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61.
Oliver Manlik Robert C. Lacy William B. Sherwin Hugh Finn Neil R. Loneragan Simon J. Allen 《Conservation biology》2022,36(4):e13897
Human-caused mortality of wildlife is a pervasive threat to biodiversity. Assessing the population-level impact of fisheries bycatch and other human-caused mortality of wildlife has typically relied upon deterministic methods. However, population declines are often accelerated by stochastic factors that are not accounted for in such conventional methods. Building on the widely applied potential biological removal (PBR) equation, we devised a new population modeling approach for estimating sustainable limits to human-caused mortality and applied it in a case study of bottlenose dolphins affected by capture in an Australian demersal otter trawl fishery. Our approach, termed sustainable anthropogenic mortality in stochastic environments (SAMSE), incorporates environmental and demographic stochasticity, including the dependency of offspring on their mothers. The SAMSE limit is the maximum number of individuals that can be removed without causing negative stochastic population growth. We calculated a PBR of 16.2 dolphins per year based on the best abundance estimate available. In contrast, the SAMSE model indicated that only 2.3–8.0 dolphins could be removed annually without causing a population decline in a stochastic environment. These results suggest that reported bycatch rates are unsustainable in the long term, unless reproductive rates are consistently higher than average. The difference between the deterministic PBR calculation and the SAMSE limits showed that deterministic approaches may underestimate the true impact of human-caused mortality of wildlife. This highlights the importance of integrating stochasticity when evaluating the impact of bycatch or other human-caused mortality on wildlife, such as hunting, lethal control measures, and wind turbine collisions. Although population viability analysis (PVA) has been used to evaluate the impact of human-caused mortality, SAMSE represents a novel PVA framework that incorporates stochasticity for estimating acceptable levels of human-caused mortality. It offers a broadly applicable, stochastic addition to the demographic toolbox to evaluate the impact of human-caused mortality on wildlife. 相似文献
62.
Furtak-Cole E. Gillies J. A. Hilgendorf Z. Walker I. J. Nikolich G. 《Environmental Fluid Mechanics》2022,22(6):1399-1420
Environmental Fluid Mechanics - Wind-driven shear stresses drive saltation and dust emissions over sand dunes. However, the complex topography of coastal dunes and practical difficulties in... 相似文献
63.
Postfire response of flood-regenerating riparian vegetation in a semi-arid landscape 总被引:2,自引:0,他引:2
Piles of large wood (LW) deposited by major floods in river corridors can interact with naturally occurring wildfires from uplands to impact the regeneration of riparian vegetation. This study examines the spatial and short-term temporal response of riparian vegetation and soil nutrients to fire along the Sabie River, South Africa, with special emphasis on the effects of burned LW piles. At the study site there were 112 species of plants recorded with 28% of species restricted to the burned plots. As expected, vegetation cover was significantly lower in burned plots as compared with the unburned plots 12 months postfire. There was a significant influence of LW on species richness with fewer species recorded in the LW plots. For both fire and LW treatments, plant cover showed a significant change over three years. After an initial increase from 12 to 24 months (postfire) there was a decline in plant cover after 36 months. Species community composition was distinctly different between burned and unburned plots 12 months postfire, and the presence of LW affected species composition for burned plots but not for unburned ones. Time series ordination of LW plots highlighted the changes in species composition over the three years of sampling. Of trees with accumulations of LW within 5 m of their base, 48% had been killed by fire as compared to only 4% with no LW accumulations in close proximity. Soil-available P was significantly higher in the burned plots and even higher with burned LW while there were no effects on soil total N. There was also a significant positive trend between available P in soils and plant vegetation cover. Soil-exchangeable K was also significantly higher and total C significantly lower in the burned and LW plots. Burned plots also had significantly higher soil electrical conductivity (EC) and soil pH. The patchy nature of the studied fire, whose complexity is exacerbated by the distribution of flood deposited LW, acted to create a mosaic of alternate successional states as the riparian community recovers from flooding and the subsequent fire. We suspect that the resultant heterogeneity will increase ecosystem resilience by providing flexibility in the form of more options for a system response to subsequent disturbances. 相似文献
64.
The crucial parameter used to calculate turbulence effects upon light waves propagating through the atmosphere is known as
the structure constant, . As Tatarski has shown, this parameter depends upon the “outer scale” of the inertial sub-range of the turbulence. Recently
there have been successful predictions of astronomical “seeing” conditions at Mauna Kea Astronomical Observatory which have
increased interest in this subject and in the use of the so-called “Dewan Optical Turbulence Model”. In the case of the Air
Force, there has been a longstanding need for such optical turbulence prediction, especially in the stratosphere. In the past
researchers have used a relation due to Tatarski, (which plays a prominent role in this model) in order to deduce values of
the “outer scale” from measurements. When doing this, they have been surprised to find values very much smaller than expected. The goal of the paper
is to explain this unexpected result. As we will show, this result can be explained by two factors: (a) the average turbulent
layer thicknesses are smaller than originally believed, and, more importantly, (b) only a minor fraction of the stratosphere
is turbulent. In order to arrive at this conclusion, we used the high-resolution (10 m) wind profiles that were originally
used to formulate the previously mentioned optical turbulence model.
The U.S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged. 相似文献
65.
Christian Mrz Felipe S. Freitas Johan C. Faust Jasmin A. Godbold Sian F. Henley Allyson C. Tessin Geoffrey D. Abbott Ruth Airs Sandra Arndt David K. A. Barnes Laura J. Grange Neil D. Gray Ian M. Head Katharine R. Hendry Robert G. Hilton Adam J. Reed Saskia Rühl Martin Solan Terri A. Souster Mark A. Stevenson Karen Tait James Ward Stephen Widdicombe 《Ambio》2022,51(2):370
Unprecedented and dramatic transformations are occurring in the Arctic in response to climate change, but academic, public, and political discourse has disproportionately focussed on the most visible and direct aspects of change, including sea ice melt, permafrost thaw, the fate of charismatic megafauna, and the expansion of fisheries. Such narratives disregard the importance of less visible and indirect processes and, in particular, miss the substantive contribution of the shelf seafloor in regulating nutrients and sequestering carbon. Here, we summarise the biogeochemical functioning of the Arctic shelf seafloor before considering how climate change and regional adjustments to human activities may alter its biogeochemical and ecological dynamics, including ecosystem function, carbon burial, or nutrient recycling. We highlight the importance of the Arctic benthic system in mitigating climatic and anthropogenic change and, with a focus on the Barents Sea, offer some observations and our perspectives on future management and policy. 相似文献
66.
67.
Ilona Riipinen Jeffrey R. Pierce Neil M. Donahue Spyros N. Pandis 《Atmospheric environment (Oxford, England : 1994)》2010,44(5):597-607
The interpretation of thermodenuder (TD) data often relies on the assumption that thermodynamic equilibrium is reached inside the instrument. We modeled the evaporation of three organic aerosol types (adipic acid, α-pinene SOA and aged OA) inside a thermodenuder with a mass transfer model, and calculated equilibration time scales for these systems at realistic conditions. The equilibrium times varied from less than a second to several hours, decreasing with increasing aerosol concentrations, decreasing particle sizes, decreasing volatilities and increasing mass accommodation coefficients. The results indicate that generally TDs measure particle evaporation rates rather than equilibria, and time-dependent modeling of the evaporation is usually needed to interpret the data. Measurements at varying residence times and temperatures, on the other hand, are desirable to investigate the equilibration of the studied aerosol and decouple the kinetic effects from the effects caused by the thermodynamic properties of the aerosol. Organic aerosol is likely to be further from equilibrium under typical field conditions compared with laboratory data. When determining the aerosol properties from TD data, assuming incorrectly equilibrium results in under-prediction of the vaporization enthalpy of the evaporating species. Similar under-estimation is predicted if multicomponent aerosols are approximated with single-component properties. 相似文献
68.
Thuan-Quoc Thach Chit-Ming Wong King-Pan Chan Yuen-Kwan Chau G. Neil Thomas Chun-Quan Ou Lin Yang Joseph S.M. Peiris Tai-Hing Lam Anthony J. Hedley 《Atmospheric environment (Oxford, England : 1994)》2010,44(11):1437-1442
We assessed confounding of associations between short-term effects of air pollution and health outcomes by influenza using Hong Kong mortality and hospitalization data for 1996–2002.Three measures of influenza were defined: (i) intensity: weekly proportion of positive influenza viruses, (ii) epidemic: weekly number of positive influenza viruses ≥4% of the annual number for ≥2 consecutive weeks, and (iii) predominance: an epidemic period with co-circulation of respiratory syncytial virus <2% of the annual positive isolates for ≥2 consecutive weeks. We examined effects of influenza on associations between nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter with aerodynamic diameter ≤10 μm (PM10) and ozone (O3) and health outcomes including all natural causes mortality, cardiorespiratory mortality and hospitalization. Generalized additive Poisson regression model with natural cubic splines was fitted to control for time-varying covariates to estimate air pollution health effects. Confounding with influenza was assessed using an absolute difference of >0.1% between unadjusted and adjusted excess risks (ER%).Without adjustment, pollutants were associated with positive ER% for all health outcomes except asthma and stroke hospitalization with SO2 and stroke hospitalization with O3. Following adjustment, changes in ER% for all pollutants were <0.1% for all natural causes mortality, but >0.1% for mortality from stroke with NO2 and SO2, cardiac or heart disease with NO2, PM10 and O3, lower respiratory infections with NO2 and O3 and mortality from chronic obstructive pulmonary disease with all pollutants. Changes >0.1% were seen for acute respiratory disease hospitalization with NO2, SO2 and O3 and acute lower respiratory infections hospitalization with PM10. Generally, influenza does not confound the observed associations of air pollutants with all natural causes mortality and cardiovascular hospitalization, but for some pollutants and subgroups of cardiorespiratory mortality and respiratory hospitalization there was evidence to suggest confounding by influenza. 相似文献
69.
Kris A. G. Wyckhuys Robert J. O’Neil 《Environment, Development and Sustainability》2010,12(3):297-311
In subsistence farming systems of the developing world, adoption of resource-conserving practices such as integrated pest
management (IPM) is often strikingly low. This has partially been ascribed to researchers’ limited understanding of how technologies
develop at the interface of the systems’ social and ecological components. In Honduras (Central America), there exists concern
about limited adoption and diffusion of IPM technologies in certain smallholder production systems. In this study, we determine
social and ecological drivers of IPM adoption in subsistence maize production in the country’s hillside environment. Honduran
small-scale maize production is typified by a key insect pest (the fall armyworm, Spodoptera frugiperda) being partly kept at bay through action of a diverse natural enemy complex, including ants, social wasps, carabid beetles,
and spiders. Local agricultural landscapes, primarily shaped through shifting cultivation, provide key resources to maintain
this natural enemy diversity. These local ecological conditions and related natural enemy abundance strongly influence farmers’
agroecological knowledge and pest management practices. In the meantime, farmer practices are also affected by local communication
networks, which help validate and spread IPM concepts and technologies. Based on our findings, we advocate a holistic approach
to improve IPM extension through mapping of agroecological opportunities, visualization of regional patterns in farmer knowledge,
and associated priority setting. Local IPM capacity could be built through institutional strengthening and adaptive comanagement,
while IPM training should be linked with natural resource management initiatives. These approaches may eventually improve
the way IPM is delivered to small-scale farmers who operate in the ecologically diverse environments of the tropics. 相似文献
70.
Regular fuel reduction burning is an important management strategy for reducing the scale and intensity of wildfires in south-west
Australian native forests, but the long term effects of this on tree and stand growth are not well understood. Five fire treatments,
including application of frequent and infrequent low intensity burns, and 25 years of fire exclusion, were applied to small
(4 ha) experimental plots in a low rainfall mixed jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) forest to investigate the effects of these treatments on tree stem diameter growth, stand basal area increment and tree
mortality. Mean tree stem growth measured over 20 years was lowest in the long unburnt treatment compared with the burn treatments,
although surface soil nutrient levels were generally higher in the unburnt treatment, suggesting these sites may be moisture
limited. There was no clear pattern of the effects of the burn treatments, including the number of fires and the interval
between fires, on tree stem growth, stand basal area increment, crown health or mortality. These factors were strongly influenced
by dominance condition, with dominant and co-dominant trees growing most and suppressed trees growing least and experiencing
the highest mortality levels. There was no evidence of deteriorating tree or stand health that could be attributed to either
regular low intensity burning or to a long period (25 years) of fire exclusion. 相似文献