Changes in Human Population Structure: Implications for Biodiversity Conservation

Human population size and growth have been recognized as important factors affecting biodiversity, but the impacts of population structural changes on biodiversity are not clear. In this paper, we made the first attempt to link human population structural changes with implications for biodiversity, using Wolong Nature Reserve (south-western China) for the endangered giant panda as a case study. From 1982 to 1996, the labor force (20–59 years of age) in the reserve jumped by 59.76 percent, although the total population size increased by only 14.65 percent. During the same time period, the sex ratio (males:females) of small children (0–4 years of age) changed from 0.98∶1 to 1.20∶1, and the percentage of children receiving education beyond the elementary school level increased from 14.04 to 27.47. The increase in labor force and the number of male-biased children could have more negative impacts on the panda habitat, whereas improving school education could help more young people move out of the reserve by going to college and finding jobs elsewhere and thus reduce destruction to the panda habitat.     

人口增长和消费模式对海洋渔业资源影响的实证分析——以舟山为例

现有研究文献显示,人口增长和消费变化是影响海洋渔业资源变化的重要动因。以舟山为例,在建立构建人口、消费与海洋渔业资源相关关系的理论框架基础上,动态地分析舟山人口增长和消费模式转换是如何影响其海洋渔业资源的。实证研究表明:①由收入水平提高所引起的消费方式转换比人口规模更直接地影响海洋渔业资源的动态变化;②尽管捕捞量持续增加,但由于捕捞强度的迅速提高,单位捕捞努力渔获量在显著下降,预示着舟山渔场渔业资源的逐渐衰减;③影响海洋渔业资源变化的动因不仅包括人口增长和消费模式变化,同时还要考虑经济增长模式、市场价格、政策引导以及当地居民行为等因素。     

加强流动妇女计划生育服务的几点思考——根据《北京市昌平区妇女维权项目基线调查》①的分析

人口流动已成为我国现代化进程中的必然趋势,流动妇女尤其育龄妇女,长期以来是各级计划生育部门工作的重点方面。本文根据《北京市昌平区妇女维权项目基线调查》数据,分析了流动妇女在流入地已获得的计划生育服务状况．了解其计划生育,生殖健康方面的服务需求,深入思考了加强流动妇女计划生育服务工作所面临的四个问题．以期进一步完善流动人口管理服务体系。     

Population dynamics of a phytophagous lady-beetle,Epilachna vigintioctopunctata (Fabricius), living in spatio-temporally heterogeneous habitats. III. Effects of habitat structure on population dynamics

Temporal changes in the population size of a phytophagous lady-beetle were analyzed to identify mechanisms affecting lady-beetle population dynamics at different spatial scales. The study area (15 ha) included 18 habitat patches. The major host plants were potato for first generation larvae and eggplant for second generation larvae. The habitat patches were classified into three groups according to the major host plants in each patch: P-E patches (both host plants available), P patches (potato only), and E patches (eggplant only). The winter disappearance of adults in the whole study area, and larval mortality in E patches were apparently the most important factors disturbing the overall population density. Density-dependent movement of females appeared to have the greatest stabilizing effect on the yearly fluctuation of population density. Rate of increase of female adults from the first to the second generation,R, was generally higher on eggplants in E patches than in P-E patches because the adult density of the first generation was much higher in P-E patches. The yearly fluctuation of adult density in each generation tended to be less in patches with all habitat components necessary for the full life cycle (P-E patches). However, such patches were not favorable for first generation females, as indicated by the lower rate of increase from the first to the second generation. The density and stability of lady-beetle populations is discussed in relation to habitat structure.     

Women's autonomy,women's status and fertility-related behavior in Zimbabwe

Women's household decision-making autonomy is a potentially important but less studied indicator of women's ability to control their fertility. Using a DHS sample of 3,701 married black African women from Zimbabwe, I look at women who have no say in major purchases, whether they should work outside the home,and the number of children. When men dominated all household decisions, women were less likely to approve of contraceptive use, discuss their desired number of children with their spouse, report ever use of a modern method of contraception, and to intend to use contraception in the future. However, women's decision-making autonomy was not associated with current modern contraceptive use. Women who had no decision-making autonomy had 0.26 more children than women who had some autonomy. These autonomy measures provide additional independent explanatory power of fertility-related behavior net of traditional measures of women's status such as education and labor force participation.     

Population policy: Personal notes

Abstract These are the population years: throughout the world, in both developing and developed countries, there has been a growing debate on population policy. In this paper population policy refers to governmental actions that are designed to alter population events, or that do alter them. The concern with policy seems to center in the relationships between four demographic variables (size, rates, distribution, composition) and four 'quality of life' categories as both determinants and consequences (comprehended here as economic, political, ecological/environmental, social). As to policy means, they can be seen as being five in number (information, voluntary programmes, change in social institutions, incentives and disincentives, and coercion) with the potential of affecting the three factors of fertility, mortality, and migration. The relationships and effects of these conceptual cross tabulations are illustrated.     

Mortality risks,sequential decisions on births,and population growth

The population growth rates implied by parental attempts to be highly certain of having a surviving son for old-age support are investigated. At life expectancies of 40 to 65 years, family-planning “strategies” using contraception are found to imply markedly lower growth rates (1.01.5 percent vs. 2.5 percent) than are both commonly observed and also previously derived by Heer and Smith. In contrast to strategies relying only on sterilization, contraceptive spacing of births permits parents to buy time and information. In particular, they can postpone deciding whether to have another child until they see if their infant son will survive the earliest years of childhood. These results suggest that many less developed countries might achieve a substantial reduction in birth rates, provided that family-planning programs emphasized contraception as well as sterilization and effectively communicated the idea of spacing births. Factors bearing on the range of applicability of the old-age-security hypothesis, and any results and policies derived from it, are also briefly analyzed.     

The malleability of fertility-related attitudes and behavior in a filipino migrant sample

The malleability of fertility-related attitudes and behavior was studied by analyzing data collected from cross-sectional groups of Filipino migrants who had lived in the United States for varying lengths of time, in conjunction with data from a comparison group of Caucasians from the Filipinos’ neighborhoods. With increasing number of years lived in the United States, Filipino migrants’ fertility-related knowledge, attitudes, and desires became increasingly similar to those of the Caucasian group, but their contraceptive behavior did not. While approximately equal numbers of Filipinos and Caucasians were contracepting, Filipino couples regardless of duration of stay in the United States were using less effective methods with less regularity. Despite these contraceptive behavior patterns, Filipino migrants perceived that they would have 0.32 fewer children in the United States than they would have had had they remained in the Philippines. By far the most predominant reason given by Filipino respondents for changing fertility patterns in the United States was the difficulty of obtaining child care in the new environment.     

Convergence of a Discrete-Time Age-Structured Population Toward a Given Steady State Through Controlled Immigration

To explore the concept of stability in an age-structured population with migration, a Markov transition matrix model is built, where age classes can be of different length, and the time step is not necessarily equal to the length of the age class. The conditions under which a vector of the model has a steady population structure are identified, as well as those under which the age structure converges to a given steady state, through a series of decisions or controls of letting immigrants in or forbidding them entry into the country. The decisions are expressed as vectors of proportions of immigrants. In the steady state, when the increment of population is proportional to its size, the age- or stage-structure remains unchanged between transitions.     

Analyses of spatial patterns and population processes of clonal plants

The nonrandom spatial structure of terrestrial plants is formed by ecological interactions and reproduction with a limited dispersal range, and in turn this may strongly affect population dynamics and population genetics. The traditional method of modelling in population ecology is either to neglect spatial pattern (e.g. in transition matrix models) or to do straightforward computer simulation. We review here three analytical mothods to deal with plant populations in a lattice-structured habitat, which propagate both by seeds that scatter over the whole habitat and by vegetative reproduction (producing runners, rhizomes, etc.) to neighboring vacant sites. [1]Dynamics of global and local densities: Dynamical equations of population density considering nearest-neighbor correlation (spatial clumping) are developed as the joint dynamics of global average density and local density (comparable to mean crowding) based onpair approximation. If there is a linear trade-off between seed production and vegetative reproduction, the equilibrium abundance of the population may be maximized by engaging both means of reproduction. This result is accurately predicted by the pair approximation method, but not by mean-field approximation (neglect of spatial structure). [2]Cluster size distributions: Using global and local densities obtained by pair approximation, we predicted cluster size distribution, i.e. the number of clusters of occupied sites of various sizes. [3]Clonal identity probability decreasing with distance: Multi-locus measurement of allozymes or other neutral molecular markers tells us whether or not a given pair of individuals belong to the same clone. From the pattern of clonal identity probability decreasing with the distance between ramets, we can estimate the relative importance of two modes of reproduction: vegetative propagation and sexual seed production.     

Values and fertility change in Japan

This paper analyses how value change and economic and social change have jointly affected fertility in Japan since 1950, and especially since 1973 when fertility resumed declining after some 15 years at near-replacement level. The resumption of fertility decline since 1973 has been driven primarily by underlying economic and social changes. Value change has tended to lag behind fertility change, and this lag has tended to be larger in Japan than in other advanced nations, primarily because underlying economic and social conditions have evolved more rapidly in Japan, and because it takes time for values to adjust to changes in underlying conditions. Because of Japan's high degree of cultural homogeneity, values tend to be widely and quickly shared, so that under certain conditions value change tends to occur in spurts. In Japan, many of the more important value changes affecting fertility in recent decades are bound up with major educational and job gains by women, which have led to greater economic independence and more emphasis on values of individualism and equality between the sexes.     

Immigration,below-replacement fertility,and long-term national population trends

The long-term demographic effects of immigration on a population experiencing below-replacement fertility are studied by assuming that the size and age composition of the immigrant population do not change over time. The size of the first-generation immigrant population becomes stationary within a time period not greater than the human life span. Thereafter, the number dying equals the number entering over any given time interval. The stationarity of the native population, among which deaths exceed births, is maintained by the compensating number of births to the immigrant population. The limiting age distribution of the country's population, although stationary, may not decline monotonically with age and may look like a camel's back, with one or two humps.     

Ecological studies on a dragonfly,Nannophya pygmaea ramber (Odonata: Libellulidae) I. seasonal changes of adult population and its distribution in a habitat

Summary Adult population of a dragonflyNannophya pygmaea Ramber inhabited in a damp ground was investigated with mark-and-recapture method in 1975. The following results about the seasonal changes of the population size and distribution in the habitat were obtained. Adults emerged from late May to mid August. The number of the adults was most abundant in early June, but that of matured males in early July. From the recapture data, the estimate of daily survival rate was 0.82, and the length of immature stage in males was estimated as 5 days or so. Total number of post-teneral adults emerged in the habitat was estimated as about 9,000. The mean crowding-mean density regression method was applied for the analysis of the distribution pattern of the adults. Matured males showed a spaced-out distribution, while females and immatured males distributed themselves rather aggregatively. Such a distribution pattern of the matured male would be attributed to their territorial behaviour. The territorial behaviour was considered to force the matured males to extend the distribution area in July when they were most abundant. From the above-mentioned results and some observations, the meaning of the territoriality in this species was discussed.     

中国的离婚率与社会结构变化分析

从中国的离婚率与社会结构变化的时间序列分析中可以看出 :离婚率随非农产业人口比重的提高而提高 ,并有三年的时滞 ;离婚率也和人口城市化的发展有密切的关系 ,两者的比重一并提高 ,但约有五年的时滞。因这两方面社会结构的变化 ,直接影响妇女就业率提高和妇女职业结构的变化 ,而由此引起的人口迁移流动的大变动 ,也必然影响婚姻家庭观念的变化     

Small town growth in the United States: An analysis by size class and by place

Small town population change is an important factor in the urbanization process. We analyzed changes in incorporated places under 10,000 in the United States during the 1940-60 period, making a distinction between changes in population size classes and changes in places grouped by initial size. We made balance sheets for size classes under 1,000, 1,000-2,500, and 2,500-10,000 in order to divide the percent increase by size class into five additive components: (1)growth of places staying in the class, (2) net shifts of growing towns into and out of the class, (8) net shifts of declining towns into and out of the class, (4) addition of new places, and (5) disappearance of places during the time period. Separate tabulations were made by metropolitan location, region, and decade. p ]Places under 10,000 population the initial year grew during both census decades considered. Growth differentials paralleled those generally found for the total population, with the most rapid growth near large cities in the West and (except for non-metropolitan places) over the 1940-60 decade.We found results to be different for population changes of particular size classes. Except in some Urbanized Area locations, the two larger size classes increased in population over both decades. In contrast, the under-1,000 size class declined in almost every case. This decline was not due to decreasing population of places within the class or to the disappearance of places between censuses but rather to the growth of places into larger classes not compensated for by decline of other places into the class or new incorporations.     

Long-term dynamics of household size and their environmental implications

Little is known about the environmental implications of long-term historical trends in household size. This paper presents the first historical assessment of global shifts in average household size based on a variety of datasets covering the period 1600–2000. Findings reveal that developed nations reached a threshold in 1893 when average household size began to drop rapidly from approximately 5.0 to 2.5. A similar threshold was reached in developing nations in 1987. With the notable exceptions of Ireland, and England and Wales in the early 1800s, and India and the Seychelles in the late 1900s, the number of households grew faster than population size in every country and every time period. These findings suggest accommodating housing may continue to pose one of the greatest environmental challenges of the twenty-first century because the impacts of increased housing present a threat to sustainability even when population growth slows. Future research addressing environmental impacts of declining household size could use an adapted IPAT model, I = PHoG: where environmental impact (I) = population × personal goods (P) + households × household goods (HoG).     

Changes in household formation and composition in China since the mid-twentieth century

China has experienced great changes in household formation and composition since the mid-twentieth century, and its mean size of households has fallen from 54 persons in 1947 to 3.1 in 2005. Many of these changes, especially those taking place in the early years of the People’s Republic, have not been systematically investigated. This paper examines the impact of China’s major political, social, demographic and economic changes on household formation and composition. The study shows that changes in Chinese households have not followed a simple linear trajectory, but shown, considerable fluctuations. A drastic increase in the number of households and a sharp reduction in the mean size of households were recorded after the land reform in the early 1950s. In the next twenty years, high fertility was promoted by a generally pronatalist environment, and the mean size of households increased. Since the early 1970s, the nationwide family planning campaign has led to a rapid fertility decline and great chanes in kinship structure. The recent rise in rural-urban migration has also resulted in many unprecedented changes, and they have become major forces affecting household formation and family life in contemporary China.     

人口学界对“以人为本”思想的理解和研究

“以人为本”思想起源甚早,国内外许多领域的专家、学者以及实际工作者对这一思想都有过阐述和研究。从我国人口学的视角出发,结合三十多年以来我国计划生育政策的实践与发展,系统地总结了国内人口学界对“以人为本”思想的理解和研究。     

黑龙江省黑河市生育补偿机制构建研究

全面做好人口工作,切实提高计划生育家庭发展能力,是新形势下研究和化解社会矛盾的切入点之一,也是政府"关注民生、走近群众",贯彻落实科学发展观的具体实践。生育补偿机制是一项基本的公共政策和制度建设,对全面做好人口工作具有明显的促进作用,分析研究在实施过程中存在的问题,总结有价值的经验,会进一步促进生育补偿机制逐步完善,对维护社会公平和社会稳定,化解社会矛盾意义深远。     

Renewable resources and population growth: Past experiences and future prospects

The links between population growth, resource use, and environmental quality are too complex to permit straightforward generalizations about direct causal relationships. Rapid population growth, however, has increased the number of poor people in developing countries, thus contributing to the degradation of the environment and the renewable resources of land, water, and nonhuman species on which humans depend. Demands of the rich industrial countries have also generated environmental pressures and have been foremost in the consumption of the so-called nonrenewable resources: fossil fuels, metals, and minerals. On the other hand, population and economic growth have also stimulated technological and management changes that help supply and use resources more effectively. Wide variations in the possible ultimate size of world population and technological change make future interrelationships of population, resources, and the environment uncertain as well as complex. But those interrelationships are mediated largely by government policies. Responsible governments can bring about a sustainable balance in the population/resource/environment equation by adopting population and development policies that experience has shown could reduce future population numbers in developing countries below the additional five billion indicated in current United Nations medium projections, coupled with proven management programs in both developing and developed countries that could brake and reverse the depletion and degradation of natural resources.This article is adapted from: Robert Repetto, "Population, Resources, Environment; An Uncertain Future,"Population Bulletin, Vol. 42, No. 2 (Washington, D.C.: Population Reference Bureau, 1987).