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841.
The simplest type of model describing animal habitats is a “cover-type model,” in which a species is assumed to be present
in certain vegetation types and absent in others. Ecologists and managers use these models to predict animal distributions
for gap analysis and conservation planning. Critics, however, have suggested that the models are overly simplistic and inaccurate.
We reviewed the use of cover-type models including assessing their error rates, diagnosing the problems with these models,
and determining how they should best be used by managers. To determine models’ accuracy rates, we conducted a meta-analysis
of 35 studies in which cover-type models were tested against data on animal occurrences. Models had a mean accuracy rate of
0.71 ± 0.18 (SD). Rates of commission error averaged 0.20 ± 0.16, and omission errors averaged 0.09 ± 0.11. A review of the
effects of errors in conservation planning suggests that the observed error rates were high enough to call into question any
management decisions based on these models. Reasons for the high error rates of cover-type models include the fallibility
of expert opinion, the fact that the models oversimplify how animals actually use habitats, and the dynamic nature of animal
populations. Given the high rate of errors in cover-type models, any conclusions based on them should be taken with extreme
caution. We suggest that these models are best used as coarse filters to identify locations for further study in the field. 相似文献
842.
W. Scott Hall Kenneth L. Dickson Farida Y. Saleh John H. Rodgers Douglas Wilcox Azam Entazami 《Journal of the American Water Resources Association》1986,22(6):913-920
ABSTRACT: Current procedures for setting site-specific water quality criteria consider abiotic and biotic factors. Suspended solids were shown to be important in reducing zinc toxicity to water column organisms. At zinc concentrations of ~ 1 mg/L in solutions with < 100 mg/L of all suspended solids tested, zinc toxicity to D. magna was reduced. Sorption of zinc to suspended solids and/or changes in water chemistry due to the addition of suspended solids appear to have been the factors causing reductions in zinc toxicity to D. magna. Only suspended solids levels of 483–734 mg/L of a type that increased total alkalinity, total hardness, and total dissolved carbon clearly reduced the toxicity of ~ 20 mg/L zinc to P. promelas. The toxic form of zinc to these organisms appears to reside in the aqueous phase. Characteristics of suspended solids did not influence the partition coefficient of zinc in sorption experiments of 96 h. The slopes of dose-response curves proved to be useful for assessing the potential of an organism to respond to changes in aqueous phase zinc concentrations, and may be a useful biological parameter when considering site-specific water quality criteria for chemicals. 相似文献
843.
The consequences of land use change on nutrient exports: a regional scale assessment in south-west Victoria, Australia 总被引:14,自引:0,他引:14
Ierodiaconou D Laurenson L Leblanc M Stagnitti F Duff G Salzman S Versace V 《Journal of environmental management》2005,74(4):305-316
Estimation of nutrient load production based on multi-temporal remotely sensed land use data for the Glenelg-Hopkins region in south-west Victoria, Australia, is discussed. Changes in land use were mapped using archived Landsat data and computerised classification techniques. Land use change has been rapid in recent history with 16% of the region transformed in the last 22 years. Total nitrogen and phosphorus loads were estimated using an export coefficient model. The analysis demonstrates an increase in modelled nitrogen and phosphorus loadings from 1980 to 2002. Whilst such increases were suspected from past anecdotal and ad-hoc evidence, our modelling estimated the magnitude of such increases and thus demonstrated the enormous potential of using remote sensing and GIS for monitoring regional scale environmental processes. 相似文献
844.
We compared the nesting success of a disturbance-dependent species, the Indigo Bunting ( Passerina cyanea), on different kinds of habitat edges in five sites (225 total nests) in southern Illinois from 1989 to 1993. Nest predation rates along agricultural and abrupt, permanent edges (e.g., wildlife openings, campgrounds) were nearly twice as high as rates along more gradual edges where plant succession was allowed to occur (e.g., treefalls, streamsides, gaps created by selective logging ). Levels of brood parasitism by Brown-headed Cowbirds ( Molothrus ater) varied significantly among sites and years, but not among edge types. Clutch sizes, however, were significantly smaller at agricultural edges where nest predation rates were also high, which suggests either decreased food availability or a population dominated by younger and/or lower-quality ( poor condition) birds. The results of this study illustrate the need to reevaluate management practices (e.g., wildlife openings) that are designed to promote populations of disturbance-dependent wildlife. 相似文献
845.
846.
Ecological risk assessment for aquatic species exposed to contaminants in Keelung River, Taiwan 总被引:9,自引:0,他引:9
Chen CS 《Chemosphere》2005,61(8):1142-1158
An ecological risk assessment was conducted for Keelung River in northern Taiwan. The objective of this study was to assess the risk to fish, aquatic insects, and benthic macroinvertebrates associated with chemical-of-potential-concern (COPC) in the river and to rank ecological risk for these chemicals. The protection of at least 95% of the species 90% of the time from acute and chronic COPC exposures was the defined assessment endpoint. Nine inorganic and organic contaminants were selected to evaluate the impact to aquatic community in the Keelung River. The quotient method served as screen level estimation of risk. The Aquatic Ecological Risk Assessment model was used to analyze exposure and ecological effects and to estimate community level risk. The logarithmic regression model between probability and lethal concentration was established. The combined risks of multiple chemicals were evaluated under assumption of additive risk. The results indicated that zinc and copper pose higher risk among metals. Ammonia, copper, and zinc posed virtually all of the risk, while organic COPCs posed a negligible risk. Potential ecological risk from ammonia exposure was greatest. The probability of more than 5% of the species being affected by acute or chronic toxicity of COPCs is about 100%. In average (50% of the time), 99% of the species would be affected by acute toxicity of COPCs, and about all the species would be affected by chronic toxicity of COPCs. Uncertainties in this assessment were associated with variability in ecosystem stressors, exposure data, ecological effect data, and risk characterization. 相似文献
847.
LIU Jiangying XU Dimin XIONG Lan Colin HILLS Paula CAREY Kevin GARDNER 《环境科学学报(英文版)》2008,20(5):593-598
The investigation of the long-term performance of solidified/stabilized (S/S) contaminated soils was carried out in a trial site in southeast UK. The soils were exposed to the maximum natural weathering for four years and sampled at various depths in a controlled manner. The chemical properties (e. g. , degree of carbonation (DOC), pH, electrical conductivity (EC)) and physical properties (e. g. , moisture content (MC), liquid limit (LL), plastic limit (PL), plasticity index (PI)) of the samples untreated and treated with the traditional and accelerated carbonated S/S processes were analyzed. Their variations on the depths of the soils were also studied. The result showed that the broad geotechnical properties of the soils, manifested in their PIs, were related to the concentration of the water soluble ions and in particular the free calcium ions. The samples treated with the accelerated carbonation technology (ACT), and the untreated samples contained limited number of free calcium ions in solutions and consequently interacted with waters in a similar way. Compared with the traditional cement-based S/S technology, e. g. , treatment with ordinary portland cement (OPC) or EnvirOceM, ACT caused the increase of the PI of the treated soil and made it more stable during long-term weathering. The PI values for the four soils ascended according to the order: the EnvirOceM soil, the OPC soil, the ACT soil, and the untreated soil while their pH and EC values descended according to the same order. 相似文献
848.
Robert M. Chiles Eileen E. Fabian Daniel Tobin Scott J. Colby S. Molly DePue 《Journal of Agricultural and Environmental Ethics》2018,31(3):341-348
The purpose of this paper is to provide further clarity to the technical and policy difficulties associated with mitigating greenhouse gas emissions from agriculture by identifying and distilling the core tensions which propagate and animate them. We argue that these complexities exist across four critical dimensions: the epistemological, the ethical, the political, and the practical. Adequately confronting the challenge of agricultural emissions will require improved transparency in emissions measurement, increased science communication, enhanced public participatory mechanisms, and the integration of ethical deliberation in scientific and policy discussions. 相似文献
849.
Kaninga Belinda Lark R. Murray Chishala Benson H. Maseka Kakoma K. Sakala Godfrey M. Young Scott D. Tye Andrew Hamilton Elliott M. Watts Michael J. 《Environmental geochemistry and health》2021,43(9):3699-3713
Environmental Geochemistry and Health - A field experiment was undertaken on farmers’ fields adjacent to a large mine tailings dam in the Zambian mining town of Kitwe. Experimental plots were... 相似文献
850.
Tisa L. Girard Edward W. Bork Scott E. Neilsen Mike J. Alexander 《Environmental management》2013,51(2):435-447
Public lands occupied by feral horses in North America are frequently managed for multiple uses with land use conflict occurring among feral horses, livestock, wildlife, and native grassland conservation. The factors affecting habitat use by horses is critical to understand where conflict may be greatest. We related horse presence and abundance to landscape attributes in a GIS to examine habitat preferences using 98 field plots sampled within a portion of the Rocky Mountain Forest Reserve of SW Alberta, Canada. Horse abundance was greatest in grassland and cut block habitats, and lowest in conifer and mixedwood forest. Resource selection probability functions and count models of faecal abundance indicated that horses preferred areas closer to water, with reduced topographic ruggedness, situated farther from forests, and located farther away from primary roads and trails frequented by recreationalists, but closer to small linear features (i.e. cut lines) that may be used as beneficial travel corridors. Horse presence and abundance were closely related to cattle presence during summer, suggesting that both herbivores utilise the same habitats. Estimates of forage biomass removal (44 %) by mid-July were near maximum acceptable levels. In contrast to horse-cattle associations, horses were negatively associated with wild ungulate abundance, although the mechanism behind this remains unclear and warrants further investigation. Our results indicate that feral horses in SW Alberta exhibit complex habitat selection patterns during spring and summer, including overlap in use with livestock. This finding highlights the need to assess and manage herbivore populations consistent with rangeland carrying capacity and the maintenance of range health. 相似文献