This chapter offers an assessment for Canada, the United States, and three border regions—the Arctic, U.S.-Mexican, and U.S.-Caribbean borders. More detailed assessments for the Arctic, Mexico, and the Caribbean appear in Chapters 16, 14, and 17, respectively.

The IPCC's Special Report on Regional Impacts of Climate Change (IPCC, 1998) provides a review of more than 450 research publications concerned with impacts in North America, generally covering work done during 1975-1997. That review focused on six key sectors:

• Hydrology and water resources.
• Nonforest terrestrial and forested ecosystems.
• Food and fiber, including agriculture, production forestry, and fisheries.
• Coastal systems.
• Human settlements and industry.
• Human health.

Our update of key regional concerns (see Section 15.2) uses similar categories, with a couple of modifications. First, we consider coastal and marine ecosystems together with terrestrial ecosystems, within the review of natural resources (Section 15.2.2). Second, human settlements are reviewed as a separate category, with extended discussion of infrastructure (Section 15.2.5). Impacts on tourism and insurance are treated separately (Sections 15.2.6 and 15.2.7, respectively). We also include a series of subregional cases that highlight adaptation challenges and opportunities (see Section 15.3).

This categorization of key regional concerns in North America reflects growing interest in higher order impacts. Recent increases in financial losses from extreme weather events (hurricanes, winter storms, floods) have raised new questions about changing frequencies of atmospheric events superimposed on changing development and investment patterns. In the United States, there were 28 such events during the 1980-1997 period with losses exceeding US$1 billion. The most costly were the droughts and heat waves of 1988 and 1990, Hurricane Andrew in 1992, and the 1993 Mississippi River flood, with combined costs exceeding US$100 billion. In Canada, the 1996 Saguenay flood and 1998 ice storm in Ontario and Quebec each cost more than US$0.7 billion (CDN$ 1 billion) (Etkin, 1998). It is important to understand the extent to which these loss trends hinge on changes in climate or changes in vulnerability that may be independent of any changes in climate.

In recent years, the North American nations have undertaken intensive region-specific assessments of impacts and vulnerability (Canada Country Study, U.S. National Assessment, regional case studies). Although some of these assessments are still in progress at this writing, several themes have emerged. The involvement of stakeholders (commercial entities, local and regional governments, natural resource managers, and citizens) has brought new perspectives and refocused the definition of research questions. In nearly all regions, stakeholders perceive changes in variability to be far more threatening than decadal-scale gradual change. Many stakeholders see limited problems in adaptation and possible benefits to slow predictable change. However, there may be appreciable changes in ecosystem distributions and water resources, with significant economic impacts, leading to requirements for substantial changes in infrastructure (e.g., in coastal and permafrost regions, major urban centers). There clearly will be winners and losers.

Overall, available information suggests that if projected levels of climate changes occur, North America will become quite a different place.

North America includes economies and resources that might be comparable to those in developed countries and the more developed of the developing countries. Areas within highly urbanized and industrial zones or intensively managed agriculture, forests, and nonrenewable resource extraction all represent large-scale, highly managed resources and human-dominated ecosystems. Within this context, however, there continues to be a great deal of "extensive" land management. Many Canadian and U.S. forests are managed in relatively large tracts compared to other regions and are rather lightly managed aside from harvest schedules. Some are more intensively managed, including post-harvest site preparation for reforestation.

Table 15-1 shows a range of development indicators for Canada and the United States and compares these indicators to Mexico and the rest of the world. Higher levels of resource consumption, urbanization, life expectancy, and gross domestic product (GDP) are obvious, as are the higher rates of CO₂ emissions. At the same time, the two countries also are unusual in preserving extensive rangelands and other landscapes, so a unique feature is the juxtaposition of intensive management with "extensive" management of huge and sparsely populated areas. Some of these areas remain very much a part of the national economy, but other areas are used for subsistence. Areas that are undeveloped or are under aboriginal land claims that support traditional subsistence lifestyles include features that are found in developing country rural economies. These include low levels of built infrastructure, informal barter systems, close ties to the land, and strong historical and cultural attachments to subsistence-based communities, even in the face of opportunities in the modern wage economy.

In wage and nonwage circumstances, climate change scenarios become scenarios of changing opportunities and risks. Given the multi-objective and multi-stakeholder aspects of North American regions, a climate-related change in potential (e.g., longer growing season, higher fire risk, altered hydrological cycle) may not lead to an immediate, linear response by stakeholders (see Section 15.3). An important factor that must be considered is the extent to which individual rights are valued relative to community interests in the management of landscapes. Changing vulnerabilities may occur as a result of coupling of management to current climatic variability (e.g., watersheds developed for hydroelectric production and flood control must continue to adjust to seasonal and yearly variations in natural streamflow, as well as changing management objectives).

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