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571.
Critically evaluating best management practices for preventing freshwater turtle extinctions 下载免费PDF全文
Ex situ conservation tools, such as captive breeding for reintroduction, are considered a last resort to recover threatened or endangered species, but they may also help reduce anthropogenic threats where it is difficult or impossible to address them directly. Headstarting, or captive rearing of eggs or neonate animals for subsequent release into the wild, is controversial because it treats only a symptom of a larger conservation problem; however, it may provide a mechanism to address multiple threats, particularly near population centers. We conducted a population viability analysis of Australia's most widespread freshwater turtle, Chelodina longicollis, to determine the effect of adult roadkill (death by collision with motor vehicles), which is increasing, and reduced recruitment through nest predation from introduced European red foxes (Vulpes vulpes). We also modeled management scenarios to test the effectiveness of headstarting, fox management, and measures to reduce mortality on roads. Only scenarios with headstarting from source populations eliminated all risks of extinction and allowed population growth. Small increases in adult mortality (2%) had the greatest effect on population growth and extinction risk. Where threats simultaneously affected other life‐history stages (e.g., recruitment), eliminating harvest pressures on adult females alone did not eliminate the risk of population extinction. In our models, one source population could supply enough hatchlings annually to supplement 25 other similar‐sized populations such that extinction was avoided. Based on our results, we believe headstarting should be a primary tool for managing freshwater turtles for which threats affect multiple life‐history stages. We advocate the creation of source populations for managing freshwater turtles that are greatly threatened at multiple life‐history stages, such as depredation of eggs by invasive species and adult mortality via roadkill. 相似文献
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Effects of land clearing techniques and tillage systems on runoff and soil erosion in a tropical rain forest in Nigeria 总被引:2,自引:0,他引:2
This work reports runoff and soil loss from each of 14 sub-watersheds in a secondary rain forest in south-western Nigeria. The impact of methods of land clearing and post-clearing management on runoff and soil erosion under the secondary forest is evaluated. These data were acquired eighteen years after the deforestation of primary vegetation during the ‘ West bank’ project of the International Institute for Tropical Agriculture (IITA). These data are presented separately for each season; however, statistical analyses for replicates were not conducted due to differences in their past management. Soil erosion was affected by land clearing and tillage methods. The maximum soil erosion was observed on sub-watersheds that were mechanically cleared with tree-pusher/root-rake attachments and tilled conventionally. A high rate of erosion was observed even when graded-channel terraces were constructed to minimize soil erosion. In general there was much less soil erosion on manually cleared than on mechanically cleared sub-watersheds (2.5 t ha−1 yr−1 versus 13.8 t ha−1 yr−1) and from the application of no-tillage methods than from conventionally plowed areas (6.5 t ha−1 yr−1 versus 12.1 t ha−1 yr−1). The data indicate that tillage methods and appropriate management of soils and crops play an important role in soil and water conservation and in decreasing the rate of decline of soil quality. 相似文献
573.
U.K. Chakrabarti J.K. Parikh 《Journal of Loss Prevention in the Process Industries》2013,26(4):723-736
Risk-based route evaluation is necessary for decision making by authorities for regulating hazardous materials (hazmats) transport vehicles. The paper highlights risk estimation and its representation for three highway study routes in western India using frequency analysis through logic diagrams and scenario based detailed consequence analysis of accidental releases considering 26 hazmats from UN Classes-2, 3, 6 and 8 categories. The 3 routes have been evaluated based on several layers of analysis namely hazmat-wise, route-segment-wise, route-wise and overall assessment including presentation of normalized risk figures. The results show that compared to the risk on city route segment, individual risks on other two routes are higher and extend beyond ALARP (As Low As Reasonably Practicable) region when assessed against HSE, UK risk criteria, whereas, societal risks on all three routes are within the ALARP except some part in the higher fatality area. But, considering the general mortality rates in India and sustained economic growth, the authors proposed widening of the ALARP region for individual risk tolerability of transportation activity of essential commodities that benefits society to a large extent in this developing economy. However, specific risk reduction measures have also been suggested to improve upon the risk picture in the study area. 相似文献
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When in the vicinity of a metal reclamation plant in Tyrol, Austria, increased PCDD/PCDF levels were found in soil and spruce needles, the extent of grass contamination as well as the PCDD/PCDF content in milk of cows fed with hay from this area was determined. The milk samples showed a significant increase in PCDD/PCDF levels compared to control samples. In a blood sample of a farmer a significant increase in PCDD/PCDF levels was found. Correlations in PCDD/PCDF levels between soil, spruce needles, grass, cow's milk and human blood will be presented. 相似文献
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