Working Group II: Impacts, Adaptation and Vulnerability

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Marine Fisheries

Climate-related variations in the marine environment—including changes in sea-surface temperatures, nutrient supply, and circulation dynamics—play 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.

Human Health

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 air pollution.

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 systems—such as drainage basins, barrier islands, and coastal margins—influence 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.

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