The TAR attempts to place the issue of climate change more centrally within the evolving socioeconomic context. This context is critical to evaluation of the vulnerability of sectors or regions to climatic changes and thus must be borne in mind by anyone who attempts such assessments, as well as policymakers who will need to consider the wide range of implications of technological or organizational choices on the resilience of natural and social systems to climatic changes.

Development of social institutions and technological innovations over the past 10,000 years (the era of civilization after the glacial age when ice largely disappeared) has led to rapid advancement in material well-being but also, very importantly, population growth and resource pressures (e.g., Cohen, 1995; Meyer, 1996). This development process has accelerated and become much larger in scale in recent decades. Globally, growth in annual per capita income has been estimated to have risen from about 0.6% in the 19th-century period of industrial expansion to more than 2% yr^-1 in the post-World War II era of high technological innovation and global economic cooperation (Cooper, 2000). Some analysts attribute this boom to the combination of stabilization of national economies by governmental management and liberalization of trade allowed by international organizations. Indeed, in this vision�which has been labeled the �cornucopian world view� (Ehrlich and Ehrlich, 1996)�a competitive system that fosters and rewards innovation has led to a prolonged period of development and growth that will increasingly embrace currently less-developed nations as well. Furthermore, according to Kates (1996), it is possible to achieve a world without famine, with little seasonal or chronic undernutrition and virtually no nutrient deficiencies or nutrition-related illnesses. In the area of energy and natural resources, according to von Weizs�cker et al. (1998), it is possible to increase resource productivity by a factor of four: The world would then enjoy twice the wealth that is currently available, simultaneously halving the stress placed on our natural environment.

However, this level of development continues to be an elusive goal for a large fraction of the world�s population. There is a noticeable disparity between the levels of development that have been achieved in various societies. These differences are obscured by globally averaged income growth data such as those reported by Cooper (2000). For example, gaps between the rich and the poor are widening between developed and developing countries and within tropical African, Asian, and Latin American countries (UNDP, 1999). Although there have been notable successes, many countries in these regions have experienced increases in economic instability, social insecurity, environmental degradation, and endemic poverty. Despite spectacular gains in the means of development�such as advances in science, technology, and medicine during the past century�development planning at national and global levels has not always alleviated poverty and inequity (see Box 1-2; Munasinghe, 2000).

Global food security clearly has improved in recent years as the focus of famine has shifted from large, heavily populated countries to sparsely populated and small nations, but the number of people at risk of hunger still is very high, even in parts of heavily populated nations. Chen and Kates (1996) estimate that the population at risk of outright starvation could be as high as 35 million; FAO (1999) estimates that about 800 million people in developing countries and 34 million people in developed countries suffer from undernourishment. Achieving global food security is complicated by growth in human population and political instability that disrupts food delivery systems. Projections vary widely, ranging from stabilization of population at near-present levels sometime in the 21st century to a greater than three-fold increase by the end of the century (e.g., Fischer et al., 1996; Lutz, 1996; IPCC, 2000). At current population growth rates, world food production must double within the next 40 years to feed this population; such a doubling of food production may require expansion of agricultural land into forests and areas that presently are considered marginal for agriculture (but not necessarily marginal in other respects). On the other hand, some authors (e.g., Waggoner et al., 1996) have argued it is possible to increase the dietary standard of all humans up to a doubling of current populations and at the same time to �spare land for nature� (Ausubel, 1996). This expansive vision follows from the belief that resources can be made available for the extension of current intensive agricultural practices to currently low-technology regions. The extent to which such practices can be extended is debated, on social and environmental grounds, by those who hold an opposing worldview, which has been called �limits to growth� (e.g., Ehrlich et al., 1995). Moreover, even if such agricultural intensification were to occur, there is no guarantee that extensive land use for economic development activities other than growing food would not simultaneously occur. Thus, the hope of �sparing land for nature� via intensification likewise is a controversial vision.

The need to improve productivity per unit area has led to more intensive methods in developing countries�which, together with low or negative economic support for agricultural products, often has driven smallholders off their land and led to emigration to urban centers (WCED, 1987). The influx of poor, unskilled, and often unemployable people has led to explosive and difficult-to-manage growth in these centers (O�Meara, 1999). This sets the stage for the gestation of a new set of environmental problems, including substandard housing, squatter settlements, solid waste buildups, unsatisfactory sewage disposal, urban floods, and urban water pollution, as well as the characteristic problems of large cities such as crime and social insecurity.

In opposition to the aforementioned expansive visions, others (e.g., Daily, 1997) express concern that services provided by ecosystems to society may be undermined by a combination of unsustainable population growth, destruction of natural habitats, and pollution of air, soils, and waters. Three decades ago, debate raged about whether indefinite economic expansion would be limited by environmental and other resource constraints. Meadows et al. (1972) postulated in a controversial work that environmental protection and economic growth are not compatible; there are �limits to growth.� For those holding this worldview, current development patterns will not allow continued improvement of the human condition for much longer; instead, such development will ensure continuing degradation of natural assets such as biodiversity (e.g., Pimm, 1991). Thus, it is feared that the environment may be losing part of its capacity to support life and therefore may be imposing another set of constraints on the development process�disturbances to air, waters, soils, and species distributions brought about by human activities�that will require responses to reduce additional risks. Several sharp critiques appeared (e.g., Cole et al., 1973), noting that the �limits� paradigm ignored enhanced productivity brought about by innovation and that although limits eventually might become a problem, increased knowledge generated by economic expansion could create substitutes for resources that were being used nonrenewably, and much less energy and materials would be needed to produce economic growth as technology blossomed (e.g., Grossman and Krueger, 1995; but see Myers and Simon, 1994). Moreover, it has been argued that enhanced wealth and knowledge also can reduce vulnerability to environmental stresses such as climatic change.

Subsequently, a modified view that considered both the �cornucopian� and �limits� paradigms emerged: the strategy of sustainable development. It is designed to promote conservation of resources and protection of the environment while sustaining a healthy society whose needs are securely provided. In response to requests from governments participating in the IPCC process, the TAR is attentive to the concept of sustainable development.

Technology and organization clearly have reduced the vulnerability of humans in some countries to a variety of hazards. In the context of the IPCC process, this would include, for example, flood control engineering projects that have reduced lives lost in catastrophic flooding. However, pioneering analyses in the natural hazards literature (e.g., Burton et al., 1993) note that large-scale dependence of massive populations on the functioning of giant engineering projects or social institutions often has simply transformed our risks from the predevelopment state of high-frequency, low-amplitude risk (many localized threats to small numbers of people in each instance) to the present state of low-frequency, high-amplitude vulnerability (where a rare levee failure or the simultaneous occurrence of drought in several major exporting granaries poses the risk of infrequent but very catastrophic losses). Moreover, the consequences of these risks are unlikely to be equitably distributed within and across income groups and nations, which requires assessment of the distributional implications of developmental risks and benefits (e.g., Box 1-2). In many developing regions, population pressures and poverty have led to occupation of hazardous lands (e.g., steep slopes, valley bottoms) and has greatly increased vulnerability to climate extremes. Of course, many factors other than those mentioned above can contribute to vulnerability (e.g., Etkin, 1999).

In addition to this huge list of challenges, potential threats to the global environment are connected to the development process. The TAR identifies scientific and policy linkages among key global environmental issues, one of which is climate change. Other global environmental issues include loss of biological diversity, stratospheric ozone depletion, marine environment and resource degradation, and persistent organic pollutants (Watson et al., 1998). Other contemporary issues are evident in many places across the globe�though each instance is not global in scale (e.g., Turner et al., 1990)�such as freshwater degradation, desertification, land degradation, deforestation, and unsustainable use of forest resources. None of these threats implies that the net effects of human developments are necessarily negative, only that embedded in many development activities are a host of negative aspects that many analysts and policymakers believe must be considered in development planning. Strategies to modify the amount and/or kinds of development activities to account for these threats are considered more comprehensively in the report of Working Group III. The TAR also focuses on linkages between climate change on one hand and local and regional environmental issues�for example, urban air pollution and regional acid deposition�on the other. (Strategies to deal with these issues that also help with adaptive or mitigative capacity for climate change often are called co-benefits.) Among the new areas of emphasis in the TAR are linkages between global environmental issues and the challenges of meeting key human needs such as adequate food, clean water, clean air, and adequate and affordable energy services.

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