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171.
The relationship between migration and deforestation in the developing world continues to receive significant attention. However beyond direct population increase, the precise mechanisms that operate within the intersection of migrant/host land rights remain largely unexamined. Where migrants are provided with land and rights by the State and/or local communities, how such rights are perceived by the migrants is of primary importance in their interaction with land resources, and in aggregate it impacts the development opportunities and environmental repercussions of migration. The authors analyze the operative aspects of land rights reception (as opposed to provision) by migrant populations, and the relationship between this reception and deforestation. The article examines a case in Zambia to analyze how tenurial constructs, emerging from the way rights are perceived by migrants, lead to the continued clearing of areas much larger than needed for cultivation, even when the arrangement appears counter‐productive in terms of land rights provision and labour allocation. While valuable policy efforts have focused on providing resource rights to migrants, how such rights are received and the relationship of this reception to resource management needs greater policy attention. 相似文献
172.
Discharge of WHO toxicity equivalents (TEQs) of PCDF/PCDDs to Frierfjorden, Norway has been reduced from an estimated sum of 50-100 kg in the period 1951-1975 to about 6-7 kg in 1976-1990, and further to about 20 g for 1991-2000. In accordance with this, the yearly monitoring since 1987 has shown considerably decreasing contamination in organisms, first highly significant in all indicator species from 1990 to 1991, then levelling off. Present concentrations thus are still high. Compared with estimated "high background" (reference) concentrations of 10 ng TEQ(PCDF/PCDD)/kg w.w. in liver of cod and in hepatopancreas ("brown meat") of crabs, Frierfjord samples in 2001 were about 60 and 70 times higher, respectively. With considerable uncertainty due to large fluctuations, the rate of yearly decrease for TEQ(PCDF/PCDD) in cod liver 1991-2001 has been calculated to 10-12%. A hypothetic target value of 50 ng TEQ/kg w.w. will not be reached until 2015-2020, possibly even later. Including contributions from dioxin-like PCBs and PCNs, the weekly maximum tolerable amount of cod liver and crab hepatopancreas from Frierfjorden in 2001 were about 2-3 g. Multivariate analysis of PCDF/PCDD congener profiles in four fish species, mussels and crabs resulted in five distinct groups, separating four of the species and grouping the remaining two together, hence demonstrating examples of species specific accumulation characteristics. 相似文献
173.
Bryan D. MacGregor 《Journal of Environmental Planning and Management》1985,28(2):98-104
The landed estates may be divided into four groups according to land use and use intensity: crofting, sheep, sporting, mixed use. While sheep and mixed use estates have held sheep numbers constant, other estates have shown dramatic declines. All estates, and in particular sporting estates, have increased deer culls. Many sporting estates are supported by external private finance which makes land development unnecessary. Private enjoyment is an important ownership motivation on many estates. This, rather than lack of profitability or lack of finance, prevents development. However, significant employment creation can come only through extensive land developments beyond those on even the more productive estates. Such a strategy would require a development plan and a challenge to existing property rights. 相似文献
174.
过去十年中,几例放牧引起植被退化的事件曝光已经使瑞典官方认为一些山区有过度放牧现象以及驯鹿养殖在生态学上可能并非是可持续的.我们从时间和管理角度对这些例子进行研究,进而评价放牧对瑞典山区夏季草场的影响程度.有关驯鹿种群长期动态的数据表明,上个世纪驯鹿的数量在225000头左右波动,没有变化的趋势.根据达拉纳(Dalarna)的郎格夫贾莱特(Langfjallet)和海里耶达(Harjedalen)的米塔克勒盆(Mitaklappen)的数据,对放牧影响进行了详细的讨论.我们将这些数据与近几十年养殖在生态学上似乎不可持续的挪威芬马克地区以及芬兰北部的情况进行了比较,我们的结论是大规模的驯鹿过度放牧在瑞典山区不明显.但在封闭和围栏养殖时,可见过度放牧和践踏的影响. 相似文献
175.
A. Allen Bradley Christa Peters‐Lidard Brian R. Nelson James A. Smith C. Bryan Young 《Journal of the American Water Resources Association》2002,38(5):1393-1407
ABSTRACT: A general framework is proposed for using precipitation estimates from NEXRAD weather radars in raingage network design. NEXRAD precipitation products are used to represent space time rainfall fields, which can be sampled by hypothetical raingage networks. A stochastic model is used to simulate gage observations based on the areal average precipitation for radar grid cells. The stochastic model accounts for subgrid variability of precipitation within the cell and gage measurement errors. The approach is ideally suited to raingage network design in regions with strong climatic variations in rainfall where conventional methods are sometimes lacking. A case study example involving the estimation of areal average precipitation for catchments in the Catskill Mountains illustrates the approach. The case study shows how the simulation approach can be used to quantify the effects of gage density, basin size, spatial variation of precipitation, and gage measurement error, on network estimates of areal average precipitation. Although the quality of NEXRAD precipitation products imposes limitations on their use in network design, weather radars can provide valuable information for empirical assessment of rain‐gage network estimation errors. Still, the biggest challenge in quantifying estimation errors is understanding subgrid spatial variability. The results from the case study show that the spatial correlation of precipitation at subgrid scales (4 km and less) is difficult to quantify, especially for short sampling durations. Network estimation errors for hourly precipitation are extremely sensitive to the uncertainty in subgrid spatial variability, although for storm total accumulation, they are much less sensitive. 相似文献
176.
Jin‐Yong Choi Bernard A. Engel Suresh Muthukrishnan Jon Harbor 《Journal of the American Water Resources Association》2003,39(3):623-635
ABSTRACT: To adequately manage impacts of ongoing or future land use changes in a watershed, the magnitude of their hydrologic impacts needs to be assessed. A grid based daily streamflow model was calibrated with two years of observed streamflow data, using time periods when land use data are available and verified by comparison of model predictions with observed streamflow data. Streamflow data were separated into direct runoff and baseflow to estimate the impacts of urbanization on each hydrologic component. Analysis of the ratio between direct runoff and total runoff from 30 years of simulation results and the change in these ratios with urbanization shows that estimated annual direct runoff increased from 49.2 percent (1973) to 63.1 percent (1984) and 65.0 percent (1991), indicating the effects of urbanization are greater on direct runoff than on total runoff. The direct runoff ratio also varies with annual rainfall, with dry year ratios larger than those for wet years. This suggests that the impact of urbanization on areas that are sensitive to runoff ratios, such as stream ecosystems, might be more serious during drier years than in wetter years in terms of water quality and water yield. This indicates that sustainable base‐flow is important to maintaining sound stream ecosystems. 相似文献
177.
Bryan Boulanger Nikolaos P. Nikolaidis 《Journal of the American Water Resources Association》2003,39(2):337-345
ABSTRACT: A modeling framework was developed for managing copper runoff in urban watersheds that incorporates water quality characterization, watershed land use areas, hydrologic data, a statistical simulator, a biotic ligand binding model to characterize acute toxicity, and a statistical method for setting a watershed specific copper loading. The modeling framework is driven by export coefficients derived from water quality parameters and hydrologic inputs measured in an urban watershed's storm water system. This framework was applied to a watershed containing a copper roof built in 1992. A series of simulations was run to predict the change in receiving stream water chemistry caused by roof aging and to determine the maximum copper loading (at the 99 percent confidence level) a watershed could accept without causing acute toxicity in the receiving stream. Forecasting the amount of copper flux responsible for exceeding the assimilation capacity of a watershed can be directly related to maximum copper loadings responsible for causing toxicity in the receiving streams. The framework developed in this study can be used to evaluate copper utilization in urban watersheds. 相似文献
178.
Jon Birger Skjærseth 《环境政策》2018,27(3):498-518
European Union (EU) climate/energy targets and policies are poised for the first full climate policy cycle – from adoption and implementation of the policy package for 2020, to reform for 2030. A dynamic approach to the ways in which EU policies affect policy development is developed by applying theories of domestic implementation, policy feedback and integration. Implementation experiences in Poland – the ‘least climate ambitious’ EU member state – affected Polish preferences for reformed EU policies. Existing EU policies, their ‘fit’ with Poland’s energy interests and change in anticipation of future EU policies explain much of the variation in preferences. Second, policy feedback from Poland significantly affected the EU 2030 climate and energy framework. As yet, the EU has succeeded only partly in gathering momentum through a ‘snowball’ effect whereby positive policy feedback from implementation generates further steps. 相似文献
179.
Li Maotian Finlayson Brian Webber Michael Barnett Jon Webber Sophie Rogers Sarah Chen Zhongyuan Wei Taoyuan Chen Jing Wu Xiaodan Wang Mark 《Regional Environmental Change》2017,17(4):1153-1161
Regional Environmental Change - Many of the world’s major cities are expected to face significant water shortages in coming decades, largely due to increased demand arising from economic and... 相似文献
180.
This paper studies the practice of semi-domestic reindeer (Rangifer t. tarandus) herding in Finnmark county in northern Norway. In this area, the Saami reindeer herders compete for space and grazing areas and keep large herds, while at the same time, the reindeer population is heavily exposed to carnivore predation by the lynx (Lynx lynx), the wolverine (Gulo gulo), and the golden eagle (Aquila chrysaetos). It is demonstrated that predation actually may improve the economic lot of livestock holders in this unmanaged local common setting. There are ecological as well as economic reasons as to why this happens. The ecological reason is that predation compensates for natural mortality; that is, increased predation reduces natural mortality, indicating that the net loss due to predation actually may be quite small. When predation reduces livestock density, the feeding conditions of the animals will improve, resulting in increased livestock weight and higher per animal slaughter value. At the same time, a smaller stock reduces the operating costs of the herders. 相似文献