North America

14 North America Coordinating Lead Authors: Christopher B. Field (USA), Linda D. Mortsch (Canada) Lead Authors: Michael Brklacich (Canada), Donald L. Forbes (Canada), Paul Kovacs (Canada), Jonathan A. Patz (USA), Steven W. Running (USA), Michael J. Scott (USA) Contributing Authors: Jean Andrey (Canada), Dan Cayan (USA), Mike Demuth (Canada), Alan Hamlet (USA), Gregory Jones (USA), Evan Mills (USA), Scott Mills (USA), Charles K. Minns (Canada), David Sailor (USA), Mark Saunders (UK), Daniel Scott (Canada), William Solecki (USA) Review Editors: Michael MacCracken (USA), Gordon McBean (Canada) This chapter should be cited as: Field, C.B., L.D. Mortsch,, M. Brklacich, D.L. Forbes, P. Kovacs, J.A. Patz, S.W. Running and M.J. Scott, 2007: North America. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 617-652. North America Chapter 14 Table of Contents .....................................................619 14.4.2 Ecosystems..........................................................629 Executive summary 14.4.3 Coastal regions ....................................................630 ........................................................619 14.1 Introduction 14.4.4 Agriculture, forestry and fisheries.........................631 14.1.1 Key findings from Third Assessment Report (TAR) .........................................................................620 14.4.5 Human health .......................................................632 14.1.2 Key differences from TAR.....................................620 14.4.6 Human settlements ..............................................632 Box 14.3 North American cities integrate impacts ...................620 across multiple scales and sectors.......................633 14.2 Current sensitivity/vulnerability 14.2.1 Freshwater resources...........................................621 14.4.7 Tourism and recreation.........................................634 14.2.2 Ecosystems..........................................................622 14.4.8 Energy, industry and transportation .....................634 14.2.3 Coastal regions ....................................................622 14.4.9 Interacting impacts...............................................635 Box 14.1 Accelerating wildfire and ecosystem disturbance dynamics...........................................623 14.5 Adaptation: practices, options and ...........................................................635 14.2.4 Agriculture, forestry and fisheries.........................623 constraints 14.5.1 Practices and options ..........................................636 14.2.5 Human health .......................................................625 14.5.2 Mainstreaming adaptation ...................................637 14.2.6 Human settlements ..............................................625 14.5.3 Constraints and opportunities..............................638 14.2.7 Tourism and recreation.........................................626 14.2.8 Energy, industry and transportation .....................626 .........................................................639 14.6 Case studies ..................626 14.3 Assumptions about future trends 14.7 Conclusions: implications for sustainable ........................................................639 14.3.1 Climate .................................................................626 development 14.3.2 Social, economic and institutional context ..........627 ...639 14.8 Key uncertainties and research priorities .......627 ......................................................................640 14.4 Key future impacts and vulnerabilities References 14.4.1 Freshwater resources...........................................627 Box 14.2 Climate change adds challenges to managing the Columbia River system ..................628 618 Chapter 14 North America Executive summary Climate change impacts on infrastructure and human health and safety in urban centres will be compounded by ageing infrastructure, maladapted urban form and building stock, North America has experienced locally severe economic urban heat islands, air pollution, population growth and an damage, plus substantial ecosystem, social and cultural ageing population (very high confidence). disruption from recent weather-related extremes, including While inertia in the political, economic, and cultural systems hurricanes, other severe storms, floods, droughts, heatwaves complicates near-term action, the long life and high value of North and wildfires (very high confidence). American capital stock make proactive adaptation important for Over the past several decades, economic damage from severe avoiding costly retrofits in coming decades. [14.4.5, 14.4.6, 14.5, weather has increased dramatically, due largely to increased value Box 14.3] of the infrastructure at risk. Annual costs to North America have Without increased investments in countermeasures, hot now reached tens of billions of dollars in damaged property and temperatures and extreme weather are likely to cause economic productivity, as well as lives disrupted and lost. [14.2.3, increased adverse health impacts from heat-related mortality, 14.2.6, 14.2.7, 14.2.8] pollution, storm-related fatalities and injuries, and infectious The vulnerability of North America depends on the diseases (very high confidence). effectiveness and timing of adaptation and the distribution of Historically important countermeasures include early warning and coping capacity, which vary spatially and among sectors (very surveillance systems, air conditioning, access to health care, high confidence). public education, vector control, infrastructure standards and air Although North America has considerable adaptive capacity, quality management. Cities that currently experience heatwaves actual practices have not always protected people and property are expected to experience an increase in intensity and duration of from adverse impacts of climate variability and extreme weather these events by the end of the century, with potential for adverse events. Especially vulnerable groups include indigenous peoples health effects. The growing number of the elderly is most at risk. and those who are socially or economically disadvantaged. Water-borne diseases and degraded water quality are very likely Traditions and institutions in North America have encouraged a to increase with more heavy precipitation. Warming and climate decentralised response framework where adaptation tends to be extremes are likely to increase respiratory illness, including reactive, unevenly distributed, and focused on coping with rather exposure to pollen and ozone. Climate change is likely to increase than preventing problems. ‘Mainstreaming’climate change issues risk and geographic spread of vector-borne infectious diseases, into decision making is a key prerequisite for sustainability. including Lyme disease and West Nile virus. [14.2.5, 14.2.6, [14.2.6, 14.4, 14.5, 14.7] 14.4.5, 14.4.6, 14.5] Coastal communities and habitats will be increasingly Disturbances such as wildfire and insect outbreaks are stressed by climate change impacts interacting with increasing and are likely to intensify in a warmer future with development and pollution (very high confidence). drier soils and longer growing seasons (very high confidence). Sea level is rising along much of the coast, and the rate of change Although recent climate trends have increased vegetation growth, will increase in the future, exacerbating the impacts of progressive continuing increases in disturbances are likely to limit carbon inundation, storm-surge flooding and shoreline erosion. Storm storage, facilitate invasive species, and disrupt ecosystem services. impacts are likely to be more severe, especially along the Gulf Warmer summer temperatures are expected to extend the annual and Atlantic coasts. Salt marshes, other coastal habitats, and window of high fire ignition risk by 10-30%, and could result in dependent species are threatened by sea-level rise, fixed structures increased area burned of 74-118% in Canada by 2100. Over the blocking landward migration, and changes in vegetation. 21st century, pressure for species to shift north and to higher Population growth and the rising value of infrastructure in coastal elevations will fundamentally rearrange North American areas increases vulnerability to climate variability and future ecosystems. Differential capacities for range shifts and constraints climate change. Current adaptation is uneven and readiness for from development, habitat fragmentation, invasive species, and increased exposure is low. [14.2.3, 14.4.3, 14.5] broken ecological connections will alter ecosystem structure, function and services. [14.2.4, 14.2.2, 14.4.2, Box 14.1] Climate change will constrain North America’s over-allocated water resources, increasing competition among agricultural, municipal, industrial and ecological uses (very high 14.1 Introduction confidence). Rising temperatures will diminish snowpack and increase The United States (U.S.) and Canada will experience climate evaporation, affecting seasonal availability of water. Higher changes through direct effects of local changes (e.g., demand from economic development, agriculture and population temperature, precipitation and extreme weather events), as well growth

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