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THE HUMAN CAUS ES OF GLOBAL ENVIRONMENTAL CHANGE B. L. Turner II Recognition of humankind as an awesome power in transforming the earth is not new. George Perkins Marsh heralded this theme in the nineteenth century, W. I. Vernadsky, among others, recognized the impending global dimensions of this power in the first half of this century, the now classic work Man's Role in Changing the Face of the Earth, (Vol. 1 and 2, William L. Thomas, Jr., ea., University of Chicago Press, Chicago, 1971) placed it in historical context, and recently the sustainability of human uses of the biosphere has been explored. The human impress on the earth--its present magnitude and enormous potential for still further transformation--is now conventional wisdom. This wisdom is complemented by the maturation of the study of the human causes of change. We have identified many of those human actions that are the major sources of environmental change, and we continue to document the degree to and manner in which they propel the transformation of the biosphere. In concert with these efforts, the rudiments of a conceptual framework that groups and links the components and processes of human- induced change have emerged. That the general structure of this frame- work has remained relatively unchanged during this half-century implies a consensus about it. Major research efforts are now aimed at refining the framework by detailing the relative weights and positions of its compo- nents and, more recently, by grounding it within a general understanding of human behavior. The conceptual framework we seek is one that will help us understand the three principal types of environmental change: those in material and energy flows, in biota, and in the physical structure of the biosphere (Figure 11.1~. It must be remembered, however, that while the relation- ships between these changes and human activity are the ultimate focus of study, these relationships are mediated by the very nature of the physi- cal environment in which they are taking place: a tropical wetland, a midlatitude desert, or a semitropical grassland, for example. In our quest to understand the global condition, we must not lose sight of the fact that human actions are very much grounded in place, that the dif- ferences among places are extreme, and that the human action and envi- ronmental change relationship will vary accordingly. The human side of the framework is characterized by at least three broad parts: the prox- imate sources of change, the human driving and mitigating forces, and human behavior.] 90

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91 :::: :::: ::: ::: - ::::: :::::: :: ::::::::: :::: ::::: : :::::: ::::::::::::: :: .:: ::::::: : :l Types of Environmenta! Change 1 . . . .... ... . .. . . . . .. . . . . . . ... . . Materials & Energy Biota Physical structure ~ 1 ................................................... . . . . . . . , , .. ., ~ :~1u:man Driving Frees . . . Land use Industry ~~ | Human ~ ~ ~ | , ~ Authoritative Population I / \ | regulation Technological / \ | adjustments Socio-cultural organization ~ ~ Informal social regulation .. . ....... . . . .. ......... . ... . .. . . . . . . .. .. .. . . . . Human Behavior ..................... .. ................ \ \ / , human agency / asocial structure FIGURE 11.1 Components and linkages of the human causes of global environmental change. PROXIMATE SOURCES OF CHANGE The proximate sources of change constitute the near-end or end products of human activity whose immediate consequences are alterations and transformations of the environment. As such, proximate sources can be viewed as lenses through which human forces are directly translated into environmental change; they represent, therefore, the observational points of departure for empirical examinations of the human dimensions of global change. A simple scheme recognizes two major proximate sources: those of land use and industry.2 Land use involves the kind, scale, and spatial r

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92 distribution of human activity, primarily as captured in the changes made in the landscape components of the environment, the so-called 'faces of the earth." Industry involves the same dimensions, but primarily as captured in the flows of inputs and outputs of the production processes that affect the basic biogeochemical flows of the biosphere. Examination of land use change informs us, for example, that the net loss of forests owing to human action from time immemorial amounts to about 8 million km2 or about 15 to 20 percent of the world's forested area; that over the last 300 years there has been a 450 percent expansion of the world area devoted to croplands, constituting an increase of about 12.4 million km2, at the expense of forests, grasslands, wetlands, and deserts; and that during the past 3 centuries the population of the largest 40 urban areas has increased some 25-fold, with an even greater estimated increase in land area under urbanization.3 Studies of industry as a proximate source of change inform us that the human-induced contribution to the sulfur budget, accounted for almost entirely by the burning of fossil fuels, now exceeds the natural contri- bution; that the 1980 emissions of carbon from fossil fuels were 3 times greater than those from all forms of land use change; and that the global use of chemical fertilizers has increased more than 83 percent since 1950, exacerbating nutrient loadings in the global water systems. HUMAN DRIVING AND MITIGATING FORCES OF CHANGE Empirical examinations of the material relationships between the various elements of land use and industry, and their environmental impacts are, however, only the first step in developing a more complete understanding of the human causes of environmental change. These re- lationships must be linked with the underlying or deeper social forces that drive the proximate sources. For the sake of clarity, it is im- portant to distinguish between two broad categories of these forces. The first category involves those attributes and actions of humankind that have altered the biosphere from its state as it existed at the dawn of civilization, before human impact was significant, particularly at the global scale. These I refer to as the human driving forces of change. In the second category are those actions that, both indirectly and directly, impede, alter, or counteract the driving forces or their im- pacts. These actions that diminish the net change are referred to as human mitigating forces. In reality this division is not exclusive. Mitigating forces can have unintended consequences such that they themselves become driving forces. For instance, flood control dikes built in China over the centuries had the unintended consequence of raising riverbeds, which created even larger problems of flooding. And the switch in the Basin of Mexico to unleaded gasoline, undertaken to reduce lead emissions to the sensitive atmosphere, has greatly increased the production of ozone, creating major new impacts on local vegetation. Mitigating forces some- times divert the driving forces of environmental change rather than pre- venting or eliminating them and, in these cases, play a role that is complementary to driving forces. The appearance of new driving forces

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93 of change may also mitigate other changes, as when the adoption of a new energy source relieves the impacts created by the source it replaced. Our discussion is simplified, however, if the two types of forces are distinguished. Human Driving Forces Human driving forces are the sum of individual and group actions, but more manageable, collective categories of these actions or action and impact relationships are needed for comparative analysis of the type that is especially important for understanding global change. Only broad typologies or classifications of these forces have so far been developed. Population, or more correctly, population change, constitutes one cate- gory that is almost universally recognized and, as noted below, is logi- cally and factually fundamental among the driving forces. There is less agreement over the other possible categories and their relative posi- tions within our framework. Here, we recognize technological capacity, a category that has received considerable attention, and sociocultural organization, which encompasses a myriad of proposed forces, including culture, institutions, and social, economic, and political structure. The strong impact of population on the transformation of the earth is undeniable and well known and does not need to be expounded at length here. Population is a fundamental driving force because each individual minimally requires living space, shelter, food, and water, regardless of the social and technical actions that determine how these needs are met. The demand for these basic needs stimulated by population growth over the last 300 years, but especially during the past 50 years, has created exceptional levels of ''living pressures" on that 25 percent of the world that historically has been the most intensely utilized, and it has led to new levels of pressures in other areas, most of which are thought to offer more constraining conditions for human use.4 The amount of and trends in global transformation attributable to the basic needs of population are difficult to specify for a number of reasons that cannot be detailed here, such as the variable meaning of "basic" for different cultures and socioeconomic conditions at different times. We can, however, draw on case studies for illustrations and insights. The ninth-century Classic lowland Maya civilization serves as an interesting baseline for comparison with the present. It involved a vibrant and healthy population in a premodern but sociotechnically advanced culture that met its basic or subsistence needs but probably did not consume excessively beyond them.5 The population, situated in the heartland of the civilization at the base of the Yucatan Peninsula, grew for over 2 millennia, peaking at densities that may have exceeded 100 people per square kilometer. The environmental impacts were consider- able, particularly in the transformation of the landscape. Ultimately, perhaps more than 75 percent of the upland tropical forest was altered for agriculture, settlement, and fuel, and 10 percent of the wetlands was transformed for cultivation through ditching and mounding, resulting, at a conservative estimate, in 0.4 ha of land altered per capita for cultivation and in O.5 ha of total land altered during times of peak

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94 population. These changes created an "open landscape" and exacerbated problems of soil erosion and nutrient sequestering, both of which may have had major impacts on ground water in this karstic zone. I suggest that not more than 10 percent of this change was attributable to a surplus of consumption and production over the requirements for com- fortable subsistence. This transformation of the heartland was driven largely by population growth, although the causes for that growth are speculative at best. But of course, as technology has developed, along with the organi- zational capacity of society to employ it, so has its role as a driving force in amplifying and extending the range of the impacts of population alone. Technological capacity is considered a driving force because it can amplify the very demand for resources and because its development hat both intended and unintended consequences for the environment. At least two qualities of technology have been fundamental to its role as a driving force; these are elaboration and mobilization. The first involves the development and expansion of technological knowledge; the second refers to the organizational ability to marshal the materials and energy required for the use of that knowledge. The premodern Maya, for illustration, mobilized local human labor and materials to transform primarily regional landscapes through land clearance, creating paved civic and ceremonial centers, terraces and field walls, and wetland fields and canals. Modern world history stands in stark contrast to the Maya case. The elaboration of technological capacity is such that enormous, global-scale increases in production capacity have been possible, even at lowered energy efficiency: witness the global increase in food production, which has kept pace with global population growth, in part through technologies that have increased the intensity of production by some 80 percent since the midpoint of this century. This elaboration through fossil fuel technologies has increased enormously the impacts on the basic biogeo- chemical flows of the biosphere, placing this kind of transformation on a par with or ahead of basic landscape change. The spatial (and temporal) separation of production and consumption has increased: witness the almost 20-fold rise in the total tonnage of international seaborne freight during this century and the 7-fold per capita increase, even accounting for the massive growth in global population. And the spatial separation of the sources and consequences of environmental change is also increasing: witness the afforestation of many regions and zones within the developed world, despite the overall unprecedented density of settlement there, and witness also the location of the so-called ''ozone hole" in relation to the locations of the major activities that have created it. The third and most diffuse category of driving forces is socio- cultural organization, the intricate web of economic and political structures, and social values and norms. This category is critical to global environmental change in several ways. The forces within it are instrumental in driving the level of demand for physical resources well beyond basic subsistence needs, in the extreme case creating a culture of mass consumption such that items or levels of consumption once considered luxuries are seen as necessities. The estimated surplus of 10 percent

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9s over subsistence needs in Maya production and consumption pales in comparison to modern conditions throughout the developed world. For example, various estimates indicate that, accounting for waste and loss, the average American consumes between 3400 and 3600 kcal of food each day, perhaps 50 percent more than that required for basic needs.6 Associated with these same forces has been the "democratization of accumulation," which has made possible the satisfaction of that increased demand by giving rise to the capacity for mass consumption throughout the wealthier segments of the world.7 The impacts apparently extend even to the most socially planned societies of the developed world; for instance, not only has Sweden's consumption of material goods increased by more than 200 percent since 1950, but much of it is also apparently related to the desire to keep up with stylistic changes, such as in kitchenware.8 Of course, this phenomenon is not new; even the Maya built larger and more elaborate palaces and pyramids as their wealth permitted, but the range and magnitude of this accumulation were severely restricted. Whereas we estimated 0.5 ha per capita of the total land altered by the Maya, the current global average for cultivated and grazing land alone is about 1 ha per capita. It is noteworthy that these changes in the forces of demand and accumulation affect the distribution of resources and of the associated environmental impacts. The inequities that exist among regional patterns of consumption are well known. For instance, the wealthy countries of the world, constituting about one-quarter of the global population, consume 80 percent of the world's commercial energy; stated another way, each person in the ''have" world consumes, on average, about the equi- valent of 32 barrels of crude oil per year, whereas each person in the "have not" world consumes only 3.5 barrels. Likewise, the sources of environmental consequences, many global in scale, are unequal; for example, about 40 percent of all carbon dioxide emissions to the atmo- sphere, apparently leading to global climatic change, is attributable to seven wealthy countries, comprising only 11 percent of the world's population.9 Other sociocultural variables may significantly influence the changes made in the environment. This subject requires scrutiny because little effort has been expended so far toward empirical assessments of it. One variable cited as important is environmental ethics and atti- tudes. As an example, premodern cultures are commonly taken to have shown greater care for the environment than do modern ones. Yet ex- amples of environmental degradation among these cultures exist, be it salinization of irrigated lands in the Tigris-Euphrates basin or massive deforestation in the central Maya lowlands. Whether these were excep- tions to a general rule and whether they represent mismanagment that had clear-cut cultural and population consequences remain to be documented. It has been claimed that political organization of resources affects the degree of environmental impact. Yet it appears that many centrally planned economies with state control over physical resources have problems of environmental degradation similar to those of capitalist economies based on private ownership, although pure cases of each system are difficult to find. Common or public property is often identified as either unusually prone or unusually resistant to environmental

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96 degradation, but in fact, it seems to vary greatly in that regard according to circumstances.l In the absence of sufficient comparative assessments, these roles of culture remain in question; the degree of influence they may have beyond population, technology, and wealth has not been established. Human Mitigating Forces To the driving forces of human-induced change and their environ- mental consequences are counterposed the human mitigating forces. It is perhaps important to recognize that the most straightforward force of this kind, direct regulation of the exploitation of specific resources, is not a recent phenomenon. For example, concerns about deforestation in sixteenth-century Britain, seventeenth-century France, and eighteenth- century Russia led to regulations designed to control and monitor forest loss. But, of course, international, national, and local institutions dedicated to mitigating environmental change have proliferated in the latter half of this century. Mitigating forces can be viewed in terms of the particular driving forces that they counter, distinguishing, for example, those that slow population growth from those that decrease technological waste output. An alternative approach identifies the means by which the mitigation is effected. Based on this approach, three types of mitigating forces can be identified: those based on authoritative regulation, on market ad- justments, and on informal social regulation. Authoritative regulation involves the enactment of rules enforced by a designated control agency that can take punitive action against violators. Market adjustments refer to changes in production and consumption as influenced by changes in economic value and cost, for example the relationship between gasoline or water consumption and its cost to the consumer. Informal social regulation includes at least two broad types: social norms and values that give rise to shared views or practices, and changes in production and consumption based on reasons other than purely economic ones. Of the three types, informal social regulation is the least understood, and its mitigating impacts are the most contentious among students of the subject. Those forces of mitigation involving regulatory environmental control have been most successful when addressed to specific environmental issues and driving forces or to specific regions and zones, for instance, the regulation of the whaling industry, the soil conservation measures im- plemented on the Great Plains of North America after the Dust Bowl, the decrease in the global use of DDT, and the apparent leveling off of industrial emissions in much of the developed world. It is important, though, to distinguish mitigation effected because of environmental con- cern from that resulting from other processes: oil price increases in the 1970s and consequent market adjustments, rather than authoritative regulation, were responsible for a significant part of the reduction in automotive pollution at that time. It is also important to recognize that mitigating forces apparently have had their greatest success within the well-developed service and industrial economies of the world,

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97 indicating the significance of wealth in the larger structure of mitigation.ll Identification of the key driving and mitigating forces and documentation of the manner in which they interact to generate the proximate sources of change--land use and industry--are essential contributions of the social sciences to our current study of global environmental change. Attention must be given to the ways in which these forces are affected by changes in scales of time, space, magnitude, and clustering. Just as agglomeration of economic activities increases production efficiency, so too may the agglomeration of production and consumption lead to changes in the driving and mitigating forces, in the proximate sources, and, ultimately, in the environment. For example, some evidence and interpretations indicate that the increasing size of cities is related to increasing per capita municipal waste.12 And a recent attempt to examine global historical trends in the changes in some of the components of the biosphere suggests that even with expanded production and consumption, mitigating forces designed to counteract some industrial effluents have led to decreases in the rates of delivery of some chemical elements and compounds to the environment. It is note- worthy that the impacts of such mitigation were realized quickly, after only some 10 to 20 years of regulation, in part because the major sources of the effluents are found within those regions that have the capacity to enforce regulation. HUMAN BEHAVIOR Future research on driving and mitigating forces obviously must be anchored on a strong, empirical base that documents the relationships among them and with environmental change. Complementing this research, however, must be an increase in the efforts to place these forces in the contexts of individuals and of society at large. To understand why the human forces operate as they do--that is, to explain why humankind transforms the biosphere in the way it does--ultimately will require us to embed these forces and the changes that they produce within an under- standing of human behavior. This will require that the frontiers of the study of global environmental change be expanded and that the natural sciences work hand-in-hand with the social sciences and the humanities. This objective, of course, is complex and cannot be detailed here. Theories of behavior have been proposed from various realms of knowledge, and each realm claims privileged status in the explanation of human behavior. This poses no small problem for which resolution must be sought. Research may indeed contribute to a resolution by examining human behavior on several planes. Clearly much is to be learned from detailed assessments of behavior as it occurs in specific contexts. Likewise, much is to be gained from the search for broader, pan-cultural attributes of human behavior that can be linked to environmental change. As we contemplate the impact of humans on nature, we need to understand our humanity and the unique ways in which we, as a unique species, use and alter the earth. Problems to explore include the variable roles of human territorial strategies and the conditions that give rise to this

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98 variability; the ability to expand both the number of niches used and the ways in which they are used; the persistence of cultures in the face of global interconnectivity; the changing array of and flexibility in the pathways by which societies draw sustenance from nature; and the will- ingness and ability of humans to alter their behavior reflexively when confronted with new conditions or information. The heritage of social science research on human relationships with nature and on human agency in environmental change has begun to unravel the complex networks of the linkages involved. This research informs us of both the awesome power of human actions to transform the earth bene- ficially and detrimentally, and of the ingenuity of humankind in adjust- ing to its environmental blunders, albeit not without substantial and unequal sacrifices.13 The messages from this work and its brief explore, ation here are simple. We are the cause and the solution, and both of these attributes of ourselves are extremely complex and are made even more so by their connection to the global environmental system. NOTES 1. Human driving and mitigating forces constitute the core of all frameworks. These are typically linked to the proximate sources of change or to human behavior, depending on the primary objective of the study. Here all three parts are included to illustrate the relationships among them. 2. See, for example, W. C. Clark, The Human Dimensions of Global Environmental Change, report prepared for the National Research Council's Committee on Global Change, in Toward an Understanding of Global Change: Initial Priorities for the International Geosphere- Biosphere Program, National Research Council, 1988. 3. Unless stated otherwise, estimates of global change are taken or derived from the papers of the 1987 Earth Transformed symposium held at Clark University. Revised papers are forthcoming in B. L. Turner II et al., eds., The Earth as Transformed by Human Action, Cambridge University Press, Cambridge, 1990. 4. See, for example, P. A. Sanchez and S. W. Buol, Soils of the Tropics and the World Food Crisis, Science 188, 1975. Very few examples exist of good quality agricultural soils that are sparsely occupied or utilized. One such is the central Maya lowlands of the lower Yucatan peninsular region. 5. The Classic lowland Maya represent a much more sophisticated case than, say, hunter-gatherers in that the range of resource use was larger and involved a small portion of luxury production and con- sumption. The assessment presented is culled from an extensive literature, but see B. L. Turner II, Issues Related to Subsistence and Environment Among the Ancient Maya, in Prehistoric Lowland Maya Environment and Subsistence Economy, M. Pohl, ea., Peabody Museum, Harvard University, Cambridge, Mass., 1985, pp. 195-209; B. L. Turner II, The Rise and Fall of Population and Agriculture in the Central Maya Lowlands: 300 BC to Present, in Hunger in History: Food

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99 Shortage, Poverty and Deprivation, L. Newman et al., eds., Basil Blackwell, London, in press. Most of the energy and food estimates have been taken or derived from V. Smil, Energy, Food, Environment: Realities, Myths, Opinions, Clarendon Press, Oxford, 1987. The term "democratization of accumulations' was suggested to me by R. W. Kates. L. Uusitalo, Environmental Impacts of Consumption Patterns, St. 78 and 104. Martin's Press, New York. 1986. cc. 9. For carbon dioxide, (Oak Ridge National ~ ~ Nations Conference on Trade and Development, Handbook of Inter- national Trade and Development Statistics, 1981 Supplement, UNCTAD, New York, 1982. 10. B. M. McCay and J. 8. , . . Communications, Carbon Dioxide Information Center LaboratorY), Winter 1989; for energy, United M. Acheson, eds., The Question of the Commons: The Culture and Ecology of Communal Resources, University of Press, Tucson, 1987. 11. See R. W. Kates, B. L. Turner II, and W. C. Clark, The Great Trans- formation, in The Earth as Transformed by Human Action, B. L. Turner II et al., eds., Cambridge University Press, Cambridge, 1990, forthcoming. 12. From Uusitalo, 1986 (above), p. 74. 13. I am grateful for discussions with and comments from R. W. Kates, W. C. Clark, W. B. Meyer, J. Emel, R. C. Mitchell, and the various members of the Graduate School of Geography, Clark University, associated with The Earth as Transformed by Human Action program. The paper, of course, is my responsibility. Arizona r

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