6

Understanding Population Dynamics and Global Change

There is a need for more fundamental understanding of the linkages between population processes and global environmental changes. Population growth, composition, and distribution have important interrelationships with land use, land cover, and global climate change. They also affect demand for other kinds of natural resources because, for any given combination of technology, energy use patterns, and social organization, population can have important multiplying effects in relation to global change. The need for policy responses to global change varies with the size, composition, and distribution of populations, and demand for policy responses is also affected by the populations that will feel the impacts of global change. Consequently, integrated assessment and policy analysis need to take into account the likely size and distribution of affected human populations.

The three fundamental processes determining population growth and distribution are fertility, mortality, and migration. All three processes are likely to affect and be affected by global change. In the short term (5 to 15 years), migration (both within and across national boundaries) is likely to be highly dynamic and correlated with global change. Shifts in population age structure may also have important effects on resource demand.

In considering population processes, it is imperative not to assume that causality flows in just one direction. Although some writers have treated population as an independent or exogenous variable in terms of its relationship to global change, environmental factors also influence population processes. For example, environmental quality, including climate, is one of the prime factors influ-



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Science Priorities for the Human Dimensions of Global Change 6 Understanding Population Dynamics and Global Change There is a need for more fundamental understanding of the linkages between population processes and global environmental changes. Population growth, composition, and distribution have important interrelationships with land use, land cover, and global climate change. They also affect demand for other kinds of natural resources because, for any given combination of technology, energy use patterns, and social organization, population can have important multiplying effects in relation to global change. The need for policy responses to global change varies with the size, composition, and distribution of populations, and demand for policy responses is also affected by the populations that will feel the impacts of global change. Consequently, integrated assessment and policy analysis need to take into account the likely size and distribution of affected human populations. The three fundamental processes determining population growth and distribution are fertility, mortality, and migration. All three processes are likely to affect and be affected by global change. In the short term (5 to 15 years), migration (both within and across national boundaries) is likely to be highly dynamic and correlated with global change. Shifts in population age structure may also have important effects on resource demand. In considering population processes, it is imperative not to assume that causality flows in just one direction. Although some writers have treated population as an independent or exogenous variable in terms of its relationship to global change, environmental factors also influence population processes. For example, environmental quality, including climate, is one of the prime factors influ-

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Science Priorities for the Human Dimensions of Global Change encing migration destination choices. Declining environmental quality and decreasing productivity of land may force people to move. Drastic environmental or climate change may also lead to increased mortality. Thus, it is important to conduct empirical research on both the effects of population dynamics on global change and of global change on population dynamics. In addition, it is important to recognize that relationships between population and global change can operate through or be mediated by other driving forces, such as economic or policy changes. For example, the effect of a resettlement program on an area may depend on the policies of the resettlement agency. RELATION TO USGCRP PRIORITIES The importance of population processes and trends is already well recognized. Population processes are a central interest of researchers on the human dimensions of global change. We place special emphasis on migration research because we see this as the most urgent need, and as readily linked to other global change research efforts. A focused research effort will support the wider needs of the USGCRP in the following ways: it will allow a clearer link between human migration and climatic changes. It will provide information on the likely human impacts of events predicted by climate models, identify model outputs of particular importance for impact studies, and possibly alter parameters used as inputs to climate models; it will provide important socioeconomic and population characteristics as inputs into land use models, thus improving the accuracy of forecasts from such models; it will provide inputs into models of demand for other environmentally relevant resources, including energy, water, agricultural chemicals, and manufactured goods, thus improving forecasts of burdens on the environment mediated by such demand; and it will assist the wider USGCRP initiative on integrated assessment by providing straightforward links between projected impacts and possible policy responses on one hand, and the size and distribution of affected populations on the other. TIMELINESS OF EFFORT Focused research on population and global change is particularly timely for at least the following reasons: the population research community has made significant advances toward understanding the relationship between population and socioeconomic change. These advances are the result of techniques and theories that integrate

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Science Priorities for the Human Dimensions of Global Change multiple levels of analysis (macro and micro), reciprocal causation, and both qualitative and quantitative methodologies. Because of the prominent role of fertility in the concern over population growth over the past 25 years, scientific advances in this area have been strongest. The population research community is now ripe for similar advances in the migration area. substantial advances have been made in geographic information systems, which allow the merging of population data with other data using geographic location as a join point. geographic information systems allow the population research community to bring its considerable statistical, methodological, and theoretical skills to issues that heretofore have not been researchable. There is emerging activity within the population research community, as evidenced by the papers being presented at recent meetings of the Population Association of America and activities of the NRC's Committee on Population (Jolly and Torrey, 1993). In the past, the population research community sat on the sidelines when global change issues were discussed, and as a result demographic expertise was not brought into discussions of population and global change. examining the human dimensions of global change will require multidisciplinary research teams. The population research community has considerable experience with multidisciplinary research teams and can provide a model for other areas of research on human dimensions of global change. RESEARCH GOALS The following are examples of research topics that could be addressed in the short term: To what extent do patterns of environmental change in agricultural areas affect migration? For example, does migration lead to increased urbanization or resettlement in other agricultural areas? What are the interrelationships between migration processes on one hand, and climate, climate change, and the physical environment on the other? For example, knowledge of migrant characteristics and motivations may explain patterns of settlement abandonment and establishment during periods of climatic change. How does the interaction between population growth and changes in technology and consumption patterns affect global environmental changes? For example, what combinations of these driving forces account for deforestation or for the trajectories over time of greenhouse gas emissions in different countries? What is the role of the frontier in shaping migration patterns and household formation patterns? Modeling efforts in all these areas would include feedback loops.

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Science Priorities for the Human Dimensions of Global Change In the longer term, research should also examine interrelationships of global change with human fertility and mortality processes. RELATION TO INTERNATIONAL RESEARCH The International Union for the Scientific Study of Population has a committee on population and the environment, which has been active with other international organizations in sponsoring research seminars. For example, in October 1994 it will hold a conference on population and the environment in arid regions, cosponsored with the International Geographic Union and the Population Division of UNESCO. The HDP has identified research on demographic changes as an element of its research focus on Social Dimensions of Resource Use. Its plans include developing and experimenting with models of global scale that include population variables and developing methods for analyzing population-environment dynamics within particular countries. The research directions we identify here are quite compatible with the international plans for HDP, making it likely that U.S. research and international efforts will be mutually reinforcing. IMPLEMENTATION ISSUES The research program should represent a mix of institutional support and investigator-initiated research. Appropriate use of the advances being made in the general area of geographic information systems requires specialized hardware, software, and personnel that could not be funded on any single investigator-initiated research grant. This type of infrastructure should be made available through institutional support. At least 75 percent of the research funding in this area, however, should be made available through investigator-initiated research grants. Because this is a new area requiring multidisciplinary teams, it will be necessary at first to rely on Requests for Applications to generate high-quality proposals. Much of the federally funded scientific research in the population area is funded through the Demographic and Behavioral Sciences Branch of the National Institute of Child Health and Human Development. Coordination between that agency and USGCRP is essential.