Spatial policy and the behavior of fishermen     

Branka Valcic 《Marine Policy》2009

Fishery policy makers would often benefit from information on how a policy might change fishermen behavior before the policy is implemented. This paper contributes to the literature by comparing simulated behavioral response with actual response to a spatial policy using a discrete choice model of fishing location choice. The results point to the inherent problem of the simulation's inability to capture the fundamental change in the nature of the choice problem that occurs with the change in policy. Addressing this problem will be important as these models continue to be used to inform policy makers.  相似文献   

具有不同到达率的带有启动时间及不耐烦策略的多级适应性休假M^X/G/1排队     

王莉  朱翼隽 《成都信息工程学院学报》2008,23(6):704-710

研究了具有不同到达率的带有启动时间及不耐烦策略的多级适应性休假M^X/G/1排队模型,通过嵌入马尔可夫链方法推导出稳态队长的母函数、等待时间的LST（先到先服务规则）,并验证了稳态队长和稳态等待时间具有随机分解性,而且给出了忙期、全忙期及在线期均值。  相似文献   

基于贝叶斯网络的海洋生态环境状况评价——以山东省为例     

杨湘艳  余静 《海洋通报》2021,40(4)

在海洋开发利用活动日益增多,海洋环境保护压力日益增大的背景下,进行海洋生态环境状况科学评价方法的研究可以为开展海洋生态环境监测评估与海洋生态环境保护政策制定提供科学依据,促进改善海洋生态环境状况。本文首先基于贝叶斯网络基本理论,构建了海洋生态环境状况贝叶斯网络评价模型;再以山东省为例,充分融合专家经验知识与客观数据,从定性与定量两个角度评价了2013—2019年山东省近海生态环境状况,分析了各评价指标间关系及其对近海生态环境状况的影响程度。评价结果表明2013—2019年山东省近海生态环境状况保持一般状态,海洋环境质量与海洋生态灾害类指标对评价结果影响最大,山东省海洋环境保护工作初见成效。研究结果表明该评价模型能有效评价海洋生态环境状况,分析结果对于环境保护政策制定具有一定的借鉴意义。  相似文献   

早上新世非洲季风与地中海表层生产力变化的岁差节律   总被引：1，自引：0，他引：1  

黄恩清  田军 《地球科学》2007,32(3):313-321

地质历史上留下了许多反映非洲季风的记录, 意大利南方晚新生代的海相地层便是其中著名的一例.Cape Sper-tivento剖面位于意大利卡拉布里亚半岛, 属于早上新世(5.3~4.8Ma) 地中海泥灰岩-灰岩沉积物.在借鉴前人工作的基础上, 重新为该剖面建立一个精度更高的天文年代标尺.反映古生产力的指标显示, 早上新世在北半球夏季辐射量增大期间, 地中海有机碳含量及其堆积速率增大, C/N出现高值, 碳酸盐含量及其堆积速率减小, G. obliquus稳定氧碳同位素出现负偏移, 这是非洲夏季风带来的降雨增强的结果.尼罗河泛滥让更多陆源营养物和淡水输入地中海.各个古环境指标的频谱分析结果存在强烈的岁差周期和丰富的半岁差周期, 说明早上新世非洲季风主要受低纬过程控制.   相似文献   

从政策视角探讨我国地理信息标准化问题   总被引：1，自引：0，他引：1  

蒋景瞳  刘若梅  姜作勤  曾澜  陈倬 《地理信息世界》2007,5(6):18-21

分析了发达国家标准化相关政策特点,概括介绍了我国现有标准化法律法规,归纳了我国地理信息标准化的主要成就,并从政策视角侧重分析我国地理信息国家标准、行业标准和标准体系研制3方面存在的问题。认为需要加强对标准化法律法规的实施力度,并研究提出进一步促进我国地理信息产业发展的标准化相关政策建议。  相似文献   

基础地理信息的保密政策问题   总被引：1，自引：0，他引：1  

张清浦  苏山舞  赵荣 《地理信息世界》2007,5(6):15-17

首先讨论了基础地理信息及基础地理信息保密政策的基本概念,进而通过对国外地理信息安全保密政策的研究,提出了六点分析结论;随后,对我国现行基础地理信息保密规定现状及存在的主要问题进行了分析,最后提出了完善我国基础地理信息保密政策的具体建议。  相似文献   

Gene flow and demographic history of the mangrove crab Neosarmatium meinerti: A case study from the western Indian Ocean     

Lapo Ragionieri  Stefano Cannicci  Christoph D. Schubart  Sara Fratini 《Estuarine, Coastal and Shelf Science》2010

Most marine organisms are characterized by at least one planktonic phase during their life history, potentially allowing interconnection of populations separated by several hundred kilometers. For many years, the idea that marine species are genetically homogenous throughout their range of distribution, due to passive larval transport, has been a paradigm. Nowadays, a growing number of studies underline the existence of boundaries in the marine realm and highlight how larval dispersal is a complex process depending on biotic as well as abiotic factors. Marine fragmented habitats, such as atolls, mangroves and estuaries, are optimal systems for investigating the marine dispersion process under a metapopulation approach, since populations can be geographically defined a priori as opposed to those occupying open marine environments. Within this frame, the present paper investigates the population genetic structure and the demographic history of the mangrove crab Neosarmatium meinerti within the western Indian Ocean by partial sequences of the mitochondrial DNA cytochrome oxidase subunit I. A total of 167 specimens were sampled from six mangrove sites distributed along the East African coast, from Kenya to South Africa, also including a mangrove forest located on Mahé Island, Seychelles. A sharp genetic break between the mainland and the Seychelles is recorded, revealing the existence of two historically distinct groups that can be defined as independent evolutionary units. Gene flow along the East African coast appears to be high enough to form a single metapopulation, probably by means of stepping stone populations. Otherwise, this mainland metapopulation is currently under expansion through a gradual moving front from the subtropical toward the equatorial populations.  相似文献   

我国资源利用现状及节约机制框架的构建   总被引：1，自引：0，他引：1  

苑韶峰 《地域研究与开发》2007,26(1):50-53

对于资源的态度无非"开源"、"节流"2种,"开源"由于其较高的成本和有限性使得"节流"逐渐受到人们的重视.资源的可持续性是一个长期困扰人类的全球性问题,尤其对我国这样的人多地少、资源匮乏的国度而言,更是关系到生存与发展的迫在眉睫的问题.在分析了我国能源、水、土地、矿产等资源利用特点及供求矛盾的基础上,提出了对我国建设资源节约型社会的关键是有效地激励与约束机制的观点,并且构建了从法律法规、政策、经济、监督等角度建立约束机制,从产权、经济和声誉的角度建立激励机制的思路.  相似文献   

Extreme events as drivers of early human behaviour in Africa? The case for variability,not catastrophic drought     

David S. G. Thomas  Sallie L. Burrough  Adrian G. Parker 《第四纪科学杂志》2012,27(1):7-12

Extreme Late Quaternary climatic events, sometimes of considerable continental extent, are being proposed as major contributors to ancestral human behaviour, particularly migration, in Africa. Most recently, a catastrophic drought in the Afro‐Asian monsoon region has been proposed for 16 000–17 000 years ago, driven by global impacts of the Heinrich event 1 (H1), with potentially significant consequences for Palaeolithic cultures. We provide a new analysis of the assertion and find, on examination of a wide set of palaeoenvironmental records, that the scale and extent of the proposed drought is not supported. While some parts of the African tropics, close to the equator, do appear dry at this time, data for the tropics as a whole suggest markedly variable terrestrial conditions, with some environmental systems experiencing very positive hydrological excursions during H1. We contend that in the quest for evidence of climate drivers of ancestral human behaviour, the variability associated with spatially and temporally complex climatic conditions is a significant factor in itself. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Perceptions and responses to climate policy risks among California farmers     

Meredith T. Niles  Mark Lubell  Van R. Haden 《Global Environmental Change》2013,23(6):1752-1760

This paper considers how farmers perceive and respond to climate change policy risks, and suggests that understanding these risk responses is as important as understanding responses to biophysical climate change impacts. Based on a survey of 162 farmers in California, we test three hypotheses regarding climate policy risk: (1) that perceived climate change risks will have a direct impact on farmer's responses to climate policy risks, (2) that previous climate change experiences will influence farmer's climate change perceptions and climate policy risk responses, and (3) that past experiences with environmental policies will more strongly affect a farmer's climate change beliefs, risks, and climate policy risk responses. Using a structural equation model we find support for all three hypotheses and furthermore show that farmers’ negative past policy experiences do not make them less likely to respond to climate policy risks through participation in a government incentive program. We discuss how future research and climate policies can be structured to garner greater agricultural participation. This work highlights that understanding climate policy risk responses and other social, economic and policy perspectives is a vital component of understanding climate change beliefs, risks and behaviors and should be more thoroughly considered in future work.  相似文献