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Human driving forces

The human causes of environmental change are numerous and interrelated. The extent to which any cause is present and the precise ways in which causes interact vary by location and through time. The search for cause is influenced by the way questions are posed and the "depth" of explanation sought. A single event of deforestation, for example, can be variously attributed to burning, agricultural expansion, population and market-driven land pressures, government policies towards population and markets, or international leverages on governments. What is a fundamental human cause in one analysis becomes merely a proximate or mediating cause if the question or level of analysis is redirected (Stern, Young, and Druckman 1992; Turner 1989).

Leaving aside this conceptual problem, the literature points to recurring sets or clusters of human driving forces - those facets of individuals and societies that significantly and directly influence the decisions that, intentionally or not, lead to actions that change the environment (e.g. Palo and Mery 1990). Various analysts and committees addressing the subject have synthesized these driving forces into several major clusters: population, technological capacity, affluence/ poverty, political economy/structure, and beliefs/attitudes (Clark 1988; Stern, Young, and Druckman 1992; Turner and Meyer 1991; WCED 1987).

The nine case-studies illustrate some of the variety in the relationship between driving forces and environmental change. Each case describes a particular set of variables (see table 11.2) that have interacted to create local and regional environmental change, as well as linking in some cases to systemic global change through greenhouse gas emissions or albedo change. Here we distill each case, using summary diagrams for illustration. The specific variables identified are associated with the clusters of driving forces that appear in table 11.2. Each case is treated in terms of the broad human forces of change identified. The case-studies do not treat all such forces; rather, attention is directed to those that most significantly affect the environment and the human occupance of the region. The discussion that follows first summarizes each of the cases, then assesses more general issues.

Amazonia (fig. 11.6)

The countries of the Amazon Basin suffer from poverty and foreign debt and seek the means to alleviate both. Amazonia is a region of immense mineral and biotic riches and its "frontier" development offers one means to improve the national economy and generate wealth for international and national investors (markets). Save for some local market demands, almost all of the forces of change lie outside the basin. They affect Amazonia primarily through governmental policy, which has promoted industrial and agricultural growth as well as migration into the region. The commercialization of agriculture and the agglomeration of landholdings outside Amazonia have promoted migration into the region, rapidly increasing its population. This population increase and exogenous investments have led to major increases in the use of land for livestock production, agriculture, mining, generation of hydroelectric power. and (more recently) extraction of timber.

Amazonia, therefore, is a case of a frontier invaded by forces of production and consumption partly in response to directly or indirectly state-created incentives and subsidies. Historically, extractive and environmentally damaging activities characterize such frontier invasions in the short run, but they often shift through time to activities that have less immediate extractive consequences. From a regional perspective, the forces of change may be slowing and their consequences moving toward less overall damage.

Table 11.2 Human driving forces of environmental change: Association of specific variables from the case-studies with clusters of driving forces

Cluster of human driving forces
Populationa Technological capacityb Affluence/povertyc Political economy/structured Beliefs/attitudese
Population growth Irrigation development Urbanization International market Frontier development
Migration Mechanization Poverty National market Ethnic/religious views
Natural growth Fertilization   State policy Mass-consuming view of nature
  Pasture improvement   Shift to commodity production Acceptance of corruption
  Industrialization infrastructure   Foreign debt, balance of trade  
  Agricultural intensification   Resource allocation rules & institutions  
      Capital extraction  
      Political corruption  

a. Population: increase or decrease in number of people per unit area.
b. Technological capacity: movement to a different technology, including shifts in suites of technology.
c. Affluence/poverty: level of wealth of an area, generally measured by per capita consumption and well-being.
d. Political economy/structure: economic, political, and social institutions that govern resource and environmental use.
e. Beliefs/attitudes: ideas and norms of behaviour that underlie formal institutions.

Fig. 11.6 Amazonia

Eastern Sundaland (fig. 11.7)

The forces of change in eastern Sundaland are variable, showing differing degrees of impact and intensity in different parts of the region. All countries controlling the region espouse development strategies and look to the tropical forests of the eastern Sundaland as a rich source of timber, for which a large international market exists. In addition, some segments of the region are experiencing significant population growth and an increase in associated demands. These forces have led to central governmental policy promoting growth in the timber/lumber industry (sawmills and plywood) and, in some cases, to agricultural development of tree estates. In addition, corruption supports this system and also impedes enforcement of regulations designed to protect the forests by determining the kinds, extent, and places of logging.

The case of eastern Sundaland, therefore, strongly resembles that of Amazonia in that the forces of change are largely external to the region, having more to do with the prevailing political economy of the countries controlling the region than with local demand for resources and benefits from their use. This tropical forest frontier differs from Amazonia in that timber extraction has been a major immediate cause of change and some ecologically successful agricultural systems have developed rapidly.

Ukambani (fig. 11.8)

The long-term trend in Ukambani has been, for many, toward a lower quality of life and increased vulnerability to future drought or other stressful events. Since the 1920s, a spiral of land degradation has been apparent that has resulted in periodic famines and periods of food shortage. In this context, the regional populace continues to rely upon out-migration as the primary response to drought and famine. For others, however, the intensification of land use in the region has led to economic gain, largely through improved farming on more favourable land.

The key driving forces have been those of political economy. Changes in state intervention, land tenure, and settlement arrangements, and legal and policy initiatives for land use and management have largely guided the spiral of land degradation and food shortages. While population increase has been a factor, its contribution has largely been to exacerbate the effects of these other driving forces. Land alienation to conserve resources for future use by the state or commercial interests has underlain much of the societal response to land degradation and propelled the trajectory to greater endangerment.

Fig. 11.7 Eastern Sundaland

Fig. 11.8 Ukambani

The Nepal middle mountains (fig. 11.9)

The middle mountains of Nepal, unlike the two frontier cases described above, have a long history of significant traditional occupance and use based on cultivation and pastoralism. Population and poverty have grown at the same time that the country has sought to develop markets to alleviate foreign debt and promote development. These forces have combined to influence a government policy of market-oriented development aided by subsidized infrastructure and technical inputs, as well as changed rules of resource allocation. Perhaps most important in this policy has been the dramatic shift from traditional rules of allocation (common property) to private ownership (cropland) and state control (e.g. protected forests), and the behavioural changes associated with the increasing commodity production (Ives and Messerli 1989; Jodha 1992). Concurrently, such services as health-care facilities have promoted rapid population growth.

The situation in the middle mountains of Nepal resembles that of many other regions experiencing a transition from traditional to capitalist economies. The disruptive impacts of this change are heightened here, however, by the high-energy environment of the Himalayas, as in other mountain environments (Jodha, Banskota, and Partap 1992).

Ordos Plateau (fig. 11.10)

The Ordos Plateau is an arid sandstone environment that has been a focus of development within a centrally planned economy. The goals of development have been to generate capital income for national development goals, to redress an unfavourable international balance of trade and foreign debt, and to settle farmers from the more crowded areas to the south. National strategies have promoted agricultural and industrial growth as well as in-migration. Population increases have led to significant land stresses, particularly through cropland expansion on natural grasslands and fuelwood harvesting. Agricultural and industrial growth has promoted intensive livestock production, particularly of sheep for the new wool industries. In addition, extensive coalmining has begun in various sections of the region, largely serving the needs of the Chinese state outside the Ordos proper.

Fig. 11.9 The Nepal middle mountains

Fig. 11.10 The Ordos Plateau

The Ordos Plateau is a case of the invasion of an arid frontier region a frontier relative to the long-term density of occupance of the Chinese lands on its southern border. The invasion has been orchestrated to a large degree by central political authority. Interestingly, though, once the plan for agricultural development was set in motion, it was difficult to control, with migration and expansion of agriculture occurring spontaneously and rules about land use and management difficult to enforce.

Aral Sea (fig. 11.11)

The Aral Sea region has experienced a massive, centrally planned expansion of irrigated agriculture in a narrow band of lands along the two exotic rivers feeding the sea. Particularly in the second half of this century, the former USSR sought to develop the Aral region, in large part to serve its needs for hard currency for international markets, trade, and debt payment. This effort, in tandem with regional cultural values, has precipitated skyrocketing population growth. Moscow dictated the entire course of land use in the region, including the crops to be grown and the land- and water-management systems to be employed. The emerging regional economy involved the construction of massive but highly inefficient surface irrigation systems, an emphasis primarily on cotton production, involving harvesting techniques that severely pollute the irrigation water, a reward system based on the amount of water used (leading to inefficient use), and the development of urban-industrial settlements lacking adequate infrastructures for water and sanitation. Meanwhile, technological inefficiency and mismanagement have exacerbated the impacts that would have arisen from the scale of the agricultural system alone.

The Aral Sea is a case of environmental catastrophe, spawned by knowing exploitation by a distant central government in a politically marginal region. It suggests the kinds of problems that can occur in marginal areas of a political economy considered expendable by the centre. It is unique among our regions in that the main locus of change exploitation by the central government in the USSR - has evaporated. The process of environmental degradation that it set in motion, however, remains uncorrected.

Fig. 11.11 The Aral Sea

Llano Estacado (fig. 11.12)

The semi-arid Llano Estacado region of the Southern High Plains of the United States, situated mostly in the Panhandle of Texas, has been significantly transformed over the last century from an extensive to an intensive agricultural economy, with an emphasis on irrigated cotton production. Landowners have responded to international markets for cotton and national markets for grains and cattle. They have relied upon modern technologies of large-scale groundwater irrigation, mechanization, and fertilization, and governmental policies have subsidized and insured agricultural activities and infrastructures (e.g. agricultural research stations and transportation). All of these factors have promoted the expansion of cropland, both irrigated and rainfed, and an intensification of the livestock industry. In turn, these agricultural activities, coupled with an oil industry and the development of a service sector, have promoted urban and industrial growth, with a rise in the population of cities and towns (although this growth may have ended).

The Llano Estacado is a case of a semi-arid land frontier closely linked to national and international markets, with a relatively affluent population and little regulation of the draw-down of a critical resource stock (groundwater). How the system will adjust depends on the market, resource regulation, and technological change.

Basin of Mexico (fig. 11.13)

The Basin of Mexico may constitute the largest nucleated settlement in the world, and certainly the largest occupying a closed hydrological basin. Two major forces have driven the city's growth. The first has been a long-standing state policy emphasizing the basin as the financial and industrial centre of Mexico, to be developed first and foremost by concentrating the resources of the country there. The second, partly the result of the first, has been the massive migration to the basin, by both rich and poor, from elsewhere in the country. Technologies and infrastructures that allow the importation of water from, and the export of wastes to, adjacent basins have largely sustained these developments.

The current use of the basin requires enormous subsidies drawn from Mexico at large. If these subsidies were diminished, the system would collapse. At the same time, the continued use of these subsidies has contributed to trajectories of change that threaten dire long-term consequences and possible collapse. The Basin of Mexico represents the problems of concentration of all kinds within an environment that is capable of immediately "biting back" (enclosed air inversions and a basin floor sinking from a lack of water). The problems of groundwater have been abated at high cost by engineering solutions; those of air pollution have not.

Fig. 11.12 The Llano Estacado

Fig. 11.13 The Basin of Mexico

North Sea (Fig. 11.14)

The North Sea case has two distinctive aspects: it involves a common-pool resource (and an oceanic one at that), surrounded by a very large, affluent, and urban-industrialized society on its rimland. Since this rimland has long sustained a large population, and this population is not growing at a substantial rate (at least by world standards), population change per se is not a critical driving force; high per capita consumption (affluence) of the large population, however, is. As important as the urbanized population and industrialized economy are, both are predicated on international markets. These factors coalesce to create demands for North Sea resources. These demands are mediated by: a high technological capacity that facilitates fishing, oil and gas extraction at sea, heavy sea-borne traffic, and waste disposal and marine pollution (from both sea and land activities); variable intergovernmental regulation of this common-pool resource (subsidies for certain activities, non-regulation of others); and a "false consciousness" among the population about its impacts on the sea (what Sack, 1990, refers to as "a myth of mass consuming societies," an unrealistic view of the environmental associations of modern consumption).

The North Sea exemplifies the impacts of industrialized society on an unregulated common-pool resource. Change can be swift. The affluence and technological capacity of the region, however, provide an enormous ability to address this degradation, assuming that society continues to judge the benefits of doing so to be worth the cost.

Driving forces in perspective

Each case displays different clusters of the driving forces identified above, operating in different contexts. Here we focus on what each case says about these clusters.

Population growth within the region was a major driving force in six cases (Amazonia, the Nepal middle mountains, the Ordos Plateau, the Aral Sea, the Basin of Mexico, and part of eastern Sundaland), all involving regions or regional systems of underdevelopment. Such growth, of course, was usually the product of other forces (largely those of political economy and structure) that stimulated migration into or natural growth within the region.

Fig. 11.14 The North Sea

Technological capacity entered in two ways: changes in technology permitting new uses of the region and enhancing the overall level of technology available to users. Technological innovation supported the introduction of modern infrastructures and enlarged means of production, usually to frontiers or sparsely inhabited areas (Amazonia, eastern Sundaland, the Nepal middle mountains, the Ordos Plateau, and the Llano Estacado). Damage initially followed from technologies unsuited to specific environments, in some cases producing initial impacts that were reduced over time by the adoption or development of new techniques (as in Amazonia). At least three broad types of interactions occurred: (1) poorly constructed, inefficient, and highly polluting technologies (the Ordos Plateau, the Aral Sea, the Basin of Mexico), (2) state-of-the-art technologies that exacerbate impacts, intended or not (the North Sea, the Llano Estacado, the Basin of Mexico), and/or (3) technologies that abate problems through substitution, such as water transfers or changes in fuel types (as in the Basin of Mexico).

Affluence was directly identified as a driving force only for the North Sea case, where high per capita consumption has had obvious impacts, and in the Basin of Mexico, where high per capita use of cars, for example, contributes to major pollution problems. It was implied for the Llano Estacado in the sense that local producers who are seeking to sustain and improve an already very high standard of living drive economic activities there. Increased per capita consumption, of course, is occurring in several other cases (especially in rural, developing areas), but its contribution as a driving force has been relatively small.

The opposite of affluence, or poverty, appears as an important driving force in four cases (Amazonia, the Nepal middle mountains, the Basin of Mexico, and Ukambani). In each of these cases, poverty drove inappropriate resource use that exacerbated resource consumption or loss. In rural areas, this involved the intensification of land use without appropriate inputs (as in the Nepal middle mountains) and, in the case of Mexico, was a "push" stimulus for migration. Finally, if poverty is expanded to country-scale "underdevelopment" or imbalance of trade and debt, then all of the cases, save the Llano Estacado and the North Sea, had this force operating through its influence on the policy of use.

Two broad political-economic forces operated in all cases through state policy and the character of the economy. The role of state policy was obvious and direct in centrally planned economies (the Aral Sea, the Ordos Plateau, the Basin of Mexico), but it was also important in poorly developed marginal areas and frontiers having little power vis--vis the national government (Amazonia, eastern Sundaland) or seeking state assistance to develop (the Nepal middle mountains). In the developed-world cases, the state operated through more individually directed policy, such as subsidies for farming in the Llano Estacado or the lack of regulation in the North Sea.

The economy operated as a driving force in several major ways. First, the region provided a desired resource that would not necessarily have been exploited without external intervention (eastern Sundaland, Amazonia). Related to this was resource use predicated on external demands regulated through the market or government controls (the Aral Sea, the Llano Estacado, the North Sea). Second, shifts from a pre-capitalist (traditional) toward a capitalist (market) economy heightened environmental change because of the transaction costs of changing the rules of resource allocation (the Nepal middle mountains). Finally, two regions - the North Sea and the Ogallala aquifer (Llano Estacado) suffered from inadequate or improper valuation of environmental impacts on a common-pool resource. (Air pollution in the Basin of Mexico may also reflect a common-pool situation.)

Beliefs and attitudes are usually difficult to identify as autonomous forces of change. Nevertheless, the case-studies identified three forces that qualify for consideration here. The first is a "frontier" outlook, prevalent in the Amazonia and eastern Sundaland (and once prevalent in the Llano Estacado), that emphasizes rapid development. This orientation is not purely economic, but takes root as part of a new world-view. The second is ethnic identity and associated religious beliefs that serve to increase natural population growth and hence resource demands (as in the Aral Sea region). This same force may also operate, though less directly, in the case of the Basin of Mexico. Finally, the underestimation - perhaps denial - by mass-consuming, industrialized, and urbanized societies of the environmental consequences of their activities was apparent in the North Sea and Basin of Mexico cases.

Toward a synthesis

The different emphases in the case-studies and the absence of standardized quantitative data for the major driving forces preclude any statistical explorations of their roles (singly or interactively) in inducing environmental change. The case-studies do, however, provide qualitative evidence of the role of certain characteristic clusters of driving forces, showing (save for the category of beliefs/attitudes) rather marked consistency among the specific variables identified or implied. As expected, these regional studies identified the cluster of driving forces in political economy and structure as particularly significant. These forces were important in all cases and perhaps dominant in a number (the Basin of Mexico, Amazonia, the Aral Sea, eastern Sundaland, Ukambani, and the Llano Estacado).

This result stands in contrast to global aggregate assessments (e.g. CEQ 1980; Meadows et al. 1972; WCED 1987), which typically emphasize the triad of population, affluence, and technology (e.g. I = PAT assessments). Such differences are not necessarily irreconcilable, given that the spatial and temporal scales and the mode of analysis used affect the findings. At the global scale, the I = PAT formula sums up the human pressures on resources in a closed system, but it says nothing about where within the system those pressures will be felt or how they will be mediated. Regions are not closed systems, and, as our cases show, the export of demands and degradation from their source areas to distant points (or distant generations) is a common occurrence.

Indeed, driving forces external to the region affected were typically more important than internal forces. These external forces tended to be those of resource extraction or production for distant national and international markets and those causing in-migration from densely settled areas. In every case, resource extraction or production for external consumption was an important factor, and only in the highly urbanized-industrialized cases (the North Sea and the Basin of Mexico) was consumption internal to the region a major force of change. Also, in every case, state policy and institutions affecting resources and environment were key forces of change, and, with the exception of a few regions totally controlled from afar, external demands operated in the context of state policy and institutions, illustrating the confluence of external and internal forces of change. One institutional force that stood out was legal and institutional structures affecting common-pool resources, in which minimal or no rules of allocation or use operated.

The I = PAT formula can also be criticized for treating only affluence, or high levels of consumption, as a driving force, while neglecting the ways in which poverty may drive environmental degradation (Leonard 1989; Kates and Haarmann 1992). Our two cases of agglomerated environmental stressors (the North Sea and the Basin of Mexico) represent the I = PAT scenario of relatively high levels of consumption taxing the capacities of the regional environment. As noted above, however, in at least as many cases (e.g. Amazonia, the Nepal middle mountains, and the Basin of Mexico) poverty rather than affluence has driven unsustainable resource use. Overall, the fact that regional population, affluence, and technology did not predominate compared with external forces suggests that some rethinking of the conventional wisdom of the relationship between human driving forces and environmental change may be needed.


The nine cases explore the vulnerability of the environment-human use relationship in less depth than they do the human driving forces of change. None the less, they do indicate several common features, mostly involving the social dimensions of vulnerability. Ecosystem fragility receives less systematic attention. The case-studies deal with multiple changes that pose multiple threats. In general, the discussions focus not on differential abilities to respond to a specific threat but on a general regional ability to respond to a broad spectrum of changes and variability in the environment.

Our concern here is with the vulnerability of the environment-human use relationship, not with the vulnerability of the human-use system to other types of social and economic threats. Some socioeconomic processes that threaten to lower regional wealth and wellbeing can at the same time lead to ecological recovery. In the Llano Estacado, for example, competition from other cotton producers in the world economy is one non-environmental source of downward pressure on regional wealth. To the extent that it leads to land being taken out of production, it reduces soil erosion and aquifer draw-down. A past case of regional economic and demographic decline (resulting in reduced environmental stress) stemming from similar external competition is that of Amazonia, which grew wealthy from rubber exports but experienced a dramatic and long-lasting collapse in 1912 when the successful cultivation of rubber in South-East Asia undercut its profits.

The nine regions illustrate some obvious ways in which vulnerability has declined over time. Technological interventions have reduced the vulnerability of some regions to fluctuations in the physical environment. In the North American High Plains, of which the Llano Estacado is a part, the widespread adoption of groundwater irrigation has insulated productive activities against the droughts that caused several major collapses of regional population and economy in earlier decades. Advanced pumping technology delivers water to a water-stressed Basin of Mexico, as well as removing pollution from the basin. (It should be noted, however, that these technological solutions bring with them potentially greater environmental vulnerability - to the loss of irrigation water in the Llano Estacado and the sustained growth of Mexico City in the basin.) A different form of reduced vulnerability appears in the North Sea and Llano Estacado cases. The increased wealth of the societies in which the regions are embedded has expanded the ability to mitigate environmental degradation and its consequences. Finally, improved access to the world market expands the range of options for use and response in a variety of ways: creating new uses and demands for regional resources once little valued, allowing resources to be imported as substitutes for ones locally exhausted, and making possible the adoption of innumerable technologies (developed elsewhere) to mitigate problems or increase the efficiency of resource use.

In the nine case-study chapters, however - perhaps because they represent a sample weighted toward failure rather than success - processes that have increased vulnerability or made it manifest in actual impacts appear more prominently. The two major types of change identified as increasing vulnerability result from human uses that (1) immediately alter the physical characteristics of the environment, and (2) link the use-environment system more closely with a highly variable, unreliable, or exploitative political economy.

Our regional case-studies suggest that environmental degradation involves such fragile or vulnerable settings as (1) extensive old growth forests (Amazonia, eastern Sundaland); (2) arid lands or water sources in arid lands (the Ordos Plateau, the Aral Sea, the Llano Estacado, Ukambani, and, partly, the Basin of Mexico); (3) high-energy environments (e.g. the Nepal middle mountains); and (4) common-pool resources (the North Sea, the Llano Estacado, the Aral Sea, and the Basin of Mexico). The Basin of Mexico dramatically illustrates the significance of the biophysical environment and regional ecology. Here an enclosed basin and thermal inversions exacerbate air pollution, aridity accentuates water delivery problems, an ancient lakebed subsiding because of groundwater depletion creates basic problems of land-surface stability, and steep slopes provide a high energy source for erosion and other degrading processes. These environmental or resource characteristics do not in themselves create environmental change or degradation, which is a function also of the nature of the human uses. In an earlier agrarian era, the Basin of Mexico responded positively to use.

Such physical changes may increase the potential for surprise and disruption of an environment-use system, reduce the options and the buffering and regenerative capacity of the land, or deplete resources so that the ability to meet human-induced stresses erodes. The degree of regional dependence on the particular environmental uses undergoing change is a key dimension of vulnerability in all of the cases. Regional vulnerability to management initiatives and the long-term biophysical vulnerability created by losses of genetic resources are specifically treated in the North Sea and the eastern Sundaland cases.

In Amazonia, Smith and colleagues suggest that, as humans increasingly alter forest and aquatic environments, their activities could become increasingly vulnerable to ecological surprises. In addition, to the extent that increased reliance on development and technology accompanies alterations in resource-use patterns, vulnerability to production failure increases with development. This increased potential for biophysical surprise is a key dimension of vulnerability, given the growing linkage of regions with the global economy, fluctuations in world markets, and the impacts of such fluctuations on regional livelihood systems.

In the Nepal middle mountains, Jodha identifies several types of vulnerability that relate to the resource endowments of subregions. He also describes social and ecological processes that create vulnerabilities. The first type occurs in an economically stagnant area that is reliant on subsistence agriculture, where vulnerability appears in:

1. the reduced range, dependability, and payoffs of production or resources use options, because of (a) the breakdown and infeasibility of traditional diversified, resource-regenerative practices, and (b) a degradation of the resource base;

2. the slackening or disruption of collective risk-sharing institutions and resource-management systems (such as common-property re sources) and the introduction of more formal, legalistic arrangements to regulate people's relationship to their natural resources. The second type involves rapidly commercializing areas in which potential vulnerability reflects changing linkages with distant markets. On a macro level, in this case a nation, uneven trade also is a source of vulnerability, which is expressed in widespread food deficits and the state's inability to implement effective development policies (as in the Ukambani case).

In the Llano Estacado, various social supports have propped up an economy based on agriculture and little else. Here cotton operates at its biophysical margin. The land use is vulnerable to groundwater depletion and rapid erosion under cropping (whereas grazing would provide a more ecologically sustainable alternative). A situation has developed with a high dependence on agriculture, an increasingly restricted range of regional options, and a dependence on volatile agricultural commodity markets. Ukambani exhibits a similar dependence on commercialization of agriculture and on agricultural commodity markets. But here state policies restricting access to land and pushing poorer farmers onto more marginal lands have increased vulnerability to droughts and to market shifts. Meanwhile, the subsidies and safety nets that support agriculturalists in the Llano Estacado are unavailable, so that periodic famines and food shortages occur.

The Basin of Mexico is also increasingly precarious. Indeed, it represents strikingly a situation of resource use supporting urbanization that is reaching its ecological limits. Some of these limits are set by the biophysical characteristics of the basin, as noted above, whereas others involve technological and social abilities to substitute or to import needed resources. Pollution and deforestation are reducing some capacities to self-regulate the water supply and to maintain the requisite self-sufficiency, whereas the political-economic structures that subsidize the basin's water and waste disposal may also be approaching their limits.

The final two cases provide a somewhat different perspective on vulnerability. In the North Sea, environmental changes undoubtedly have had particularly severe impacts on the fishing industry and some other users of the sea. In eastern Sundaland, by contrast, the picture of vulnerability among social groups is more mixed. There, the biophysical dimensions of vulnerability raise several broader issues. First, considerable uncertainty surrounds the future consequences of environmental changes; insufficient knowledge renders it difficult to determine which forest systems will recover quickly. Second, irreversible losses in biodiversity are occurring, and the lack of alternatives to these species places those losses in a unique category that is difficult to evaluate over the near term and for the region. Similar long-term problems of biodiversity loss are apparent in Ukambani.

All nine cases address changing vulnerability primarily in terms of changes in the overall vulnerability over time as a region copes with a myriad of threats and environmental change. The internal vulnerability of different social groups or genders generally receives less attention (but see chaps. 5 and 6). The severity of the impacts on local peoples of changes supported by national and international policies does appear repeatedly, particularly where local groups are marginal to the political process. In the Nepal middle mountains, Amazonia, the Aral Sea region, eastern Sundaland, and Ukambani, the people with an established history of resource use in the area seem almost always to lose more, gain less, and receive less compensation from the environmental changes that have accompanied development.

On a regional level, three aspects of changing environmental and socio-economic conditions suggest an increasing potential for higher or catastrophic losses and merit further scrutiny.

1. Vulnerability and overshoot. In the Basin of Mexico, increasing demands are overwhelming finite sources of non-substitutable resources, such as clean air and water. The momentum of growth is outpacing the ability both to procure other supplies of necessary resources and to limit demand or mitigate damage. Meanwhile, the scale of the problems is growing relentlessly, suggesting an "overshoot" type of vulnerability.

2. Market conditions and overcapitalization. Several regions confront narrowing options and growing demands in more flexible global markets. The capital investments involved in the unsustainable production levels of cotton products (the Aral Sea region, the Llano Estacado) and timber products (Amazonia, eastern Sundaland) for the world market create livelihood systems dependent on those markets yet vulnerable to their fluctuations. Growing regional economic dependence on these environmental resources portends higher risks; transitions to other options and greater diversity, meanwhile, are increasingly painful. The difficulties faced by the fishing industry in the North Sea illustrate this case for a narrow portion of a regional population.

3. Loss of options and safety nets. For part of the Nepal middle mountains, environmental degradation has narrowed agricultural options, and changes in the production system have eroded the capabilities of existing risk-management systems while failing to replace them with new systems. Environmental changes in Amazonia hold an increased potential for environmental surprises, and the extent to which the new productive systems will provide new buffers and sources of security is uncertain. Meanwhile, failures are likely to have far-reaching consequences because of the lack of entitlements and of back-up societal and livelihood options.

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