.25)] after adjusting for other factors. Conclusions: Interpersonal influence appears to have modest impact on ownership and use of bed nets by pregnant women in an urban area of Ghana. Further investigations would need to be conducted to determine if the relationship is causal or if individuals who associate are simply more likely to have similar practices.
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  THE POPULATION DYNAMICS OF SUBSISTENCE AGRICULTURE IN THE WEST AFRICAN SAVANNA: A VILLAGE IN NORTHEAST GHANA

  Netting, Robert M.; Cleveland, David A. (The University of Arizona., 1980)

  The West African savanna is characterized by limited and erratic rainfall in one rainy season, increasing degradation of plant and soil resources, a rapidly growing population, and annual food shortages. Zorse is a Kusasi village in Bawku District, Upper Region, northeast Ghana. The Kusasis are intensive farmers of millet and sorghum who live in villages of houses dispersed over the savanna. Surrounding each house is the continuously cultivated field called the saman whose fertility is maintained by annual applications of manure and compost. Field work in Zorse from October, 1978, to March, 1978, included an intensive study of a 50% sample of all houses in the village (n = 126) containing 900 people. In the traditional farming system each household grows and consumes its food as a unit. During the wet season there is a high demand for labor, especially for weeding, but food supplies are at an annual low. In the dry season farming activity is limited to those with dry season gardens. Agricultural development began in earnest in the 1930's but annual food shortages continue to worsen and famine, such as the one in 1976-77 has not been uncommon. Population growth and structure is determined by fertility, mortality, and migration, and reflects the population's relationship to its environment. Population pyramids for Zorse are like those for other areas of the savanna. Their broad bases reflect high mortality and fertility and their skewed sex ratios are the result of excessive outmigration by males 15-45 years old. Migration has been increasing since the beginning of the century and presently about 50% of males 15-45 years old are absent from Zorse and the Upper Region for extended periods of time. Fertility has also been increasing, primarily as a result of decreasing birth intervals, but also as a result of decreasing age at marriage. Birth intervals are controlled by postpartum sexual abstinence. Kusasi couples make the decision to resume intercourse based on the health and development of the youngest child. The shortening of birth intervals reflects the decreased mortality and increased personal security. The pace of social change has increased greatly since the establishment of the British in 1900. The endemic warfare and feuding were stopped and personal security was greatly increased. Public health programs and Western medical treatment were introduced and links with the rest of Ghana and the world were established and began to grow. The savanna environment is fragile and agriculture in Bawku depends on highly variable rainfall of about 1000 mm per year, and on maintaining fertility on the thin, erosion-prone soils. In areas of high population density like Bawku, there is much evidence of soil erosion, loss of soil structure and fertility, and degraded vegetation. The rapid population growth and high emigration rate in Bawku and similar areas of the savanna jeopardize the possibility of improving the food supply. People's decisions about migrating and birth spacing are adaptations to an intensive agricultural system in an environment where productive potential is decreasing under the present system. For the situation to improve it will be necessary for community resources management systems to develop so that demographic and farming behavior by individuals and households will be linked to community well being.