Are network indices robust indicators of food web functioning? A Monte Carlo approach

Indices based on network theory are often used to describe food web functioning. These indices take as input food web flows that are estimated based on merging of (scarce) data with linear inverse methods (LIMs). Due to under sampling, most food webs are highly uncertain and can only be quantified within a specific uncertainty range. The linear inverse method (LIM) can estimate food web flows using a variety of techniques, e.g. the parsimonious or minimum norm (MN) solution, which selects one food web, based on a quadratic minimization technique or the Monte Carlo solution where a finitely many random solutions are generated which are then averaged. We use the Monte Carlo approach (MCA) to estimate the values of several indices from four published food webs, the Gulf of Riga for the autumn, summer and spring seasons, and the Takapoto atoll system. We first show that network indices are much better constrained than the uncertain food webs from which they are calculated. Therefore, even in the face of food web uncertainty, they are robust estimators of food web functioning. We then use the MCA-derived network indices to generate cumulative density functions for each index. These serve to compute the probabilities of the MN indices estimates being an extreme solution as compared to the median values. Our findings show that 82% of the MN solutions are smaller than the MCA solutions, and 63% of the network indices are significantly under-estimated.     

Dispersal, pair formation and social structure in gibbons (Hylobates lar)

We report observations on reproduction, natal dispersal, pair formation, and group structure based on longitudinal observations of several white-handed gibbon (Hylobates lar) groups spanning 18 years. Our observations are at odds with the traditional view that gibbons live in nuclear family groups consisting of a pair of adults and their offspring, and that parents exclude young from the family territory when they reach adult size. In the relatively dense Khao Yai study population, dispersing young usually obtain mates by replacing adults in existing territories, which creates non-nuclear families. Six subadults, five males and one female, matured and dispersed at an average age of 10 years, or about 2 years after reaching adult size. Average natal dispersal distance was 710 m, or between one and two territories away. At least two dispersing males replaced adults in neighboring groups. In one case, forcible displacement of the resident male resulted in a group which included a young juvenile presumably fathered by the previous male, two younger juveniles (probably brothers) from the new male's original group, and (later) offspring of the new pair. Social relations within this heterogeneous group remained harmonious: the adults groomed all the young and play occurred between all preadult members. In only two out of a total of seven cases of dispersal seen did two subadults pair and disperse into new territorial space. Nonreproducing subadults which delay dispersal may be tolerated by the adults provided that they contribute benefits to the adults or their offspring. Possible benefits include behaviors such as grooming, social play with juveniles, and support of the adult male in defending the territory. Delayed dispersal is probably advantageous in a saturated environment where there is no room for floaters, but subadults may also gain indirect fitness benefits by aiding siblings and other relatives. Received: 24 January 1997 / Accepted after revision: 12 January 1998     

Integrating Social Marketing into Sustainable Resource Management at Padre Island National Seashore: An Attitude-Based Segmentation Approach

High demand for outdoor recreation and increasing diversity in outdoor recreation participants have imposed a great challenge on the National Park Service (NPS), which is tasked with the mission to provide open access for quality outdoor recreation and maintain the ecological integrity of the park system. In addition to management practices of education and restrictions, building a sense of natural resource stewardship among visitors may also facilitate the NPS ability to react to this challenge. The purpose of our study is to suggest a segmentation approach that is built on the social marketing framework and aimed at influencing visitor behaviors to support conservation. Attitude toward natural resource management, an indicator of natural resource stewardship, is used as the basis for segmenting park visitors. This segmentation approach is examined based on a survey of 987 visitors to the Padre Island National Seashore (PAIS) in Texas in 2003. Results of the K-means cluster analysis identify three visitor segments: Conservation-Oriented, Development-Oriented, and Status Quo visitors. This segmentation solution is verified using respondents’ socio-demographic backgrounds, use patterns, experience preferences, and attitudes toward a proposed regulation. Suggestions are provided to better target the three visitor segments and facilitate a sense of natural resource stewardship among them.     

Economic valuation of damages originated by major accidents in port areas

Due to special features of ports – variety of activities: storage and loading/unloading of hazardous materials; circulation of ships, lorries and trains; proximity to urban zones; etc. – major accidents can be associated with severe damages. The cost of such accidents must be known to allow for compensation to people and companies. A procedure is presented to estimate the cost of damages suffered by people, equipment and environment. Criteria to assess the cost of damage to people – a controversial issue – are discussed, establishing a method to predict the number of people killed, injured and evacuated. Economic compensation is proposed. Environmental damages are also considered. These include potential damage to the atmosphere, soil, water and fauna. Estimates of the cost of the equipment and buildings affected by the accident are proposed. Finally, an assessment of the loss of profits due to activity breakdown and indirect costs is analysed. The methodology presented can easily be extended to general, inland process and storage sites.     

Efficient management of marine resources in conflict: An empirical study of marine sand mining, Korea

This article develops a dynamic model of efficient use of exhaustible marine sand resources in the context of marine mining externalities. The classical Hotelling extraction model is applied to sand mining in Ongjin, Korea and extended to include the estimated marginal external costs that mining imposes on marine fisheries. The socially efficient sand extraction plan is compared with the extraction paths suggested by scientific research. If marginal environmental costs are correctly estimated, the developed efficient extraction plan considering the resource rent may increase the social welfare and reduce the conflicts among the marine sand resource users. The empirical results are interpreted with an emphasis on guidelines for coastal resource management policy.     

Visitor perceptions of rural landscapes: a case study in the Peak District National Park, England

Maintaining national parks is an integral policy tool to conserve rare habitats. However, because national parks are funded by taxpayers, they must also serve the needs of the general public. Increasingly, and thanks to today's diverse society, there is evidence that this creates challenges for park managers who are pulled in two opposing directions: to conserve nature on the one hand and to meet different visitor expectations on the other. This tension was explored in the Peak District National Park, a rural landscape dominated by heather moorland and sheep farming in Northern England where research was conducted to determine how social class and ethnicity shaped perceptions of the park. Results uncovered that social class played a very strong role in shaping perceptions of this region with 'middle class' respondents reacting far more favourably to the park than people from more working class backgrounds. We observed ethnicity playing a similar role, though our results are less significantly different.     

Monitoring in adaptive co-management: Toward a learning based approach

The recognition of complexity and uncertainty in natural resource management has lead to the development of a wealth of conceptual frameworks aimed at integrated assessment and complex systems monitoring. Relatively less attention has however been given to methodological approaches that might facilitate learning as part of the monitoring process. This paper reviews the monitoring literature relevant to adaptive co-management, with a focus on the synergies between existing monitoring frameworks, collaborative monitoring approaches and social learning. The paper discusses the role of monitoring in environmental management in general, and the challenges posed by scale and complexity when monitoring in adaptive co-management. Existing conceptual frameworks for monitoring relevant to adaptive co-management are reviewed, as are lessons from experiences with collaborative monitoring. The paper concludes by offering a methodological approach to monitoring that actively seeks to engender reflexive learning as a means to deal with uncertainty in natural resource management.     

水资源项目治理的社会网络动态分析

水资源项目治理中的利益相关方之间相互作用而形成关系网络,这种网络结构会随着项目生命周期发生变化,目前基于单阶段静态网络的研究难以满足这种动态治理角色网络分析的需要。科学合理的分析项目治理社会网络的动态变化,引导其健康发展对提高利益相关方之间的合作水平,进而提高项目成功率意义重大。本文以某大型水资源信息系统项目为例,综合应用社会网络分析与系统动力学方法,分析水资源项目治理社会网络的动态变化过程,构建系统动力学模型,对大型水资源项目系统结构进行仿真模拟,通过敏感性分析,探索控制项目治理风险的有效途径。     

Optimizing Bankfull Discharge and Hydraulic Geometry Relations for Streams in New York State1

Mulvihill, Christiane I. and Barry P. Baldigo, 2012. Optimizing Bankfull Discharge and Hydraulic Geometry Relations for Streams in New York State. Journal of the American Water Resources Association (JAWRA) 48(3): 449-463. DOI: 10.1111/j.1752-1688.2011.00623.x Abstract: This study analyzes how various data stratification schemes can be used to optimize the accuracy and utility of regional hydraulic geometry (HG) models of bankfull discharge, width, depth, and cross-sectional area for streams in New York. Topographic surveys and discharge records from 281 cross sections at 82 gaging stations with drainage areas of 0.52-396 square miles were used to create log-log regressions of region-based relations between bankfull HG metrics and drainage area. The success with which regional models distinguished unique bankfull discharge and HG patterns was assessed by comparing each regional model to those for all other regions and a pooled statewide model. Gages were also stratified (grouped) by mean annual runoff (MAR), Rosgen stream type, and water-surface slope to test if these models were better predictors of HG to drainage area relations. Bankfull discharge models for Regions 4 and 7 were outside the 95% confidence interval bands of the statewide model, and bankfull width, depth, and cross-sectional area models for Region 3 differed significantly (p < 0.05) from those of other regions. This study found that statewide relations between drainage area and HG were strongest when data were stratified by hydrologic region, but that co-variable models could yield more accurate HG estimates in some local regional curve applications.