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Marine protected areas (MPAs) cover 3–7% of the world's ocean, and international organizations call for 30% coverage by 2030. Although numerous studies show that MPAs produce conservation benefits inside their borders, many MPAs are also justified on the grounds that they confer conservation benefits to the connected populations that span beyond their borders. A network of MPAs covering roughly 20% of the Channel Islands National Marine Sanctuary was established in 2003, with a goal of providing regional conservation and fishery benefits. We used a spatially explicit bioeconomic simulation model and a Bayesian difference-in-difference regression to examine the conditions under which MPAs can provide population-level conservation benefits inside and outside their borders and to assess evidence of those benefits in the Channel Islands. As of 2017, we estimated that biomass densities of targeted fin-fish had a median value 81% higher (90% credible interval: 23–148) inside the Channel Island MPAs than outside. However, we found no clear effect of these MPAs on mean total biomass densities at the population level: estimated median effect was –7% (90% credible interval: –31 to 23) from 2015 to 2017. Our simulation model showed that effect sizes of MPAs of <30% were likely to be difficult to detect (even when they were present); smaller effect sizes (which are likely to be common) were even harder to detect. Clearly, communicating expectations and uncertainties around MPAs is critical to ensuring that MPAs are effective. We provide a novel assessment of the population-level effects of a large MPA network across many different species of targeted fin-fish, and our results offer guidance for communities charged with monitoring and adapting MPAs.  相似文献   
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This paper describes an analytical solution for turning and milling stability that includes process damping effects. Comparisons between the new analytical solution, time-domain simulation, and experiment are provided. The velocity-dependent process damping model applied in the analysis relies on a single coefficient similar to the specific cutting force approach to modeling cutting force. The process damping coefficient is identified experimentally using a flexure-based machining setup for a selected tool-workpiece pair (carbide insert-AISI 1018 steel). The effects of tool wear and cutting edge relief angle are also evaluated. It is shown that a smaller relief angle or higher wear results in increased process damping and improved stability at low spindle speeds.  相似文献   
366.
Disturbance to ecosystems in parks and protected areas from nature-based tourism and recreation is increasing in scale and severity, as are the impacts of climate change—but there is limited research examining the degree to which these anthropogenic disturbances interact. In this perspective paper, we draw on the available literature to expose complex recreation and climate interactions that may alter ecosystems of high conservation value such that important species and processes no longer persist. Our emphasis is on ecosystems in high demand for tourism and recreation that also are increasingly experiencing stress from climate change. We discuss the importance of developing predictive models of direct and indirect effects, including threshold and legacy effects at different levels of biological organization. We present a conceptual model of these interactions to initiate a dialog among researchers and managers so that new research approaches and managerial frameworks are advanced to address this emerging issue.  相似文献   
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The international development community is off-track from meeting targets for alleviating global malnutrition. Meanwhile, there is growing consensus across scientific disciplines that fish plays a crucial role in food and nutrition security. However, this ‘fish as food’ perspective has yet to translate into policy and development funding priorities. We argue that the traditional framing of fish as a natural resource emphasizes economic development and biodiversity conservation objectives, whereas situating fish within a food systems perspective can lead to innovative policies and investments that promote nutrition-sensitive and socially equitable capture fisheries and aquaculture. This paper highlights four pillars of research needs and policy directions toward this end. Ultimately, recognizing and working to enhance the role of fish in alleviating hunger and malnutrition can provide an additional long-term development incentive, beyond revenue generation and biodiversity conservation, for governments, international development organizations, and society more broadly to invest in the sustainability of capture fisheries and aquaculture.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01451-4) contains supplementary material, which is available to authorized users.  相似文献   
368.
Fifty years have elapsed since the first publication of Ambio. Throughout this period, fundamental changes have occurred in societal attitudes to biodiversity conservation. Ambio has published numerous papers that have aligned with these new approaches. High citations numbers suggest that Ambio papers have had a significant impact on conservation strategies. We review these publications and find that they align well with changed societal perspectives on biodiversity. Ambio papers have called for greater contributions of local and indigenous peoples and for conservation in multi-functional landscapes. The 1992 Convention on Biological Diversity built on these principles. Negotiations are now underway for a post-2020 framework for biodiversity. Ambio papers have argued for a stronger scientific basis for conservation and for the need to adapt to changing conditions and to the rich diversity of societal preferences for conservation. International processes favor simple, generalizable approaches to conservation but we call for recognition of the diversity of ecological and human conditions in which conservation occurs. There is a need to build capacity to support a diversity of conservation approaches that are adapted to changing local conditions and to the priorities of diverse human societies.  相似文献   
369.
Research on human dimensions of ecosystems through the ecosystem services (ES) concept has proliferated over recent decades but has largely focused on monetary value of ecosystems while excluding other community-based values. We conducted 312 surveys of general community members and regional researchers and decision-makers (specialists) to understand local perceptions and values of watershed ES and natural resource management in South America’s southern Patagonian ecoregion. Results indicated that specialists shared many similar values of ES with community members, but at the same time their mentalities did not capture the diversity of values that existed within the broader community. The supporting services were most highly valued by both groups, but generally poorly understood by the community. Many services that are not easily captured in monetary terms, particularly cultural services, were highly valued by community members and specialists. Both groups perceived a lack of communication and access to basic scientific information in current management approaches and differed slightly in their perspective on potential threats to ES. We recommend that a community-based approach be integrated into the natural resource management framework that better embodies the diversity of values that exist in these communities, while enhancing the science-society dialog and thereby encouraging the application of multiple forms of ecological knowledge in place-based environmental management.  相似文献   
370.
A model is developed to enable estimation of chloramine demand in full scale drinking water supplies based on chemical and microbiological factors that affect chloramine decay rate via nonlinear regression analysis method. The model is based on organic character (specific ultraviolet absorbance (SUVA)) of the water samples and a laboratory measure of the microbiological (F m ) decay of chloramine. The applicability of the model for estimation of chloramine residual (and hence chloramine demand) was tested on several waters from different water treatment plants in Australia through statistical test analysis between the experimental and predicted data. Results showed that the model was able to simulate and estimate chloramine demand at various times in real drinking water systems. To elucidate the loss of chloramine over the wide variation of water quality used in this study, the model incorporates both the fast and slow chloramine decay pathways. The significance of estimated fast and slow decay rate constants as the kinetic parameters of the model for three water sources in Australia was discussed. It was found that with the same water source, the kinetic parameters remain the same. This modelling approach has the potential to be used by water treatment operators as a decision support tool in order to manage chloramine disinfection.  相似文献   
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