Supply and demand: causes and consequences of assortative mating in common terns <Emphasis Type="Italic">Sterna hirundo</Emphasis>

Although assortative mating is widespread among long-lived monogamous birds, the underlying mechanisms still remain unclear in many species. In this study, we analysed assortative mating by age and body mass in the common tern Sterna hirundo with special regard to mate choice decisions of newly paired birds. To assess whether assortative mating by age is an active decision involving either homotypic or directional preferences or rather a passive process due to restricted availability of potential mates, we analysed the influence of age-dependent arrival date and cohort size. Furthermore, we looked for direct benefits in terms of reproductive success. Common terns mated assortatively by age and arrival date but not by body mass at arrival. Assortative mating by age was age dependent and was detected mainly in younger birds, whereas birds older than 8 years rather re-paired with younger ones. The availability of same-aged mates was restricted by cohort size and arrival date. We found no general evidence for better reproductive performance of same-aged pairs. Instead, relative reproductive success was related to own age and the relative age of mate: It should be advantageous for any bird to acquire an old mate; hence, assortative mating by age seems to be beneficial only for old terns but not for young ones. Age-assortative mating in common terns occurred by both passive and active processes, which are not mutually exclusive. Our results do not indicate a homotypic but a directional preference and support the theory that high-quality (older/experienced) individuals tend to mate assortatively if same-aged mates are available, which leaves low-quality (young/inexperienced) individuals to mate among themselves.     

环境保护投资制度探析

从环境保护投资本质的分析入手,对环境保护投资与经济发展的关系,环境保护投资制度的概念、及其在环境资源法中的地位、建立的意义作了初步探讨。     

Effects of threat management interactions on conservation priorities

Decisions need to be made about which biodiversity management actions are undertaken to mitigate threats and about where these actions are implemented. However, management actions can interact; that is, the cost, benefit, and feasibility of one action can change when another action is undertaken. There is little guidance on how to explicitly and efficiently prioritize management for multiple threats, including deciding where to act. Integrated management could focus on one management action to abate a dominant threat or on a strategy comprising multiple actions to abate multiple threats. Furthermore management could be undertaken at sites that are in close proximity to reduce costs. We used cost‐effectiveness analysis to prioritize investments in fire management, controlling invasive predators, and reducing grazing pressure in a bio‐diverse region of southeastern Queensland, Australia. We compared outcomes of 5 management approaches based on different assumptions about interactions and quantified how investment needed, benefits expected, and the locations prioritized for implementation differed when interactions were taken into account. Managing for interactions altered decisions about where to invest and in which actions to invest and had the potential to deliver increased investment efficiency. Differences in high priority locations and actions were greatest between the approaches when we made different assumptions about how management actions deliver benefits through threat abatement: either all threats must be managed to conserve species or only one management action may be required. Threatened species management that does not consider interactions between actions may result in misplaced investments or misguided expectations of the effort required to mitigate threats to species.     

投资激励视角下农产品供应链治理结构优化

本研究针对"公司+农户"型供应链面临的双边投资意愿不足的现实困境,论文尝试在不对称纳什谈判博弈和Stacklberg博弈的框架下,分析"公司+合作社+农户"型农产品供应链提升双边投资意愿的理论依据,从而为农产品供应链的治理结构优化提出政策建议。数理模型分析显示:1与"公司+农户"型供应链相比,"公司+合作社+农户"型供应链中的农户种植投资和公司销售投资的意愿均能得到提升。2"公司+合作社+农户"型供应链的农户利润水平与合作社谈判力正相关;当合作社具有相对较强的谈判力时,即使合作社规定的资本留存率较高,农户利润水平依然能够高于"公司+农户"型供应链。3当合作社谈判力在某一特定范围内时,公司与农户利润水平均能实现Pareto改进。4当考虑到公司和农户进行长期合作时,"公司+合作社+农户"型供应链中确保农户履约的保证金阈值显著低于"公司+农户"型供应链。最后,利用数值仿真分析了合作社谈判能力、资本留存率等因素对公司与农户利润水平的影响以及农户保证金阈值的变化。论文研究结果表明,由于农户和公司在"公司+合作社+农户"型供应链中的地位更为平等,合作社能够形成对于公司的制衡力量,这大大降低了农户进行种植投资后可能面临的"敲竹杠"风险,农户的种植投资意愿得到提升。当农户加大种植投资后,合格农产品产量将会提高,这反过来又会激励公司提升销售投资意愿来获得更多的利润。因此,我国未来农业产业化经营模式的制度创新必须以农民专业合作社的壮大为基础,大力发展"公司+合作社+农户"型供应链,这不仅有助于更好地保障农产品质量安全;也有助于让农户平等参与现代化进程,共同分享现代化成果。     

中国对外投资环保企业的机遇与挑战

本文总结分析了我国环保企业“走出去”国际化发展的机遇与挑战,并提出相关政策建议,以期为政府制订相关政策和参与“走出去”战略的企业提供决策参考。     

辽河流域污染防治PPP模式的适用性研究

辽河流域是我国水污染防治的重点流域,然而在投融资方面存在资金需求缺口大、筹措渠道单一,投资结构不合理等问题。故选择适宜的投融资模式是做好辽河流域污染防治工作的关键。在了解、分析辽河流域污染防治投融资现状的基础上,指出PPP模式具有拓宽资金来源,提高财政资金总体使用效率,拓展市场主体企业生存发展空间等优点,是解决辽河流域污染防治投融资问题的重要发展途径。结合PPP模式在辽河流域污染防治中的实际应用,提出了促进PPP在流域污染防治领域发展运用的具体建议。     

基于环保投资特征的广西环境保护问题研究

以2004年-2014年中国环境统计年鉴和广西年鉴数据为基础,分析了广西环保投资水平、规模、结构、增长速度等特征,并剖析广西环保投资存在的问题.结果表明,2004年-2014年广西环保投资规模呈增加趋势,占GDP的比例低于全国平均水平,存在环保投资不足、增速与GDP速度不匹配、投资结构不合理等问题.建议应完善环保投资机制,调整环保投资核算体系,优化环保投资结构以及建立多元机制提高环保投资效率,确保环保投资与社会经济发展水平相适应.     

河南省环境保护投资现状分析与对策建议研究

环境保护投资是国民经济和社会发展固定资产投资的重要组成部分,是表征一个国家(地区)环境保护力度的重要指标,环境保护投资的总量、来源、使用方向和使用效率等,在一定程度上反映了一个国家(地区)的环境状态,环境保护投资对预防和治理环境污染、改善生态环境质量状况具有重要意义.随着河南省经济的快速发展,环境污染问题日益突出,通过对河南省2005年-2014年期间环境保护的投资规模、投资比例、投资结构进行分析研究,发现河南省环保投资存在的问题,并提出合理化对策建议.     

关于我国环境保护投资的界定与思考

对比分析了国内外环保投资范围的界定原则,解析了环保投资的内涵,从环保投资的性质、目的和内涵等方面提出了环保投资的界定原则。研究表明,目前我国环保投资统计口径比较混乱,环保投资虚高,且投资结构不尽合理,资金使用效率不高,造成污染治理和生态恢复速度一直滞后于环境污染和生态破坏速度。建议明晰环保投资定位,优化投资结构,明确投资范围,统一统计口径,拓宽投资融资渠道,保障投资金额,加强投资监管,提高投资使用效率,解决现有环境问题。     

浅谈钢铁工业环保设施的“投资-运营”模式

论述了钢铁工业污染防治设施的"投资-运营"模式的发展概况,介绍了该模式的优越性以及实施方式,并从交易结构的角度分析了钢铁企业污染防治设施采用"投资-运营"模式可能会出现的风险以及规避方法。