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The prospect of rising sea level is one of the most widely recognized potential impacts of climate change. Some parts of North America have been experiencing sea-level rise for thousands of years (Hendry, 1993; Lavoie and Asselin, 1998). Most climate models, however, project that the pace will accelerate in many regions. This acceleration would increase the difficulty of adaptation for human settlements and natural systems. The greatest vulnerability is expected in areas that recently have become much more developed, such as Florida and much of the U.S. Gulf and Atlantic coasts. Insured property value in Florida alone exceeds US$1 trillion (Nutter, 1999).
Titus and Richman (2001) have developed a data set of coastal land elevations
by using digital-elevation models and printed topographic maps to determine
areas that are vulnerable to sea-level rise along the U.S. Atlantic and Gulf
coasts. Louisiana, Florida, Texas, and North Carolina account for more than
80% of the 58,000 km2 that are vulnerable to sea-level rise.
Rising sea levels, in turn, can cause increased erosion to shores and habitat
and may contaminate some freshwater bodies with salt (Mason, 1999). Climate
extremes, such as hurricanes, can add to the adverse impact (Michener et al.,
1997). Sea-level rise and climate and weather extremes cause problems associated
with beach erosion, siltation of waterways, and flood risk in coastal communities
(Hanson and Lindh, 1996; Leatherman, 1996).
More than 65% of people in North America live in coastal communities (Changnon, 1992; see also Figure 15-2). This includes those who live near the Atlantic or Pacific oceans as well as those near the Great Lakes, where the impact of climate change is very different (see Sections 15.2.1 and 15.3.2.5). Accordingly, there is vulnerability across most of the region. Particular concern arises with regard to the combination of sea-level rise with other risks, such as storm surge. Salt intrusion and frequent flooding may adversely impact farming and manufacturing activity in low-lying areas (Gough and Grace, 1998).
Tourism frequently is the major industry in many coastal communities. The risk
of beach erosion, siltation, and flooding may become an important challenge
for some existing tourism sites, yet these same changes may open new opportunities
for some other communities. Tourism has been and will continue to be affected
by beach closures resulting from coliform from septic systems and sewage outflows
during and following storms and extreme events (see also Section
15.2.6). Sea-level rise also will be an important challenge for major ports
in many parts of North America.
A study of the impact on the United States of the increase of sea levels through
2065 found losses of US$370 million for dryland, US$893 million for wetlands,
and US$57-524 million in transient cost (Yohe et al., 1999). This estimate
is much lower than those of earlier U.S. studies because of assumed adaptation
responses, including decisions not to protect certain areas. No comparable information
is available for Canada, although several vulnerable areas have been identified—particularly
the Fraser River delta, Nova Scotia, and the Beaufort Sea region (Shaw et al.,
1998).
Investments in summer cooling, winter heating, and shelter from the elements
are common for most people and businesses in North America. Similar investments
are evident around the world, but the scope and scale often is greater in North
America. For example, the percentage of homes with air conditioning units in
the United States increased from 35% in 1970 (U.S. Census Bureau, 1975) to 76%
in 1997 (U.S. Census Bureau, 1999a). Similarly, more vehicles, schools, hospitals,
and businesses now have climate control mechanisms. Even traditional tasks have
changed, such as air-conditioned cabs on farm vehicles.
The trend of warming across North America should reduce the cost of heating
and the cost of investing in heating systems. At the same time, demand for summer
cooling is expected to rise. In turn, changes in the weather affect demand for
power: Peak demand for electricity is strongly correlated to swings in summer
temperature (Colombo et al., 1999).
Investments to manage normal fluctuations in the weather presumably have been
effective in increasing the comfort of people in North America. These investments,
however, also have increased vulnerability to systems failure. This could become
most evident for most people in North America during a summer heat wave or a
winter storm, when a failure in major support systems could place many people
at risk. For example, in January 1998, a severe ice storm caused a power failure
in Quebec and eastern Ontario (see Section 15.3.2.6).
A similar investment is in human alteration of hydrological drainage systems, including building of dikes, which may be an important factor in determining the severity of flooding (Changnon and Demissie, 1996). These interventions appear to be successful in managing most variations in the weather, but they can increase vulnerability to extreme events as new investments are made in regions that were thought to be sheltered from severe weather.
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