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41.
Ibáñez I Clark JS Dietze MC Feeley K Hersh M LaDeau S McBride A Welch NE Wolosin MS 《Ecology》2006,87(8):1896-1906
Efforts to anticipate threats to biodiversity take the form of species richness predictions (SRPs) based on simple correlations with current climate and habitat area. We review the major approaches that have been used for SRP, species-area curves and climate envelopes, and suggest that alternative research efforts may provide more understanding and guidance for management. Extinction prediction suffers from a number of limitations related to data and the novelty of future environments. We suggest additional attention to (1) identification of variables related to biodiversity that are diagnostic and potentially more predictable than extinction, (2) constraints on species dispersal and reproduction that will determine population persistence and range shifts, including limited sources or potential immigrants for many regions, and (3) changes in biotic interactions and phenology. We suggest combinations of observational and experimental approaches within a framework available for ingesting heterogeneous data sources. Together, these recommendations amount to a shift in emphasis from prediction of extinction numbers to identification of vulnerabilities and leading indicators of change, as well as suggestions for surveillance tools needed to evaluate important variables and the experiments likely to provide most insight. 相似文献
42.
Susana García-Herrero M.A. Mariscal Javier García-Rodríguez Dale O. Ritzel 《Safety Science》2012,50(9):1760-1774
Each day thousands of workers suffer occupational accidents of varying degrees of severity. Accidents at work render workers incapable of carrying out their day to day activities, either temporarily or permanently, and they also have detrimental effects on family life, the company, and the general public. In order to reduce the occupational accident rate, it is necessary to determine the causes of those accidents. Although there are many different types of accidents, they generally stem from poor working conditions. The purpose of this study was to analyze the influence of working conditions on occupational accidents from data gathered in the VI National Survey of Working Conditions (VI NSWCs) in 2007. This survey utilized a random sample of the active population of Spain. The sample comprised 11,054 people (5917 males and 5137 females). In order to carry out the study, a probabilistic model was built using Bayesian networks. The model included the following variables: hygiene conditions, ergonomic conditions, job demands, physical symptoms, psychological symptoms, and occupational accidents. The study demonstrated that there were strong relationships between hygiene conditions and occupational accidents; it has been shown that poor hygienic conditions duplicate the probability of accident. Physical symptoms increased almost 50% due to poor ergonomic conditions. And finally, high job demands almost duplicated the psychological symptoms. The investigation also showed a high degree of interdependence between physical and psychological symptomatologies and the relationship between these and occupational accidents. 相似文献
43.
44.
Effective conservation policies require comprehensive knowledge of biodiversity. However, knowledge shortfalls still remain, hindering possibilities to improve decision making and built such policies. During the last 2 decades, conservationists have made great efforts to allocate resources as efficiently as possible but have rarely considered the idea that if research investments are also strategically allocated, it would likely fill knowledge gaps while simultaneously improving conservation actions. Therefore, prioritizing areas where both conservation and research actions could be conducted becomes a critical endeavor that can further maximize return on investment. We used Zonation, a conservation planning tool and geographical distributions of amphibians, birds, mammals, and reptiles to suggest and compare priority areas for conservation and research of terrestrial vertebrates worldwide. We also evaluated the degree of human disturbance in both types of priority areas by describing the value of the human footprint index within such areas. The spatial concordance between priority conservation and research areas was low: 0.36% of the world's land area. In these areas, we found it would be possible to protect almost half of the currently threatened species and to gather information on nearly 42% of data-deficient (DD) species. We also found that 6199 protected areas worldwide are located in such places, although only 35% of them have strict conservation purposes. Areas of consensus between conservation and research areas represent an opportunity for simultaneously conserving and acquiring knowledge of threatened and DD species of vertebrates. Although the picture is not the most encouraging, joint conservation and research efforts are possible and should be fostered to save vertebrate species from our own ignorance and extinction. 相似文献
45.
Javier Atalah Saskia A. Otto Marti J. Anderson Mark J. Costello Mark Lenz Martin Wahl 《Marine Biology》2007,153(2):199-211
Natural heterogeneity in ecological parameters, like population abundance, is more widely recognized and investigated than
variability in the processes that control these parameters. Experimental ecologists have focused mainly on the mean intensity
of predictor variables and have largely ignored the potential to manipulate variances in processes, which can be considered
explicitly in experimental designs to explore variation in causal mechanisms. In the present study, the effect of the temporal
variance of disturbance on the diversity of marine assemblages was tested in a field experiment replicated at two sites on
the northeast coast of New Zealand. Fouling communities grown on artificial settlement substrata experienced disturbance regimes
that differed in their inherent levels of temporal variability and timing of disturbance events, while disturbance intensity
was identical across all levels. Additionally, undisturbed assemblages were used as controls. After 150 days of experimental
duration, the assemblages were then compared with regard to their species richness, abundance and structure. The disturbance
effectively reduced the average total cover of the assemblages, but no consistent effect of variability in the disturbance
regime on the assemblages was detected. The results of this study were corroborated by the outcomes from simultaneous replicate
experiments carried out in each of eight different biogeographical regions around the world. 相似文献
46.
Wildlife Conservation Outside Parks Is a Disease-Mediated Task 总被引:1,自引:0,他引:1
Javier A. Simonetti 《Conservation biology》1995,9(2):454-456
47.
Carles Ibàñez Antoni Canicio John W. Day Antoni Curcó 《Journal of Coastal Conservation》1997,3(2):191-202
The Ebre (Ebro) Delta is one of the most important wetland areas in the western Mediterranean. Ca. 40 % of the delta plain is less than 0.5 m above mean sea level and part of the southern margin of the delta is at mean sea level in an area protected by dikes. Both mean rates of secular subsidence in the Ebre Delta and eustatic sea level rise are ca. 1 – 2 mm/yr. Thus, the present annual relative sea level rise (RSLR) rate in the Ebre Delta may be at least 3 mm/yr. Measured accretion rates in the delta range from 4 mm/yr in the wetlands surrounding the river mouth to <0.1 mm/yr in impounded salt marshes and rice fields. The annual sediment deficit in the delta plain to offset RSLR is close to 1 million m3/yr. Accretion rates in the rice fields prior to the construction of large dams in the Ebre watershed were higher than RSLR rates, from 3 – 15 mm/yr. At present, >99 % of the riverine sediments are retained in the reservoirs and rice fields are losing ca. 0.2 mm/yr. Future management plans should take RSLR into account and include control of freshwater and sediment flows from the river in order to offset negative effects from waterlogging and salt intrusion, and maintain land elevation. This will include the partial removal of sediments trapped behind the Ribarroja and Mequinença dams. Stocks and inputs of sediments in the corresponding reservoirs are large enough for land elevation of ca. 50 cm in the whole delta plain. Advantages of this solution include (1) new sediments to the delta to offset subsidence (via rice fields) and coastal retreat, (2) enhanced functioning of the delta (productivity and nutrient processing), (3) avoidance of accumulation of sediments in the reservoirs. Hence, it is important to manage river discharges at the dams from an integrated viewpoint, whereas currently only hydropower and agricultural requirements are considered. It is also crucial to maintain periods of high discharge, to have enough river energy to transport as much sediments as possible. 相似文献
48.
Sperm competition occurs when the sperm of two or more males compete to fertilize the egg/s of a particular female. Males
of some species respond to a high risk of sperm competition by increasing the number of sperm in their ejaculates. Males may
accomplish such a response by increasing the intensity or duration of contraction of the cauda epididymidis and vas deferens.
During emission (first phase of the ejaculatory process), the vas deferens receives sperm from the cauda epididymidis and
propels the sperm to the urethra. In this paper, we tested the hypothesis that males exposed to a high risk of sperm competition
mobilize larger numbers of sperm from the cauda epididymidis to the vas deferens before initiation of copulatory behavior.
This accumulation of sperm in the vas deferens would result in a larger number of sperm in the ejaculate. To test this hypothesis,
we exposed male meadow voles, Microtus pennsylvanicus, to either low or high risks of sperm competition using soiled bedding of conspecific individuals. At three different times
after this exposure (15, 30, or 60 min), we removed both vasa deferentia and counted the sperm within them. We found a significant
increase in sperm numbers in the vas deferens of males after 30 min of being exposed to a high risk of sperm competition.
The lower sperm numbers after 15 and 60 min of exposure suggest that the observed response is relatively slow and that sperm
mobilized to the vasa deferentia may return to the cauda epididymides if ejaculation does not occur some time after the observed
response. Our results indicate that the physiological response that may result in high sperm numbers in the ejaculate in relation
to high risk of sperm competition can occur before initiation of copulatory behavior. 相似文献
49.
Identifying reproductive stocks in commercial species is relevant to fishery management strategies. We obtained muscle samples
of California spiny lobster (Panulirus interruptus) from six localities along the west coast of the Baja California Peninsula and analyzed the genetic structure using mtDNA
RFLPs. Our results indicated that all localities shared the same major haplotypes and showed a spatial homogeneity in the
distribution of haplotype frequencies. An analysis of molecular variance indicated that only 0.84% of the genetic variability
was explained by differences among localities and was not significantly different from zero. Weak divergences were found between
Bahía Magdalena, the most southerly locality, in relation to other populations. Major oceanographic processes along this coast,
combined with a long larval period that supports passive transport among localities, are suggested to explain the results. 相似文献
50.
When searching for flying insects, Molossops temminckii uses unusual echolocation calls characterized by upward modulation of frequency vs time (UFM). Call frequency increases asymptotically
in the relatively long (∼8 ms) pulses from a starting frequency of ∼40 kHz to a long narrowband tail at ∼50 kHz. When approaching
a prey, the bat progressively increases the duration of calls and intersperses in the sequence broadband downwardly frequency-modulated
signals with a terminal frequency of about 53 kHz, which totally replaces the UFM signals at the end of the approach phase.
The sequence progresses to a capture buzz resembling those from other molossid and vespertilionid bats. The M. temminckii wing morphology is characterized by an average aspect ratio and a high wing loading, suggesting that it is more maneuverable
than the typical Molossidae but less than typical Vespertilionidae. M. temminckii regularly forages near clutter, where it needs to pay attention to the background and might face forward and backward masking
of signals. We hypothesize that the UFM echolocation signals of M. temminckii represent an adaptation to foraging near background clutter in a not very maneuverable bat needing a broad attention window.
The broadband component of the signal might serve for the perception of the background and the narrowband tail for detection
and perhaps classification of prey. Bats may solve the signal masking problems by separating emission and echoes in the frequency
domain. The echolocation behavior of M. temminckii may shed light on the evolution of the narrowband frequency analysis echolocation systems adopted by some bats foraging within
clutter. 相似文献