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131.
BLAKE R. HOSSACK MICHAEL J. ADAMS CHRISTOPHER A. PEARL KRISTINE W. WILSON EVELYN L. BULL KRISTIN LOHR DEBRA PATLA DAVID S. PILLIOD JASON M. JONES KEVIN K. WHEELER SAMUEL P. MCKAY PAUL STEPHEN CORN 《Conservation biology》2013,27(6):1410-1420
Despite the high profile of amphibian declines and the increasing threat of drought and fragmentation to aquatic ecosystems, few studies have examined long‐term rates of change for a single species across a large geographic area. We analyzed growth in annual egg‐mass counts of the Columbia spotted frog (Rana luteiventris) across the northwestern United States, an area encompassing 3 genetic clades. On the basis of data collected by multiple partners from 98 water bodies between 1991 and 2011, we used state‐space and linear‐regression models to measure effects of patch characteristics, frequency of summer drought, and wetland restoration on population growth. Abundance increased in the 2 clades with greatest decline history, but declined where populations are considered most secure. Population growth was negatively associated with temporary hydroperiods and landscape modification (measured by the human footprint index), but was similar in modified and natural water bodies. The effect of drought was mediated by the size of the water body: populations in large water bodies maintained positive growth despite drought, whereas drought magnified declines in small water bodies. Rapid growth in restored wetlands in areas of historical population declines provided strong evidence of successful management. Our results highlight the importance of maintaining large areas of habitat and underscore the greater vulnerability of small areas of habitat to environmental stochasticity. Similar long‐term growth rates in modified and natural water bodies and rapid, positive responses to restoration suggest pond construction and other forms of management can effectively increase population growth. These tools are likely to become increasingly important to mitigate effects of increased drought expected from global climate change. Papeles de las Características del Fragmento, Frecuencia de Sequía y Restauración en las Tendencias a Largo Plazo de un Anfibio Ampliamente Distribuido 相似文献
132.
MATTHEW P. HARE LEONARD NUNNEY MICHAEL K. SCHWARTZ DANIEL E. RUZZANTE MARTHA BURFORD ROBIN S. WAPLES KRISTEN RUEGG FRISO PALSTRA 《Conservation biology》2011,25(3):438-449
Abstract: Effective population size (Ne) determines the strength of genetic drift in a population and has long been recognized as an important parameter for evaluating conservation status and threats to genetic health of populations. Specifically, an estimate of Ne is crucial to management because it integrates genetic effects with the life history of the species, allowing for predictions of a population's current and future viability. Nevertheless, compared with ecological and demographic parameters, Ne has had limited influence on species management, beyond its application in very small populations. Recent developments have substantially improved Ne estimation; however, some obstacles remain for the practical application of Ne estimates. For example, the need to define the spatial and temporal scale of measurement makes the concept complex and sometimes difficult to interpret. We reviewed approaches to estimation of Ne over both long‐term and contemporary time frames, clarifying their interpretations with respect to local populations and the global metapopulation. We describe multiple experimental factors affecting robustness of contemporary Ne estimates and suggest that different sampling designs can be combined to compare largely independent measures of Ne for improved confidence in the result. Large populations with moderate gene flow pose the greatest challenges to robust estimation of contemporary Ne and require careful consideration of sampling and analysis to minimize estimator bias. We emphasize the practical utility of estimating Ne by highlighting its relevance to the adaptive potential of a population and describing applications in management of marine populations, where the focus is not always on critically endangered populations. Two cases discussed include the mechanisms generating Ne estimates many orders of magnitude lower than census N in harvested marine fishes and the predicted reduction in Ne from hatchery‐based population supplementation. 相似文献
133.
Abstract: Urban development is the most common form of land conversion in the United States. Using a before–after control‐impact study design, we investigated the effects of urbanization on larval and adult stages of southern two‐lined salamanders (Eurycea cirrigera) and northern dusky salamanders (Desmognathus fuscus). Over 5 years, we estimated changes in occupancy and probabilities of colonization and survival in 13 stream catchments after urbanization and in 17 catchments that were not urbanized. We also examined effects of proportion of urbanized area in a catchment and distance of the salamander population to the nearest stream on probabilities of colonization and survival. Before urbanization, adult and larval stages of the two salamander species occupied nearly all surveyed streams, with occupancy estimates ranging from 1.0 to 0.78. Four years after urbanization mean occupancy of larval and adult two‐lined salamanders had decreased from 0.87 and 0.78 to 0.57 and 0.39, respectively. Estimates of mean occupancy of larval northern dusky salamanders decreased from 1.0 to 0.57 in urban streams 4 years after urbanization; however, adult northern dusky salamander occupancy remained close to 1.0 in urban streams over 5 years. Occupancy estimates in control streams were similar for each species and stage over 5 years. Urbanization was associated with decreases in survival probabilities of adult and larval two‐lined salamanders and decreases in colonization probabilities of larval dusky salamanders. Nevertheless, proportion of impervious surface and distance to nearest stream had little effect on probabilities of survival and colonization. Our results imply that in the evaluation of the effects of urbanization on species, such as amphibians, with complex life cycles, consideration of the effects of urbanization on both adult and larval stages is required. 相似文献
134.
Abstract: The mandate to increase endangered salmon populations in the Columbia River Basin of North America has created a complex, controversial resource‐management issue. We constructed an integrated assessment model as a tool for analyzing biological‐economic trade‐offs in recovery of Snake River spring‐ and summer‐run chinook salmon (Oncorhynchus tshawytscha). We merged 3 frameworks: a salmon‐passage model to predict migration and survival of smolts; an age‐structured matrix model to predict long‐term population growth rates of salmon stocks; and a cost‐effectiveness analysis to determine a set of least‐cost management alternatives for achieving particular population growth rates. We assessed 6 individual salmon‐management measures and 76 management alternatives composed of one or more measures. To reflect uncertainty, results were derived for different assumptions of effectiveness of smolt transport around dams. Removal of an estuarine predator, the Caspian Tern (Sterna caspia), was cost‐effective and generally increased long‐term population growth rates regardless of transport effectiveness. Elimination of adult salmon harvest had a similar effect over a range of its cost estimates. The specific management alternatives in the cost‐effective set depended on assumptions about transport effectiveness. On the basis of recent estimates of smolt transport effectiveness, alternatives that discontinued transportation or breached dams were prevalent in the cost‐effective set, whereas alternatives that maximized transportation dominated if transport effectiveness was relatively high. More generally, the analysis eliminated 80–90% of management alternatives from the cost‐effective set. Application of our results to salmon management is limited by data availability and model assumptions, but these limitations can help guide research that addresses critical uncertainties and information. Our results thus demonstrate that linking biology and economics through integrated models can provide valuable tools for science‐based policy and management. 相似文献
135.
Burger J Leschine TM Greenberg M Karr JR Gochfeld M Powers CW 《Environmental management》2003,31(2):0157-0167
More than 50 years of research, development, manufacture, and testing of nuclear weapons at Department of Energy (DOE) sites
has left a legacy of on-site contamination that often spreads to surrounding areas. Despite substantial cleanup budgets in
the last decade, the DOE's top-to-bottom review team concluded that relatively little actual cleanup has been accomplished,
although milestones have been met and work packages completed. Rather than solely use regulatory constraints to direct cleanup,
many people have suggested that human and ecological health should guide long-term stewardship goals of DOE-managed sites.
The main questions are how ecological and human health considerations should be applied in deciding the extent of cleanup
that contaminated sites should receive and how near-term and longer run considerations of costs and benefits should be balanced
as cleanup decisions are made. One effort to protect ecological integrity is the designation of the largest sites as National
Environmental Research Parks (NERPs). Recently, the Competitive Enterprise Institute (CEI) suggested isolating and conserving
DOE sites as a policy priority because of their rich ecological diversity. A more effective long-term stewardship approach
for former nuclear weapons complex sites may emerge if the guiding principles are to (1) reduce risks to human and ecological
health, (2) protect cultural traditions, and (3) lower short- and long-term cleanup and remediation costs. A “net benefits”
perspective that takes both near- and longer-term costs and consequences into account can help illuminate the trade-offs between
expensive cleanup in the near term and the need to assure long-term protection of human health, cultural values, and high
levels of biodiversity and ecological integrity that currently exist at many DOE sites. 相似文献
136.
Data collected from 172 sites in 20 major river basins between 1993 and 1995 as part of the US Geological Survey's National
Water-Quality Assessment Program were analyzed to assess relations among basinwide land use (agriculture, forest, urban, range),
water physicochemistry, riparian condition, and fish community structure. A multimetric approach was used to develop regionally
referenced indices of fish community and riparian condition. Across large geographic areas, decreased riparian condition was
associated with water-quality constituents indicative of nonpoint source inputs—total nitrogen and suspended sediment and
basinwide urban land use. Decreased fish community condition was associated with increases in total dissolved solids and rangeland
use and decreases in riparian condition and agricultural land use. Fish community condition was relatively high even in areas
where agricultural land use was relatively high (>50% of the basin). Although agricultural land use can have deleterious effects
on fish communities, the results of this study suggest that other factors also may be important, including practices that
regulate the delivery of nutrients, suspended sediments, and total dissolved solids into streams. Across large geographic
scales, measures of water physicochemistry may be better indicators of fish community condition than basinwide land use. Whereas
numerous studies have indicated that riparian restorations are successful in specific cases, this analysis suggests the universal
importance of riparian zones to the maintenance and restoration of diverse fish communities in streams. 相似文献
137.
CHARLES M. PETERS MICHAEL J. BALICK FRANCIS KAHN ANTHONY B. ANDERSON 《Conservation biology》1989,3(4):341-349
Abstract: Tropical forests dominated by only one or two tree species occupy tens of millions of hectares in Ammonia In many cases, the dominant species produce fruits, seeds, or oils of economic importance. Oligarchic (Gr. oligo = few, archic = dominated or ruled by) forests of six economic species, i. e., Euterpe oleracea, Grias peruviana, Jessenia bataua, Mauritia flexuosa, Myrciaria dubia, and Orbignya phalerata, were studied in Brazil and Peru Natural populations of these species contain from 100 to 3,000 conspecific adult trees/ha and produce up to 11.1 metric tons of fruit/hd/yr. These plant populations are utilized and occasionally managed, by rural inhabitants in the region. Periodic fruit harvests, if properly controlled have only a minimal impact on forest structure and function, yet can generate substantial economic returns Market-oriented extraction of the fruits produced by oligarchic forests appears to represent a promising alternative for reconciling the development and conservation of Amazonian forests. 相似文献
138.
Olympic Mountain Goat Controversy Continues 总被引:1,自引:1,他引:0
MICHAEL HUTCHINS 《Conservation biology》1995,9(5):1324-1326
139.
140.
Public values toward forests have changed since the late 1980s, from a commodity-oriented perspective toward a more inclusive
(commodity and non-commodity) orientation. This study examines the influence of four indicators of population diversity (age,
ethnic background, place of residence, and gender) on amenity values of forests, environmental attitudes, and forest value—attitude
correspondence. Four values of public and private forests were assessed, wood production (utilitarian value), clean air (a
life support value), scenic beauty (an aesthetic value), and heritage (a spiritual value). Environmental attitudes were measured
using a modified version of the New Environmental Paradigm scale. Five hundred and forty-eight randomly selected residents
of households in 13 states of the Southern United States participated in a telephone interview. Age and ethnic background
were found to moderate the value—attitude relationship, with the strength of the association being dependent upon the type
of forest (i.e., public or private) and the forest value (i.e., utilitarian, life support, spiritual, and aesthetic). Females,
younger persons (less than 43 years old), and whites reported lower utilitarian values of forests than their respective counterparts.
Results are interpreted within the context of an emerging post-material society, in which a biocentric orientation to forests
and the natural environment may be favored more by a younger (versus older) generation and increasingly racially diverse U.S.
population. Implications for managing forests using a multiple-values (versus multiple-uses) approach are discussed. 相似文献