Climate-related variations in the marine environmentincluding changes
in sea-surface temperatures, nutrient supply, and circulation dynamicsplay
an important role in determining the productivity of several North American
fisheries (high confidence).
Projected climate changes have the potential to affect coastal and marine ecosystems,
with impacts on the abundance and spatial distribution of species that are important
to commercial 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 are complex and difficult to observe,
so climate variability constitutes a significant source of uncertainty for fishery
managers. Recent experiences with Pacific salmon and Atlantic cod suggests that
sustainable fisheries management will require timely and accurate scientific
information on environmental conditions that affect fish stocks, as well as
institutional flexibility to respond quickly to such information.
Increased frequency and severity of heat waves may lead to an increase in illness
and death, particularly among young, elderly, and frail people, especially in
large urban centers. The net effect of reduced severity of extreme cold is likely
to have a beneficial effect. Acclimatization may be slower than the rate of
ambient temperature change.
Increased frequency of convective storms could lead to more cases of thunderstorm-associated
asthma. More frequent flood events and other extreme events may result in an
increase in deaths, injuries, infectious diseases, and stress-related disorders,
as well as other adverse health effects associated with social disruption, environmentally
forced migration, and settlement in urban slums.
Vector-borne diseases, including malaria and dengue fever, may expand their
ranges in the United States and may develop in Canada. Tick-borne Lyme disease
also may also expand its range in Canada. However, socioeconomic factors such
as public health measures will play a large role in determining the existence
or extent of such infections. Diseases associated with water may increase with
warming of air and water temperatures, combined with heavy runoff events from
agricultural and urban surfaces.
Respiratory disorders may be exacerbated by warming-induced increases in the
frequency of smog (ground-level ozone) events, acidic deposition, and particulate
Human Settlements and Infrastructure
Potential impacts of climate change on cities include fewer periods of extreme
winter cold; increased frequency of extreme heat; rising sea levels and risk
of storm surge; and changes in timing, frequency, and severity of flooding associated
with storms and precipitation extremes.
Communities can reduce their vulnerability to potential adverse impacts from
climate change through investments in adaptive infrastructure. These adaptations
can be expensive. Rural, poor, and indigenous communities may not be able to
make such investments. Furthermore, infrastructure investment decisions often
are based on a variety of needs beyond climate change, including population
growth and aging of existing systems.
Changes in the frequency, severity, and duration of extreme events may be among
the most important risks associated with climate change. The rising cost of
natural disasters in North America illustrates the vulnerability of current
settlement practices. Human alterations of natural systemssuch as drainage
basins, barrier islands, and coastal marginsinfluence the impact of extreme
weather hazards. Adaptations such as levees and dams often are successful in
managing most variations in the weather, but they can increase vulnerability
to the most extreme events.
Shifts in temperature and precipitation patterns would lead to shifts in outdoor
tourism and recreation opportunities (e.g., winter sports, fishing, parks, beaches).
The extent to which ecological changes in parks will affect tourism is uncertain.
Future shifts in water management, in response to development pressures as well
as climate change, also could affect recreational opportunities and associated
property values. Opportunities and challenges for recreational industries and
destination areas need to be assessed in a systematic manner before net economic
impacts can be reported with sufficient confidence.