中国西北地区人口增长对土地退化的驱动作用分析

文章通过定性定量分析西北地区人口增长与粮食生产系统和土地压力响应之间的相关关系,发现人口的增长主要与耕地面积的扩展有较强相关性,与单位粮食亩产增加等变量指标的关系较弱。进一步分析发现,即便是在人口增长与耕地扩大的关系中,实际的耕地增长和粮食需求也远远大于实际人口增长的需求,由此可以看到在西北地区粮食生产和耕地面积扩大的过程中,人口增长并不如人们一般认为的那样大,人口增长对土地退化只能承担一部分责任,不构成最重要的原因。     

Projected consumption patterns for a stationary population

Abstract Recently economists have demonstrated a renewed interest in the population problems of a mature society. This revival of interest has been sparked by the general recognition of the relationship between population growth and environmental problems and has led to general acceptance of the proposition that ' ... a zero rate of population growth is the only equilibrium rate that can be sustained'.(1) Consequently the literature produced during the discipline's last period of similar concern, a period running from the late 1920's through the 1940's, needs re-examination. At that time economists were primarily occupied with the implications of a declining rate of population growth and most anticipated the arrival of a stationary population within the foreseeable future. For most of the economists of this earlier period the onset of a stationary or declining population was fraught with dangers for mature capitalism.     

The population of British Borneo

The population of British Borneo is small. Population growth since 1900 has been unspectacular but has been aided by Chinese immigration beginning from the middle of the 19th century until 1939, and also by the immigration of the Javanese and other peoples from the surrounding islands during the same period. The Chinese form by far the majority of the immigrant population and are important not only in terms of the numbers involved but also in terms of the powerful economic position assumed by them.

Besides affecting population growth, immigration has also had significant effects on the population composition and also on the birth rates, death rates and sex ratio. The significant fact about the population composition is that the number of Chinese is very large. It is not often realised that, though forming the second largest group in each of the three territories, the Chinese together form the largest single ethnic group in British Borneo.

The differential rates of growth in the various districts, owing largely to the presence or absence of immigrant populations and to the degree of economic development, have produced a very uneven distribution of population, with a very definite centering of peoples in certain areas. The coastal concentration of the immigrant peoples is another outstanding feature, a fact due as much to Borneo's position as it is to the easy entry by sea and difficult land access. These coastal pockets reflect broadly the former points of entry of the peoples, but such population centres are not necessarily stable since there was incomplete knowledge of the country during the period when immigrants were coming in, and the richer lands of the east coast were still undiscovered. It is clear that there will be further shifts of population centres when the advantages of the country are fully known. However, it is more important in this multi-racial society, that the ethnic types converging upon Borneo have been of separate groups and their movement has extended over different lengths of time, with the result that the country's ethnic map shows different degrees of their absorption into the Bornean setting. Absorption has been going on in some instances, but in view of the wide differences in economic status between immigrant and indigene, the fusion of the different groups is difficult.     

Soil Nutrient Depletion and Population Growth in Sub-Saharan Africa: A Malthusian Nexus?

Soil nutrient mining and other forms of soil degradation threaten future soil productivity, especially in sub-Saharan Africa (SSA). Data from 36 countries in SSA show a significant relationship at the supra-national level between soil nutrient depletion (including erosion), reduced fallow periods, and population pressure and thus illustrate the unsustainable population-agriculture-environment nexus on the continent which so far has been described in case studies only. It appears that Malthusian mechanisms are at work, despite encouraging indications of farmers' concerns and adaptation to changing conditions. It is agreed that a re-examination of the common land degradation assessments and farmers' response to changing conditions would be useful, however, this should not delay other recommended interventions.     

环境退化地区家庭人口对土地利用的影响研究——以中国西北毛乌素沙地为例

微观层面模型对于区分不同的人口群体以更好地明确环境退化的责任主体及其原因具有重要价值,对不同的土地利用方式进行经济区分是联接家庭人口特征与土地覆盖结果的重要手段。基于扩展的恰亚诺夫理论框架,文章利用2007—2008年两次调查所获293个农户样本数据,采用OLS和logit多变量模型实证分析毛乌素沙地家庭人口和其他因素对土地利用的影响。研究结果表明:(1)家庭人口因素对毛乌素沙地农户的土地利用产生重要影响;(2)毛乌素沙地主要土地利用的环境影响也遵循家庭生命周期的过程;(3)毛乌素沙地农户在减少有助于土壤修复利用活动的同时面临上升的退化风险。     

A Quantitative Investigation of the Population-Land Inequality-Land Clearance Nexus

This paper provides a quantitative investigation of the population-land inequality-land clearance nexus. Drawing on the literature on farmer optimization behaviour, the study formalizes and empirically tests a model of population-induced agricultural land clearance. The model makes several assumptions about this process: (a) The rate at which agricultural land is brought into production due to rising population pressures accelerates with the level of inequality in access to land, (b) Egalitarian systems have a greater capacity to absorb rising numbers of people per unit of land area and, thus, will have lower rates of agricultural land clearance than higher ones and (c) Irrespective of its degree of egalitarianism, the capacity of any system to hold people in one place will eventually break down once a critical population threshold is reached. Due to their lower population absorptive capacity, this level will be reached sooner under unequal systems of land distribution. Thus, the model also hypothesizes that the stimulatory impact of population growth on the demand for new land will exhibit a non-linear threshold pattern. For the farmer, the decision to clear a new plot of land will reflect these population-inequality interactions: Earnings from farming in settled areas will tend to fall as population densities and inequality in access to land increase. Time series results confirm that rural population growth is a significant factor driving agricultural land clearance in many of the 59 developing countries of our sample. Results also suggest that this rate of clearance is largest in countries with highly inegalitarian patterns of distribution. In contrast, cross-sectional regression results do not suggest any direct role for land inequality in population-agricultural land use outcomes. Contrary to the models assumption that this relationship should follow a non-linear threshold pattern, cross-sectional results also find no evidence that the absorptive capacity of highly densely populated land systems has been reached on average. However, they do provide support for an indirect linear relationship: Population induced agricultural land clearance is significantly magnified as inequality in access to land increases. Drawing on the empirics of the growth-inequality literature, the study suggests that this magnifying role may be linked to inequalitys impact on the assets of the poor. That is, by undermining the capacity of the rural poor to make productive investments in the land base, inequality in land distribution mediates population pressures in a way that affects both the quality and quantity of assets available to the poor to raise incomes, invest in skills accumulation, and spur demand in the rural economy as a whole.     

Areal Interpolation of Population Counts Using Pre-classified Land Cover Data

The need to combine spatial data representing sociodemographic information across incompatible spatial units is a common problem for demographers. A particular concern is computing small area trends when aggregation zone boundaries change during the trend interval. To that end, this study provides an example of dasymetric areal interpolation using the pre-classified land cover data available through the US Geological Survey’s National Land Cover Dataset (NLCD) program. Areal interpolation of population estimates is preferable to traditional reaggregation techniques, and the use of land cover data as a weighting factor in interpolated estimation has been shown in earlier studies to be highly accurate. In this study, the NLCD data set performs well and, because it requires no classification, it compares favorably with other land cover data sets for areal interpolation when considered on the basis of accuracy, precision and ease of use.     

Frank Fetter on Population Versus Prosperity

How population change affects human welfare was a central concern of economists during the decades that followed publication of Malthus's Essay. But from the middle of the nineteenth century, continuing for some one hundred years, population issues played a marginal role in economics, with leading figures of that discipline, particularly in the New World, turning their attention to the topic only episodically. The presidential address delivered by Frank Fetter to the American Economic Association in 1913 is a notable example of such attention. Frank Albert Fetter (1863–1949), much of whose career was spent as professor on the faculty of Princeton University, was a prominent economic theorist of the early decades of the twentieth century and author, among numerous other works, of the influential texts Principles of Economics (1904) and its two-volume successors, Economic Principles (1915) and Modern Economic Problems (1916 and 1922). Population was an early interest of Fetter's, as is shown by the topic of his doctoral dissertation, which he wrote, after studies at Indiana University, Cornell, and the Sorbonne, at the University of Halle (Versuch einer Bevölkerungslehre ausgehend von einer Kritik des Malthus'schen Bevölkerungsprincips, Jena: G. Fischer, 1894). His address to the AEA recalls that interest, looking back on the decade ending in 1910, a period of rapid population increase in the United States, fueled by heavy immigration. In the first part of the address, Fetter offers insightful comments on Malthus's novel humanitarian and democratic formulation of the population problem and on the contrasting demographic situation between Europe and the United States. But with the closing of the land frontier he sees American exceptionalism coming to an end, as the economic forces—abundant natural resources and progress in science and the “technical arts”—that heretofore counteracted the depressing effect of population growth on wages “have spent themselves.” At a time when the US population was about one-third of its present size, he argued that “we have passed the point of diminishing returns in the relation of our population to our resources.” Therefore “it is high time to revise the optimistic American doctrine of population.” To control “the fate and fortunes of the children of this and future generations,” the US would need a policy of conserving natural resources and retarding the increase of population. Of the two components of population growth—natural increase and immigration—only the latter is “controllable in large measure by legislative action.” Fetter thus devotes the second part of his address to a discussion of the effects of immigration on the American economy. His line of argument closely parallels an influential strand in the contemporary US debate on that issue. In the first decade of the century, the population of the United States grew by some 16 million and the number of immigrants was nearly 9 million. Fetter sees the potential for further immigration as nearly limitless, given an open-door policy. The motive to migrate to the United States would not cease “until real wages in America are leveled down to those of the most impoverished populations permitted to enter our ports.” Yet reducing American prosperity would afford “no permanent relief to the overcrowded lands,” as “natural increase quickly fills the ranks of an impoverished peasantry.” While unrestricted immigration is against the interest of the mass of the people, conflicting interests, ideas, and sentiments paralyze remedial action: individual or class advantage comes before consideration of the “larger national welfare.” Unless immigration is restricted, Americans may find “that they have bartered the peace and security of their children for the pleasures of a brief season.” The text of Fetter's address is reproduced below in full from American Economic Review, vol. 3, no. 1: Papers and Proceedings of the Twenty-fifth Annual Meeting of the American Economic Association, March 1913.     

Differences in egg wastage by superparasitism, contrastingVenturia (=Nemeritis) canescens searching singly versus searching in groups

Summary A statistical and graphic study is presented of the wastage of eggs byVenturia (=Nemeritis) canescens when searching singly and in groups of 10 among hosts at four different host densities in laboratory universes as described byHuffaker andMatsumoto (preceding paper of this journal). The host insect was the fluour mothAnagasta kühniella and the host densities used were 10, 30, 100 and 200 per universe. Intensity of egg wastage due to superparasitim varied significantly according to host density, and between the two parasite densities employed, 1 and 10, using bothF-tests and chi-square tests. Plots ofk-factor analysis on this egg wastage showed high negative correlations with host density, and the raw data for single parasites was well represented by a parabola while that for the grouped parasites departed from this relationship only at the lowest host density. These studies were conducted as a part of a general investigation into the processes operating in the population dynamics of arthropods under grants from the National Institutes of Health, U. S. Public Health Service (#A10-1611), and the National Science Foundation and Environmental Protection Agency (NSF DEB7504223) to the University of California. The findings, opinions and recommendations expressed herein are those of the authors and not necessarily those of the University of California, the National Institutes of Health, the National Science Foundation or the Environmental Protection Agency.     

Institutional impediments to population policy in Australia

Despite being near the top of the OECD league in rate of population growth, Australia does not have any explicit population policy. The potential constituent parts of one, particularly on immigration, family and environment, are firmly enmeshed in separate political domains and responsive to separate clusters of interests. Vague, demographically ill-informed, and mutually inconsistent views of a desired population size or trajectory for Australia co-exist, with no arena for systematic engagement and considered debate among them. Australia is not alone in this respect: instructive parallels can be drawn from Canada and the United States. Indeed, population policy may well be one of the issues that modern liberal democracies find peculiarly difficult to deal with. However, there are also specific historical circumstances that led to this outcome, and that perpetuate it. Revised version of a paper presented at the Seventh National Conference of the Australian Population Association, held in Canberra in September 1994.     

Computing a population budget from sequentially sacrificed, replicated cultures

Summary When a population budget must be obtained from censuses based on replicated, sacrificed cultures, it is difficult to obtain estimates of transition probabilities and of the errors of such estimates, because there is no logical basis for pairing successive census counts. In a study of this nature estimating a population budget of immature stages of the housefly, the problem was solved by a randomization treatment of the original census results obtained at two densities. One hundred randomly generated census matrices over all census times for each density were smoothed to remove the effects of sampling error and a population budget constructed according to defined rules. Transition probabilities computed from the population budget were plotted on triangular coordinate paper and mean probabilities, 95% confidence regions for these means, and 95% equal frequency ellipses computed. All computations and the graphing of the results were carried out on a digital computer. The computer program, available from the authors, is written in FORTRAN IV and could be easily modified for similar studies. Contribution No. 1364 from the Department of Entomology, The University of Kansas. This study has been supported by the Medical Research and Development Command of the Office of the Surgeon General of the Army under contract No. DA-49-007-MD-738, U.S.A. and by a Public Health research career program award (No. 3-K3-GM-22, 021-01S1) from the National Institute of General Medical Sciences, U.S.A. to RobertR. Sokal. It was carried out during the tenure of a National Science Foundation predoctoral fellowship by EdwinH. Bryant. The authors appreciate the help of Dr.F.J. Rohlf with computational aspects.     

J. R. Hicks on the Economics of Population

Sir John Hicks (1904–89), professor of political economy at Oxford University from 1952 to 1965, was one of the foremost economists of his time, making notable contributions to the theory of wages, general equilibrium theory, and welfare economics. He received (jointly with Kenneth Arrow) the 1972 Nobel prize in economics. Value and Capital (1939), his best-known book, is held as a classic; his 1937 exegesis of Keynes's General Theory has long been a staple of undergraduate economics. Population does not figure appreciably in his writings, although an almost offhand footnote attached to the concluding paragraph of Value and Capital suggests that it could have: “[0]ne cannot repress the thought that perhaps the whole Industrial Revolution of the last two hundred years has been nothing else but a vast secular boom, largely induced by the unparalleled rise in population.” (He added: “If this is so, it would help to explain why, as the wisest hold, it has been such a disappointing episode in human history.”) In his late work, A Theory of Economic History (1969), however, the principal driving force in economic development is depicted as the expansion of markets. A sustained discussion of the topic of population by Hicks is contained in one of his earlier books. The Social Framework: An Introduction to Economics (Oxford University Press, 1942). Chapters 4 and 5 of this book treat “Population and Its History” and “The Economics of Population”; one of the appendixes is “On the Idea of an Optimum Population.” Chapter 5 and this appendix are reprinted below. The Social Framework was written as an introductory text, although its lucid style characterized all of Hicks's work. It covered both theory and applications with particular attention to the then novel subject of national accounting. Hicks described the book as “economic anatomy” in contrast to the “economic physiology” of how the economy works. Chapter 5 gives equal attention to under- and overpopulation, both seen as posing dangers. The Preface to the 1971 (fourth) edition of The Social Framework notes that the population and labor force chapters “have been rather substantially altered—to take account of the curious things that have happened in these fields (which one might have expected to be slow moving).” In 1971 he is more cautious than in 1942 about suggesting that slowing population growth might have been a factor in the 1930s depression, and readier to admit of countries where “a continuing rise in population, even while there is some continuing agricultural improvement, is likely to lead in the end to unemployment and destitution.” The appendix on optimum population was retained through all editions.     

Population Scenarios Based on Probabilistic Projections: An Application for the Millennium Ecosystem Assessment

Probabilistic population forecasts offer a number of advantages to users. However, in some cases population is one component of a larger analysis that may take a different approach to uncertainty. For example, integrated assessments of environmental issues such as climate change or ecosystem degradation have typically used a small number of alternative scenarios to explore uncertainty in future environmental outcomes. In such cases, population projections that are provided only as probability distributions are difficult to use. I present a method of employing probabilistic population projections to derive individual, deterministic projections that can be used within scenarios for integrated assessments. The principal advantages of this approach are that (1) it provides a less ad hoc way of defining deterministic projections intended to be consistent with more comprehensive scenarios that describe, among other things, future socio-economic developments; (2) it provides more flexibility in specifying input assumptions for deterministic projections as compared to choosing off-the-shelf projections, allowing population assumptions to be tailored to the scenario; and (3) it provides a quantitative assessment of the uncertainty associated with any given deterministic projection. I describe the application of the method to the development of population projections used in integrated scenarios for the Millennium Ecosystem Assessment, an international scientific effort to assess the current conditions of and future outlook for global ecosystem goods and services. Results show that the MA scenarios are each consistent with a relatively wide range of demographic outcomes. For some scenarios, ranges of plausible outcomes in some regions overlap substantially, indicating that particular population projections could be consistent with more than one scenario. In other cases, uncertainty ranges for different scenarios are distinct, indicating that a projection consistent with one scenario is unlikely to be also consistent with another. Comparing variances of the conditional projections also provides insight into how much different storylines constrain future demographic developments. The development of the MA projections points to important areas of future research on correlations among demographic rates and on uncertainty across scales. It also serves as an illustration of how probabilistic and alternative scenario-based approaches to uncertainty can be combined within a single integrated analysis.This revised version was published online in April 2005 with corrections to figures 1-3.     

Modelling the effects of population aggregation on the efficiency of insect pest control

Summary A methodology is developed to assess the effects of spatial distribution on the efficiency of insect pest control. This methodology is especially applicable to pest control methods whose efficiency of action depends either positively or negatively on pest density It is applied here to the sterile insect technique and pheromone trapping for male annihilation, which both depend negatively on density. This methodology relies on quantifying clumps of various size and then relating this to efficiency of control and predicting the total pest production given the information on clump sizes and efficiency of control for each clump size. It is found that control is about four times as difficult for a population that is highly clumped (k of the negative binomial distribution=0.25) as for a regularly dispersed population.     

Water Resources,Land Exploration and Population Dynamics in Arid Areas - The Case of the Tarim River Basin in Xinjiang of China

Water resources are the root of life and development in arid areas like the Xinjiang Autonomous Region of China. In the Tarim Basin in Xinjiang, one of the driest places in the world, melting glaciers are the exclusive water source. Population growth, in particular in-migration, has greatly changed the ecological conditions of the Tarim River Basin in the past 2,500 years. Our research aims to study the interactions between population growth and changes in water and land resources, crossing the boundaries of the different reaches in the Tarim River Basin over the past 50 years. Time series data on population changes and economic development, water volume and quality, land use and land cover changes, and prevalence of morbidity relevant to water quality are collected to study the relationship between these factors. Adopting a statistical analysis and systems dynamics approach, we quantify the effect of population growth on water use and land degradation. ¹This paper results from the research project “Population changes and land degradation in Xinjiang of China,” funded by the Wellcome Trust Foundation (grant no. 065867). The authors appreciate the comments from the anonymous reviewers, and wish to extend thanks to the Asian MetaCentre for Population and Sustainable Development Analysis, and to Warren Sanderson, Wolfgang Lutz, Brenda Yeoh, Vipan Prachuabmoh, Min Weifang, Zheng Xiaoying, Brian O’Neill, Steve Hamburg, Laura Sadovnikoff, Verene Koh, and Sam Balakrishnan, for their invaluable support and help.     

An outline of study on China's population / environment issues

Attention is given to population and growth and the impact on the environment and resources in China. Policies for managing the environment and instituting population education are also addressed. The first position paper of the National Environmental Protection Agency (NEPAC) on June 2, 1990 is summarized. The population of China was 1.11 billion in 1989. The rate of growth in 1988 was 14.2/1000 in 1988. 91% live in the southeast on 43% of the land. Land area is 9.6 million square miles. 65% can be made arable, and 14% is cultivated. China has 7% of the world's arable land and 20% of the world's population. Population growth has reduced arable land/captia. The impact on forests has been deforestation. 13% of land is currently forested, and timber reserves encompass 9.14 billion cubic meters, or 9 cubic meters/person. The demand for firewood and timber will increase. The impact on grasslands has been overgrazing and desertification at a current rate of 1560 square kilometer/year. The impact on energy resources is a greater demand for coal which will increase and thus increase pollution of the environment. The impact on water resources is greater demand and increased pollution. Water resources are 2700 cubic meters/person or less than the world average. 26.8 billion tons of waste water were industrially discharged out of 36.8 billion tons. 436 of the 532 rivers are polluted. The impact on the environment is a decreased standard of living. NEPAC reported that air pollution was slightly reduced in 4% of the cities in 1988, increased in 4%, and stable in the remaining cities. Water quality improved through the lowering of industrial waste water discharges, but 72% of river segments are still above the standards. Each major river system is discussed. Noise increased, and industrial solid wastes increased. Forest reserve is 9.141 billion cubic meters; the man-made forest has increased. The loss of grasslands is .13 million hectares/year. Cultivated land is 95.72 million hectares, but 100,000 hectares/year are damaged by natural disasters and 6 million are polluted by industrial wastes. 606 nature preserves have been established. In 1989, a complete legal system of environmental protection was established and investment increased.     

农地制度、土地依附效应与半城镇化问题研究 ——基于人口农村退出视角

研究的学术逻辑在于突破“城市融入”的惯常认识,从“农村退出”视角,探讨农地制度与半城镇化的关系,并试图破解劳动力意义上的“人地分离”与保障意义上的“人地依附”这一矛盾。中国的城镇化过程可以分解为农业退出、城市进入、农村退出三个阶段。本文重新修正了托达罗模型,并构建了人口农村退出模型。基于调查数据,本文通过构建logit、截面门槛、双Probit模型,证实农地制度引致农村人口对土地具有依附效应,土地禀赋对农村人口的退出决策具有显著抑制效应。     

Economic development with limited supplies of family labor: Chinese peasant families in balancing demographic and economic requisites

Family planning (FP) in rural China, particularly the ramifications of the 1-child policy, has profound implications and ramifications for family-centered social and economic life in addition to demographic control. Under a constitutionally endorsed policy of strict birth control, favorable economic opportunities coexisted with the problem of familial labor shortages. Recent reform policies have led to a more relaxed FP environment. The Chinese state is in a dilemma between the need to allow peasant's autonomy in determining the familial work situation and the population pressure on the limited cultivated land. The Chinese experience of rural reform is examined in terms of the complex relationship between population change and economic development which are influenced by the production and welfare activities of the peasant family. The theoretical argument is that a family reliant strategy of economic reform undercuts the effectiveness of population control programs. The ultimate solution lies with sustained industrialization with high labor absorption. National trends and the Dahe People's Commune/Township experience are analyzed. Discussion is focused on the dilemma of FP and family production, old and new evidence of family size and economic performance, welfare outcome of family size, the role of the state in altering the demographic balance sheet, and the strategic response of peasant families to bring families of old designs back and urban migration and proletarianization. It is concluded that there is growing understanding that the causal relationships between population growth and economic development do not clearly support universal population control. Human social organization, not the man/land ratio, shapes the consequences of population growth. The implications for the Malthusian vs. Marxian debate for developing countries are that the resources/population imbalance needs to consider more carefully the human organizational factors. Mao's notions that a revolutionary transformation of the social organization of production in China would resolve overpopulation have since been rectified by opposing ideological positions: changing the basic mode of production through institutional decollectivization and checking population growth with the 1-child policy. This dilemma in rural areas translates to greater productivity and diversification with Chinese families having abundant adult labor and secured by the number of sons. It is difficult to substantiate the benefit of small families for peasants theoretically. Political rewards have been curtailed by economic declines. The peasant family has adapted by reconstituting old family forms and kin networks and by out-migration and nonagricultural employment.     

Apocalypse when? Population growth and food supply in South Asia

Food demands for staple grains are expected to almost double over the next 25 years in South Asia, due to population growth and increased standards of living. Trends in the mid-1990s suggest that neither pessimism nor optimism prevails in the region. There is wide diversity among and within countries. Trends suggest that population densities are already the highest in the world, and the amount of arable land is declining. Urban growth has moved onto farm land and farmers have been pushed onto more marginal lands or have become landless. Land intensification has produced mixed results. Cereal production per capita has increased since the 1950s in India, with about 75% of the region's population, but Pakistan's increases were not sustained into the 1980s. Average daily caloric intake per person in the region of 2214 is below the level in Sub-Saharan Africa. In Bangladesh, levels are particularly worrisome at 2037. The environmental impact has not been easily quantified, but experts have suggested that pressure on farm land has contributed to loss of soil fertility and water resource loss. Further intensification of farming is feasible, but difficult and more expensive than in the past. Regardless of production problems and solutions, there is also the very real problem of poor food distribution and lack of purchasing power. Farm management skills must be utilized, if environmental degradation is to be avoided. There is the added unknown of what climate changes will occur and how agricultural production will be affected. The policy implications are that increased food production must be made a political priority. Policies must support agricultural research into improved technologies and support distribution of technological advances to a wider number of farmers. Rural infrastructures such as roads, market outlets, and credit agencies must be established. Policies must be removed that disadvantage farmers, such as inappropriate subsidies for irrigation water, inadequate tenure agreements, and price setting. Slowing population growth provides time to adjust to expanding production and saving the environment.     

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).