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"The main purposes of this paper are (1) to identify the primary population distribution problems in Asia, and (2) to identify the range of explicit population policy instruments or packages designed to alleviate or solve existing maldistribution. As a corollary to these main goals, attempts are made to classify types of spatial population problems and policies and to compare them across nations. Additionally, a qualitative analysis is made to assess the effectiveness of population distribution policies in those cases where there are reasonable data available."  相似文献   
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In the modern era, the world's refugee problem has changed magnitude and location; it has expanded from a local to a continental, and now global, scale issue. About 90% of the world's 10 million refugees are from developing countries, and over 90% of these will stay there. Refugee generating and receiving countries are concentrated in 5 world regions: Central America, Southwest Asia, Southeast Asia, and Sub-Saharan Africa. Each concentration is unique and is associated with a particular set of regional conflicts. International efforts address short-term relief needs, whereas political instability and repression that generate refugees continue unabated. Refugees along sensitive border regions affect bilateral relations, large groups of refugees can pose political and security problems for the host country, and disputes over refugee policies and their implementation can complicate diplomatic ties. Some highlights of the data follow. 1) The 3 million cross-border refugees and 5.5 million internally displaced persons make the many governments in Sub-Saharan Africa increasingly dependent on Western assistance to solve their problems. Refugees are fleeing armed conflict, tribal violence, and drought, and often generate additional regional turmoil. 2) 3-4 million Afghans have fled their country since the 1978 Marxist coup; about 2.5 million have entered Pakistan. Most choose to remain in camps near the Afghanistan border where they are targets of cross-border attacks. 3) 1.2 million Salvadorans, Guatemalans, and Nicaraguans live outside their native countries. Official refugee and unofficial migrant populations are active in various rebel insurgencies, contribute to strained bilateral relations and tensions in border areas, and are the subject of heated political debate in host countries. 4) 90% of the 1.7 million Indochinese who fled from 1975-May 1986 have been resettled; 168,000 refugees remain in 1st-asylum camps, not including 240,000 Khmer without refugee status, in temporary camps in Thailand. Thailand's large refugee population is involved in factional strife, smuggling, and guerrilla activities. The Thai are particularly concerned about Hmong refugees, who are accused of opium cultivation and destruction of Thai forests through slash-and-burn cultivation. 5) Nearly 62% of the thousands of present Vietnamese refugees to Hong Kong have been in camps 3 years, and 17% 6 years. Many have turned to crime, alcohol, drugs, or prostitution.  相似文献   
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This study aimed at comparing toxic element (Hg, Cd) bioaccumulation in relation to age for bottlenose (Tursiops truncatus) and striped dolphins (Stenella coeruleoalba) from Mediterranean and Atlantic waters. Metal concentrations were also measured in selected prey to infer metal exposure through the diet. As expected, Mediterranean prey exhibited the highest Hg levels, probably as a consequence of the Hg enrichment of the Mediterranean Sea. Comparing the predators from each area and taking age into account, Mediterranean bottlenose dolphins displayed higher Hg levels than Atlantic dolphins (p = 0.032), whereas Mediterranean striped dolphins did not (p = 0.691). The consumption of Myctophid fish, which showed the highest Hg levels (105+/-80 ngg(-1) w.wt.) among Atlantic prey, may explain the high Hg levels in the liver of the Atlantic striped dolphins and suggested a preferential offshore feeding behaviour in this area. Concerning Cd, no clear differences were found between geographical areas.  相似文献   
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Densities of fishes, invertebrates and plants at rocky intertidal and shallow subtidal sites were censused 1-2 days prior to the Jessica oil spill and compared with information obtained for the same sites one month after the spill, both for sites impacted by oil and unaffected reference sites. While the availability of pre-spill data made this analysis one of the most powerful to date for testing impacts of oil on shoreline environments, no clear changes attributable to oiling could be identified. Discharged oil appeared to cause very little impact in the intertidal and shallow subtidal zones, with such impacts lying within the range of natural spatial and temporal variation at sites investigated. Factors considered to minimize impact in Galápagos included paucity of fully sheltered shores in spill path, moderate wave action, warm temperature, high levels of sunlight, and mixing of bunker oil with diesel.  相似文献   
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Impacts of the grounding of the oil tanker Jessica off San Cristóbal island, Galápagos, included both effects of oil on biota and also mechanical effects associated with a shallow furrow 50 m x 30 m gouged across the rocky seafloor and wreckage strewn over 7500 m(2). The wreckage represented a minor but potentially chronic source of pollution to the surrounding environment through delayed releases of oil, antifouling compounds and other toxic chemicals, and a possible source of exotic marine taxa. Investigation at the wreck site indicated that impacts on subtidal plant and macro-invertebrate communities were largely confined within 100 m of the wreck site itself. Observed population effects included significant increases in cover of opportunistic algae (filamentous green algae, filamentous red algae and Ulva sp.) and the hydroid Ectopleura media adjacent to the wreck, while densities of the green sea urchin Lytechinus semituberculatus significantly decreased from 0.3 m(-2) adjacent to the wreck to 11 m(-2) at 100 m distance.  相似文献   
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