Working Group II: Impacts, Adaptation and Vulnerability

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15.4. Synthesis

Our impacts and adaptation assessment indicates that changing climate and changing patterns of regional development have challenged North America and will continue to do so. Damage costs from recent climatic events have increased, and conflicts over climate-sensitive resources (e.g., fish) continue to occur. Future climatic changes may exacerbate these problems and indeed create new ones. Opportunities may arise from a warming climate, and some innovative adaptation mechanisms (e.g., water banks) are being tested to address current problems. However, the literature provides few cases on how adaptive strategies could be implemented in the future as regional climates continue to change.

Recent studies in agriculture point to greater crop diversity and possibilities for adaptation as factors in reducing estimates of future damage. Production forestry is regarded in much the same way, except in high-latitude regions where vulnerabilities to changing climate-related risks (pests, fire, permafrost thaw) still are considered significant challenges for management. Estimates of future damage to U.S. coastal zones have declined despite the recent series of high-cost extreme events. However, studies also have documented changing vulnerabilities of built (urban) environments to atmospheric events, risks to indigenous lifestyles, and the challenge of managing resources within a changing climatic regime to meet multiple objectives. Climate change along the U.S.-Mexican border may result in social and economic problems related to transboundary water resources. Unique natural ecosystems such as prairie wetlands, alpine tundra, and coldwater ecosystems are at risk, and effective mitigation is unlikely.

As impact studies of North America attempt to include adaptation in a more significant way, damage estimates in some sectors decline or become benefits. Mendelsohn and Neumann (1999) illustrate this trend for agriculture, production forestry, and coastal zone impacts in the United States. What also emerges, however, is that high damage costs are still calculated for water-related activities and summer energy demand. Most important, there are several outstanding methodological issues related to the evolution of economic activities, adaptation assumptions, and the value of nonmarket components, resulting in continued difficulties in estimating the cost of impacts and the costs and benefits of adaptation responses. If optimistic views about adaptation were realistic, North America should have been better able to plan for extreme events. Recent experience demonstrates high capability in emergency response, but long-term problems remain.

During recent extreme weather events, synergies between development pressures and environmental changes have resulted in substantial damages. Examples documented in Sections 15.2.1, 15.2.3, 15.2.7, and 15.3.2 include water-quality problems resulting from North Carolina hurricanes, damage from the 1998 ice storm, reductions in fish stocks as a result of climatic shifts combined with fishing pressure, and various impacts from recent water-level fluctuations in the Great Lakes. Unfortunately, only a few climate change scenario studies explore these kinds of synergies. Besides the challenge of projecting future economies, scenario studies of impacts and adaptation also have to consider the varied demands of regional stakeholders from the same resource and/or location. A summary of adaptation issues for North American subregions is provided in Table 15-6.

A wide range of factors—including changing political and institutional arrangements, technologies, and perceptions—may influence regional development futures. Concerns about development, equity, and sustainability are emerging in international negotiations of the United Nations Framework Convention on Climate Change and the Kyoto Protocol, and regional impacts/adaptation concerns can play an important role in this debate (Munasinghe and Swart, 2000). How could development paths alter a region's vulnerability to climate change? Could incentives related to emission reduction also enhance adaptation? Or, could management for certain environmental objectives lead to difficulties in meeting others? The example from the Columbia basin (Section 15.3.2), in which managing for fish protection could lead to increases in GHG emissions (Cohen et al., 2000), illustrates the dilemma that many subregions could face as they consider options for responding to climate change scenarios. How can these interactions be addressed in scenario studies? How can the various economic and social dimensions be accounted for so that there could be more confidence in estimates of impacts damages and adaptation costs/benefits?

Additional information on alternative climate scenarios and regional development futures will be needed in order to improve estimates of the costs of subregional impacts of climate change and the costs and benefits of adaptation responses. As measures associated with the Kyoto Protocol attract more attention from governments and industries, consideration also should be directed at studies on the interplay of mitigation and adaptation at the subregional scale.

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