As temperatures warm, plants and animals in wild ecosystems will need to move to higher, cooler places to survive. Human-made barrierssuch as suburban areas, farms, and clear-cut forestsand mountains can make migration difficult, if not impossible, for many species, scientists say.
In the case of people, U.S. residents are better equipped than citizens in many other countries to deal with global climate change, according to Janetos and Arroyo. Construction of sea walls, for example, could protect some U.S. coastal cities from encroaching waters. Crops once grown in southern states could be transplanted north.
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"We have a large national landscape, so we can move things around," Arroyo said. "We also have the wealth to do thatsomething developing countries don't have."
Due to the complexity of global climate systems, it is possible that the Earth will respond to climate change differently than expected. "Clearly climate models are better now than they were five years ago. But there's always some degree of uncertainty," Janetos said.
How and when U.S. citizens adapt to global warming, however it manifests, largely depend on the ability of scientists to accurately forecast climate change, the researchers say. As Janetos notes, while this ability is improving, uncertainties and surprises remain.
Climate Change Scenarios
Who knows what will truly happen as Earth's average temperature continues to rise this century? The following potential scenarios for various U.S. regions come from two sources: The 2000 National Assessment, a U.S. federal government climate change study, and a 2004 synthesis report (based on previously published studies and analysis) by the Pew Center on Global Climate Change.
Northeast/Mid-Atlantic: Rising sea levels could destroy wetlands in environmentally sensitive estuaries, such as the Chesapeake Bay. Lobster and maple syrup, signature regional products, may disappear. Ski resorts may hold less snow. Higher sea levels with even moderate storms may damage beachfront property. Heat-related deaths in big cities like New York and Philadelphia may increase.
Southeast: Sea level rise combined with more intense storms on the populated coasts poses the biggest global warming threat in the U.S. Protective barrier islands and wetlands may disappear. Crops may shift northward, and grasslands and savannahs may break up the forests. People without access to air conditioning may swelter. The region's warmth and wetness may also lead to more outbreaks of infectious disease.
Midwest: More rain and snow may lead to an increase in flooding. Paradoxically, evaporation rates are also expected to increase, resulting in drier soils and lower lake levels. Such changes would impact agriculture and ship navigation. In cities such as Chicago, heat-stress-related deaths could increase, especially among the elderly and poor.
Great Plains: Heat waves could be painful for people and livestock. A projected precipitation increase will likely be surpassed by greater evaporation, leading to drier conditions. Extreme drought akin to the Dust Bowl era of the 1930s is a possibility. Invasive plant species, such as spotted knapweed, may out-compete native grasses. Southern Plains states may lose crops to the north.
Southwest: Competition for already scarce water resources may increase among all users, from farmers and cities to boaters and environmentalists. Both extremely wet and dry years are forecasted. Wet years could increase flooding risk; dry years drought. The wet-dry combination may allow fuels for wildfire to build and then burn. Mountains and human development may impede the ability of plant and animal species to move more suitable habitat; many will go extinct.
Northwest: Rising sea levels threaten to inundate the Puget Sound region. Warmer freshwater resources may damage already stressed salmon populations. Drier summers may increase summertime water shortages. Heavier winter rains may cause flooding and landslides.
Alaska: Permafrost may continue its thaw, posing new challenges to buildings, roads, and pipelines. Loss of sea ice could threaten populations of polar bears and other marine mammals and the native peoples who depend on them. Forests may be more prone to fire and insect damage.
Caribbean and Pacific Islands (Puerto Rico, Hawaii) Warmer temperatures may cause widespread extinction of native species with no place to go. Coral bleaching events may increase. Rising sea levels could threaten freshwater supplies. Hurricanes and tropical storms may increase in intensity, causing more damage to property and people.
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