Over the past three decades, Earth's temperature has increased on average about 0.6°C. In some areas of the globe, however, the changes are happening more rapidly. Arctic temperatures are rising at a rate nearly twice as fast as the rest of the world. This rapid change produces noticeable differences in the physical environment and affects the people, animals, and plants of the region. For example, the changing climate is causing the boreal forest to encroach on the Arctic tundra, which impacts the Alaska Native communities whose lifestyles depend on the tundra's land and wildlife.

In Alaska, the winters are long and cold, and there is little annual precipitation. However, the underlying permafrost prevents drainage and keeps sufficient water trapped near the surface for vegetation. The boreal forest—also called taiga—is located in the interior regions of the state, where summer temperatures can be quite warm (about 30°C). Spruce trees dominate the forest, although other trees, such as birch and aspen, together with other vegetation, are also found. North of the boreal forest and along the coast of the state, the land becomes tundra. In this region, the proximity to the ocean moderates climate so that summer temperatures remain cool (about 12°C). With a cooler growing season, even less precipitation than in interior regions, and a windier environment, there are few trees. Tundra vegetation is characterized by low-lying shrubs, forbs (leafy, flowering plants), mosses, and lichens. A variety of animals, including caribou, musk ox, wolves, and bears, inhabit boreal forest and tundra. There are also many migrating animals that make use of the land for only part of the year. During spring and summer, the tundra is covered with marshes and lakes—formed by the annual melting of the top layer of permafrost—that become key breeding grounds for migrating birds.

Global warming is altering Alaska's ecosystems. For example, warmer temperatures and longer growing seasons foster the growth of taller, denser vegetation. The disappearance of the permafrost that underlies the tundra further encourages the transition to boreal forest. As the tree line moves northward and toward the coast, some of the Arctic tundra is transitioning to forested land. But while the edge of the boreal forest may advance into tundra, the tundra is delimited to the north by the Arctic Ocean and has nowhere to go—the tundra is disappearing. In addition, other potential environmental impacts can result from climate change—a term that encompasses changes in temperature as well as changes in other measures of climate, such as wind and precipitation. These include increased risk of forest fires and insect outbreaks, and decreased range and availability of traditional harvests. All these changes pose significant challenges to Alaska Native communities, who are forced to adapt to maintain their subsistence lifestyles.

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