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Droughts and famines: The underlying factors and the causal links among agro-pastoral households in semi-arid Makueni district, Kenya 总被引：4，自引：0，他引：4
Chinwe Ifejika Speranza Boniface Kiteme Urs Wiesmann 《Global Environmental Change》2008,18(1):220-233
Famines are often linked to drought in semi-arid areas of Sub-Saharan Africa where not only pastoralists, but also increasingly agro-pastoralists are affected. This study addresses the interplay between drought and famine in the rural semi-arid areas of Makueni district, Kenya, by examining whether, and how crop production conditions and agro-pastoral strategies predispose smallholder households to drought-triggered food insecurity. If this hypothesis holds, then approaches to deal with drought and famine have to target factors causing household food insecurity during non-drought periods. Data from a longitudinal survey of 127 households, interviews, workshops, and daily rainfall records (1961–2003) were analysed using quantitative and qualitative methods. This integrated approach confirms the above hypothesis and reveals that factors other than rainfall, like asset and labour constraints, inadequate policy enforcement, as well as the poverty-driven inability to adopt risk-averse production systems play a key role. When linking these factors to the high rainfall variability, farmer-relevant definitions and forecasts of drought have to be applied. 相似文献
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P. R. J. Boniface 《The Photogrammetric Record》1967,5(30):492-497
This paper discusses a method of analytical aerial triangulation which may be carried out on the majority of stereo-plotters. A precise réseau engraved on each plate-holder glass enables a plotter to be used as a réseau stereocomparator. Since the plotter is used merely to measure distances of 1 cm. or less, the projection errors are, to all intents and purposes, eliminated. Test area results indicate an accuracy similar to that obtained with a stereo-comparator. There is no reason why similar results should not be achieved on relatively simple plotters such as the Kern PG2 or the Wild B8. 相似文献
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Nguemhe Fils Salomon César Mimba Mumbfu Ernestine Nyeck Brunot Nforba Melvin Tamnta Kankeu Boniface Njandjock Nouck Philippe Hell Joseph Victor 《Natural Resources Research》2020,29(6):3457-3477
Bétaré-Oya is one of the gold mining districts in the eastern region of Cameroon. Structural controls on gold mineralization were examined along the Bétaré-Oya Shear Zone, providing further clues on favorable areas for mineral exploration. GIS-based methods combining point pattern (i.e., quadrat count, Fry analysis) and distance distribution analysis were employed here to delineate the spatial patterns of known gold deposits and to evaluate their spatial association with geological structures. Results show that the gold deposits in this area are spatially clustered. At the regional scale, the Fry plot indicates an alignment of deposits, suggesting that gold mineralization is controlled by structures oriented NNE–SSW and NE–SW. At the deposit scale, an alignment is also evident, indicating that the mineralization is also controlled by ENE–WSW-trending structures. The cumulative relative frequency distribution of distances from lineament features to gold occurrence points (DM) and to non-occurrence points (DN) ratio (DM/DN) was used to rank these two major structural trends and their relative importance as mineralization control. The yielded grades show that NE–SW-trending lineaments, akin to P-type structures, play a major role in controlling the gold mineralization in the area compared to other structures. Beyond the goal to foster mineral prospection in the Bétaré-Oya gold district, information yielded in the present study provides relevant criteria for further exploration in the eastern region of Cameroon.
相似文献5.
Field, microstructural, and anisotropy of magnetic susceptibility (AMS) or magnetic fabric studies were applied to identify the sequence and character of the Pan-African structures in the basement of Eastern Cameroon at both sides of the regional scale Bétaré-Oya Shear Zone (BOSZ). The NE-SW trending BOSZ separates older gneisses and migmatites towards SE (domain I) from the younger rocks of the Lom meta-volcano-sedimentary basin towards NW (domain II). In domain I, early, ductile compressional deformation occurred in two events, D1 and D2, under relatively high T conditions. During subsequent cooling, strain partitioned between the competent basement gneisses with only mild compression and the bordering shear zone (BOSZ) with intense simple shear-wrenching (D3). Strain in the less competent rocks of domain II is dominated by simple shear, strike-slip wrenching (D3), with an earlier stage of compressional deformation preserved only in some low strain pods.Magnetic fabrics (AMS) document a progressive change from oblate ellipsoids towards prolate ellipsoids in domain I, when proceeding from the south towards the BOSZ. Foliations are mostly steep but define a girdle with a pole plunging gently towards WSW. The magnetic lineations also plunge mostly towards WSW at shallow angles. These fabrics indicate a compression approximately normal to the BOSZ, which is also the SE margin of the Lom Basin. In the Lom metasediments (domain II), AMS ellipsoids are typically oblate. Foliations trend NE-SW with mostly steep dips. Magnetic lineations plunge gently NE or SW. This fabric with foliations mostly steep and subparallel with the major BOSZ, combined with generally subhorizontal lineations implies the BOSZ as a Pan-African strike–slip shear zone with a subordinate component of compression.At a larger scale, the area is part of a continent-scale shear zone, separating external Pan-African domains of compression along the northern margin of the Congo craton from internal domains dominated by high-angle strike–slip and transpressional deformation. Together with published data, the present study thus demonstrates that transpression is a regional phenomenon in the Pan-African orogen of central and eastern Cameroon. 相似文献
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Henrik Stendal Sadrack Flix Toteu Robert Frei Joseph Penaye Urbain Olivier Njel Jean Bassahak Jean Nni Boniface Kankeu Vincent Ngako Joseph Victor Hell 《Journal of African Earth Sciences》2006,44(4-5):443
Rutile, as an important component in alluvial or eluvial heavy mineral deposits, is known in southern Cameroon. These deposits are underlain by the Neoproterozoic low- to high-grade Yaoundé Group. Geochemical, thermometric, fluid inclusion and Pb isotopic studies of the rutile from alluvial and eluvial concentrates and from medium-grade micaschist from the nearby Yaoundé region permit the following conclusions: (1) alluvial and eluvial rutile of the Yaoundé region are derived from the degradation of metapelites, metamafic rocks and pegmatites of the nearby Yaoundé Group; (2) rutile in the Yaoundé Group formed during the Pan-African metamorphism, or was inherited as detrital rutile from a 900 Ma source. The study also shows that the rutile can be used to trace the history of the Pan-African belt north of the Congo craton. 相似文献
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Indigenous knowledge related to climate variability and change: insights from droughts in semi-arid areas of former Makueni District,Kenya 总被引：1，自引：1，他引：0
Chinwe Ifejika Speranza Boniface Kiteme Peter Ambenje Urs Wiesmann Samuel Makali 《Climatic change》2010,100(2):295-315
This article describes the indigenous knowledge (IK) that agro-pastoralists in larger Makueni District, Kenya hold and how
they use it to monitor, mitigate and adapt to drought. It examines ways of integrating IK into formal monitoring, how to enhance
its value and acceptability. Data was collected through target interviews, group discussions and questionnaires covering 127
households in eight villages. Daily rainfall data from 1961–2003 were analysed. Results show that agro-pastoralists hold IK
on indicators of rainfall variability; they believe in IK efficacy and they rely on them. Because agro-pastoralists consult
additional sources, the authors interpret that IK forms a basic knowledge frame within which agro-pastoralists position and
interpret meteorological forecasts. Only a few agro-pastoralists adapt their practices in anticipation of IK-based forecasts
partly due to the conditioning of the actors to the high rainfall variability characteristic of the area and partly due to
lack of resources. Non-drought factors such as poverty, inadequate resources and lack of preparedness expose agro-pastoralists
to drought impacts and limit their adaptive capacity. These factors need to be understood and effectively addressed to increase
agro-pastoralists’ decision options and the influence of IK-based forecasts on their decision-making patterns. The limited
intergenerational transfer of IK currently threatens its existence in the longer term. One way to ensure its continued existence
and use is to integrate IK into the education curriculum and to link IK with formal climate change research through the participation
of the local people. However, further studies are necessary to address the reliability and validity of the identified IK indicators
of climate variability and change. 相似文献
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Boniface O Oindo Rolf A de By Andrew K Skidmore 《International Journal of Applied Earth Observation and Geoinformation》2000,2(3-4)
Species richness, or simply the number of species in a given area, is commonly used as an important indicator of biological diversity. Spatial variability in species richness has been postulated to depend upon environmental factors such as climate and climatic variability, which in turn may affect net primary productivity. The Advanced Very High Resolution Radiometer (AVHRR) derived Normalized Difference Vegetation Index (NDVI) has been shown to be correlated with climatic variables including rainfall, actual evapotranspiration and net primary productivity. To determine factors favoring high species richness, we examined the relationship between interannual NDVI variables and species richness of birds at a quarter degree scale (55 × 55 km). Results revealed a strong positive correlation between species richness and maximum average NDVI. Conversely, species richness showed negative correlation with standard deviation of maximum NDVI and the coefficient of variation. Though these relationships are indirect, they apparently operate through the green vegetation cover. Understanding such relationships can help in mapping and monitoring biological diversity, as well as in estimating changes in species richness in response to global climatic change. 相似文献
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Simon Willcock Oliver L. Phillips Philip J. Platts Andrew Balmford Neil D. Burgess Jon C. Lovett Antje Ahrends Julian Bayliss Nike Doggart Kathryn Doody Eibleis Fanning Jonathan M. H. Green Jaclyn Hall Kim L. Howell Rob Marchant Andrew R. Marshall Boniface Mbilinyi Pantaleon K. T. Munishi Nisha Owen Ruth D. Swetnam Elmer J. Topp-Jorgensen Simon L. Lewis 《Carbon balance and management》2017,12(1):20