It’s International Day of Forests – Do You Know What A Healthy Forest Looks Like?

As Washington state and much of the West struggles with more damaging wildfire seasons, you might hear policy experts and elected officials use terms like “forest health” or “forest resiliency” when talking about ways to reduce wildfire risk – but what exactly does that mean? And what does a healthy forest look like here in The Evergreen State?

The answer might surprise you. This International Day of Forests, we break it down:

What is a healthy forest?

Simply put, a forest is healthy if the trees can access the nutrients, water and sunlight they needs to thrive and reproduce, and the forest is resilient to disturbances such as insects, disease, and fire. A healthy forest will also have a better chance of withstanding the effects of climate change.

It’s a common misconception, however, that for a forest to be healthy, it must be lush – filled with a dense under story and an abundance of trees – and that a landscape is healthier if it has more trees in it. Depending on the region, a healthy forest can look much different.

The upper photo, taken in 1934 in the Kittitas County area before excluding fire from the ecosystem, shows a more resilient forest (Photo by Reino R. Sarlin/USDA Forest Service). The lower photo of the same area, taken in 2010 after constant fire suppression, shows an over-crowded forest (Photo by John F. Marshall)
The upper photo, taken in 1934 in the Kittitas County area before excluding fire from the ecosystem, shows a more resilient forest (Photo by Reino R. Sarlin/USDA Forest Service). The lower photo of the same area, taken in 2010 after constant fire suppression, shows an over-crowded forest (Photo by John F. Marshall).

Historic photos of Washington’s forests, like the one above, show that prior to European settlement our landscapes didn’t have as many trees. That’s because wildfires were a frequent part of the ecosystem, coming through regularly and keeping the amount of trees and other vegetation in balance. More than a century of wildfire suppression has allowed these forests to fill in, creating fuel for uncharacteristically severe fires.

That’s one reason why forest health has become a hot topic among state leaders. According to the Washington State Department of Natural Resources’ 20-Year Forest Health Strategic Plan, 2.7 million acres of forest in Central and Eastern Washington alone need active management to increase the forest’s resiliency to insects, diseases, climate change, and wildfire.

In 2015, Washington had a recording-breaking fire season: more than 1 million acres and 230 houses burned, and wildfire-related spending cost taxpayers $89 million. Projections indicate that if we don’t take action, the Pacific Northwest will experience four times more acres burned annually by 2080.

“Restoring forest health and reducing wildfire risk go hand in hand,” said Commissioner of Public Lands Hilary Franz, who leads DNR. “Through bold action taken with our national, state, and local partners, our forests can become more resilient, reducing wildfires and keeping The Evergreen State true to its name.”

Supporting forest health initiatives benefits us all. Healthy and resilient forest ecosystems trap and store carbon from our atmosphere, provide timber and recreation jobs, wildlife habitat, wood products, and clean drinking water.

What are the different types of forests in Washington?

Washington State is home to four general forest regions, each with their own characteristics. There are forests east of the Cascade Mountains, mountain forests, coastal forests along the Pacific Ocean, and Western lowland forests primarily along the Interstate 5 corridor.

Historical photographs often show open, park-like stands of ponderosa pine, such as this one from the Blue Mountains
Historical photographs often show open, park-like stands of ponderosa pine, such as this one from the Blue Mountains. (Photo courtesy of Baker County Library, Baker City, Oregon)
  • Low-elevation eastside forests. Shown above, these are often forests predominantly composed of ponderosa pine, Douglas-fir, and grand fir. Common in the hills and lowlands of Central and Eastern Washington, these forests historically experienced low and mixed severity fires every 5 to 25 years, and they often thrive when they have open spaces between trees.
mountain hemlock
Many picturesque timberline views in Western Washington are framed by mountain hemlock — our high-elevation conifer found in the wettest and snowiest locations.
  • High elevation forests. Predominantly subalpine fir, Engelmann spruce, lodgepole pine, and other conifers. Shown above, these types of forests historically experienced mixed to high severity fires every 80 to 300 years.
A mature (300-400 years old) Western Washington forest, a mature forest is characterized by towering Douglas firs with hemlocks present in all size classes, from juveniles to large canopy trees.
This mature (300-400 years old) Western Washington forest is characterized by towering Douglas firs with hemlocks present in all size classes, from juveniles to large canopy trees.
  • Western lowland forests. Forests in the Olympic Mountains’ rain shadow (around Sequim and Port Townsend), and southern Puget Sound lowlands, historically had mixed severity fires every 80 to 200 years.
  • Coastal forests. Moist forests in Washington are dominated by Douglas-fir, western hemlock, Sitka spruce or western red cedar and historically have high severity fires every 200 to 500+ years.

What threatens healthy forests?

A healthy forest may be affected by one of more of the following threats:

  • Climate change. Climate change is affecting the temperature and precipitation patterns in Washington, which can contribute to tree stress. Tree stress makes trees more susceptible to insects and diseases, which can lead to increased tree mortality.
  • Wildfires. Fire is a natural renewal process that promotes biological diversity and healthy ecosystems in our forests. However, projections suggest that fire frequency, intensity and extent will increase due to increased temperatures, earlier spring snow melt, longer fire seasons, and overcrowded forests.
  • Insects. Insects such as bark beetles can present a serious threat to forests when trees are stressed. Even though they are a native species, on an already weakened tree bark beetles can contribute to tree mortality. Defoliating insects can cause foliage loss in trees, contributing to tree stress and possibly bark beetle attacks.
  • Disease. Trees are susceptible to bacteria, viruses, and fungi. These diseases can affect tree health in a variety of ways, such as wood decay, tree growth, and tree mortality.
  • Invasive species. Invasive species are plants, animals, and organisms that are not native to Washington. These species can grow and spread quickly, harming the local plants and wildlife.

Want to take a deep dive into the most recent threats seen in Washington’ forests? Read our state’s 2018 Forest Health Highlights report.

How can we make our forests healthier?

There are several ways to make an unhealthy forest healthy again, depending on the type of forest and its purpose.

  • Mechanical treatments. This refers to the physical removal of small and densely packed trees that have accumulated due to fire suppression, through the use of chain saws, chippers and mastication. These mechanical treatments improve forest health by opening up the understory in Eastside forests, diversifying wildlife habitat, and reducing the possibility of a fire spreading quickly from the forest floor into the upper crowns of large trees.
  • Prescribed fire. Because fire frequently occurred in eastside forests, engaging in controlled burning there can improve forest health. Controlled burns – also called prescribed fire – allow professionals to apply fire to the right landscapes, in the right intensity, and at the right time to boost forest health. Prescribed fire reduces wildfire fuels, increases the effectiveness of mechanical treatments, improves forage conditions for grazing animals, and can reduce the risk of insect spread.
  • Active management practices. In moist Western Washington forests, an abundance of vegetation can be healthy, and these forests don’t experience wildfires as often. But because of our changing climate and historic logging practices, these forests will still require some active management to ensure a healthy ecosystem.
  • Regeneration harvests. Sometimes, all of the trees on a plot of land need to be harvested so the area can be replanted with trees that are better suited for the region and environment.
  • Teamwork. Collaboration is the key to improving forest health in Washington. Landowners –state agencies, federal agencies, tribes, the timber industry and homeowners – all need to work together to coordinate landscape-scale and cross-boundary projects in priority forests. Collaboration among landowners will help speed our progress on creating more resilient and sustainable forests. Read Washington state’s forest health strategy at www.dnr.wa.gov/foresthealthplan.

Want to learn even more? (It is International Day of Forests, after all.) Watch longtime forest researcher Paul Hessburg’s TED Talk about the history of forests in the Pacific Northwest and their relationship to fire: