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991.
Haug R 《Disasters》2002,26(1):70-84
The Hawaweer, a nomadic, pastoralist group in northern Sudan, were seriously affected by the drought in the Sahel during the mid-1980s. Their experience illustrates the connection between internally displaced people, normal mobility, forced migration, dilemmas and opportunities of return and how new livelihoods can be successfully constructed based on traditional rights, strong local institutions and external resources. Some displaced Hawaweer got the chance to return to their homeland as new livelihood opportunities were established; others did not get this opportunity nor would they have returned if they had been given the chance. In both situations, the processes of displacement and return had an impact on the sense of belonging and identity. 相似文献
992.
Human impacts on the stream-groundwater exchange zone 总被引:13,自引:0,他引:13
Hancock PJ 《Environmental management》2002,29(6):763-781
Active exchanges of water and dissolved material between the stream and groundwater in many porous sand- and gravel-bed rivers
create a dynamic ecotone called the hyporheic zone. Because it lies between two heavily exploited freshwater resources—rivers
and groundwater—the hyporheic zone is vulnerable to impacts coming to it through both of these habitats. This review focuses
on the direct and indirect effects of human activity on ecosystem functions of the hyporheic zone. River regulation, mining,
agriculture, urban, and industrial activities all have the potential to impair interstitial bacterial and invertebrate biota
and disrupt the hydrological connections between the hyporheic zone and stream, groundwater, riparian, and floodplain ecosystems.
Until recently, our scientific ignorance of hyporheic processes has perhaps excused the inclusion of this ecotone in river
management policy. However, this no longer is the case as we become increasingly aware of the central role that the hyporheic
zone plays in the maintenance of water quality and as a habitat and refuge for fauna. To fully understand the impacts of human
activity on the hyporheic zone, river managers need to work with scientists to conduct long-term studies over large stretches
of river. River rehabilitation and protection strategies need to prevent the degradation of linkages between the hyporheic
zone and surrounding habitats while ensuring that it remains isolated from toxicants. Strategies that prevent anthropogenic
restriction of exchanges may include the periodic release of environmental flows to flush silt and reoxygenate sediments,
maintenance of riparian buffers, effective land use practices, and suitable groundwater and surface water extraction policies. 相似文献
993.
Three mathematical models, the runoff curve number equation, the universal soil loss equation, and the mass response functions,
were evaluated for predicting nonpoint source nutrient loading from agricultural watersheds of the Mediterranean region. These
methodologies were applied to a catchment, the gulf of Gera Basin, that is a typical terrestrial ecosystem of the islands
of the Aegean archipelago. The calibration of the model parameters was based on data from experimental plots from which edge-of-field
losses of sediment, water runoff, and nutrients were measured. Special emphasis was given to the transport of dissolved and
solid-phase nutrients from their sources in the farmers' fields to the outlet of the watershed in order to estimate respective
attenuation rates. It was found that nonpoint nutrient loading due to surface losses was high during winter, the contribution
being between 50% and 80% of the total annual nutrient losses from the terrestrial ecosystem. The good fit between simulated
and experimental data supports the view that these modeling procedures should be considered as reliable and effective methodological
tools in Mediterranean areas for evaluating potential control measures, such as management practices for soil and water conservation
and changes in land uses, aimed at diminishing soil loss and nutrient delivery to surface waters. Furthermore, the modifications
of the general mathematical formulations and the experimental values of the model parameters provided by the study can be
used in further application of these methodologies in watersheds with similar characteristics. 相似文献
994.
Huntington HP Brown-Schwalenberg PK Frost KJ Fernandez-Gimenez M Norton DW Rosenberg DH 《Environmental management》2002,30(6):0778-0792
Traditional ecological knowledge (TEK) and the information and insights it offers to natural resource research and management
have been given much attention in recent years. On the practical question of how TEK is accessed and used together with scientific
knowledge, most work to date has examined documentation and methods of recording and disseminating information. Relatively
little has been done regarding exchanges between scientific and traditional knowledge. This paper examines three workshop
settings in which such exchanges were intended outcomes. The Barrow Symposium on Sea Ice, the Exxon Valdez Oil Spill Restoration Program Synthesis/Information Workshops, and the Alaska Beluga Whale Committee illuminate certain features
of the preparation, format, and context of workshops or series of workshops and their eventual outcomes and influence. The
examples show the importance of long-term relationships among participants and thorough preparation before the actual workshop.
Further research should look more systematically at the factors that influence the success of a given workshop and the various
ways in which participants perceive success. 相似文献
995.
We examined the impact of single-tree selective logging and fuel reduction burns on the abundance of hollow-nesting bird species
at a regional scale in southeastern Queensland, Australia. Data were collected on species abundance and habitat structure
of dry sclerophyll production forest at 36 sites with known logging and fire histories. Sixteen bird species were recorded
with most being resident, territorial, obligate hollow nesters that used hollows that were either small (<10 cm diameter)
or very large (>18 cm diameter). Species densities were typically low, but combinations of two forest management and three
habitat structural variables influenced the abundances of eight bird species in different and sometimes conflicting ways.
The results suggest that habitat tree management for biodiversity in production forests cannot depend upon habitat structural
characteristics alone. Management histories appear to have independent influence (on some bird species) that are distinguishable
from their impacts on habitat structure per se. Rather than managing to maximize species abundances to maintain biodiversity, we may be better off managing to avoid extinctions
of populations by identifying thresholds of acceptable fluctuations in populations of not only hollow-nesting birds but other
forest dependent wildlife relative to scientifically valid forest management and habitat structural surrogates. 相似文献
996.
A GIS/Simulation Framework for Assessing Change in Water Yield over Large Spatial Scales 总被引:1,自引:0,他引:1
Recent legislation to initiate vegetation management in the Central Sierra hydrologic region of California includes a focus
on corresponding changes in water yield. This served as the impetus for developing a combined geographic information system
(GIS) and simulation assessment framework. Using the existing vegetation density condition, together with proposed rules for
thinning to reduce fire risk, a set of simulation model inputs were generated for examining the impact of the thinning scenario
on water yield. The approach allows results to be expressed as the mean and standard deviation of change in water yield for
each 1-km2 map cell that is thinned. Values for groups of cells are aggregated for typical watershed units using area-weighted averaging.
Wet, dry, and average precipitation years were simulated over a large region. Where snow plays an important role in hydrologic
processes, the simulated change in water yield was less than 0.5% of expected annual runoff for a typical watershed. Such
small changes would be undetectable in the field using conventional stream flow analysis. These results suggest that use of
water yield increases to help justify forest-thinning activities or offset their cost will be difficult. 相似文献
997.
Differences between scientist and policy-maker response types and times, or the “how” and “when” of action, constrain effective
water resource management in suburbanizing watersheds. Policy-makers are often rushed to find a single policy that can be
applied across an entire, homogeneous, geopolitical region, whereas scientists undertake multiyear research projects to appreciate
the complex interactions occurring within heterogeneous catchments. As a result, watershed management is often practiced with
science and policy out of synch. Meanwhile, development pressures in suburban watersheds create changes in the social and
physical fabric and pose a moving target for science and policy. Recent and anticipated advances in the scientific understanding
of urbanized catchment hydrology and pollutant transport suggest that management should become increasingly sensitive to spatial
heterogeneities in watershed features, such as soil types, terrain slopes, and seasonal watertable profiles. Toward this end,
policy-makers should encourage funding scientific research that characterizes the impacts of these watershed heterogeneities
within a geopolitical zoning and development framework. 相似文献
998.
长江流域生态环境的意义及生态功能区段的划分 总被引:15,自引:3,他引:12
虞孝感 《长江流域资源与环境》2002,11(4):323-326
中国加入WTO之后,中国经济进一步与国际市场接轨,融入世界经济体系,机遇和挑战同在。欧美各国近年大力推行的环境标志产品认证,对第三世界商品质量设置入关的环境门槛。长江产业带作为世界最大的内河产业带和制造业基地,现在世界通行的环境管理认证体系和环境标志产品的认证,对长江流域产业尤其是外贸出口产业有长远而深刻的影响。这种认证制度,一方面对我出口商品设置了新的障碍,另一方面又将环境保护压力直接施加到企业。重视流域生态环境将从政府行为、公民压力扩展到企业行动,由于流域生态环境的负荷愈来愈重,流域生态环境的自我调节和恢复功能大幅下降,引起了日益严重的流域性生态安全问题。根据长江流域生态环境特征、不同的生态功能及存在的主要生态安全问题,将长江流域划性生态安全问题。根据长江流域生态环境特征、不同的生态功能及存在的主要生态安全问题,将长江流域划分成以下五个不同的生态功能区段,即长江源地区、金少江段(直门达至宜宾)、长江上游段(宜宾至宜昌)、长江中游段(宜昌至湖口段)、长江下游段(湖口至入海口)。针对不同区段主要的生态安全问题,应因地制宜采取相应的防范和整治措施。为保护与恢复生态功能服务。 相似文献
999.
Edward B. Barbier 《Environment, Development and Sustainability》2003,5(3-4):437-458
The following paper examines the main factors determining long-run agricultural land expansion in Latin America compared to other tropical regions. Given the importance of natural resource-based sectors for most economies in Latin America, the impact of price-induced "resource booms" on economic growth in the region is explored. In addition, the paper examines whether there is an inherent "boom and bust" pattern of economic development associated with agricultural land expansion in Latin America, and the extent to which economic policies in the region exacerbate this problem. The paper concludes by examining the role of targeted policies in alleviating the structural obstacles to Latin American agricultural and economic development. 相似文献
1000.
Lake Erie water quality has improved dramatically since the degraded conditions of the 1960s. Additional gains could be made,
but at the expense of further investment and reductions in fishery productivity. In facing such cross-jurisdictional issues,
natural resource managers in Canada and the United States must grapple with conflicting objectives and important uncertainties,
while considering the priorities of the public that live in the basin. The techniques and tools of decision analysis have
been used successfully to deal with such decision problems in a range of environmental settings, but infrequently in the Great
Lakes. The objective of this paper is to illustrate how such techniques might be brought to bear on an important, real decision
currently facing Lake Erie resource managers and stakeholders: the choice of new phosphorus loading targets for the lake.
The heart of our approach is a systematic elicitation of stakeholder preferences and an investigation of the degree to which
different phosphorus-loading policies might satisfy ecosystem objectives. Results show that there are potential benefits to
changing the historical policy of reducing phosphorus loads in Lake Erie. 相似文献