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281.
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
282.
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
283.
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
284.
Public involvement is recognized by legislators, practitioners, academics, nongovernment organizations and, most importantly,
affected communities, as a fundamental component of environmental assessment (EA) processes. Experience with public involvement
in EA has proven, however, that despite good intentions, there are formidable barriers to participation. This paper examines
this issue, largely through a case study of a new Can$120 million hog processing facility in Brandon, Canada. Primary data
were collected in three phases, using multiple methodological techniques, including document review, qualitative interviews,
and a mail questionnaire. Results included a diverse list of barriers to involvement, grouped into two primary categories:
structural and individual. A significant structural barrier was a belief that becoming involved would not make a difference
as the ultimate decision in the case was a foregone conclusion. An important individual barrier was that people did not know
about the EA. Finally, the results indicated that lack of interest was not an important reason for nonparticipation. 相似文献
285.
Power line rights-of-way provide a major portion of the shrub habitat in New York. Since this habitat type is on the decline,
many of the birds dependent on shrub habitat are also declining. The methods used to control right-of-way vegetation could
therefore have serious impacts on several birds of conservation concern. Since New York is increasingly using selective herbicide
treatments in vegetation management, we sought to investigate the potential impacts of these treatments on nesting birds.
The study looked at plots in two adjacent rights-of-way before and after a selective herbicide treatment in one of the rights-of-way.
We investigated three bird species: alder flycatcher (Empidonax alnorum), chestnut-sided warbler (Dendroica pensylvanica), and gray catbird (Dumetella carolinensis). All three species exhibited a preference for shrub vegetation around nest sites. The selective herbicide treatment did
not significantly decrease that shrub vegetation, and neither the density nor the nesting success of the three species declined
following the treatment. We conclude that selective herbicide vegetation management encourages the development of shrub habitat
without negatively impacting the birds nesting in the habitat. 相似文献
286.
287.
288.
The purpose of this research was to explore the concept of an environmental racism claim through the use of several environmental
management tools. The EPAs Toxics Release Inventory, Cumulative Exposure Project, and the Los Angeles County Department of
Health Services' Hot Zone Census Tract Assessment were combined with racial and socioeconomic data to test claims that minorities
in South Central Los Angeles are disproportionately exposed to environmental lead. Multivariate analysis indicated that race
is strongly associated with the number of cases of elevated blood lead levels in South Central, irrespective of poverty status.
Proximity to point sources, a common focal point for studies of environmental racism, was not a contributing factor to health
outcomes. Proximity to transportation corridors was consistently the strongest indicator of environmental lead exposure, while
median home values were significantly and positively related to elevated blood lead levels. Implications for environmental
justice advocates and social and environmental scientists are discussed. 相似文献
289.
It is now widely accepted that members of the public should be involved in environmental decision-making. This has inspired
many to search for principles that characterize good public participation processes. In this paper we report on a study that
identifies discourses about what defines a good process. Our case study was a forest planning process in northern New England
and New York. We employed Q methodology to learn how participants characterize a good process differently, by selecting, defining,
and privileging different principles. Five discourses, or perspectives, about good process emerged from our study. One perspective
emphasizes that a good process acquires and maintains popular legitimacy. A second sees a good process as one that facilitates
an ideological discussion. A third focuses on the fairness of the process. A fourth perspective conceptualizes participatory
processes as a power struggle—in this instance a power play between local landowning interests and outsiders. A fifth perspective
highlights the need for leadership and compromise. Dramatic differences among these views suggest an important challenge for
those responsible for designing and carrying out public participation processes. Conflicts may emerge about process designs
because people disagree about what is good in specific contexts. 相似文献
290.
To evaluate the accounts of local fishermen, Landsat TM images (1986, 1993, 1999) were examined to assess potential losses
in the mangrove forests of the Teacapán–Agua Brava lagoon system, Mexico. A binary change mask derived from image differencing
of a band 4/3 ratio was employed to calculate any changes within this forested wetland. The results indicate that by 1986
approximately 18% (or 86 km2) of the mangrove area under study was either dead or in poor condition. The majority of this damage had occurred in the eastern
section of the Agua Brava basin, which coincides, with the reports of the elderly fishermen. Examination of aerial photographs
from 1970 revealed no adverse impacts in this area and would suggest, as postulated by the fishermen and other scientists,
that modifications in environmental conditions following the opening of a canal, Cuautlá canal, in 1972 may have initiated
the large-scale mortality. Although these areas of impact are still developing, the results from the satellite data indicate
that the majority of the more recent changes are occurring elsewhere in the system. Obvious in the 1999 satellite data, but
not so in the 1993, are large areas of mangrove degradation in the northern section of the Teacapán region. In the Agua Brava
basin, the more recent transformations are appearing on the western side of the basin. Since long-term records of environmental
conditions are absent, it is difficult to determine why these latest changes are occurring or even if the earlier losses were
the result of the canal. Potential agents of change that have recently been observed include a hurricane, a second canal,
and the uncontrolled expansion of the Cuautlá canal since 1994. 相似文献