Over the past century, the air and water temperatures in Alaska have warmed considerably faster then in the rest of the United States. Because Alaska is the only Artic state in the Nation, Alaskans are likely to face some climate change challenges that will be different than those encountered in other states. For example, permafrost currently underlies 80% of Alaska and provides a stable foundation for the physical infrastructure of many Alaska communities. As has already been seen in numerous villages, the groundcover that overlies permafrost is vulnerable to sinking or caving if the permafrost thaws, resulting in costly damage to physical infrastructure. The reliance on subsistence resources is another contrast to many other states. Many Alaskans depend upon subsistence harvests of fish and wildlife resoruces for food and to support their way of life. Some Alaskans report that the changing environment has already impacted their traditional practices.