Forests—acres upon acres of fragrant trees huddled closely together, a paradise for hikers, campers, and wildlife alike. In the United States, forests cover about 749 million acres, or about 33 percent of all land.
That’s a lot of trees. In fact, decades of land management and wildfire suppression have resulted in increasingly dense forests. With more trees clustered together wildfires can be more devastating, claiming millions of acres per year, many human and wildlife lives, and homes and other property.
Now, Pacific Northwest National Laboratory (PNNL) scientist Mark Wigmosta is leading research, partnering with the U.S. Department of Agriculture's Forest Service to evaluate forest restoration for mitigating wildfire risk. Specifically, they are developing a planning and decision method that helps prioritize locations where restoration should take place that reduces wildfire risk, increases water habitat for fish, improves the overall ecosystem—and even provides biomass for energy use.
Tradeoffs for Water, Fire, Biofuels, and Fish
Forest restoration activities like selective timber harvest and thinning help to reduce the risk of wildfire. But forest restoration efforts on a wide scale typically use prescribed burning and are often stymied by air quality standards and limited budgets. Organizations that help maintain the nation’s forests must have a way to easily and quickly evaluate where restoration activities should be a priority.
In their research managed by the U.S. Department of Energy's Bioenergy Technologies Office, the PNNL-Forest Service team used a combination of vegetation data, models, and analytic techniques for the study—coupled with a Forest Service decision support software tool that has also been used to establish budget allocation priorities for forest restoration. Their goal—to understand how fire restoration can impact water flow needed to assure fish health while also evaluating the economics for biomass that can be used for energy sources such as wood pellets for heating or converted to biofuels to power cars, trucks, and airplanes.
They performed their study in a 70,000-acre forest demonstration basin in mountainous central Washington state. The basin, with its mass of trees and foliage, has the very highest potential for wildfire.
The team evaluated scenarios for a range of forest conditions. Since forests with the greatest wildfire potential have a complex mosaic of trees under existing conditions, the team pursued the scenario of adding gaps in the canopy of trees, representing a more realistic picture found in unmanaged landscapes with more natural fire regimes.
Nothing Fishy about these Findings
The team demonstrated that restoration using the “tree gap” scenario signaled significant advantages to the environment. They found that where snowpack supplies late season water flow, forest restoration can help improve habitat suitability, especially for salmon.
Specifically, a thick tree canopy cover affects snow accumulation and melt, altering the volume and timing of flow of water in streams or rivers in the warmer months. The gaps in the tree canopy scenario showed increased water collection in the snowpack and improved flow conditions for salmon habitat during the critical summer months.
Kicking Biomass for Energy
The team also focused on biomass from commercial thinning and timber harvest. Previous research suggests that 0.6 to 2.1 billion dry tons of biomass could be amassed from residues and small-diameter trees in five western states over any number of years.
Early findings of the study indicated that 1.4 million tons of biomass could be recovered economically in the demonstration basin examined in this study. A total of up to nearly 395,000 tons of wood chips, much from near Leavenworth, Washington alone, would cost $60 per ton or less delivered, depending on mill location. Another 1,019,000 tons could come from mill residue. According to the research team, these numbers may have since increased.
Looking Forward through the Trees
While the initial focus of this research was on high-risk areas in the Pacific Northwest, the data, models, and analysis techniques being used can be applied throughout forests across the nation.
The team also investigated changes to smoke emissions that affect air quality and health, and they are planning more research in simulating vegetation growth to better estimate long-term, sustainable biomass supply and changes in streamflow.