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排序方式: 共有169条查询结果,搜索用时 31 毫秒
81.
Anders Henrik Sirén 《国际发展与全球生态学杂志》2013,20(5):363-374
Wild game and other renewable resources in tropical rainforests inhabited by indigenous peoples are currently often exploited in unsustainable ways. This article shows, for a Kichwa community in the Ecuadorian Amazon, that this can to some extent be explained as a 'tragedy of the commons'. However there are also other mechanisms at work. In particular, there has been some unawareness of the impact of hunting on game populations, and the expansion of fallows at the expense of old growth forest is a result of population growth that increases the need for farmland, and thus decreases the socially optimal area of old growth forest. Whereas many resources are harvested under conditions resembling open access, there have long been established rules for the harvest of thatch leaves, and the community has recently also adopted several measures in order to regulate hunting. Obviously, experiences of resource scarcity may spark conservationist thinking and behaviour. This is a process that scientists can and should support. 相似文献
82.
Experience with fire safety engineering under a performance-based fire safety regulation regime shows that the majority of the analyses performed are scenario based. A comparison with purely pre-accepted performance requirement is made in order to assess the relative safety level of the alternative design compared with the pre-accepted design. We find this approach problematic because it undermines the value of performing analyses. The approach accepts oversimplification and justifies unrealistic assumptions on the basis that it will not affect the comparison. This distances the analyses from reality and reduces their value to answer a yes/no question on acceptability. The considerable time and resources spent on searching for and analyzing a pre-accepted design could be spent on analyzing the design at hand. If fire safety analyses are to have any real impact on design, it is necessary that regulators strengthen the position of analytical design. This must include a provision of a clear set of performance goals, which are possible to transform into quantitative evaluation criteria by the engineers, to avoid comparisons with pre-accepted performance requirements. 相似文献
83.
Many voluntary incentive programs for provision of forest ecosystem services (ES) have low participation rates, insufficient enrollment areas, and inefficient ecological outcomes. Understanding participation behavior in such programs has therefore become a crucial part of policy success. We synthesized a large body of literature on the behavior of nonindustrial private forest owners based on surveys of stated (intended) participation or data on actual participation in existing or hypothetical programs. Using metaregression analysis, we examined how methodological, program-characteristic, and economic-incentive variables affected participation rate estimates. Participation rates tended to be overestimated when landowner participation was elicited in hypothetical choice situations (compared with real situations) and when dichotomous choice surveys (compared with census data) were used. The marginal effect sizes were quite large, for example, a 31% increase with use of stated choices in hypothetical scenarios, and practitioners should therefore be aware of them. However, use of choice experiment surveys in a modified scenario based on existing programs had no effect on participation when all other determinants were controlled for. Participation rates decreased significantly as length of the contract increased and when there was no withdrawal option. These results suggest that perpetual contracts have a lower negative impact on participation than time-limited contracts with a duration of over 50 years. We confirmed that as compensation amounts increased, participation increased. One-time up-front payments were more effective in increasing initial participation than annual payments for contracts of over 5 years. We identified the robust determinants and the effect sizes of those determinants on landowner participation rate estimates, thereby contributing to a better understanding of forest owner behavior and offering useful insights to enable researchers and resource managers to improve the design and efficiency of new and existing forest ES programs. 相似文献
84.
Filling and cleaning of pesticide sprayers presents a potential risk of pollution of soil and water. Three different solutions for handling sprayers have been suggested: Filling and cleaning in the field, filling and cleaning on hard surfaces with collection of the waste water, and filling and cleaning on a biobed, which is an excavation lined with clay and filled with a mixture of chopped straw, sphagnum and soil with turf on top, and with increased sorption capacity and microbial activity for degradation of the pesticides. In the present study the degradation and leaching of 21 pesticides (5 g of each) was followed in an established full-scale model biobed. Percolate was collected and analysed for pesticide residues, and the biobed material was sampled at three different depths and analysed by liquid chromatography double mass spectrometry (LC-MSMS). During the total study period of 563 days, no traces of 10 out of 21 applied pesticides were detected in the percolate (detection limits between 0.02 and 0.9 μg l−1) and three pesticides were only detected once and at concentrations below 2 μg l−1. During the first 198 days before second application, 14% of the applied herbicide bentazone was detected in the leachate with maximum and mean concentrations of 445 and 172 μg l−1, respectively. About 2% of the initial mecoprop and fluazifop dose was detected in the percolate, with mean concentrations of 23 μg l−1, while MCPA and dimethoate had mean concentrations of 3.5 and 4.7 μg l−1, respectively. Leachate concentrations for the remaining pesticides were generally below the detection limit (0.02–0.9 μg l−1, below 1% of applied). Sorption studies of five pesticides showed that compounds with a low Kd value appeared in the leachate. After 169 days, all pesticides in the biobed profile were degraded to a level below 50% of the calculated initial dose. Pesticides with Koc values above 100 were primarily found in the uppermost 10 cm and degraded slowest due to the low bioavailability. The 11 most degradable pesticides were all degraded such that less than 3% remained in the biobed after 169 days.
Following second pesticide application of the biobed, leachate was sampled 215 and 365 days after the treatment. This showed the same pesticides to be leached out and at concentrations comparable to those of the first treatment. The same pesticides as after the first treatment were retained in the biobed. 相似文献
85.
Morten Frederiksen Henrik Jensen Francis Daunt Roderick A Mavor Sarah Wanless 《Ecological applications》2008,18(3):701-710
Fisheries management across the world is moving toward an ecosystem-based approach, implying that fishery effects on nontarget species should be taken into account. However, such effects are often not well understood, partly because, they can be difficult to distinguish from impacts of environmental fluctuations. We evaluated the effects of an industrial sand lance (Ammodytes marinus) fishery off the North Sea coast of the United Kingdom, which has been opened and closed in a quasi-experimental fashion, on sand-lance-dependent breeding seabirds. Controlling for environmental variation (sea surface temperature, abundance of larval sand lance, and size of adult sand lance), we found that, when the fishery was operating, breeding productivity in the intensively studied seabird colony on the Isle of May was significantly depressed for one surface-feeding seabird species, the Black-legged Kittiwake (Rissa tridactyla), but not for four diving species. Analyzing Kittiwake data from 12 colonies inside and outside the closure zone in a replicated before-after control-impact design, we again found that breeding productivity was significantly depressed in the closure zone when the fishery was active, whereas no effect was found in the control zone. Furthermore, Kittiwake breeding productivity was negatively correlated with fishery effort during the fishery period in the closure zone, but not in the control zone. The contrasting findings in the two zones could be related to environmental differences or to the fact that only one study colony in the control zone was exposed to high fishery effort within the typical foraging range of Kittiwakes during the breeding season. The strong impact on Kittiwakes, but not on diving species, could result from (1) inherently high sensitivity to reduced prey availability, (2) changes in the vertical distribution of sand lance at lower densities, (3) sand lance showing avoidance behavior to fishery vessels, or a combination of some or all of these factors. These findings indicate that local fishery closures can benefit sensitive predators and should be considered as a tool for future ecosystem-based fisheries management. 相似文献
86.
Sheng Fulai Gary Flomenhoft Timothy J. Downs MaÁngeles Grande‐Ortiz Dana Graef Bert Scholtens Arthur P.J. Mol David A. Sonnenfeld Gert Spaargaren Rajeev K. Goel Edward W.T. Hsieh Serban Scrieciu Reinhard Steurer Christine Polzin Genia Kostka Tiho Ancev Elke Pirgmaier Frank Boons Karl‐Henrik Robèrt Christopher Bryant Ke Zhou Surya Raj Acharya David Huberman Denis J. Sonwa Michelle Mycoo Dabo Guan Klaus Hubacek U. Rashid Sumaila Hector G. Lopez‐Ruiz G. Jason Jolley Michael L. Dougherty André Francisco Pilon Ravi Prakash Tulus Tambunan Sebastian Hermann 《Natural resources forum》2011,35(1):63-72
87.
Sigr��n H. J��nasd��ttir J?rg Dutz Marja Koski Lidia Yebra Hans Henrik Jakobsen Charles Vidoudez Georg Pohnert Jens C. Nejstgaard 《Marine Biology》2011,158(9):1943-1963
Egg and faecal pellet production and egg hatching success of the calanoid copepod Calanus finmarchicus were monitored over a period of 14?days (14?C28 April, 2008) while fed water from 4 differently treated mesocosms and ambient water. Two of the mesocosms used were inoculated with the polyunsaturated aldehyde (PUA)-producing diatom Skeletonema marinoi, while 2 received only nutrient additions with or without silica. The mesocosms developed blooms of S. marinoi, mixed diatoms or the haptophyte Phaeocystis pouchetii, respectively. Faecal pellet production of C. finmarchicus increased with increasing food availability. Egg production increased with time in all mesocosms to a maximum single female production of 232 eggs female?1?day?1 (average of 90 eggs female?1?day?1) and followed the development of ciliates and P. pouchetii, but was not affected by the observed high (up to 15?nmol?L?1) PUA production potential of the phytoplankton. The hatching success of the eggs produced on the mesocosm diets was high (78?C96%) and was not affected by either aldehydes in the maternal diet or exposure to the dissolved aldehydes in the water. 相似文献
88.
89.
Olle Ericsson Tarja Ahola Fredrik Dahl Filip Karlsson Fredrik Persson Olof Karlberg Fredrik Roos Ida Alftrén Björn Andersson Emelie Barkenäs Ani Boghos Birgit Brandner Jenny Dahlberg Per-Ola Forsgren Niels Francois Anna Gousseva Faizan Hakamali Åsa Janfalk-Carlsson Henrik Johansson Johanna Lundgren Atefeh Mohsenchian Linus Olausson Simon Olofsson Atif Qureshi Björn Skarpås Peter Svahn Anna Sävneby Eva Åström Anna Sahlberg Aino Fianu-Jonasson Jérémie Gautier Jean-Marc Costa Bo Jacobsson Kypros Nicolaides 《黑龙江环境通报》2019,39(11):1011-1015
90.
Henrik Kylin 《Environmental science and pollution research international》1996,3(4):218-223
Many environmental contaminants known today are semivolatile organic compounds (SOC) and are present in the atmosphere. Airborne SOC are taken up and enriched by the epicuticular wax that covers leaves of higher plants. The purpose of the present work was to use pine needles 1) to map the distribution of airborne SOC in Europe, 2) to identify source regions, and 3) to identify hitherto unknown anthropogenic and/or natural substances. Some of the results were a confirmation of a suspected release of DDT in the former East Germany, high levels of pentachlorophenol were noted in Scandinavia, hexachlorocyclohexanes were higher in southern than in northern Europe, whereas PCB and hexachlorbenzene were rather evenly distributed throughout Europe. Elemental sulphur was identified as a previously unknown natural substance in higher plants. 相似文献