Viewpoint: The Forest After The Fire

by Pat McElroy, Washington’s State Forester

Record-breaking wildfires that were seen once in a generation now occur nearly every year. During the past three years, virtually every state in the West has experienced a catastrophic forest fire season. Last year, in Washington alone, the price tag was more than $100 million for fighting more than 1,300 fires that consumed 227,000 acres on private, state and federal lands.

This year, everyone is familiar with the massive fires in Colorado and Arizona that destroyed more than 500,000 acres of forestland. California's great sequoias survived a recent threat and Oregon saw nearly one million acres scorched.

This has started a public discussion about how the forests became vulnerable to these catastrophic fires. Many factors are involved, including a lack of proper forest stewardship—allowing forests to become crowded with trees competing for limited water and nutrients—leaving them vulnerable to predatory insects, diseases and fire.

There has not, however, been adequate discussion of the consequences of catastrophic fires to our forests, including damage to soils, increased runoff and the effects on wildlife. Understanding the effects of catastrophic fire on the forest is as important as knowing why these fires occur so frequently.

Forests are different today

One reason wildfires are more destructive today is that forests are different than in the 1800s. In eastern Washington, where wildfires are more common, the two prominent human influences that created forests vulnerable to fire are:

• Early logging of the native ponderosa pine, while leaving the smaller Douglas-fir, white fir and other species, which are more vulnerable to fire.

• Successful fire suppression programs, instituted to protect life and property, left woody debris piled high on the forest floors. (Before the 1900s, most eastern Washington forests experienced low intensity ground fires every 15 years on average, which effectively “cleaned out” the fuel load by burning the limbs, branches and dead trees and brush, and killed smaller trees.)

As a result, the average eastern Washington forest, which was predominately fire-resistant ponderosa pine, is crowded with Douglas-fir and white fir trees that grow in a thick, flammable bed and provide a ladder for fire to reach into the crowns and spread.

Combined with the usual hot summer weather and wind, forests have become potential bombs waiting for a spark or careless flame. In addition, unlike natural low-intensity ground fires, super-hot contemporary fires can vaporize nutrients, wipe out organic material, and essentially sterilize the soil.

A 1998 review, written by DNR scientists Dr. Richard Bigley and Sabra Hull, analyzed this potential loss of nutrients and the impact on forest re-growth. (A link to the review is at: http://www.dnr.wa.gov).

Soil tests done at the Entiat Experimental Forest reveal that many of the organic nutrients and minerals necessary for plant life were gone following the catastrophic 1970 fire. For instance, nearly 40 percent of soil nitrogen was lost.

During a very hot fire, minerals and nutrients are converted to gas or powdery ash and lost to the winds or dissolved in streams and leached away.

The extent of the damage depends on the forest conditions. Some forest floors are better insulated against the destructive heat. But in forests with thin organic layers, such as in Washington’s high elevation Cascade Range, the soil could be rendered poorly productive for decades, severely limiting the forest’s ability to grow back.

The long-term effects of severe wildfires may not appear for several years. Plant life may seem to return quickly because the disturbed soil released nutrients. But as much as 15 years later, plant vigor could deteriorate, as the “nutrient capital” of the soil is depleted.

Many of these forests will not immediately jump back to a healthy cycle. Rehabilitation will be a struggle—you can’t expect bountiful green shoots next spring. You may need to wait several decades.

Fighting wildfires

A century ago—as now—we were concerned about the immediate effects of wildfires. Rural properties, valuable timber, beautiful landscapes, wildlife habitat and human life were threatened. With courageous efforts, we stopped the large, damaging fires. Unfortunately, we also stopped the necessary, low intensity fires.

Today we have more reasons to protect nature, property and lives. Removal of flammable fuel from the forests is obvious. Returning forests to a more natural state by removing Douglas-fir and other fire-sensitive species in the dry site forests in eastern Washington and thinning thickets of pine and larch to give the remaining trees the opportunity to grow and resist fire, are critical elements.

Allowing wildfires to burn, however, can have some severe, unintended consequences for decades to come.

Good stewardship of Washington’s forests requires that we actively manage our forests with responsible harvests and thinning to return our forests to a healthy balance. That balance can provide healthy ecosystems as part of fire resistant forests while continuing to provide protection to communities near our forests and ensuring that the forest habitat so critical to wildlife isn’t destroyed by a growing tide of catastrophic fires.

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