Denali provides one of the few intact and naturally regulated subarctic ecosystems in the world because of its long history and substantial size. Landscape scale processes such as fire, succession, and outbreaks of disease have not been significantly altered by human intervention. These components and processes of the system are still responding naturally to other primary processes such as weather or geologic events.

The high mountains of the Alaska Range shelter the Alaskan interior from the moist maritime air from the Gulf of Alaska creating two distinct climatic regimes within the park. South of the Alaska Range you find a warmer, moister transitional maritime zone and north of the range you find a drier continental zone where winters cold and long, and summers are warm and short. The high latitude and varying altitude within the park strongly influences plant growth, the presence and composition of forests, and the presence and extent of permafrost.

Across the largely treeless expanse of the park, the views are of a scale unknown in the lower 48 states. Denali is the only Class I air quality area of significant size in Alaska, which under the Clean Air Act was set aside to receive the most stringent degree of air quality protection. On a clear day, Mt McKinley can easily be seen from Anchorage, more than 130 air miles to the south. Outstanding views of natural features dominate the landscape and are internationally known.

Natural wildfires, mostly caused by lightning, are a critical component of the boreal forest ecosystem. Fires of considerable size and intensity are common north of the Alaska Range. A complex fire history has created a patchwork landscape of vegetation communities of different species and ages. The habitat and life cycles of many plants and animals rely on the rejuvenating process of fire. These communities have adapted to fires that have been occurring on this landscape for the past ten thousand years.

Denali National Park and Preserve offers a unique subarctic environment to study climate, glaciers, geologic processes, and fire ecology. The role of humans and human-induced changes such as air and water pollution are monitored as well. Everything we do affects the park in ways both great and small; from transcontinental air pollution, to the non-native species we introduce from seeds carried on the soles of our shoes, to our efforts at preservation. Park scientists and managers continuously monitor the natural environment to assess these impacts in order to protect the natural resources of the park.