The effect of population growth on environmental quality

This paper summarizes research on the effect of population growth on environmental quality. Land transformations induced by the spatial expansion of agriculture are probably the major route by which population growth has affected features of the natural environment. These transformations are not automatic and their extent is influenced by social institutions. Intensification of agricultural land use is an alternative response with its own set of environmental implications. These are especially salient in the case of expanded irrigation. In contrast to relations in the agricultural sector, a new version of the conventional I = PAT equation is introduced to suggest that population growth is a minor influence on the extent of industrial pollution. Nevertheless, population policy may play a useful role in strategies to reduce industrial pollution.     

The population,agriculture, and environment nexus in Latin America: country-level evidence from the latter half of the twentieth century

Unprecedented population growth and migration accompanied equally unprecedented land use and land cover change in Latin America during the latter decades of the twentieth century. Country-level data are examined with bivariate statistics to determine relationships between changes in population patterns and land use (agriculture and forest cover) from 1961 to 2001. In South America, large forest areas were eliminated during the period, while exceptionally high rates of forest clearing were ubiquitous in the Central America/Caribbean region. These environmental changes accompanied dissimilar initial population densities and different effects of population change on agriculture. While interacting with a host of political, socio-economic, and geographic processes, it appears that both Malthusian and Boserupian demographic processes were important drivers of deforestation. Given continued, though slowing, population growth, increased urban consumption, and future land use constraints, policy makers face myriad challenges in advancing sustainable agriculture-population dynamics in Latin America.     

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.     

Population growth,changing agricultural practices,and environmental degradation in Zaire

This paper examines linkages between the demographic changes taking place in Zaire, particularly overall population growth and rapid urbanization, changes in agricultural practices, and related environmental degradation. Pressures to feed Zaire's rapidly increasing urban population, which fall on a rural population that has been growing relatively slowly in recent years, as well as population growth and increased population density in certain areas of the country, have resulted in changes in agricultural practices that are described in the paper. These changes in turn are leading to declining soil fertility, deforestation, and degradation of the natural resource base. Given present technology and the state of Zaire's economy, the changes in agricultural practices that have emerged in response to population growth, increased population density, and growth in demand for food production do not appear to be sustainable in the long run.     

Household and farm transitions in environmental context

Recent debate in the literature on population, environment, and land use questions the applicability of theory that patterns of farm extensification and intensification correspond to the life course of farmers and to the life cycle of farm families. This paper extends the debate to the agricultural development of the United States Great Plains region, using unique data from 1875 to 1930 that link families to farms over time in 25 environmentally diverse Kansas townships. Results of multilevel statistical modeling indicate that farmer’s age, household size, and household structure are simultaneously related to both the extent of farm operations and the intensity of land use, taking into account local environmental conditions and time trends as Kansas was settled and developed. These findings validate farm- and life cycle theories and offer support for intergenerational motivations for farm development that include both daughters and sons. Environmental variation in aridity was a key driver of farm structure.     

Population,resources, environment: an uncertain future

This issue analyzes the economic and environmental consequences of rapid population growth in developing countries (LDC), the population decline in developed countries, the limits that life on a finite planet impose on economic and demographic expansion and progress, and the proper governmental response to promote the welfare of its current and future citizens. The links between population growth, resource use, and environmental quality are too complex to permit straightforward generalizations about direct causal relationships. However, rapid population growth has increased the number of poor people in LDC, thus contributing to 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 consumption of the nonrenewable resources of fossil fuels, metals, and nonmetallic 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 accelerating technological change make future interrelationships of population, resources, and the environment uncertain as well as complex. 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 LDC below the additional 5 billion indicated in current UN medium projections. This coupled with proven management programs in both LDC and developed countries could brake and reverse the depletion and degradation of natural resources.     

Preliminary discussion on the current over-population in agriculture in China]

The population devoted to agriculture constitutes more than 80% of China's total population. This high percentage is not very common in today's world. In the last 30 years, the population devoted to agriculture has increased by 81.9%, but the area of arable land has decreased in the same period of time. This situation has created problems, such as a surplus of agricultural labor, an imbalance between the agricultural population growth and agricultural means of production, a serious contradiction between the agricultural population growth and mechanization of agriculture, an imbalance between the agricultural population growth and means of livelihood, and the current low standard of living for populations engaged in agricultural work. In order to solve the problems of overpopulation, various measures must be taken in different places. The economic structure of agriculture is to be reasonably arranged, and various operations in agriculture are to be carried out. In addition to the production of main agricultural crops, forestry, animal husbandry, the fishing industry, and family supplementary income are to be developed in order to provide more job opportunities. Communes and production teams should emphasize labor intensive plans for more profit with less investment. Agriculture should focus on intensive farming in order to increase productivity. Arable land can be expanded with reclamation projects, and water and soil conservation is necessary. The surplus agricultural population should be utilized for productive activities.     

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.     

Land and leña: linking transnational migration, natural resources, and the environment in Guatemala

This article examines the relationships between international migration, natural resources, and the environment. Rather than looking at environmental change as a cause of population movements, the article reveals how migration affects the environment in sending countries. Empirically, we rely on a case study in Guatemala. Although migrants and cash remittances make significant contributions to Guatemala’s changing economy, little is known about the relationships between migration and the environment in this Central American country—a country, which continues to have a large rural population and that relies heavily on its natural resources. Drawing on ethnographic research and household surveys in a Maya community, we reveal how migrants and their earnings, as well as their ideas, behavior and attitudes, affect land use, land cover, and firewood use. We reveal, for example, how in addition to investments in land for home building and pick-up trucks to help improve agricultural production, some migrant households purchase more land and often dedicate it to the cultivation of vegetable crops for local and foreign markets. Cultural practices and beliefs directly linked to land and the environment, particularly maize cultivation, also alter due to migration processes. And, despite the ability of migrant households to transition to more efficient fuels like liquid propane gas (LPG), we show how they continue to use firewood. In all, the study contributes important insights into the environmental implications of migration.     

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.     

Property Size and Land Cover Change in the Brazilian Amazon

This paper considers the size of a farmer’s property as a key variable influencing land cover and land cover change in rural areas of developing countries. Data from 126 rural familial properties in the region around the city of Santarém, Pará, in the Brazilian Amazon, indicate that property size is important for understanding the trajectories of land cover change. Past research has focused on the distinction between small family farms and large capitalized farms, arguing that family farmers have a higher deforestation intensity, or on estimating the strength of the effect of property size relative to economic or demographic factors. This paper shows that larger familial properties are able both to retain a larger area in forest and to have long enough cycles of use and fallow to allow previously used land to become forested again. Based on these analyses and discussion, we argue that land use and land cover research must consider property size as an organizing principle in order to better comprehend the reciprocal relationship between population and environment in frontier areas of the Brazilian Amazon and other rural landscapes.     

Population and land use change in the California Mojave: Natural habitat implications of alternative futures

Demographic and land use dynamics have important implications for the natural environment within both developed and developing nations. Within the context of developed nations, popular and policy debates surrounding contemporary patterns of suburbanization attest to the salience of demographic and development issues. We examine the implications of land-use patterns as related to population and development within the context of the California Mojave Desert ecosystem. In a general sense, we aim to better understand the land requirements inferred by varying levels of population growth and density, as well as the natural habitat implications of those requirements. We develop a GIS including remotely sensed imagery, and demographic, economic, and biophysical data to examine of the implications of various demographic scenarios on species diversity. Spatial and statistical models are designed to develop possible alternative land use `futures'. Within the context of the California Mojave region, our results suggest that high-density development could reduce conflict with regions providing potential habitat for threatened or endangered species by over 80 percent. The process of model development demonstrates a potentially useful tool for policymakers, allowing for estimation and visualization of the land use implications of policy decisions.     

Proximate Population Factors and Deforestation in Tropical Agricultural Frontiers

Forest conversion for agriculture expansion is the most salient signature of human occupation of the earth's land surface. Although population growth and deforestation are significantly associated at the global and regional scales, evidence for population links to deforestation at micro-scales—where people are actually clearing forests—is scant. Much of the planet's forest elimination is proceeding along tropical agricultural frontiers. This article examines the evolution of thought on population–environment theories relevant to deforestation in tropical agricultural frontiers. Four primary ways by which population dynamics interact with frontier forest conversion are examined: population density, fertility, and household demographic composition, and in-migration.     

Urban influences on farmland use in New York State

This article assesses the relationship between demographic change and structural adjustments in agriculture. A number of demographic and economic analyses have posited an inverse relationship between post-1950 exurban population growth and agricultural viability, especially in the Northeast Region of the USA. To test this hypothesis, a multivariate model of percent change in county land in farms over the period 1950–1987 is estimated, and the findings only partially support the population hypothesis. Estimation results indicate that the effect of core metropolitan status is significant, but that the effects of rural population change, rural nonfarm population change, and county population deconcentration are not. The analysis demonstrates that maintenance of land in farm use largely depends upon economic forces that are national and regional in scope, and almost exclusively outside the purview of state and local farmland protection programs.     

农业人口流动与农村土地流转

农村土地制度在我国农村经济制度体系中起着基本的作用,而农业人口的流动是我国实现城乡一体化过程中的必然现象,这两者之间存在着很强的互动关系。因此,在我国城乡经济发展过程中,一方面农村土地制度变迁推动和影响农业人口的流动,另一方面农业人口的流动也迫切要求我国的农村土地制度进行相应的变革。     

Population and housing

The analysis described here was carried out in response to a political crisis in Australia. In 1994, a Member of Parliament who opposed the use of foreign aid funds for family planning programs blocked the passage of the national budget. The impasse was resolved through a compromise. The use of foreign assistance for population activities was frozen pending an independent inquiry into the impact of population on economic development. A team of nine researchers prepared background papers on population and economic development, health, education, food supply, housing, poverty, the environment, family planning, and human rights. The overall conclusion of the inquiry was that slower population growth will yield more rapid development in most countries, especially in relatively poor, agricultural nations. The purpose of this contribution to the inquiry was to assess how population growth was affecting the housing sector and, in turn, economic development. Among other questions, does population growth increase the demand for residential land, housing, and urban infrastructure? Demographic methods were critical to answering the questions, especially assessing the impact of population growth on the demand for housing.     

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。     

Population density,urban centrality,and agricultural intensification in Jordan

This paper explores the relationship between population growth, agricultural production, and urban development. Ongoing debate in the literature regarding the relationship between population and economic development is restricted by the limited availability of time series data and the difficulty of evaluating causality using cross-sectional data. This analysis uses the special case of Jordan with its massive refugee flows to evaluate the influence of a sudden and exogenous change in population in urban areas on the intensification of agricultural production. Spearman Rank Order correlations are calculated from time series data to show that the districts which experienced the most rapid population growth and increases in population density also exhibited the largest increases in agricultural intensity. Cross-sectional analysis in which measures of agricultural intensification were predicted by population density and urbanization factors reveals a significant interaction between density and urban centrality, where centrality is an indicator of the accessibility of urban goods to rural communities. The results suggest that population density has a strongly positive effect on agricultural intensity in areas with few urban goods and services available, whereas the influence of population density on agricultural intensity is substantially reduced in areas with a greater diversity of urban goods and services.This article is based on a paper presented at the 1992 Meeting of the Southern Demographics Association, Charleston, SC, 15–17 October 1992.     

Population and pavement: population growth and land development in Israel

This research examines land use change in Israel––an intriguing but understudied setting with regard to population–environment dynamics. While Israel is fairly unique with regard to its combined high levels of economic prosperity and high population growth, this case study has relevance for developed countries and regions (like the south and southwest regions of the USA) which must balance population growth and urban development with open space conservation for ecosystem services and biological diversity. The population–land development relationship is investigated during the period from 1961 to 1995 at three spatial scales: national, regional (six districts), and local (40 localities). There is a positive correlation between population growth and land development rates at the national scale, and while remaining positive, the strength of the relationship varies greatly at regional and local scales. The variation in population–land use dynamics across scales is used to garner insight as to the importance of geography, policy and historical settlement patterns.