JACKSON - Foresters tracking whitebark pine trees killed by beetles will start using GPS to map the damage.

U.S. Forest Service officials say they're using $150,000 to start a GPS survey of beetle damage in the Bridger-Teton National Forest. Foresters say the forest contains some 400,000 acres of whitebark pine, but the species is declining because of beetles and the blister rust fungus.

Pine mapping begins today with an aerial survey. Researchers will take photos and video, then use GPS to help map the pine population. Work should be completed by spring.

Foresters want to know where beetle damage is worst, and why some pockets of whitebark pine appear to be unaffected.

Determining the extent of damage is important because pine provides food for grizzly bears and other species and helps watersheds, said Liz Davy, timber and silviculture program manager for the Bridger-Teton.

"It's a keystone species," she said. "It's very important in our ecosystem."

Pilot Bruce Gordon will fly the plane while technicians sync video and still cameras with a GPS device to develop the map. Gordon said he's seen dramatic changes to the forest from the infestation.

"In all these years doing conservation flying, we've had outbreaks before, but never anything of this magnitude," he said. "I've seen it every flight, and over the last year or so it's become really pronounced."

Natural Resources Defense Council senior wildlife advocate Louisa Willcox helped organize the project after a smaller-scale effort last year.

"We couldn't afford to do the whole ecosystem," she said of the previous attempt. "We missed little bits between the flight lines."

Even if the survey reveals bad news for the forest, she said, getting accurate information will help.