These changes, which have altered global environmental parameters, are also associated with improved quality of life for many people: average life expectancy has increased 40 percent since 1955—from 47.5 years then to 65 years in 1995—and infant mortality decreased 60 percent—from 155 deaths per 1,000 in 1955 to 60 in 1990.3 The rising global averages of per capita energy use, life expectancy, and infant mortality subsume vast disparities. People do not all contribute equally to global change nor benefit equally from progress. The processes determining these changes, sometimes called driving forces, also differ substantially across regions and populations, affecting future trends in both environmental quality and human well-being.
Regional differences in rates of environmental transformation reflect variations in the human driving forces of global change. In the case of greenhouse gas emissions the increase in coal production in China from 7,400 to 21,700 petajoules from 1970 to 1990 represents a doubling of per capita energy consumption due to economic development and national policies. In Mexico oil production grew from 980 to 6,046 petajoules over the same period, reflecting a doubling in per capita energy consumption, significant population growth, and national development policy choices to increase the export of oil. A loss of 40 million hectares of forest in Brazil since 1970 has significant implications for tropical biodiversity, as do losses of almost 10 million hectares each in Indonesia, Thailand, and Mexico. These trends in deforestation result from different combinations of population growth, migration, and economic and policy forces.4 A major focus of human dimensions research is explaining patterns and changes in the rates of environmental transformation in terms of driving forces that act globally, regionally, and at the level of responsible decision makers.
The impacts of global change on societies and economies are expected to increase greatly in the next century. For example, much of the global change that will eventually result from past human activities has yet to occur, and current trends in these activities portend potential large increases in global change. As the major climatic changes lie in the future, so do their implications for humanity. This may also be true for the human consequences of ecological transformations now occurring through deforestation and other anthropogenic land cover changes. Thus, another major focus of human dimensions research is estimating the social and economic consequences of anticipated global environmental changes. This research integrates information about anticipated environmental changes with information on the social parameters that determine the impact of those changes: demand for affected natural resources, vulnerability of geographical regions and social groups to particular environmental changes, and the potential for adaptive response. In addition, human dimensions research addresses the workings of social systems that manage environmental resources—markets, property rights regimes, treaties, legal and informal norms, and so forth—and the potential to modify those institutions through policy and thus to mitigate global change or increase adaptive capability.