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191.
Jon D. Unruh 《GeoJournal》1995,36(1):19-26
Indigenous resource tenure systems in Africa have evolved to meet the constraints and opportunities of often difficult biophysical environments, while facilitating the operation of complex spatial and temporal land use patterns. Traditional systems provide security of tenure in culturally relevant ways that permit adaptation to new circumstances. On the other hand imposed tenure structures in Africa have often not strengthened individual rights and have often blocked indigenous tenure development and adaption in response to new situations.Pastoralists in Africa have in particular been negatively impacted by the imposition of national tenure systems which in many cases have served to marginalize nomadic populations, with repercussions in land degradation, food security, and instability.In Somalia the transient resource rights and resource use arrangements that are critical to transhumant pastoralism were ignored in the formulation of the national tenure regime which favored crop cultivation. The results were increased land degradation, resource use conflicts, declines in pastoral production, and impacts on Somali clan alliances which in many cases regulate rational resource access and use.Somalia possesses the greatest proportion of pastoralists in Africa. Transhumant pastoralism, as the most widespread agricultural enterprise in the country, will play a critical role in food production for the foreseeable future. However, the relationship between indigenous pastoralist tenure and state imposed tenure has, in many locations decreased the ability of pastoralism to reproduce itself, thereby compromising the rational utilization of very large areas of rangeland interior, which have very few alternative uses. 相似文献
192.
Jon Lasse Bratli 《Marine pollution bulletin》1994,29(6-12):435-438
Lake Frøylandsvatn is a shallow eutrophic lake which has frequent blooms of various species of blue-green algae, often producing toxins. The lake receives heavy nutrient loads, mainly from agriculture, as well as a large internal load from its own sediments. It also shows several signs of being an unbalanced ecosystem. It has been calculated that phosphorus and chlorophyll levels need to be reduced by approximately 50% to improve the water quality enough for swimming. The analysis presented here makes it possible to compare the cost-effectiveness of different measures, including both catchment area and lake-internal methods. In addition to conventional means of reducing phosphorus pollution caused by agricultural activities and sewage, other measures, including biomanipulation and self-purification processes through artificial ponds and wetlands, will be necessary to achieve the ambitious goal that has been set. 相似文献
193.
Light and temperature are two of the most important physical factors affecting rates of growth of reef corals. The effect of light has been determined by X-radiographic measurement of long-term growth rates for 89 colonies of the coralMontastrea annularis collected over a 27.5-m depth range from St. Croix, U.S. Virgin Islands. These measurements, in conjunction with measurements of skeletal density, have established thatM. annularis calcifies most rapidly at intermediate depths, and they have confirmed the identification of two distinct populations within this important frame-building species. 相似文献
194.
This article examines whether the European Union (EU) could be seen as a normative power at the recent World Summit on Sustainable Development. We explain how the EU operationalised its commitment to the concept of sustainable development before highlighting the impact the EU had on the final summit outcomes. It shows that although in many areas the EU was able to offer leadership, internal policy coherence prevented it fully being able to develop that role and thus fully promoting the norm of sustainable development. 相似文献
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K. B. Atkinson A. H. Holmes I. J. Dowman M. J. Smith P. R. T. Newby S. Robson D. A. Tait R. P. Kirby P. R. Thomas 《The Photogrammetric Record》1997,15(89):765-789
The XVIIIth International Congress of Photogrammetry and Remote Sensing was held in the Austria Center, Vienna from 9th to 19th July, 1996. Reports on the Technical Commission Activities, on the Congress Exhibition and on the General Assembly were given at a meeting of the Photogrammetric Society on 7th October, 1996. Papers from the Congress were published in the International Archives of Photogrammetry and Remote Sensing, 31. 相似文献
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