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1.
The current and dominant theory about the origin of modern humans is the out-of-Africa hypothesis, which asserts that populations of Homo sapiens left Africa 100,000 years ago and replaced indigenous populations of humans in Eurasia. Many scholars equated the out-of-Africa dispersal of humans with paleoenvironmental changes. However, until now, few have paid special attention to the faunal data and whether or not faunal patterns are supportive of the popular theory. Recent comparative study of the Chinese fauna shows that the communication of faunas between Africa and East Asia could have occurred during the Neogene, but it was very limited during the Pleistocene. In the Chinese Quaternary fauna, only 16% of the genera are also present in the sub-Saharan African fauna. There is also no element among the dominant taxa of the Chinese Quaternary fauna which can be related to the African fauna. There is no reliable proof for the existence of Hippopotamus and Giraffa, as well as Panthera leo, during the Quaternary in China. Two controversial taxa are Acinonyx and Crocuta, about which there is still argument concerning their species identification in Eurasia. It is possible that both of the genera have co-specific taxa in Africa and Eurasia. Although the two genera are confined to Africa today, they did have a long evolutionary history in China. For the Out of Africa hypothesis for Homo sapiens, the implications of the limited faunal interchanges between China and Africa are not completely clear yet.  相似文献   

2.
Sustaining and increasing crop production and productivity has to be a major policy thrust for developing countries. Using a simulation approach different production strategies were evaluated conditioned on climate information to derive optimal strategies to help farmers reduce risk and increase productivity. By examining the existence of options in this case planting dates the study provides an analyses of the expected value and risks associated with changing decisions based on the availability of climate forecasts. The 15-March planting date produced the highest mean yield for the two cultivars examined although 1-April, 15-April and 1-May plantings had one to zero probability of crop failures compared to 15-March with crop failures in 4 out of 20 years. Results indicate losses of between 25 and 35 kg/day due to delays in planting from 15-March planting to 1-June planting for the 120- and 150-day cultivar. El niño years were associated with positive yield deviations for both cultivars and most planting dates. Farmers are known to make tactical adjustments to their management in light of information perceived relevant to the prospects of forthcoming crop. Although in its present form most current forecast products do not provide information on onset of the rainfall, however the information they do provide could play a crucial role in helping farmers reduce the risks posed by climatic variability.  相似文献   

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4.
Cleophas Lado 《GeoJournal》1998,45(3):165-176
In many developing countries, research institutions or centres have been established to develop and/or adapt technologies that would help agricultural development. This is particularly true in Africa where national efforts have been supplemented with international research institutes. Although some modest progress has been achieved in improving agricultural technology, on the whole, the improvement record is not quite encouraging among the small-scale farmers. In many areas, either there are no improved technologies, or where they exist, are unacceptable by farmers. However, where useful technologies exist, their spread has been very limited and where they have been adapted, the benefits only accrue to a small segment of the community. The logical question posed is: why and how do we find ourselves in the current situation? This paper considers the view that to understand fully why the available technologies have remained largely at the research centres, there is need to examine the whole process of research, development, dissemination and utilization of agricultural technology. It is significant to investigate the structural constraints and prospects under which those involved in the process work, their motivations and the interactions between different groups. The traditional ‘top-down’ of development strategy should be supplemented with farmers' indigenous knowledge, and programmes encouraging transfer of agricultural technology should include institutional support. Only by the identification of farmers' environmental and resource utilisation, preferences, socio-economic circumstances and constraints can a development programme of optimum meaning to farmers be devised and implemented with success.  相似文献   

5.
Charles Kelly 《GeoJournal》1995,37(3):381-385
Megacities are extreme manifestations of urban complexity that present aid agencies with major disaster assessment challenges. Geographers can contribute to improving megacity disaster assessments by: 1) defining megacity disasters; 2) improving socioeconomic measures of disaster to allow for clearer differentiation of effects among different population sub-groups; 3) specifying criteria for identifying thresholds of disaster and trends in the status of disaster-affected populations; and 4) developing credible data collection and analysis methods appropriate for complex urban environments. In addition, long term research is needed to encourage the formulation of models of megacity life that provide better understanding of human survival under normal conditions of severe adversity.The views expressed herein are entirely those of the author and are not attributable to organizations which have sponsored the author's research.  相似文献   

6.
GeoJournal - In recent times, food security has received growing attention as a means to alleviate hunger, and to ensure sustainable supply of nutritious, secure and accessible food to the...  相似文献   

7.
Loss of life and property caused by landslides triggered by extreme rainfall events demonstrates the need for landslide-hazard assessment in developing countries where recovery from such events often exceeds the country's resources. Mapping landslide hazards in developing countries where the need for landslide-hazard mitigation is great but the resources are few is a challenging, but not intractable problem. The minimum requirements for constructing a physically based landslide-hazard map from a landslide-triggering storm, using the simple methods we discuss, are: (1) an accurate mapped landslide inventory, (2) a slope map derived from a digital elevation model (DEM) or topographic map, and (3) material strength properties of the slopes involved. Provided that the landslide distribution from a triggering event can be documented and mapped, it is often possible to glean enough topographic and geologic information from existing databases to produce a reliable map that depicts landslide hazards from an extreme event. Most areas of the world have enough topographic information to provide digital elevation models from which to construct slope maps. In the likely event that engineering properties of slope materials are not available, reasonable estimates can be made with detailed field examination by engineering geologists or geotechnical engineers. Resulting landslide hazard maps can be used as tools to guide relocation and redevelopment, or, more likely, temporary relocation efforts during severe storm events such as hurricanes/typhoons to minimize loss of life and property. We illustrate these methods in two case studies of lethal landslides in developing countries: Tegucigalpa, Honduras (during Hurricane Mitch in 1998) and the Chuuk Islands, Micronesia (during Typhoon Chata'an in 2002).  相似文献   

8.
Dynamic simulation models allow an integrated representation of human and biophysical driving forces, to test their influence on land use. Dynamic models emphasise the interactions among the components of the system and take into account feedback loops and threshold effects. In this paper, the SALU model was used to generate “what-if” scenarios to explore hypotheses on the relative role of driving forces of land-use change in the Sudano-sahelian countries of Africa. The model simulations provided useful insights to better understand the processes of land-use change. Rural population growth represents a larger stimuli for land-use change than urban population growth. Demographic variables have a greater impact on land use than recurring droughts. The demographic driving forces are slow variables while rainfall is a fast variable. Recurring droughts could be viewed as trigger events, and urban population growth and consumption as mediating factors, while rural population growth defines long-term trends. Technological change defines thresholds in land use. Land-use change results from interactions between driving forces. The timing of occurrence of drought with respect to transitions in land use has a major impact on land-use change. Polices aimed at protecting pastoral land and supporting agricultural intensification both contribute to maintain pastoral activities. Simulating a conservative carrying capacity has a major impact on land use predictions. By examining environmental, social and economic implications of various land-use scenarios, the modelling approach adopted in SALU can provide support for decision-making.  相似文献   

9.
Important as water is to man's manifold activities, a significant percentage of mankind still do not have access to clean water for drinking and personal hygiene. According to a WHO survey of facilities available in developing countries to the end of 1975, 75 % of urban population and 20 % of rural population have access to potable water. Studies carried out by the UN system estimate that investment necessary to provide clean water and sanitation by 1990 to both rural and urban areas is on the order of $ 132,940 million in constant 1977 dollors. Furthermore, provision of clean water alone is unlikely to eliminate all water-borne diseases, since it is only one of several complex factors affecting human health.The situation in developing countries on water requirements for agriculture, industry and generation of hydroelectric power also requires attention because of large amounts of water involved. Effectiveness and efficiency of the supply and distribution systems must be given top priority. There is a considerable potential for improving the efficiency of water use in virtually every developing country and in every sector.  相似文献   

10.
K. Priestley 《Lithos》1999,48(1-4):45-56
The velocity model for southern Africa of Qiu et al. [Qiu, X., Priestley, K., McKenzie, D., 1996. Average lithospheric structure of southern Africa. Geophys. J. Int. 127, 563–587] is revised so as to satisfy both the regional seismic waveform data and the fundamental mode Rayleigh wave phase velocity data for the region. The revised S-wave model is similar to the original model of Qiu et al. except that the high velocity, upper mantle lid extends to 160 km depth in the revised model rather than to 120 km in the original model. Sensitivity tests of the regional seismic data show that the minimum velocity in the S-wave low velocity zone can be as high as 4.45 km s−1 compared to 4.32 km s−1 in the Qiu et al. model. The vertical S-wave travel time for the revised south African model is compared with the vertical S-wave travel times for the global tomographic models S12WM13 and S16B30, and they are found to be similar.  相似文献   

11.
The present article examines the dynamic linkages between biomass energy consumption, capital stock, human capital and economic growth across selected Sub-Saharan African countries based on dynamic heterogeneous panels of a mean group (MG) and pooled mean group (PMG) techniques. The finding based on PMG as the preferred method reveals that biomass energy consumption, capital stock and human capital are statistically significant, which means aforementioned variables have positive significant impact on economic growth in the countries studied. When an alternative panel estimation techniques of panel cointegration, dynamic OLS (DOLS) and fully modified OLS (FMOLS) are applied, the result based on panel cointegration technique reveals that biomass energy consumption, capital stock, human capital and economic growth are cointegrated as null hypothesis of most statistics are rejected at 1 % level of significance. The finding based on FMOLS shows that biomass energy consumption, capital stock and human capital positively influences economic growth at 1 % level and same result is obtained from panel OLS. The result based on DOLS however reveals that biomass energy consumption and capital stock are significant at 1 % on economic growth while human capital is insignificant. Considering its positive effect on economic growth with little or no environmental degradation when compared with fossil fuel uses, consumption of biomass energy is more preferable in these countries therefore is the best option to adopt by the policy makers of Sub-Saharan African countries.  相似文献   

12.
Urmilla Bob 《GeoJournal》2004,61(3):291-300
This article contributes to a greater understanding of the linkages between women's roles, responsibilities and their use of technology in poor rural communities. The ways in which poor rural women conceptualize technology is examined. Furthermore, how they use their knowledge and skills to develop, modify and adapt the techniques and technical processes in which they are involved are also explored. Additionally, the links between indigenous and modern technologies in relation to gender considerations in poor rural contexts are examined. This article draws from findings of primary research undertaken in two marginalized rural communities in Kwazulu-Natal, South Africa. The study reveals that the use of technologies are highly gendered and differentiated among women. Poor rural women utilize a range of technologies in both productive and reproductive activities which are central to their livelihood strategies, especially at the household level. Furthermore, although women are adapting and innovating technologies their expertise remains largely unrecognized. A range of problems and constraints exist which limit women's access to and use of technologies. A key tension identified in the study is that between the use of locally-based, indigenous technologies and modern, external technologies. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

13.
《Comptes Rendus Geoscience》2015,347(4):201-211
Fossil remains are embedded in a continually evolving landscape. Earth scientists have the methods and approaches to study the processes that shape the landscape at various temporal and spatial scales. Some of these methods can generate insights that are of potential use for researchers in other fields, such as archaeology and palaeoanthropology. Here we present two case studies to illustrate how a broader landscape perspective can provide new insights into the land use by Pliocene hominins in southern Africa, and more recently, by Palaeolithic hominins in the southern Levant. Key landscape attributes can help explain why humans, hominins and the wider animal community exploit certain types of landscapes in predictable ways. Our first case study examines how active tectonics or volcanism appears to be important in creating fertile regions with reliable water sources and complex topography. While relatively easy for agile primates such as hominins to negotiate, zones of complex topography are harder for certain predators and prey animals to traverse. In the second case study, we consider that differences in soil edaphics can exert a major control on animals by supplying or failing to supply necessary trace elements, such as selenium, copper, phosphate and potassium (Henkin et al., 1995). We show that the pattern of trace element distribution can accurately map animal movements between areas of suitable grazing. This predictability could have enabled Levantine humans to ambush megafauna during these seasonal migrations. By studying the landscape attributes around fossil site locations, Earth scientists can offer new insights and perspectives into the past, particularly on the ways in which the inhabitants would have used their landscapes.  相似文献   

14.
Alistair Fraser 《Geoforum》2007,38(2):299-311
Market-Led Agrarian Reform (MLAR), which is advocated by the World Bank and is being implemented in various contexts around the world, is a more neo-liberal approach to land reform than that we have seen implemented in the past. MLAR principles have underpinned South Africa’s land reform programme, being based on the ‘willing-seller, willing-buyer’ principle, which guarantees market-related prices to sellers. Evidence presented in this paper, however, raises serious questions about the extent to which the South African government has held on to MLAR principles. Specifically, the paper argues that South Africa’s peculiar geo-historical context has in some instances led the government to fuse market-led approaches with more authoritarian interventions that dictate to land reform beneficiaries how the land will be used. A case in point is the government’s approach to the restitution of land rights to communities dispossessed from the Levubu area of Limpopo province. As the paper illustrates, the government has imposed on the intended beneficiaries a so-called ‘strategic partnership’ between them and agribusinesses. Although the government touts the approach as a way to protect the commercial viability of the land and to transfer skills from white farmers to the beneficiaries, the terms of the Levubu solution may turn out to be less than favourable for the beneficiaries.  相似文献   

15.
B. McCusker  E.R. Carr 《Geoforum》2006,37(5):790-804
Land use change and livelihood systems are often analyzed separately or with one “driving” the other. This “driver-feedback” relationship has been buttressed by approaches to social process that are often far too static. Actors are confronted with a bundle of choices that they must negotiate as they create pathways of change. These choices are always bound up in relations of power and the knowledges that are the conditions for and results of these relations. We suggest that land uses and livelihood are different manifestations of the social processes by which individuals and groups negotiate the everyday conditions that shape their lives. We propose a framework that extends current understandings of the relationship between land use change and livelihoods by treating social relations of power as the entry point into this complex relationship. We underpin our arguments with empirical examples from South Africa and Ghana that locate power/knowledge relations in the context of social change in both study areas.  相似文献   

16.
17.
The rapid expansion in agricultural groundwater use in the last few decades has transformed rural economies in large parts of the developing world, in particular South Asia and North China. There has been no such “Groundwater Revolution” in most of sub-Saharan Africa and little is known about the actual role of groundwater use in supporting agricultural livelihoods in the region or opportunities to expand this role in the future. Published literature has been reviewed to paint a preliminary, region-wide picture of the contribution groundwater makes to agriculture, and in turn to rural livelihoods, within sub-Saharan Africa. The findings indicate that groundwater is used on only 1–2 million hectares of cropped area, directly contributing to the livelihoods of 1.5–3% of the rural population. Groundwater also plays a critical role in the vital livestock sector as well as an important indirect role in the supply of domestic water to agricultural households. While data are lacking, these latter two roles likely surpass the direct importance of groundwater to crop production. This suggests that an understanding of the value of agricultural groundwater use in support of rural livelihoods in sub-Saharan Africa should be based on different models than have typically been applied in Asia.
Mark GiordanoEmail: Phone: +94-11-2787404Fax: +94-11-2786854
  相似文献   

18.
Integrated water resources management (IWRM) forms the widely accepted ecosystem approach to managing water and its related resources in a sustainable way. Nevertheless, its implementation is still lagging behind, especially in developing and transition countries which are often short of essential resources and face complex political dynamics. IWRM often requires a fundamental realignment of governance structures. This may lead to problems of fit and institutional interplay as particular challenges of multi-level governance. Against this background, a case study of Mongolia was carried out, a transition country suffering from extreme climatic conditions and increasing depletion of its resources. While an attempt to introduce IWRM exists on paper, it is less clear how it will be made politically and institutionally applicable. A document review and stakeholder interviews were carried out to understand the progress and problems of introducing IWRM in Mongolia in the face of its transition and decentralisation process. Problems of fit and interplay—which are in part results of the transformation—were identified, as well as the approaches for their solution. Attempts are underway to overcome problems of fit such as the establishment of river basin councils which are presently facing the challenges concerning their room for manoeuvre. Problems of interplay arise when it comes to the cooperation and coordination of numerous water-related organisations which often lead to inconsistent water governance.  相似文献   

19.
非洲乍得盆地玄武岩K-Ar和39Ar-40Ar年代学及其动力学背景   总被引:1,自引:0,他引:1  
乍得的Doba、Bongor和Lake Chad盆地是早白垩世中非右行走滑应力场控制下形成的一系列中新生代陆内拉分盆地,形成与中、赤道及南大西洋打开有关。钻井揭示了盆地内分布有大量的中新生代玄武岩。系统的K-Ar、Ar-Ar法年代学研究发现,至少可识别出2个周期的火山活动旋回,即(1)95-75Ma,只分布于Doba盆地;(2)66-52Ma,分布于Bongor和Lake Chad盆地。研究表明,乍得盆地内中新生代火山活动是板内伸展应力机制下的产物,与白垩纪整个西中非地区的区域构造背景相一致,岩浆作用与裂谷作用密切相关。  相似文献   

20.
This paper documents a continuous  44,000-yr pollen record derived from the Mfabeni Peatland on the Maputaland Coastal Plain. A detailed fossil pollen analysis indicates the existence of extensive Podocarpus-abundant coastal forests before  33,000 cal yr BP. The onset of wetter local conditions after this time is inferred from forest retreat and the development of swampy conditions. Conditions during the last glacial maximum ( 21,000 cal yr BP) are inferred to have been colder and drier than the present, as evidenced by forest retreat and replacement of swampy reed/sedge communities by dry grassland. Forest growth and expansion during the Holocene Altithermal ( 8000–6000 cal yr BP) indicates warm, relatively moist conditions. Previous records from Maputaland have suggested a northward migration of Podocarpus forest during the late Holocene. However, we interpret a mid-Holocene decline in Podocarpus at Mfabeni as evidence of deforestation. Forest clearance during the mid-Holocene is supported by the appearance of Morella serrata, suggesting a shift towards more open grassland/savanna, possibly due to burning. These signals of human impact are coupled with an increase in Acacia, indicative of the development of secondary forest and hence disturbance.  相似文献   

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