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961.
962.
A resident population of 13 black rhinoceros ( Diceros bicornis ) persist in Ngorongoro Crater, Tanzania. The effective population size ( N e ) may be as few as 5 animals. Projected growth for this population suggests that the effective population size will remain small for the near future, threatening this Iocal population with extinction due to the stochastic factors associated with small population size. A summary of historic and recent demographic data for this population reveals a population crash during the period of heavy poaching that affected this species throughout its range. Although poaching of this species has been brought under control the population remains small. These data and models of projected population growth argue for consideration of more-intensive management within the framework of the small population paradigm. This case is an example of applied conservation resulting from this paradigm used in conjunction with rather than competing with the declining population paradigm. We identify additional monitoring, particularly of density-dependent behaviors, that will be necessary for designing a successful management program. Finally, the use of molecular markers for developing an accurate pedigree for this population is suggested in order to maintain a genetically healthy population. These strategies have broad applicability to black rhinoceros conservation throughout Africa. 相似文献
963.
At the new Marais des Cygnes National Wildlife Refuge in Linn County, Kansas, and Bates County, Missouri, USA, we evaluated
long-lived contaminants before acquisition of the land for the refuge. We sampled sediments at 16 locations and fish at seven
locations. The samples were analyzed for metals and for chlorinated hydrocarbon compounds. Selected sediment samples also
were analyzed for aliphatic hydrocarbons. Arsenic concentrations in sediment samples from six locations were elevated compared
to US norms, but arsenic was not detected in any fish composite. Mercury concentrations in largemouth bass from two locations
were comparable to the 85th percentile concentrations in nationwide fish collections. Most sediment concentrations of other
metals were unlikely to have detrimental effects on biota. No chlorinated hydrocarbons were detected in any sediment sample.
Chlordane compound concentrations in fish composites from two sites at the eastern end of the sampling area were 0.127 and
0.228 μg/g wet weight, respectively, which are high enough to cause concern. Most aliphatic hydrocarbons detected were found
at low concentrations and probably were natural in origin. We concluded that there are no serious contaminants concerns within
the project area, but past use of arsenical pesticides may mean a legacy of elevated soil arsenic levels in parts of the area
and some use of banned pesticides such as chlordane and DDT likely is still occurring near the refuge. 相似文献
964.
Albert Rango Arlen Feldman Thomas S. George III Robert M. Ragan 《Journal of the American Water Resources Association》1983,19(2):165-174
ABSTRACT: In a cooperative demonstration project, NASA and the U.S. Army Corps of Engineers (Corps) compared conventional and Landsat-derived land-use data for use in hydrologic models, and the resulting discharge frequency curves were analyzed. When a grid-based data-management system was used on a cell-by-cell basis (size about 1.1 acres or 0.45 hectare), Landsat classification accuracy was only 64 percent, but, when the grid cells were aggregated into watersheds, the classification accuracy increased to about 95 percent. When both conventional and Landsat land-use data were input to the HEC-1 model for generating discharge frequency curves, the differences in calculated discharge were judged insignificant for subbasins as small as 1.0mi2 (2.59 km2). For basins larger than 10mi2 (25.9km2), use of the Landsat approach is more cost-effective than use of conventional methods. Digital Landsat data can also be used effectively by local and regional agencies for hydrologic analysis by incorporating the data into grid-based data-management systems. The transfer of this new technology is well under way through inclusion in some Corps training courses and through use by both county government personnel and private consultants. 相似文献
965.
George F. Ray 《Resources Policy》1984,10(2):75-80
This article analyses the lifetimes of reserves of three dozen important minerals. Despite the high rate of their extraction in the past 30 years, the recorded reserves of these non-renewable materials were higher in 1981 than in 1950 and they seem to meet foreseeable demand for a long time to come, as indicated by the estimated static lifetime for each of the minerals covered. The dynamic nature of ‘reserves’ is emphasized: further exploration and scientific and technological advance will add to the present proven reserves, and at a higher price further resources will be ‘upgraded’ into commercially exploitable reserves. Apparent long-term security can be disturbed by natural disasters, political events or other factors, especially in the case of minerals whose reserves and production are highly concentrated in one country. However, any such interruption in the continuity of supply is likely to be short-lived. 相似文献
966.
Hourly measurements of radon level at four houses in Butte, Montana were analyzed. Previous studies suggestes that there are diurnal cycles, spectral analysis confirms this assertion. Moreover, there are also long term trends and weekly cycles at certain locations. The periodical cycles highly suggest that indoor radon level can be dependent on the ventilation condition of the house and the activities of the residents.The relationship of indoor and outdoor radon level was investigated by cross-spectral analysis. In view of the possible different patterns caused by different seasons, data from the winter and summer are analyzed separately. The results shows that winter and summer data do display different patterns. 相似文献
967.
George A. Whetstone Ernst W. Kiesling 《Journal of the American Water Resources Association》1971,7(4):684-688
ABSTRACT .The major purpose of existing and proposed diversions of water to the Prairies is for irrigation. Being flat lands adaptable to mechanized agriculture and possessing a good network of rail and highway access, they are well suited for such use. Wheat surpluses, currently a serious problem in Canada, can be expected to melt under world population pressures and conversion of wheat lands to other crops with the advent of irrigation. The water sources envisaged are in the Canadian Arctic watershed with the United States purchasing Canadian water at the boundary. There is an increasing interest in the Canadian Prairie Provinces in regarding water as a commodity and selling some of it to pay for the development required to put the portion retained in Canada to use. 相似文献
968.
Remediation of halogenated organic compounds—such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs)—poses a challenge because these compounds are resistant to microbial attack and to degradation by many common chemicals. Since the mid-1980s, the Environmental Protection Agency's (EPA's) Office of Research and Development in Cincinnati, Ohio—the National Risk Management Research Laboratory (NRMRL)—has funded research and development efforts to develop specialized, chemical dehalogenation processes for detoxifying PCBs and related compounds. NRMRL owns domestic rights for “basic process” patents on a chemical dehalogenation process commonly known as Base Catalyzed Decomposition (BCD). EPA has licensed the process to two firms for use in the United States. This article summarizes laboratory-scale, pilot-scale, and field performance data on BCD technology collected to date by various governmental, academic, and private organizations. 相似文献
969.
Lauren E. Hay George H. Leavesley Martyn P. Clark Steve L. Markstrom Roland J. Viger Makiko Umemoto 《Journal of the American Water Resources Association》2006,42(4):877-890
ABSTRACT: The ability to apply a hydrologic model to large numbers of basins for forecasting purposes requires a quick and effective calibration strategy. This paper presents a step wise, multiple objective, automated procedure for hydrologic model calibration. This procedure includes the sequential calibration of a model's simulation of solar radiation (SR), potential evapotranspiration (PET), water balance, and daily runoff. The procedure uses the Shuffled Complex Evolution global search algorithm to calibrate the U.S. Geological Survey's Precipitation Runoff Modeling System in the Yampa River basin of Colorado. This process assures that intermediate states of the model (SR and PET on a monthly mean basis), as well as the water balance and components of the daily hydrograph are simulated consistently with measured values. 相似文献
970.
Places of natural beauty and/or cultural value in the Mediterranean Sea are presenting adverse effects due to pollution. These environmental threats caused by point and nonpoint sources are mainly the reason why these areas represent “pollution-sensitive areas,” where the risk of deterioration is immediate. However, the risk will decrease and eventually disappear if protective measures are applied. In the present article, a multicriteria decision-making method is proposed for the prioritization of the Mediterranean sensitive coastal areas, taking into consideration criteria of pollution risk such as impact on human health, aquatic ecosystems, and socioeconomic value of the area. Weighting factors were then attributed to the different criteria according to their regional priorities, and a total pollution risk score was calculated for every sensitive area. However, some sensitive areas are more vulnerable than others because of their natural characteristics. Therefore, the total pollution risk score was then multiplied by a vulnerability weighting factor and a Total Sensitivity Score was calculated for every sensitive area. With this method, Mediterranean sensitive areas in coastal zones can be ranked on a priority list and then categorized according to their “sensitivity,” in a way that decision-makers can select the most urgent cases to direct their attention for the effective protection of the Mediterranean marine environment. The method is rapid and practicable and has already been used with existing data and information in several Mediterranean countries. 相似文献