The earth has entered a period of hydrological, climatological, and biological change that differs from previous episodes of global change in the extent to which it is human in origin. Human beings, both individually and collectively, have always sought to transform their surroundings. But for the first time, they have begun to play a central role in altering global biogeochemical systems and the earth as a whole. The global changes looming largest on the horizon are cases in point. The depletion of the ozone layer attributed to the accumulation of chlorofluorocarbons (CFCs) in the stratosphere is an unintended side effect of human industrial activities. The increase of atmospheric carbon dioxide, a trend that has been accelerating since the onset of the Industrial Revolution, is driven by the increasing use of fossil fuels and the elimination of forests. And the loss of biological diversity is a by-product of varied human activities, including the clearing of tropical moist forests for agricultural purposes.
To explain or predict the course of such global environmental changes, one must therefore understand the human sources of these changes. Because people engage in purposeful behavior, it is also important to focus on human responses to global changes. For example, after people learned that CFCs rising into the stratosphere would deplete the ozone there and threaten human health, they made serious efforts to phase out industrial and commercial uses of these chemicals. Such human responses can alter the course of global environmental change.
THREE GLOBAL CHANGES
The human behavior in question is both complex and poorly understood. To illustrate this point and to provide a backdrop for the analysis to come, we begin with three vignettes that convey a sense of the range of concerns addressed in this book. These three examples reappear later on to illustrate issues in the human dimensions of global change.
GREENHOUSE GASES AND CLIMATE CHANGE
Human activities threaten to alter the global climate by releasing so-called greenhouse gases, principally carbon dioxide, methane, CFCs, and nitrous oxide, that have the effect of increasing the proportion of heat from the sun that is retained at the top of the atmosphere. While it is easy to establish a connection between the onset of the Industrial Revolution and increases of carbon dioxide in the earth's atmosphere, the story of greenhouse gases is far more complicated. An examination of emissions of carbon dioxide, a by-product of the combustion of fossil fuels to produce energy and the most important of the anthropogenic greenhouse gases, suggests a clear link between economic development and a global increase in greenhouse gases. Yet there are striking disparities between otherwise similar economies in how much energy they use to produce a unit of economic output. Japan uses less than half the energy the United States does; Bangladesh uses about half what India or Pakistan does; the range in sub-Saharan Africa includes the least energy-intensive economy in the world (Lesotho) and one of the most intensive (Zambia), which differ by a factor of 56 (World Bank, 1989). Other human activities, such as the destruction of tropical moist forests, are major contributors to carbon dioxide emissions worldwide. In the case of methane, population pressure appears to be a key factor, since the expansion of rice paddies to feed the growing human populations of East and South Asia is a major source of methane emissions. The case of CFCs points to the role of technology as a source of the greenhouse effect; CFCs were developed initially to eliminate problems with existing refrigerants, like ammonia, rather than as a response to population pressure or the forces of economic development (although, of course, population growth and economic production add to the demand for CFCs). Nitrous oxide tells yet another tale. The largest single source of this greenhouse gas is the use of nitrogenous fertilizers to increase crop yields, mainly in advanced agricultural systems.
CHLOROFLUOROCARBONS AND THE STRATOSPHERIC OZONE LAYER
In 1987 an international protocol was signed at Montreal, in which signatory countries declared their intention to cut CFC production and consumption in half by the end of the century. The Montreal Protocol is remarkable for the fact that it constitutes an anticipatory response to global change. Although held up by many as a model for those working on other global environmental issues, in its initial form this international agreement left much to be desired: it did not cover a range of chemicals (for example, methyl chloroform, carbon tetrachloride) whose effects are similar to those of CFCs; it allowed developing countries to actually increase their use of CFCs; it offered minimal assistance to governments seeking to reduce the use of CFCs within their own jurisdictions; it provided little guidance on compliance; and it did not succeed in drawing in key players like China and India. But the pressure of worldwide public opinion, driven by dramatic recurrences of sharp yearly reductions in ozone over Antarctica and by a growing scientific consensus concerning the dangers of ozone depletion, led to a renegotiation of the protocol that has strengthened its provisions in a number of areas. Under a series of amendments to the Montreal Protocol negotiated in London in 1990, CFCs and halons are to be phased out by the year 2000, and methyl chloroform and carbon tetrachloride have been added to the list of chemicals to be eliminated. The creation of an international fund to assist developing countries in switching to alternatives to CFCs has persuaded China and India to say they will join the agreement.
Nevertheless, the new provisions do not solve all the problems associated with ozone depletion. CFCs already in the atmosphere are expected to cause significant reductions in stratospheric ozone over a period of several decades. There is no guarantee that the chemicals developed as substitutes for CFCs will prove benign over the long run (CFCs themselves were thought to have ideal properties when they were introduced in the 1930s). Hydro-chlorofluorocarbons (HCFCs) and hydrohalocarbons (HFCs), prominent among the candidates to be used as substitutes for CFCs, have already provoked opposition from those concerned about their potential contribution to the greenhouse effect. That opposition makes prospective producers such as DuPont reluctant to invest heavily in facilities needed to initiate large-scale production of the chemicals (Holusha, 1990a, b). Still, the international response to the problem of ozone depletion has been note-
worthy as a quick and decisive reaction to a threat whose impact lies largely in the future. Many now wonder whether this case offers lessons of value for those struggling to come to terms with other global changes, such as climate change and the loss of biological diversity.
AMAZONIAN DEFORESTATION AND THE LOSS OF BIOLOGICAL DIVERSITY
Human activities are decreasing biological diversity on land, in fresh waters and the seas, in industrialized and developing nations, from the coldest inhabited lands to the tropics. But because of the huge variety of species confined to the tropical moist forests, their destruction is likely to cause more loss of biological diversity at the species level than any other human activity. Although the scale of this destruction is hard to measure accurately, recent estimates indicate that, on a world scale, an area of tropical moist forest roughly the size of Honduras is deforested or converted annually (Erwin, 1988), resulting in the extinction of species at a rate that has been estimated at 17,500 species per year, assuming 5 million species in the tropical moist forests (Wilson, 1988). The immediate, or proximal, causes of deforestation are easy to identify: the conversion of forest to agricultural use, logging, mining, industrial development (e.g., hydroelectric power), and the search for fuel wood and fodder. But what lies behind these proximal causes? A popular notion associates the destruction of tropical moist forests with population pressure. But the best analyses suggest that in some important forest regions, such as the Amazon, this argument explains, at most, only a small part of deforestation (see Chapter 3).
In fact, a constellation of distinct, though interacting, forces appears to be at work. The destruction of the tropical moist forest of Brazil's Amazon Basin offers an example. One key force manifests itself in the pressure of international markets for mineral and wood products, coupled with the country's interest in encouraging exports for the purpose of reducing its international debt. Public policies intended to promote economic development also contribute to the destruction of Amazonian forests (for example, government-sponsored road construction, hydroelectric power projects, and favorable tax treatment for large ranching operations, though the last has recently been withdrawn). Corporations cut trees to initiate mining and smelting operations, and more trees to fuel the processes. A frontier mentality encourages rapid use of forest resources on the assumption that there will
always be new frontiers to open up when current areas are exhausted. And a history of nationalistic feelings—only now changing—encourages forest clearing: people have felt that Brazil must develop all of its resources to assume its rightful place as a world power. The incentives for policy makers to promote conservation have been weak: many of the costs of destroying tropical moist forests (for example, the resultant loss of biodiversity) are unknown or borne by those residing in other parts of the world, and consequently were ignored until recently by Brazilian policy makers. Under prevailing institutional arrangements, the incentives for individuals and corporations favored "mining" the forests, not conserving them. Although the proximal causes of the destruction of ancient forests are not difficult to pinpoint, the story becomes much more complex as we shift our attention to underlying causes that must be understood in order to control or redirect the behavior in question. The story is even more complex when one moves beyond Brazilian Amazonia and considers that the underlying causes and their relationships can be quite different from one country to another.
What do these stories tell us? They support the general notion that global environmental change is driven by trends in global production and consumption. But to recognize this is not necessarily useful for understanding specific types and rates of change or the complex set of factors influencing production and consumption. Single-factor explanations of the anthropogenic sources of global environmental change are apt to be misleading at best. It follows as well that simple, one-dimensional policies, such as a carbon tax or a uniform law of the atmosphere, cannot by themselves control global environmental change.
The stories also suggest the need to build stronger links between the natural sciences and the social sciences in efforts to understand global environmental changes and to devise public policies to respond to them in an effective manner. To project such changes, natural scientists must also project human behavior: what actions might affect the environment, how people might respond to environmental changes, and how people might use information in making decisions about their relationship to the environment. The quality of the environmental analysis is limited by the quality of the behavioral analysis that it includes. Erroneous assumptions about the future course of human behavior can lead analysts
to incorrect projections of environmental change. Erroneous assumptions about how environmental change affects people can lead to neglect of feedback processes, including policy responses, that may mitigate or accelerate natural processes. Erroneous assumptions about human decision making can lead analysts to generate information that decision makers find useless or unresponsive to their needs.
Similarly, to understand the human dimensions of global change, social scientists must understand environmental processes. They need to understand what is known about how the greenhouse effect is likely to affect climate in order to understand which changes are likely to be noticed and thus lead to spontaneous responses. To evaluate alternative policy responses, they need to know which behaviors are believed to have major effects on the balance of atmospheric gases or the habitats of threatened species, and which, only minimal effects. Erroneous assumptions may lead social scientists to waste effort studying behaviors that are unlikely to occur or to have much impact on global change.
Consequently, effective cooperation between natural scientists and social scientists is essential for making progress. But such cooperation is not easy to achieve under the best of circumstances. We have more to say about this cooperation and about ways to strengthen it at a number of points in this book.
ORGANIZATION OF THE BOOK
This book articulates the principal elements of a strategy for adding to knowledge of the human dimensions of global environmental change. It takes stock of relevant existing knowledge, identifies what is unknown but might be learned about human behavior that could improve understanding of global change, and sets forth a series of programmatic guidelines to give direction to efforts over the next 5 to 10 years to improve that understanding. Chapter 2 presents a working definition of global change and a schematic model of the relationships between environmental and human systems. Chapters 3 and 4 elaborate on these relationships: Chapter 3 explores both the proximate and the underlying sources of anthropogenic change in large physical and biological systems. Chapter 4 concentrates in turn on human consequences of global environmental changes and responses to them. In these chapters, we outline current knowledge about the human dimensions of global change, identify important feedback loops between natural and human systems and between human causes of global
change and human responses, and set forth an intellectual framework. We also identify particularly important near-term research needs whenever possible.
The report then turns to a number of problems that must be overcome in order to stimulate effective research. Chapter 5 examines a range of theoretical and methodological problems that confront efforts to broaden and deepen our understanding of the human dimensions of global change. Chapter 6 deals with data needs, including the needs to acquire baseline data on human systems, to assess and improve the quality of data, and to make relevant data more accessible to analysts. Chapter 7 takes up issues relating to human resources and organization that must be addressed in order to build a healthy program of research. These chapters include specific recommendations regarding research priorities; development of theory, methodology, and data; and improvement of human resources and the organizational basis for research. The chapters will be of particular interest to researchers and research managers concerned with providing an intellectual base for the long-term. Chapter 5, in particular, will be of interest to social scientists who are looking for ways to relate global change research to progress in their disciplines.
In Chapter 8, we present the structure of a national research program on the human dimensions of global change.