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71.
This article examines several deficiencies in the standard procedure for calculating the intensity of metal use. It then investigates the possibility that the long-term decline in the intensity of copper use in the USA, which has persisted for more than four decades, has in recent years come to an end, even though the standard measures of intensity of use indicate a continuation of the downward trend, albeit at a slower rate. If true, the implications are significant for the copper industry worldwide, because the USA is the largest national market for copper. In addition, consumption trends in many other countries in some respects follow those in the USA. The results do provide some support for the hypothesis that intensity of copper use in the USA is no longer falling. They also indicate that the standard procedure significantly underestimates USA copper consumption and in turn intensity of use.  相似文献   
72.
We evaluated the amounts and implications of changes in habitat connectivity on rural landscapes by modeling the colonization success and subsequent habitat colonization of a model edge organism within real landscapes. We first inventoried the changes in the fencerow and forest-edge network of two contiguous Ohio (U.S.A.) landscapes, an agriculturally dominated till plain and a more diverse and dynamic moraine landscape, from 1940 to 1988. On the moraine the number of fencerows changed little from 1940 to 1971. The number increased by 86 during 1971–1988 as marginal farms were subdivided. The total length of fencerows on the moraine increased 2.5-fold over 48 years. On the till plain the number and total length of fencerows remained relatively constant through the study period. The sum of fencerows and forest edges was used as a measure of total ecotonal edge. On the moraine total edge increased through the study period, whereas on the till plain it decreased. We selected two levels of landscape connectivity, low and high, to model animal habitat colonization success. As connectivity increased the earliest successful colonists preempted an increasingly large proportion of the total suitable habitat, and the probability of successful colonization by later-arriving individuals decreased. The changes in connectivity that resulted from changes in both the fencerow network and the proportion of forested land have resulted in contiguous landscapes that present very different colonization potentials to organisms with long-distance dispersal capability. Given the current uncertainty of the effects of corridors on species-preservation efforts, we suggest that further modeling of this type prior to field testing will add useful insights, especially if conducted using specific species and landscape types.  相似文献   
73.
In this paper we classify 86 published studies of participation conducted in the U.S. according to whether they are based on cognitive or motivational conceptual frameworks, then conduct a meta-analysis of 124 correlation coefficients obtained from them to determine whether distinguishing between conceptual frameworks portends differences in the findings of U.S. research on the effects of participatory processes on performance and satisfaction. Results reveal noticeable differences in the findings of participation–satisfaction research, but also indicate that these differences diminish substantially upon elimination of research based on single-source self-reports. If interpreted as evidence of percept–percept inflation, these findings are wholly consistent with those of other recent analyses. If interpreted as evidence of the greater accuracy of self-report measures of intra-psychic phenomena, they suggest that research on the relationship between participation and satisfaction has been influenced by the conceptual frameworks used to design studies and formulate conclusions. © 1997 John Wiley & Sons, Ltd.  相似文献   
74.
Strategies to mitigate climate change can protect different types of cool environments. Two are receiving much attention: protection of ephemeral refuges (i.e., places with low maximum temperatures) and of stable refugia (i.e., places that are cool, have a stable environment, and are isolated). Problematically, they are often treated as equivalents. Careful delineation of their qualities is needed to prevent misdirected conservation initiatives; yet, no one has determined whether protecting one protects the other. We mapped both types of cool environments across a large (~3.4M ha) mixed‐use landscape with a geographic information system and conducted a patch analysis to compare their spatial distributions; examine relations between land use and their size and shape; and assess their current protection status. With a modest, but arbitrary, threshold for demarcating both types of cool environments (i.e., values below the 0.025 quantile) there were 146,523 ha of ephemeral refuge (62,208 ha) and stable refugia (62,319 ha). Ephemeral refuges were generally aggregated at high elevation, and more refuge area occurred in protected areas (55,184 ha) than in unprotected areas (7,024 ha). In contrast, stable refugia were scattered across the landscape, and more stable‐refugium area occurred on unprotected (40,135 ha) than on protected land (22,184 ha). Although sensitivity analysis showed that varying the thresholds that define cool environments affected outcomes, it also exposed the challenge of choosing a threshold for strategies to address climate change; there is no single value that is appropriate for all of biodiversity. The degree of overlap between ephemeral refuges and stable refugia revealed that targeting only the former for protection on currently unprotected land would capture ~17% of stable refugia. Targeting only stable refugia would capture ~54% of ephemeral refuges. Thus, targeting one type of cool environment did not fully protect the other. Evaluación de la Distribución y Estado de Protección de Dos Tipos de Ambientes Fríos para Facilitar su Conservación bajo el Cambio Climático  相似文献   
75.
76.
This note discusses environmental aspects of the planning and consultation process undertaken for the UK aviation White Paper. The process as a whole has involved some three years of forecasting and assessment of the operational, economic and environmental implications of some 28 options for airport expansion at 14 UK locations. Unconstrained passenger demand forecasts have been used as a basis for the planning and consultation, and a mitigation approach to environment has predominated. This is inadequate, given the climate impacts of the forecast aviation expansion. Greenhouse gas emissions reduction should be a high priority in transport infrastructure planning, not the subject of post-hoc analysis.  相似文献   
77.
Abstract:  In the 1990s the federal forests in the Pacific Northwest underwent the largest shift in management focus since their creation, from providing a sustained yield of timber to conserving biodiversity, with an emphasis on endangered species. Triggered by a legal challenge to the federal protection strategy for the Northern Spotted Owl ( Strix occidentalis caurina ), this shift was facilitated by a sequence of science assessments that culminated in the development of the Northwest Forest Plan. The plan, adopted in 1994, called for an extensive system of late-successional and riparian reserves along with some timber harvest on the intervening lands under a set of controls and safeguards. It has proven more successful in stopping actions harmful to conservation of old-growth forests and aquatic systems than in achieving restoration goals and economic and social goals. We make three suggestions that will allow the plan to achieve its goals: (1) recognize that the Northwest Forest Plan has evolved into an integrative conservation strategy, (2) conserve old-growth trees and forests wherever they occur, and (3) manage federal forests as dynamic ecosystems.  相似文献   
78.
Abstract:   Conservation biology requires the development of practical tools and techniques to minimize conflicts arising from human modification of ecosystems. We applied behavioral theory of primary and secondary repellents to predator management by using aversive stimulus devices (electronic training collars) and disruptive stimulus devices (behavior-contingent audio and visual repellents) in a multipredator ( Canis lupus, Haliaeetus leucocephalus, Ursus spp.) study in the United States. We examined fladry and a newly developed disruptive stimulus device contingent upon behavior on six wolf territories in Wisconsin, (U.S.A.) and determined that the disruptive stimulus device gave the greatest degree of protection from predation. We also compared the efficacy of a primary repellent (disruptive stimulus device) versus a secondary repellent (electronic training collars) to keep captive wolves from consuming a food source. Disruptive stimulus devices effectively prevented captive wolves from consuming the food resource, but did not produce an aversion to that food resource. With training collars, logistical and behavioral variability limited our ability to condition wolves. Our studies highlight the complexity of application of nonlethal techniques in real-world situations.  相似文献   
79.
Abstract: The effects of non‐native invasive species are costly and environmentally damaging, and resources to slow their spread and reduce their effects are scarce. Models that accurately predict where new invasions will occur could guide the efficient allocation of resources to slow colonization. We assessed the accuracy of a model that predicts the probability of colonization of lakes in Wisconsin by Eurasian watermilfoil (Myriophyllum spicatum). We based this predictive model on 9 years (1990–1999) of sequence data of milfoil colonization of lakes larger than 25 ha (n =1803). We used milfoil colonization sequence data from 2000 to 2006 to test whether the model accurately predicted the number of lakes that actually were colonized from among the 200 lakes identified as being most likely to be colonized. We found that a lake's predicted probability of colonization was not correlated with whether a lake actually was colonized. Given the low predictability of colonization of specific lakes, we compared the efficacy of preventing milfoil from leaving occupied sites, which does not require predicting colonization probability, with protecting vacant sites from being colonized, which does require predicting colonization probability. Preventing organisms from leaving colonized sites reduced the likelihood of spread more than protecting vacant sites. Although we focused on the spread of a single species in a particular region, our results show the shortcomings of gravity models in predicting the spread of numerous non‐native species to a variety of locations via a wide range of vectors.  相似文献   
80.
Abstract: The amount of privately conserved land is increasing worldwide. The potential of these areas to contribute to the global conservation of biodiversity is significant, given that statutory protected areas alone will not suffice. Nevertheless, there is still inadequate support for private conservation areas, and further research on appropriate, flexible, and generally applicable incentive measures is necessary. We conducted 25 semistructured interviews with the owners of private conservation areas in the Little Karoo, South Africa, to examine landowner opinions of existing conservation policies and their relationships with the local conservation authority. We also assessed landowner preferences regarding conservation incentive measures. Landowners doubted the conservation authority's capacity to implement its stewardship program and were also discouraged by the bureaucracy of the program. The conservation authority was often viewed negatively, except where landowners had experienced personal contact from conservation staff or where strong social capital had formed among landowners. Landowners did not desire financial rewards for their conservation efforts, but sought recognition of their stewardship role and greater involvement from the conservation authority through personal contact. We conclude that conservation policies for private lands could benefit from the provision of extension services to landowners, promotion of formation of groups of landowners and other stakeholders, and public acknowledgment of the contributions private conservation areas make.  相似文献   
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