Oregon has millions of zombie trees

By Oregon Forest Research Institute,

By Mike Cloughesy, Director of Forestry, Oregon Forest Resources Institute

Meet the standing dead. Millions upon millions of gray ghosts blackened by fire, ravaged by insects and disease, or dead from lack of water. These are Oregon’s “zombie” trees. And according to an analysis commissioned by the Oregon Forest Resources Institute, more than 350 million individual trees are standing dead in the 14 million acres of national forestland in Oregon. The bad news? The number of dead trees is expected to increase, providing more fuel for catastrophic wildfires. Halloween is a great time to tell scary stories. The story I’m about to tell you is about the frightening number of dead trees in our national forests. It is based on data from the U.S. Forest Service’s Forest Inventory and Analysis program that was collected in 2010 and 2013 across all forestlands in Oregon. This story could have a happy ending, but it may not.


The story starts by looking at who owns Oregon’s forests.

The chart above shows the breakdown of the forestland into various ownership classes and major forest categories. The National Forest System (NFS) is the largest class of Oregon forestland with more than 48 percent. Bureau of Land Management (BLM) and other federal lands account for about 12 percent of Oregon’s forestland, bringing the total federal ownership to about 60 percent. Private and Native American ownership account for about 36 percent, while state and local government ownership account for 4 percent.

Number of zombie trees by ownership class

The scary part of our story starts when we compare living and dead trees per acre by ownership class. The chart below shows that National Forest lands have 17 percent dead or zombie trees, compared to 11 percent for other public lands and 8 percent for private and Native American-owned lands. The NFS having twice as many zombie trees per acre as private lands may not seem that bad, but when you consider that there is a lot more National Forest land than any other class, it becomes quite terrifying, as we shall see.

Annual mortality vs. annual harvest

It is ironic that there appears to be an inverse relationship between annual mortality and annual timber harvest among Oregon’s forest ownership classes. Private and Native American forestlands, which have the highest timber harvest rate at 71 percent of total growth, have only 9 percent mortality. NFS forestlands have a timber harvest rate of about 8 percent of total growth, but have a mortality rate of about 55 percent.

Actively managed forests have way fewer zombie trees than forests that are less actively managed. Forests that are unmanaged quickly become overcrowded as trees grow and new trees seed in. Overcrowded forests have more dead trees and increased volume of mortality.

These dead trees also fuel any wildfires that occur. Overcrowded forests burn uncharacteristically hotter and have increased tree mortality as compared to managed forests.

Conclusion – How to combat zombie trees

It’s fun to use the zombie image to discuss dead trees and mortality on National Forest lands. But this is a serious problem. There is an alarmingly high amount of mortality on NFS lands that have low levels of timber harvest. I believe that these issues are related, and the charts presented support this. Forest ownerships that have higher levels of timber harvest have lower levels of mortality.

The cure for zombie trees is active forest management. Forest policy does not always allow active management on federal lands. However, in the name of forest health, we should pursue active management strategies whenever and wherever possible.

Managing federal forests is not an easy task. Federal land managers are doing the best job possible under trying circumstances such as decreasing budgets, increasing fires and lack of consensus on management actions. Most federal land managers will agree that increasing active management is one of the keys to reducing mortality. The challenge is how to get it done.

We can combat the zombie tree apocalypse with active forest management.

Read a longer version of this story at: http://oregonforests.org/featured-stories

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