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排序方式: 共有240条查询结果,搜索用时 78 毫秒
231.
Thomas Hofer Hartmut Nies Stephan Gollasch Rolf von Ostrowski 《Environmental Sciences Europe》2007,19(4):219-225
Background and Scope
The marine shipping lanes have become the most important path for the invasion of foreign aquatic organisms. The increasing global trade results in an increase in the number of marine vessels. Without any protective measures, with every ship carrying foreign organisms the risk of biological invasions will rise.Results
The International Martime Organization (IMO) of the United Nations developed a convention to reduce the transfer of organisms with ballast water. After the entry-into-force of this convention the fleet of the world has to be equipped with effective ballast water management technology before 2016. This article discusses potential options for action. To comply with the limit values of the ballast water convention, the current state of the art demands the use of active substances. Any decision on the approval of active substances used for ballast water treatment and the environmental impact assessment lies with the IMO. Proposed to day are UV-radiation, active chlorine, active oxygen, the creation of biocides through electrolysis and a change in gases contained in the ballast water. The technologies and the potential risks are presented.Conclusions
Despite the introduction of an approval procedure by IMO any reliable assessment of the real risks involved in the use of biocides is impossible, as the risk assessment approaches have still to be developed. On the regulatory level, the main focus in data requirements for the risk assessment is on a comprehensive testing of the toxic potential of the biocides proposed. Strategies for the identification and evaluation of the chemical resulting from the treatment of limnic, marine and brackish water are not fully developed. An integrating assessment of risks involved in the introduction of foreign organisms versus the toxic effects of the substances used or created during treatment is still missing. 相似文献232.
This article attempts to study both returns to scale and optimal size of production. Specifically, the authors estimate a ray-homothetic production function which allows the returns to scale to vary with ouput size and input mix. The production model is estimated using data from the Welsh coal industry for the period 1961–1976. Findings showed that, first, the Welsh coal industry suffers from a level of production which is either too small or below its optimal level and, second, this discrepancy between actual and optimal production worsened over the period considered. 相似文献
233.
We studied the effects of winter water drawdowns (2.3 m) on beavers in Voyageurs National Park, Minnesota, USA. Our study
was designed to sample areas within the park that differed in water drawdown regime. Lodges were counted and beavers were
livetrapped and radio-implanted to study behavior, movements, and mortality. Active beaver lodge density, determined by aerial
survey in 1984 and 1986, was greatest along the shoreline of the drawdown reservoir. In winter beavers living on the drawdown
reservoir spent less time inside their lodges than did beavers from stable water environments, foraged more above ice, and
they were unable to fully use stored food. Only one case of starvation in the drawdown reservoir was documented, but beavers
in reservoirs that were drawn down survived winter in poorer condition than did beavers living in areas in which water levels
remained high. In spite of an increasing population and lack of widespread mortality, winter water drawdowns did alter beaver
behavior. To reduce these impacts, total annual water fluctuation should not exceed 1.5 m, and winter drawdown should not
exceed 0.7 m. Possible management alternatives and costs are discussed. 相似文献
234.
235.
Callaghan TV Björn LO Chernov Y Chapin T Christensen TR Huntley B Ims RA Johansson M Jolly D Jonasson S Matveyeva N Panikov N Oechel W Shaver G Henttonen H 《Ambio》2004,33(7):436-447
Species individualistic responses to warming and increased UV-B radiation are moderated by the responses of neighbors within communities, and trophic interactions within ecosystems. All of these responses lead to changes in ecosystem structure. Experimental manipulation of environmental factors expected to change at high latitudes showed that summer warming of tundra vegetation has generally led to smaller changes than fertilizer addition. Some of the factors manipulated have strong effects on the structure of Arctic ecosystems but the effects vary regionally, with the greatest response of plant and invertebrate communities being observed at the coldest locations. Arctic invertebrate communities are very likely to respond rapidly to warming whereas microbial biomass and nutrient stocks are more stable. Experimentally enhanced UV-B radiation altered the community composition of gram-negative bacteria and fungi, but not that of plants. Increased plant productivity due to warmer summers may dominate food-web dynamics. Trophic interactions of tundra and sub-Arctic forest plant-based food webs are centered on a few dominant animal species which often have cyclic population fluctuations that lead to extremely high peak abundances in some years. Population cycles of small rodents and insect defoliators such as the autumn moth affect the structure and diversity of tundra and forest-tundra vegetation and the viability of a number of specialist predators and parasites. Ice crusting in warmer winters is likely to reduce the accessibility of plant food to lemmings, while deep snow may protect them from snow-surface predators. In Fennoscandia, there is evidence already for a pronounced shift in small rodent community structure and dynamics that have resulted in a decline of predators that specialize in feeding on small rodents. Climate is also likely to alter the role of insect pests in the birch forest system: warmer winters may increase survival of eggs and expand the range of the insects. Insects that harass reindeer in the summer are also likely to become more widespread, abundant and active during warmer summers while refuges for reindeer/caribou on glaciers and late snow patches will probably disappear. 相似文献
236.
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238.
Summary Resting time in red deer (Cervus elaphus) was shown to be more than twice as long on days when harassment by head flies (Hydrotaea irritans) was considered severe compared with days when fly harassment was estimated as low. Avoidance reactions in the deer decreased as soon as the deer reclined and became stabilized at a level corresponding to approximately 50% of the initial response frequency. The present observations do not give any clear indications as to whether it is the head flies per se or climatic factors that are the primary cause of reduced locomotory behaviour in the deer. It is concluded, however, that due to a causal relationship between the appearance of flies and certain types of weather, and because lying down has a relieving effect, inactivity may be an important part of the strategy used by red deer to cope with head fly harassment. 相似文献
239.
Producer responsibility for e-waste management: key issues for consideration - learning from the Swiss experience 总被引:3,自引:0,他引:3
E-waste, a relatively recent addition to the waste stream in the form of discarded electronic and electric equipment, is getting increasing attention from policy makers as the quantity being generated is rising rapidly. One of the most promising policy options to address this issue is to extend the producers responsibility for their products beyond the point of sale, until end-of-product-life. This paper briefly introduces the concept of extended producer responsibility (EPR) and its applicability in the area of the end-of-life management of electronic and electrical equipment (EEE). It then examines the decade-long experience of Switzerland in using EPR to manage its e-waste, elaborating on the experience of the Swiss system in overcoming specific issues, and finally wrapping up with a synopsis of the lessons for policy makers. We consider each issue as an enquiry of questions confronting a policy maker and the choices that may present themselves. The five issues discussed are: (i) the challenges in getting an EPR based system started; (ii) securing financing to ensure a self-sustaining and smooth functioning system; (iii) organising a logistics network for the take back and collection of the e-waste; (iv) ensuring compliance of the various actors involved; and finally (v) reducing the threat of monopolistic practices. 相似文献
240.
Bostian Moriah Färe Rolf Grosskopf Shawna Lundgren Tommy 《Environmental Economics and Policy Studies》2022,24(4):503-531
Environmental Economics and Policy Studies - We develop a model for pollution abatement that distinguishes between prevention and treatment technologies, in order to better understand the optimal... 相似文献