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1.
Marty?L.?LeonardEmail author Andrew?G.?Horn Jackie?Porter 《Behavioral ecology and sociobiology》2003,54(6):573-577
Much of the theoretical work on the evolution of begging assumes this elaborate display is costly. The evidence for an energetic cost to begging has, however, been equivocal. Metabolic studies on nestling birds suggest that begging requires minimal energy, but some growth studies have shown that excess begging reduces growth rates. One difficulty in interpreting these results is that metabolic and growth studies have each been performed on different species. Here, we test whether high begging frequencies depress growth in nestling tree swallows, Tachycineta bicolor, a species in which the metabolic cost of begging has been measured. When we compared the growth of nestlings stimulated to beg at either high or low frequencies, we found no significant differences in their mass gained, wing growth or portion of ingested energy devoted to begging either during the experimental period or in the 24 h following the end of the experiment. We also found no significant relationship between begging intensity and growth measurements. The results of our study are consistent with previous metabolic studies on this species suggesting that the energetic cost of begging is relatively low. More generally, evidence for a fitness cost of begging via decreased growth is equivocal.Communicated by J. Dickinson 相似文献
2.
Merle Sowman Maria Hauck Lance van Sittert Jackie Sunde 《Environmental management》2011,47(4):573-583
A historical perspective on MPA identification and governance in South Africa reflects the continued influence of a top-down
and natural science-based paradigm, that has hardly changed over the past half century, despite the wealth of literature,
and a growing consensus, that advocates the need to adopt a more integrated and human-centered approach. Based on extensive
research in two coastal fishing communities, the paper highlights impacts and conflicts arising from this conventional approach
to MPA identification, planning and management. It argues that failure to understand the particular fishery system in all
its complexity, in particular the human dimensions, and involve resource users in planning and decision-making processes,
undermines efforts to achieve conservation and fisheries management objectives. The customary rights of local resource users,
and their food and livelihood needs in relation to marine resources, need to be acknowledged, prioritized and integrated into
planning and decision-making processes. Convincing ecologists, fisheries scientists and managers, that MPA success depends
on addressing the root causes of resource decline and incorporating social factors into MPA identification, planning and management,
remains a huge challenge in South Africa. 相似文献
3.
4.
Jackie Sellers Ronald M. North 《Journal of the American Water Resources Association》1979,15(1):167-181
ABSTRACT: The “principles and standards for planning water and related land resources” were made effective October 25, 1973. The document was noticeably deficient in suggestions for the necessary implementing procedures to ensure its success. Current implementing procedures are based on an incorrect premise of maximizing a single objective subject to non-quantified constraints. A successful implementation of multiple objective planning requires optimizing simultaneously several competitive goals. A system of goal programming has been developed and applied to decisionmaking situations as a test of its usefulness in planning for multiple objective water resources projects. The result is a project planning process which can be replicated for adjustments in expected resource supplies or demands to provide a tradeoff matrix between economic and environmental objectives as well as traditional functional purposes. This procedure, tested on the Cross Florida Barge Canal, is an integrated analysis of economic and environmental values which may be as effective in implementing multiple objective planning as the “Green Book” was in developing the now inappropriate benefit cost analysis. 相似文献
5.
Inadequate trade policies, globalization of the fishing industry, dominance of Europe's distant water fleets, declarations of exclusive economic zones (EEZs) by neighbouring West African nations, overfishing and a lack of good governance contributed to the decline of Ghana as a regional fishing nation, a position it had held since the 18th century. The prohibitive cost of access arrangements limited Ghana's access to distant waters. The country's marine environments have been impacted by overexploitation of stocks and the use of destructive methods. Subsistence fishing has become the sole means of survival for many fishers. The decline of the fishing sector has limited the country's ability to meet domestic demand and threatened the economic and food security of many Ghanaians. The article traces the early history of Ghana's fisheries, their gradual decline during the last four decades, and outlines recommendations for policy changes to address the situation and steer the nation on a course towards sustainable fisheries. 相似文献
6.
In this case study of a degraded tropical landscape, we examine how the protected area system in Hong Kong, China, should be modified to improve its efficiency in protecting the surprisingly rich biota. The challenge lies in the fine scale of site selection, and the absence of a core area with high species richness and rarity. Site selection was first conducted in 1 km grid units by selecting hotspots and irreplaceable sites using field records for eight groups of species (amphibians, reptiles, mammals, breeding birds, ants, butterflies, dragonflies and rare vascular plants). The habitats of conservation value within the selected grid units were then delineated on the basis of expert knowledge. Recommendations for increasing the total existing protected area by 6% (i.e. an additional 2% of Hong Kong's total land area) were submitted to the Government in August 2000. To test the robustness of the results, site selection was repeated in 2001 using updated data and different selection methods. The numbers of squares selected by complementarity-based algorithms were similar to those by the hotspots and irreplaceable site method. Sites selected for rare species were very sensitive to data completeness, implying that the application of complementarity-based algorithms at fine scales might be limited. 相似文献
7.
Henry P. Huntington Andrey Zagorsky Bjrn P. Kaltenborn Hyoung Chul Shin Jackie Dawson Maija Lukin Parnuna Egede Dahl Peiqing Guo David N. Thomas 《Ambio》2022,51(2):298
The Arctic Ocean is undergoing rapid change: sea ice is being lost, waters are warming, coastlines are eroding, species are moving into new areas, and more. This paper explores the many ways that a changing Arctic Ocean affects societies in the Arctic and around the world. In the Arctic, Indigenous Peoples are again seeing their food security threatened and cultural continuity in danger of disruption. Resource development is increasing as is interest in tourism and possibilities for trans-Arctic maritime trade, creating new opportunities and also new stresses. Beyond the Arctic, changes in sea ice affect mid-latitude weather, and Arctic economic opportunities may re-shape commodities and transportation markets. Rising interest in the Arctic is also raising geopolitical tensions about the region. What happens next depends in large part on the choices made within and beyond the Arctic concerning global climate change and industrial policies and Arctic ecosystems and cultures. 相似文献
8.
W. Keith Taulbee Christopher T. Nietch Donald Brown Balaji Ramakrishnan M. Jackie Tompkins 《Journal of the American Water Resources Association》2009,45(4):907-927
Abstract: A stream mesocosm experiment was conducted to study the ecosystem‐wide effects of two replicated flow hydrograph treatments programmed in an attempt to compare a simulated predevelopment condition to the theoretical changes that new development brings, while accounting for engineering design criteria for urban stormwater management. Accordingly, the treatments (three replicates each) differed in base flow between events and in the rise to, fall from, and duration of peak flow during simulated storm hydrographs, which were triggered by real rain events occurring outside over a 96‐day period from summer to fall, 2005. Incident irradiance, initial substrate quality, and water quality were similar between treatments. Sampling was designed to study the interactions among the treatment flow dynamics, sediment transport processes, streambed nutrients, and biotic structure and function. What appeared most important to the overall structure and function of the mesocosm ecosystems beyond those changes resulting from natural seasonality were (1) the initial mass of fines that infiltrated into the gravel bed, which had a persistent effect on nitrogen biogeochemistry and (2) the subsequent fine sediment accumulation rate, which was unexpectedly similar between treatments, and affected the structure of the macroinvertebrate community equally as the experiment progressed. Invertebrate taxa preferring soft beds dominated when the gravel was comprised of 5‐10% fines. The dominant invertebrate algal grazer had vacated the channels when fines exceeded 15%, but this effect could not be separated from what appeared to be a seasonal decline in insect densities over the course of the study. Neither hydrograph treatment allowed for scour or other potential for flushing of fines. This demonstrated the potential importance of interactions between hydrology and fine sediment loading dynamics on stream ecosystems in the absence of flows that would act to mobilize gravel beds. 相似文献
9.
Rajiv Ganguly Brian M. Broderick Roland O’Donoghue 《Environmental Modeling and Assessment》2009,14(1):113-125
A comparative evaluation of two Gaussian-based line source models namely, California line source dispersion model version
4 and the general finite line source model, is presented. The concentrations predicted by these models are compared with background-corrected
ambient concentrations measured at three different distances from a motorway and performance of both models assessed in the
context of integrated transport–environment modelling for regulatory purposes. 相似文献
10.
The first national target for reducing road accident casualties in Great Britain was set in 1987, the target year being 2000. As the year 2000 approached, preparations were made for setting a subsequent target, the target year being 2010. A major part of the preparation consisted of forecasting the number of casualties that might be expected in 2010, conditional upon predictions about how the volume of road travel by the various transport modes might change and the type of new road safety measures that the Government might introduce. The forecasts provided the numerical context for the casualty reduction target that the Government announced in March 2000.This paper summarises the statistical analyses of accident data from 1983 to 1998 upon which the forecasts were based, and compares the approach with alternatives that have been adopted elsewhere. It also describes how progress towards the target has been monitored annually, allowing the Government to judge whether additional efforts might be needed to achieve the target. This examination of the actual data from 1999 to 2007 shows how far the original forecasts have proved to be successful.The improvement of car secondary safety over the past 15 years has probably been the development that has had the most significant effect on the national casualty total. A statistical model is used to quantify this effect by analysis of accident data, and the results of the most recent analyses are included. 相似文献