15 North America STEWART COHEN (CANADA) AND KATHLEEN MILLER (USA) Lead Authors: K. Duncan (Canada), E. Gregorich (Canada), P. Groffman (USA), P. Kovacs (Canada), V. Magaña (Mexico), D. McKnight (USA), E. Mills (USA), D. Schimel (USA) Contributing Authors: G. Chichilnisky (USA), D. Etkin (Canada), R. Fleming (Canada), K. Hall (USA), S. Meyn (Canada), J. Patz (USA), R. Pulwarty (USA), D. Scott (Canada), G. Wall (Canada) Review Editor: E. Wheaton (Canada) CONTENTS Executive Summary 73 7 15 . 2 . 6 . Tourism and Recreation 76 9 15 . 2 . 7 Public and Private Insurance Systems 77 0 15 . 1 . The North American Region 74 1 15 . 2 . 7 . 1 Private-Sector Insurance Systems 77 0 15 . 1 . 1 . Previous Wor k 74 1 15 . 2 . 7 . 2 Government-Based Insurance 15 . 1 . 2 . What is Different about the and Disaster-Relief Systems 77 3 North American Region? 74 1 15 . 2 . 7 . 3 Creating and Maintaining 15 . 1 . 2 . 1 . High Level of Adaptive Capacity 77 4 Intensive Water Management 74 2 15 . 2 . 7 . 4 Equity and Sustainability Issues 15 .1 . 2 . 2.U r b a ni z a t i o n 74 3 in Relation to Insurance 77 5 15 . 1 . 2 . 3 . Continental Free Tra d e 74 3 15 . 1 . 3 . Past to Present 74 4 15 . 3 . Adaptation Potential and Vul n e r a b i l i t y 77 5 15 . 1 . 4 . Scenarios for the Future 74 4 15 . 3 . 1 . Generic Issues 77 5 15 . 3 . 2 . Subregional and Extra-Regional Cases 77 5 15 . 2 . Key Regional Characteristics 74 5 15 .3 . 2 . 1.I n t r o du c t i o n 77 5 15 . 2 . 1 . Water Resources 74 5 15 . 3 . 2 . 2 . Pacific Subregion 77 6 15 . 2 . 1 . 1 . Impacts and Adaptation Options 74 7 15 . 3 . 2 . 3 . Rocky Mountains– 15 . 2 . 1 . 2 . Water Quality 74 8 Southwest U.S. Subregion 77 7 15 . 2 . 1 . 3 . Flood Risks 74 9 15 . 3 . 2 . 4 . Prairies–Great Plains Subregion 77 8 15 . 2 . 2 . Natural Resources 75 0 15 . 3 . 2 . 5 . Great Lakes– 15 . 2 . 2 . 1 . Forests 75 0 St. Lawrence Subregion 77 8 15 . 2 . 2 . 2 . Protected Ar e a s 75 2 15 . 3 . 2 . 6 . North Atlantic Subregion 77 8 15 . 2 . 3 . Food and Fiber 75 4 15 . 3 . 2 . 7 . Southeast United States 78 0 15 . 2 . 3 . 1 . Agriculture 75 4 15 . 3 . 2 . 8 . Arctic Border 78 0 15 . 2 . 3 . 2 . Production Forestry 75 9 15 . 3 . 2 . 9 . U.S.–Mexican Border 78 2 15 . 2 . 3 . 3 . Marine Fisheries 76 0 15 . 3 . 2 . 1 0 . U.S.–Caribbean Border 78 3 15 . 2 . 4 . Human Health 76 1 15 . 2 . 4 . 1 . Potential Direct Health Impacts 15 . 4 . Sy n t h e s i s 78 3 of Climate Change 76 1 15 . 2 . 4 . 2 . Potential Indirect Health Impacts Re f e re n c e s 78 4 of Climate Change 76 2 15 . 2 . 5 . Human Settlements and Infrastructure 76 5 15 . 2 . 5 . 1 . Demographic Pressures 76 5 15 . 2 . 5 . 2 . Infrastructure Investments in Ad a p t a t i o n 76 6 15 . 2 . 5 . 3 . Coastal Regions Particularly Vul n e r a b l e 76 6 15 . 2 . 5 . 4 . Vulnerability to System Failure 76 7 15 . 2 . 5 . 5 . Development and Vulnerability to Extreme Events 76 7 EXECUTIVE SUMMARY North America has experienced challenges posed by changing with a larger proportion of runoff occurring in winter, together climates and changing patterns of regional development and with possible reductions in summer flows (high confidence). will continue to do so. Varying impacts on ecosystems and human settlements will exacerbate subregional differences in Adaptive responses to such seasonal runoff changes could climate-sensitive resource production and vulnerability to include altered management of artificial storage capacity, extreme events. Opportunities may arise from a warming climate, increased reliance on conjunctive management of ground and and some innovative adaptation strategies are being tested as a surface water supplies, and voluntary water transfers between response to current challenges (e.g., water banks), but there are various water users. It may not be possible, however, to avoid few studies on how these strategies could be implemented as adverse impacts on many aquatic ecosystems or to fully offset regional climates continue to change. Recent experience the impacts of reduced summer water availability for irrigation demonstrates high capability in emergency response to and other out-of-stream and instream water uses. extreme events, but long-term problems remain. Where lower summer flows and higher water temperatures occur, there may be reduced water quality and increased stress Climate Trends and Scenarios on aquatic ecosystems (medium confidence). North America has warmed by about 0.7°C during the past Possible changes in the frequency/intensity/duration of heavy c e ntury and precipitation has increased, but both trends are precipitation events may require changes in land-use planning h e terogeneous (e.g., seasonal reductions in precipitation in and infrastructure design to avoid increased damages arising some areas). from flooding, landslides, sewerage overflows, and releases of contaminants to natural water bodies. For a range of emission scenarios produced for this Third Assessment Report, model results suggest that North America Responses to recurring and emerging water quality and quantity could warm by 1–3°C over the next century for a low-emissions problems will provide opportunities to develop and test adaptive case (B1). Warming could be as much as 3.5–7.5°C for the management options. higher emission A2 case. Published regional impact studies have used climate scenarios with global temperature changes that are similar to these new cases, but regional scenarios may Natural Resources not be directly comparable. Forests Key Regional Concerns Climate change is expected to increase the areal extent and productivity of forests over the next 50–100 years (medium Water Resources confidence). Extreme and/or long-term climate change scenarios indicate the possibility of widespread decline (low confidence). Changes in precipitation are highly uncertain. There is little agreement across climate scenarios regarding changes in total Climate change is likely to cause changes in the nature and extent annual runoff across North America. of several “disturbance factors” (e.g., fire, insect outbreaks) (medium confidence). Of particular interest in North America The modeled impact of increased temperatures on lake are changes in fire regimes, including an earlier start to the fire e v a p oration leads to consistent projections of reduced lake season, and significant increases in the area experiencing high l e vels and outflows for the Great Lakes–St. Lawrence system to extreme fire danger. The long-term effects of fire will depend under most climate change scenarios (medium confidence). Th e heavily on changes in human fire management activities, only exception is the HadCM2 transient scenario incorporating which are uncertain, especially in remote boreal forests. IS92a sulfate aerosol emissions, which suggests slight increases in lake levels and outflows. There is a strong need for a long-term comprehensive system to monitor forest “health” and disturbance regimes over regional Where snowmelt currently is an important part of the hydrological scales that can function as an early warning system for climate regime (e.g., Columbia basin), seasonal shifts in runoff are likely, change effects on forests. 738 North America Protected Areas and circulation dynamics—play an important role in determining the productivity of several North American fisheries (high Climate change can lead to loss of specific ecosystem types, c o nfidence). such as high alpine areas and specific coastal (e.g., salt m a r s hes) and inland (e.g., prairie “potholes”) wetland types Projected climate changes have the potential to affect coastal (high confidence). There is moderate potential for adaptation to and marine ecosystems, with impacts on the abundance and prevent these losses by planning conservation programs to spatial distribution of species that are important to commercial identify and protect particularly threatened ecosystems. and recreational fisheries. The degree of impact is likely to vary within a wide range, depending on species and community characteristics and region-specific conditions. These impacts Food and Fiber are complex and difficult to observe, so climate variability c o nstitutes a significant source of uncertainty for fishery Agriculture m a nagers. Recent experiences with Pacific salmon and At l a n t i c cod suggests that sustainable fisheries management will require Food production is projected to benefit from a warmer climate, timely and accurate scientific information on environmental but there probably will be strong regional effects, with some conditions that affect fish stocks, as well as institutional areas in North America suffering significant loss of comparative flexibility to respond quickly to such information. advantage to other regions (high confidence). There is potential for increased drought in the U.S. Great Plains/Canadian Prairies and opportunities for a limited northward shift in production Human Health areas in Canada (high confidence). Crop yield studies for the United States and Canada have indicated a wide range of impacts. Increased frequency and severity of heat waves may lead to an Modeled yield results that include direct physiological effects increase in illness and death, particularly among young, elderly, of carbon dioxide (CO2), with sufficient water and nutrients, and frail people, especially in large urban centers. The net are substantially different from those that do not account for effect of reduced severity of extreme cold is likely to have a such effects.