The Last (Un-Inventoried) Frontier For the First Time, Alaska's Vast Interior Undergoes "Forest Census"

August 2017

U.S. Forest Service, Pacific Northwest Research Station

Have Helicopter, Will Travel

If you’re a Pacific Northwest Research Station scientist inventorying forests in interior Alaska, then your daily commute at the moment crisscrosses a remote area the size of Arkansas. This vastness—and the fact that much of the 53,500-square-mile initial study area is not reachable by road—means that forest access must often come by air.

Helicopters are absolutely critical for the interior Alaska forest inventory project because of limited landing zones and the remoteness of most plots.

“Helicopters are absolutely critical for the interior Alaska forest inventory project because of limited landing zones and the remoteness of most plots,” said John Chase, a geographer with the Pacific Northwest Forest Inventory and Analysis team (PNW-FIA), the group leading the inventory in partnership with the state. Chase is manager of the project.

This Pathfinder B3 Eurocopter, shown landing here, is contracted for the 2017 interior Alaska inventory season. Air operations are based out of Fairbanks, Alaska.

Helicopter travel is just one aspect of doing inventory work—where trees, living and dead; understory plants; and pieces of downed wood are sampled on a grid of one forest plot about every six miles—in interior Alaska. The Arkansas-sized Tanana Unit is the first of six in interior Alaska that PNW-FIA will inventory as part of its new Interior Alaska Forest Inventory and Analysis Project, one that will ultimately help estimate the region’s biomass stock and determine whether its forests are a carbon source or sink.

"The Nation's Forest Census"

The U.S. Forest Service’s Forest Inventory and Analysis (FIA) program is often referred to as “The Nation’s Forest Census.” Since 1930, the nationwide program has continuously collected, analyzed, and shared data gathered on forests across the United States. The PNW-FIA team—made up of research scientists, analysts, field technicians, and support staff—conducts inventories in Alaska; California; Oregon; Washington; Hawaii; the Pacific Island territories of American Samoa, Guam, and Commonwealth of the Northern Mariana Islands; and the freely associated states of the Republic of Palau, Federated States of Micronesia, and Republic of the Marshall Islands. The type of information PNW-FIA gathers helps to characterize the status and trends of forests across all land types and ownerships in these places. The group’s data help to address pressing resource issues ranging from the effects of wildfire, insects, disease, and drought to forest biomass estimation, changes in land use, and the effects of land management practices.

The Remaining Fifteen Percent

With more than 600 million square miles, Alaska is the largest state in the United States. The state’s interior boreal forests, spanning more than 170,000 square miles, are equally vast—representing 15 percent of total U.S. forest land. Although these forests play a significant role in supplying natural resources to local Alaskan communities and in sustaining global energy, water, and carbon cycles, they were not inventoried as part of the FIA program until 2015, making them the last U.S. forest type to be formally inventoried. The reason: conducting intensive sampling across this expansive, remote landscape was a daunting and logistically complex endeavor.

But, a year earlier in 2014, the Pacific Northwest Research Station, in partnership with Alaska’s Department of Natural Resources, NASA, and the University of Alaska, demonstrated that it was possible—and feasible—to conduct a formal inventory of these “remaining fifteen percent”—at the same cost per acre as any other plot in the West. The team conducted a physical, ground-based inventory of one plot out of the five that they would sample in the rest of the West, per the national FIA sampling protocol, and then used state-of-the-art remote-sensing technology—obtained by high-resolution cameras and laser scanners affixed to aircraft—to collect detailed forest structure and condition information along swaths spanning the entire inventory unit. This integrated approach, which works especially well in the interior and reduced the overall cost per acre to inventory the interior, wouldn’t be as effective in other areas with mountainous territory and dense forest canopies. Now that the inventory is formally underway, this approach allows PNW-FIA to efficiently inventory Alaska’s remaining forested area at a research-plot grid density that is one-fifth the standard national FIA sampling design.

Members of the Pacific Northwest Forest Inventory and Analysis crew who conducted the pilot inventory of interior Alaska.


In 2016, the PNW-FIA team installed and inventoried 188 permanent plots in the Tanana Valley unit; this year, they plan to complete 230, and the remainder in 2018, before moving on to the Copper Susitna unit. This critical first step of installing plots and taking initial measurements in interior Alaska will take 12 years; when it is completed, the team will have inventoried 4,500 new forest inventory plots across the region. Then, they will move into the remeasurement phase, where the real gold mine of change information becomes accessible, returning to interior Alaska in future years for follow-up measurements and analyses that steadily add to our understanding of interior Alaska’s forests.

- by Yasmeen Sands, Public Affairs Specialist

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