Ecosystem services and dis-services to agriculture

Agricultural ecosystems are actively managed by humans to optimize the provision of food, fiber, and fuel. These ecosystem services from agriculture, classified as provisioning services by the recent Millennium Ecosystem Assessment, depend in turn upon a web of supporting and regulating services as inputs to production (e.g., soil fertility and pollination). Agriculture also receives ecosystem dis-services that reduce productivity or increase production costs (e.g., herbivory and competition for water and nutrients by undesired species). The flows of these services and dis-services directly depend on how agricultural ecosystems are managed and upon the diversity, composition, and functioning of remaining natural ecosystems in the landscape. Managing agricultural landscapes to provide sufficient supporting and regulating ecosystem services and fewer dis-services will require research that is policy-relevant, multidisciplinary and collaborative. This paper focuses on how ecosystem services contribute to agricultural productivity and how ecosystem dis-services detract from it. We first describe the major services and dis-services as well as their key mediators. We then explore the importance of scale and economic externalities for the management of ecosystem service provision to agriculture. Finally, we discuss outstanding issues in regard to improving the management of ecosystem services and dis-services to agriculture.     

Industry and the Family: Two Engines of Growth

We generalize the class of endogenous growth models in which the scale of the economy has level rather than growth effects, and study the implications of different demographic and technological factors when both fertility choice and research effort are endogenous. The model incorporates two dimensions of technological progress: vertical (quality of goods) and horizontal (variety of goods). Both dimensions contribute to productivity growth but are driven by different processes and hence respond differently to changes in fundamentals. Specifically, while unbounded vertical progress is feasible, the scale of the economy limits the variety of goods. Incorporating a linearity in reproduction generates steady-state population growth and variety expansion. We thus have two engines of growth generating dynamics that we compare with observed changes in demographics, market structure, and patterns of growth. Numerical solutions yield the important insight that, while endogenous, fertility responds very little to industrial policies. Demographic shocks, in contrast, have substantial effects on growth.     

生育女性人力资本存量变动轨迹研究

由于生育行为可能带来人力资本存量贬损,故生育女性的人力资本存量变动轨迹不同于男性和不生育的女性。作为人力资本存量贬损的高发人群,生育女性应对贬损的研究迫在眉睫,该群体应对贬损的策略有防范型和补偿型两种。本文以人力资本承载者在经济生命周期内人力资本存量变动规律为基础,探讨了生育对女性人力资本存量的影响,描绘了伴随生育行为的不同人力资本市场进入选择下的人力资本存量变动轨迹,并提出了生育女性应对人力资本存量贬损的策略。     

艰难的抉择 深远的影响——关于中共中央《公开信》暨计划生育效果评估

为了控制人口过快增长,加速改变我国一穷二白的面貌,1980年中共中央发出《公开信》,号召一对夫妇只生一个孩子。在公开信指引下,我国计划生育取得了巨大成就,妇女终身生育率从6．2下降到1．8,少生了5．69亿人,减少了资源消耗,保护了生态环境,促进了经济发展。本文引用了人类发展指数和生育文化指数对各省、区、市妇女终身生育水平差别进行了解释;以印度1970年以来的总和生育率为参数,对没有生育政策的人口发展进行模拟,结果证明经济社会发展对生育率下降发挥了主要作用,贡献率为62％,而计划生育的贡献率为38％。从1991年开始,我国已进入低生育水平时期,随着我国经济社会进一步发展,生育率还将继续下降,人口发展正面临新的挑战。时代赋予了计划生育新的任务,本世纪要把我国生育率稳定在更替水平,才能为经济社会可持续发展提供良好的人口环境。     

当前农村青年的生育意愿：一项观念性的实证研究——以闽南山区B村为例

通过对闽南山区一个村庄的实地调查,对当地农村青年的生育目的、生育数量、性别偏好、生育质量作了分析,在此基础上讨论了农村青年生育意愿转变的对策。     

Mortality and Early Growth in England, France and Sweden

We set up a stochastic open‐economy growth model with endogenous fertility and mortality. A three‐country version of the model is calibrated to pre‐industrial mortality data from England, France and Sweden. By fitting parameters to match observed rates of correlation in mortality rates, the model can also account for differences in both the volatility of mortality rates and the timing of the Industrial Revolution.     

土地肥力递减规律与马克思土地肥力观的比较

土地肥力递减规律虽然是片面的，但也有其合理的一面，那就是发现了客观存在的土地肥力递减现象。在科学技术水平不变的情况下，土地肥力递减规律所描述的现象是可能变为事实的，我们不能因为土地肥力递减规律的片面性而否认土地肥力递减现象的存在。     

农村妇女孩子数量与质量偏好转化现状研究

利用 2 0 0 1年“中国农村妇女生育意愿与生育行为调查”河南省数据 ,既考证了现有的孩子数量与质量转变理论在河南农村地区的适用性 ,也为研究中国农村人口转变现状及其进程提供了实证依据。研究指出 ,妇女对孩子数量与质量偏好之间存在着显著的替代关系 ,这一关系总体上较为稳定、普遍和独立 ;被调查的农村地区人口转变已经具备了较为稳定的微观基础     

低生育稳定期：中国特色的人口转变阶段

从人口转变角度审视和分析当前中国人口发展的形势,提出中国的人口转变有一个独特的阶段,即低生育稳定期。分析了低生育稳定期的阶段性特征。这个时期问题复杂,趋向明朗,是主要矛盾转换期和生育政策调整期。还分析了这一时期中国人口发展战略目标的转换及相应的对策。     

“单独二孩”政策下新增人口测算方法及监测系统构建

"单独二孩"生育政策出台后,各地需要测算符合这一政策的潜在夫妇数、可能导致的新增出生人数、由此带来的生育水平变化,以及对未来人口发展的影响。测算的目的是为了更好地做好新政策正式实施前的准备,确保政策实施风险可控。结合2010年全国第六次人口普查数据和2013年8月国家卫生计生委组织的生育意愿抽样调查数据,提出了关于新增出生人口和新增生育水平的估计方法,以及相应的未来生育水平估计和人口预测方法。对如何构建政策实施监测系统提出了建议。