Potential Impacts in Various U.S. Regions

While some appreciation can be gained about the potential national consequences of climate change by looking at sectors such as the six considered above, the United States is a very large and diverse nation. There are both important commonalities and important differences in the climate-related issues and in the potential economic and environmental consequences faced by different regions across the country. Therefore, there are many different manifestations of a changing climate in terms of vulnerability and impacts, and the potential for adaptation. For example, while all coastal regions are at risk, the magnitude of the vulnerabilities and the types of adaptation necessary will depend on particular coastal conditions and development. Water is a key issue in virtually all regions, but the specific changes and impacts in the West, in the Great Lakes, and in the Southeast will differ.

With this variability in mind, 20 regional workshops that brought together researchers, stakeholders, and community, state, and national leaders were conducted to help identify key issues facing each region and to begin identifying potential adaptation strategies. These workshops were followed by the initiation of 16 regionally based assessment studies, some of which are already completed and others of which are nearing completion. Each of the regional studies has examined the potential consequences that would result from the climate model scenarios used in the national level analysis (the first finding in the Key National Findings box), and from model simulations of how such climate changes would affect the types and distributions of ecosystems. The box, Key Regional Vulnerability and Consequence Issues, provides highlights of what has been learned about the regional mosaic of consequences from these studies. A much more comprehensive presentation of the results is included in the National Assessment regional reports.

In summarizing potential consequences for the United States, it is important to recognize that the U.S. government represents not only the 50 states, but also has trust responsibility for a number of Caribbean and Pacific islands and for the homelands of Native Americans. In particular, the U.S. government has responsibilities of various types for Puerto Rico, the American Virgin Islands, American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, and more than 565 tribal and Alaska Native governments that are recognized as "domestic dependent nations."

For the island areas, the potential consequences are likely to be quite similar to those experienced by nearby U.S. states. With regard to Native Americans, treaties, executive orders, tribal legislation, acts of Congress, and decisions of the federal courts determine the relationships between the tribes and the federal government. These agreements cover a range of issues that will be important in facing the potential consequences of climate change, including use and maintenance of land and water resources. Although the diversity of land areas and tribal perspectives and situations makes generalizations difficult, a number of key issues have been identified for closer study concerning how climate variability and change will affect Native populations and their communities. These issues include tourism and community development; human health and extreme events; rights to and availability of water and other natural resources; subsistence economies and cultural resources; and cultural sites, wildlife, and natural resources. Closer examination of the potential consequences for tribes in the Southwest is the topic of one of the regional assessments now underway.