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101.
The Concept of Habitat Diversity Between and Within Ecosystems Applied to River Side-Arm Restoration 总被引:3,自引:0,他引:3
Amoros C 《Environmental management》2001,28(6):805-817
Since returning an ecosystem to its pristine state may not be realistic in every situation, the concept of habitat diversity is proposed to help decision-makers in defining realistic restoration objectives. In order to maintain habitat diversity and enhance the long-term success of restoration, process-oriented projects should be preferred to species-oriented ones. Because the hydrogeomorphological processes that influence biodiversity operate at different spatiotemporal scales, three scales are considered: river sectors, floodplain waterbodies, and mesohabitats within each waterbody. Based on a bibliographical review, three major driving forces are proposed for incorporation into the design of restoration projects: (1) flow velocity and flood disturbances, (2) hydrological connectivity, and (3) water supply. On the sector scale, increased habitat diversity between waterbodies can be achieved by combining various intensities of these driving forces. On the waterbody scale, increased habitat diversity within the ecosystem can be achieved by varying water depth, velocity, and substrate. The concept is applied to a Rhône River sector (France) where three terrestrialized side arms will be restored. Two were designed to be flood scoured, one having an additional supply of groundwater, the other being connected to the river at both ends. The third cannot be scoured by floods because of upstream construction and would be supplied by river backflow through a downstream connection. Habitat diversity within the ecosystem is exemplified on one side arm through the design of a sinuous pathway combined with variation of water depth, wetted width, and substrate grain size. Self-colonization of the side arms is expected owing to the restoration of connectivity to upstream sources of potential colonizers. 相似文献
102.
Manoliadis OG 《Environmental management》2001,28(4):497-504
Irrigation management calls for objective criteria capable of representing the economy, reliability, and productivity of irrigation
systems. These criteria must be compatible with long-term sustainability and conservation goals. The criteria representing
the above goals are the economic effect of management on yield reduction, economic effect, and reliability referring to plant
growth and operation of the network. In this study environmental indices are introduced to express the above criteria in quantitative
terms. The inclusion of these indices at the farm and network level create a multicriteria framework for decision-making based
on composite programming. An experimental study was conducted during the irrigation periods of 1989 and 1990 in Chania, Greece,
concerning water delivered to 40 experimental plots, soil moisture content at the rootzone, and irrigation system operational
failures. The data collected in real time were used for the calculation of the corresponding environmental indices. The variation
in time and space is high and resulted in up to 62% of yield loss and low system performance (up to 7% of system temporal
reliability). The study indicated that environmental indices could be incorporated to select alternatives and also to develop
policies on water delivery. The final decision involves a trade-off analysis between cost of application and desired system
performance. Measures of both primary objectives can be obtained using environmental indices that represent system operation
aggregation at its basic levels (on farm and network). 相似文献
103.
The flagship of the Environmental Protection Agency's regulatory reinvention initiative, Project XL has been touted as a regulatory
blueprint for a site-specific, performance-based pollution-control system, but widespread complaints about the costs of the
program beg the question of whether the costs of tailoring regulations to individual facilities are manageable. To address
this question, this paper presents original survey data on a sample of 11 XL projects. We find that the fixed costs of putting
in place XL agreements are substantial, averaging over $450,000 per firm. While stakeholder negotiations are widely cited
as the principal source for these costs, we find that they actually arise mainly from interaction between participating facilities
and the EPA. Moreover, EPA management problems are perceived by our survey respondents as having inflated project development
costs. Finally, we find that the key factors that explains differences in costs across XL projects are the scope and complexity
of the project proposal. These findings suggest that Project XL favors large firms that can afford to pay significant project
development costs, that EPA management problems must be resolved to reduce costs, and that there may be a significant economic
bias against complex and innovative proposals—precisely the type of proposals that Project XL was designed to foster in order
to improve the efficiency of the regulatory system. 相似文献
104.
This paper sheds light on changing farmers' land management practices in two mountain watersheds, with and without external
assistance, in the western hills of Nepal. Information used in the analysis were obtained through a survey of 300 households,
group discussion, key informant interviews, and field observation conducted during April–September 1999. Confronted with ever-decreasing
landholding size due to a steadily growing population and scarcity of nonfarming employment opportunities, farmers in both
watersheds have increasingly adopted assorted types of structural and biological measures to control soil erosion, landslides,
gully expansion, and soil nutrient loss to maintain or even enhance land productivity. Adoption of gully control measures,
construction of the retention walls, alley cropping, use of vegetative measures for landslide control, mulching, and use of
green manure and chemical fertilizers are found significantly high in the project area due to the provision of technical and
financial support, whereas composting is found significantly high in the nonproject area. Different from the traditionally
held beliefs, population pressure on a finite land resource has brought positive change in land management. However, the experience
from both watersheds indicates that there is limit to the extent that resource poor farmers can respond to land degradation
without any external assistance. Required is the arrangement for appropriate polices and support services and facilities enabling
farmers to adopt locationally suitable and economically attractive land management technologies. 相似文献
105.
Opio C 《Environmental management》2001,27(1):59-74
Many small holder farmers in developing countries face problems of declining soil fertility and crop yields and insufficient
money to buy expensive inorganic fertilizers. The Sesbania fallow system, an agroforestry technology, seems to hold a key to these problems. Based on field studies in eastern Zambia,
this paper reports that fallow system has the potential to improve and sustain soil productivity in the small holder farms.
However, the paper also reports that the ability for subsistence farmers to adopt the Sesbania fallow system is affected by gender differences in resource allocation to productive resources and institutional, cultural,
and social structural settings in which farmers exist and make decisions. 相似文献
106.
Sorace A 《Environmental management》2001,28(4):547-560
Urban-agricultural parks could have some advantages to wildlife because of less intensive agricultural procedures, absence
of hunting pressure, and reduced human disturbance. In this study, the breeding and wintering bird communities and the small
mammal community in an urban-agricultural park of Rome were compared to those of a close urban park and a close agricultural
area just outside the city. The aim was to assess the best destination and management of wildlife in natural areas at the
urban–rural interface. Richness and diversity of bird communities were higher in the urban-agricultural park. Due to habitat
features and probably human disturbances, but not to urbanization, predation, and competition factors, the urban park drastically
reduces the abundance of decreasing open-land bird species. Abundance of these species was not significantly different in
the urban-agricultural park and in the agricultural area. In the urban-agricultural and urban park, bird and mammal pest species
were more abundant than they were in the agricultural area. Regarding decreasing abundance of small mammal species, no significant
difference among the study areas was observed. Urban-agricultural park is a better choice than urban park for wildlife. Thus,
a higher number of preserved urban natural areas should be devoted to urban-agricultural parks. However, to increase the abundance
of open-land species and in general wildlife, a less intensive management of cultivated and pasture patches is necessary. 相似文献
107.
Benefits-based management seeks to provide recreation benefits for recreation participants by managing the physical environments
in which recreation occurs. This study investigates the relationship between benefits desired by visitors and the physical,
social, and managerial characteristics of settings that facilitate realization of recreation benefits. Data such as perceived
benefits from recreation experiences, setting attributes that significantly influenced perceived benefits, and sociodemographic
variables were collected from 376 visitors to Sorak-san National Park in the eastern part of the Korean peninsula. Cluster
analysis was used to group visitors' desired benefits into 12 domains: relationship with nature/scenery, escaping pressure,
learning about nature, family togetherness, introspection, exploration, autonomy/achievement, being with friends, leading
others, skills/learning, risk taking, and meeting/observing new people. Multiple regression was used to link benefit domains
with the characteristics of settings. The social attribute of recreation settings was linked to eight of the ten benefit domains.
There were two statistically strong multiple regression correlations: (1) between domain of “relationship with nature /scenery”
and the attributes “forest/water,”“attractive nature,” and “facility/maintenance” and (2) between the domain of “escaping
pressure” and the attributes “attractive nature” and “social.” The results of this study are useful to managers in their efforts
to provide recreation opportunities for visitors to achieve beneficial outcomes. 相似文献
108.
Evaluation of groundwater and soil pollution in a landfill area using electrical resistivity imaging survey 总被引:8,自引:0,他引:8
Landfills are sources of groundwater and soil pollution due to the production of leachate and its migration through refuse.
This study was conducted in order to determine the extent of groundwater and soil pollution within and around the landfill
of Seri Petaling located in the State of Selangor, Malaysia. The condition of nearby surface water was also determined. An
electrical resistivity imaging survey was used to investigate the leachate production within the landfill. Groundwater geochemistry
was carried out and chemical analysis of water samples was conducted upstream and downstream of the landfill. Surface water
was also analyzed in order to determine its quality.
Soil chemical analysis was performed on soil samples taken from different locations within and around the landfill in the
vadose zone (unsaturated zone) and below the water table (in the soil saturated zone). The resistivity image along line L–L1 indicated the presence of large zones of decomposed waste bodies saturated with highly conducting leachate. Analysis of trace
elements indicated their presence in very low concentrations and did not reflect any sign of heavy metal pollution of ground
and surface water or of soil.
Major ions represented by Na, K, and Cl were found in anomalous concentrations in the groundwater of the downstream bore hole,
where they are 99.1%, 99.2%, and 99.4%, respectively, higher compared to the upstream bore hole. Electrical conductivity (EC)
was also found in anomalous concentration downstream. Ca and Mg ions represent the water hardness (which is comparatively
high downstream). There is a general trend of pollution towards the downstream area. Sulfates (SO4) and nitrates (NO3) are found in the area in low concentrations, even below the WHO standards for drinking water, but are significantly higher
in the surface water compared to the groundwater. Phosphate (PO4) and nitrite (NO2), although present in low levels, are significantly higher at the downstream. There is no significant difference in the amount
of fluoride (F) in the different locations. In the soil vadose zone, heavy metals were found to be in their typical normal
ranges and within the background concentrations. Soil exchangeable bases were significantly higher in the soil saturated zone
compared to the vadose zone, and no significant difference was obtained in the levels of inorganic pollutants. With the exception
of Cd, the concentration ranges of all trace elements (Cu, Zn, Cr, Pb, and Ni) of Seri Petaling landfill soils were below
the upper limits of baseline concentrations published from different sources. 相似文献
109.
Inhaber H 《Environmental management》2001,28(4):505-517
The Nevada Test Site (NTS), north of Las Vegas, was the scene of hundreds of nuclear weapons tests over four decades, both
above- and belowground. There is considerable interest, both in neighboring communities and elsewhere, in the risks it poses.
Overall, the greatest risks are nonradioactive in origin, with occupational risks to employees and accident risks in transporting
low-level nuclear wastes to the NTS from other Department of Energy (DOE) sites ranking highest. For radiation risks, that
to workers handling radioactive materials is much higher than that to the surrounding population, either present or future.
Overall, annual risks are small, with all fatalities approximately 0.008% of total Nevada deaths. At the NTS, the government
spends about 5000 times more on radiation as opposed to nonradiation deaths. This suggests that at least some resources may
be misallocated towards cleanup of public risks and that the occupational risk of cleanup may be much higher than the public
risk. Thus risk may be multiplied by well-meaning programs. 相似文献
110.
Bogaert J Salvador-Van Eysenrode D Impens I Van Hecke P 《Environmental management》2001,27(4):493-500
A method is proposed to quantify disturbance impact on isolated habitats. For every landscape patch, the breakpoint distance,
defined as the penetration distance for which equality of interior and edge habitat is observed, can be calculated. Disturbance
with equal impact at all patch sides is assumed. Effects of patch compactness, size, convolution, and perforation are discussed.
The potential use of the measure for nature reserve design is discussed. The breakpoint distance follows the reserve design
guidelines for individual patches, based on island biogeography and is consistent with the form and function principle. A
large breakpoint distance is preferred for natural habitats. Small size, small compactness, intense convolution, and the occurrence
of many gaps depress the breakpoint distance. 相似文献