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The climate of Interior Alaska is extreme. Temperatures in the winter can plummet to as low as -50 °C in January, with the landscape often blanketed in snow and ice for more than half the year. As summer approaches, the region transforms—daylight stretches nearly 24 hours, and temperatures can soar to over 33 °C in July.

Interior Alaska’s climate is heavily influenced by its geography. The Alaska Range to the south and the Brooks Range to the north block moist, coastal air masses, leaving the region relatively dry year-round. Coupled with extreme temperature ranges and varying day lengths, these climatic conditions define the ecology and resilience of Interior Alaska’s boreal forests.

Permafrost is a defining feature of Interior Alaska. It refers to ground—soil, rock, or ice—that remains frozen for at least two consecutive years. In the boreal climate of Interior Alaska, permafrost is discontinuous and underlies approximately 40% of land area. Permafrost is typically found in cold places such as north-facing slopes and valley floors. Where present, permafrost acts like a frozen foundation for the ecosystem, influencing everything from plant growth to water resources. Permafrost keeps the soil moist, providing the vegetation with ample water despite the region’s modest rain and snowfall.

Warming temperatures and increasingly severe wildfires are accelerating permafrost thaw across Interior Alaska. Thaw can cause ground collapse, damage infrastructure, alter drainage patterns, and change water quality.

There are only six tree species present in Interior Alaska, with three of them—birch, white spruce, and black spruce—dominating the landscape. However, a closer look reveals a rich and dynamic mosaic of vegetation shaped by elevation, wildlife, soil moisture, wildfire, and permafrost thaw. The region’s major plant communities can be grouped into three categories: floodplain, upland forest, and lowlands, each supporting different ecological processes. The most widespread is the upland forest, which is made up largely of black and white spruce.

Warming temperatures are reshaping vegetation across Interior Alaska. Wildfires are becoming more frequent, forested floodplains can subside into bogs as permafrost thaws, and warmer winters allow insects and tree diseases to spread more widely. These changes alter forest structure, carbon storage, wildlife habitat, and the ways people use and benefit from boreal landscapes.

Interior Alaska is home to a remarkable diversity of wildlife, each playing a vital role in the boreal forest’s ecological and social tapestry. At the top of the food chain, predators such as wolves, lynx, and bears regulate populations of prey and in turn are regulated by them in dynamic and ever-changing relationships. Prey species ranging from moose and caribou to snowshoe hares, voles, and red squirrels shape vegetation structure through browsing and seed consumption; for instance, moose herbivory can influence forest development.

Birds—from migratory waterfowl to songbirds and year-round residents such as owls and woodpeckers—add seasonal soundscapes to the forest and contribute to pollination, seed dispersal, and insect control. For many rural and urban communities, and especially for Alaska Native peoples, wildlife holds deep cultural, nutritional, and social significance.