Analysis: Millions of ‘zombie trees’ in national forests

Posted: November 3, 2015

Source: Oregon Forest Research Institute 



Meet the standing dead. Millions of ghosts charred by fire, ravaged by insects, or dead of thirst.

These are Oregon’s “zombie” trees. And according to an analysis commissioned by the Oregon Forest Resources Institute, more than 350 million are standing dead in the 14 million acres of Oregon’s national forests.

An infographic and high-resolution photos of insect-killed trees in the Deschutes National Forest are available on OFRI’s website.

“It’s a tale of two forests,” says Mike Cloughesy, OFRI’s director of forestry. “About 17 percent of the trees on National Forest System lands in Oregon are dead, compared to 11 percent for other public lands, and 8 percent for private and Indian lands.

“While it may not seem scary, it’s a potential nightmare because there’s a lot more NFS land.”

About half of Oregon is forested. Ownership is dominated by the federal government, with about 60 percent of the state’s forestland. The National Forest System is the largest class with 48 percent – more than 14 million acres. Bureau of Land Management and other federal lands comprise 12 percent. Private and Native American ownership account for 36 percent, with state and local government ownership at 4 percent.

The analysis was prepared for OFRI by Tom Montzka, an independent forest analyst, using data from the U.S. Forest Service’s Forest Inventory and Analysis Program.

Trees are one measure; volume is another. And the timber volume represented by the dead trees is startling. The analysis shows that standing-dead volume on NFS forestland is equivalent to more than half the live volume on other federal ownerships, such as BLM.

One reason for the situation, Cloughesy says, is a lack of active forest management.

“Actively managed forests have fewer dead trees,” he says. Unmanaged forests become overcrowded as trees grow and new ones sprout. As forests become clogged with growth, the trees fall prey to insects and drought, and die. In a managed forest, many trees are thinned before they die.

“Dead trees fuel wildfires,” Cloughesy says. “Overcrowded forests burn uncharacteristically hot, killing most trees and putting other resources such as watersheds and wildlife at risk.”

One solution, Cloughesy says, is to increase harvest on federal lands.

“On federally managed lands, annual mortality exceeds harvest, so even a small increase in harvest would help,” he notes. The analysis shows that on NFS lands open to harvest, annual mortality exceeds harvest by more than 400 percent.

Cloughesy states that from an ecological perspective, standing-dead and fallen timber provide a number of benefits, including fish and wildlife habitat, carbon storage and, as the trees decompose, soil nutrients. But the alarmingly high number of dead trees create a fire risk that could outweigh these benefits.

“Preventing a zombie apocalypse will require a much stronger commitment to active forest management on federal lands,” he says. “It may not be comfortable, but the alternative could be much worse.”