Denali National Park and Preserve: Resisting Permafrost Thaw Impacts on the Denali Park Road

By Kaylin Thomas, NPS Climate Change Response Program, 2025

The Denali Park Road parallels the Alaska Range and travels through 92 miles of stunning, wild landscapes. It is the only road in the park.

NPS Photo/Kent Miller

Denali National Park and Preserve (DENA), one of Alaska’s many iconic wild landscapes, faces an escalating challenge due to climate change: the historically slow but steadily accelerating collapse of the Denali Park Road down a hillside. This 92-mile scenic route is the only road across six million acres of Denali National Park and Preserve (DENA) wilderness, and it is an important transportation route for park staff and visitors. It runs parallel to the Alaska Range, a 600-mile-long mountain range, connecting visitor centers, campgrounds, staff facilities, and businesses across deep valleys and breathtaking mountain passes. It is built on top of permafrost—permanently frozen ground that is now thawing due to rising temperatures. In response, the park has turned to the resist-accept-direct (RAD) framework to help guide its management decisions.

Click here to learn more about the RAD framework

Park managers today face growing challenges. As climate change interacts with other stressors such as land use change, increases in visitation, pollution, and nonnative species, ecosystems and park infrastructure are changing beyond the bounds of historical variability. These changes are increasingly difficult to resist. Thus, managers are thinking more broadly about how to effectively conserve resources in this rapidly changing world. In this context, the resist–accept–direct (RAD) framework helps decision makers make informed, purposeful, and strategic choices. This tool is simple and flexible, complements other important climate change adaptation approaches, and applies to a wide range of decisions that managers must make as they steward transforming environments.

Understanding the RAD Framework
The RAD framework consists of three strategies:

1. Resist: Working to maintain existing conditions or slow the rate of change based upon historical or acceptable current ecosystem conditions. This often involves direct interventions to counteract environmental changes.
2. Accept: Allowing the system to change without intervention.
3. Direct: Actively steering changes toward desired outcomes, which may involve redesigning or repurposing systems to function under new conditions.

For more information about RAD, visit the Resist–Accept–Direct Framework webpage.

An Uphill Battle

The Denali Park Road traverses steep, unstable terrain such as the Polychrome Area, where it crosses several active landslides. One of these hazards, the Pretty Rocks Landslide—which intersects the road near its midpoint—has been carrying this section of the road downslope at an accelerating rate. Historically, the landslide was a slow-moving nuisance that regularly created small cracks in the road surface since at least the 1960s. In recent years, it has evolved into a substantial threat that, by 2021, was moving at 0.65 inches per hour. NPS road maintenance staff tried to keep the slumping road intact by continually adding gravel, but the park recognized that this approach was quickly becoming unsustainable in the face of the landslide's acceleration. In August 2021, the park closed the road in this area, cutting off over half of the road access to the park and increasing costs and challenges associated with maintaining facilities and operations. In 2022, the road collapsed entirely.

Timelapse of the Pretty Rocks slump, from July 21 to August 25, 2021. In this time, the road displacement was ~21 feet.

NPS Geology Team

Resisting Change: The Pretty Rocks Bridge

Acceleration of the Pretty Rocks Landslide is a consequence of climate change-driven permafrost thaw. As average annual temperatures increase to 32 °F, ice-rich permafrost soils subside, collapse, and thaw into an unstable slurry. To address the challenge of building around an increasingly unstable landscape, one option was to avoid the landslide altogether; the park could reroute the Denali Park Road out of the landslide area and into the valley below. Based on an understanding that keeping the road within the existing corridor (i.e., as it was, where it was) is resisting change, relocating the road would be directing change. However, this solution required more money and time than was available and might have exposed that new section of the road in the valley to flooding-related impacts.

Instead of changing the road corridor by looping the road down and around the base of the landslide, the park is now resisting change by maintaining the historical road corridor and building a bridge over the landslide to restore access to this portion of the park. This bridge—expected to be completed in 2026 with an official reopening of the road in 2027 and an anticipated lifetime of 50 years—creates a sustainable near-term solution that maintains access to the park’s interior while avoiding the need for continual repairs to an unstable roadway.

A winter view of the Pretty Rocks construction site on November 11, 2024. Regular updates are available on the Pretty Rocks Construction blog.

NPS Photo

The National Park Service (NPS), in collaboration with an environmental consulting firm, prepared an Environmental Assessment before committing to construction at Pretty Rocks. After carefully analyzing resource impacts, reviewing stakeholder and public comments, and consulting with federally recognized Tribes, Alaska Native Corporations, State and local governments, and the State Historic Preservation Office, the NPS began planning to restore reliable road access west of Pretty Rocks. The Federal Highways Administration, with assistance from the NPS, developed the Polychrome Area Improvements Plan to achieve this goal. Funding for the bridge was secured through a combination of Bipartisan Infrastructure Law dollars, additional Federal Lands Transportation Fund dollars, and 2023 Disaster Relief Supplement funding. Updates on bridge construction progress at the Pretty Rocks Landslide can be found on the Pretty Rocks Construction blog.

A Model for Climate Change Adaptation

Because climate change-driven warming will continue—quickening the pace of permafrost thaw and leading to the eventual collapse of the bridge—the park recognizes that the bridge is a near-term solution, and a longer-term approach must be developed in the future. As climate change progresses, management decisions in Denali National Park and Preserve will continue to be a balancing act between capacity, time, and values. RAD provides a framework for exploring the full decision space and making forward-looking decisions so stewards at Denali National Park and Preserve will be better able to think strategically and communicate clearly as they work with uncertainty and minimize impacts to infrastructure and operations, the visitor experience, and natural and cultural resources.

Two cyclists pause while a caribou crosses the Denali Park Road.

NPS Photo / Kent Miller

Thanks to Dave Schirokauer at Denali National Park & Preserve and Alan Ellsworth at the Climate Change Response Program for providing information for this article.