排序方式: 共有7条查询结果,搜索用时 187 毫秒
1
1.
2.
The Northwest Forest Plan: Origins, Components, Implementation Experience, and Suggestions for Change 总被引:5,自引:0,他引:5
JACK WARD THOMAS JERRY F. FRANKLIN† JOHN GORDON‡ K. NORMAN JOHNSON§ 《Conservation biology》2006,20(2):277-287
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
3.
4.
Radish as a Model System for the Study of Engineered Gene Escape Rates Via Crop-Weed Mating 总被引:2,自引:0,他引:2
Abstract: Engineered genes in transgenic crops may escape into the ambient environment via crop-weed hybridization However, natural crop-weed muting rates (gene flow) are largely unknown We measured mating between wild and cultivated radishes in an experiment that simulated natural stands around seed multiplication plots. We used a genetic marker to identify, crop-weed muting events. Although weeds at the cultivar plot margin (1 m distance) received much more gene flow than distant plants, detectable gene flow occurred at our most distant site (1000 m). For insect-pollinated outcrossing crops like radish, strategies other than distance must be employed to ensure complete isolation. 相似文献
5.
JONATHAN R. THOMPSON‡ MARK D. ANDERSON† K. NORMAN JOHNSON 《Conservation biology》2004,18(6):1475-1481
Abstract: Cross-boundary ecosystem management is increasingly being advocated to address large-scale ecological issues on forested landscapes. Such management requires information about the age, composition, and distribution of trees and other vegetation in addition to the ability to coordinate management over large areas. In the United States, the forest industry owns and manages a large quantity of biologically productive forest land, and these forests are crucial to the success of regional ecosystem planning. Antitrust laws, such as the Sherman Antitrust Act of 1890, limit the industry's ability to participate in regional ecosystem planning because they restrict the ability of competing firms to coordinate activities and share information. Because antitrust courts do not consider the intentions of violators, achieving conservation or other public policy goals, even when working with government agencies, is not a sufficient defense. Therefore, the real and perceived threat of antitrust litigation is a disincentive to the forest industry's participation in large-scale ecosystem management. Potential solutions to this problem include state immunity statutes and third-party data aggregation. 相似文献
6.
NORMAN MERCADO-SILVA‡ JULIAN D. OLDEN JEFFREY T. MAXTED THOMAS R. HRABIK† M. JAKE VANDER ZANDEN 《Conservation biology》2006,20(6):1740-1749
Abstract: Rainbow smelt ( Osmerus mordax ) have invaded many North American lakes, often resulting in the extirpation of native fish populations. Yet, their invasion is incipient and provides the rationale for identifying ecosystems likely to be invaded and where management and prevention efforts should be focused. To predict smelt presence and absence, we constructed a classification-tree model based on habitat data from 354 lakes in the native range for smelt in southern Maine. Maximum lake depth, lake area, and Secchi depth (surrogate measure of lake productivity) were the most important predictors. We then used our model to identify lakes vulnerable to invasion in three regions outside the smelt's native range: northern Maine (52 of 244 lakes in the non-native range), Ontario (4447 of 8110), and Wisconsin (553 of 5164). We further identified a subset of lakes with a strong potential for impact (potential–impact lakes) based on the presence of fish species that are affected by rainbow smelt. Ninety-four percent of vulnerable lakes in the non-native range in Maine are also potential–impact lakes, as are 94% and 58% of Ontario and Wisconsin's vulnerable lakes, respectively. Our modeling approach can be applied to other invaders and regions to identify invasion-prone ecosystems, thus aiding in the management of invasive species and the efficient allocation of invasive species mitigation and prevention resources. 相似文献
7.
NORMAN OWEN-SMITH 《Conservation biology》1989,3(4):405-412
Abstract: At the end of the Pleistocene, the Americas, northern Eurasia: and Australia experienced a vast decline in large mammal diversity, while Africa and tropical Asia were hardly affected. The elimination of the megaberbivores (animals weighing >1000 kg, probably by human predation, removed the vegetation impact of these species. The resultant reduction in habitat mosaic diversity and in forage quality probably precipitated the extinctions of lesser large mammalian species. Surviving megaherbivores in the form of elephants and rhinoceroses are currently being exterminated from many African conservation areas. African savanna ecosystems could prove more resistant to species losses than north temperate ecosystems, because geomorphic factors plus low and erratic rainfall enhance spatial heterogeneity and vegetation quality independently of large herbivore impact Nevertheless, the history of the Hluhluwe Game Reserve in South Africa suggests that certain African ecosystems may become susceptible to an inexorable decline in populations of some large herbivores following the extermination of elephants. If elephants and rhinoceroses cannot be conserved active habitat manipulation will be needed to retain a diverse fauna of large mammals in such regions. 相似文献
1