The value of thinning forests adds up to as much as $5,000 per acre if you take into account the benefits of preventing devastating wildfires, reducing carbon emissions that spur global warming and other non-market values, concluded a team of Northern Arizona University researchers.
The researchers from NAU have played a key role in developing support for the Four Forest Restoration Initiative (4FRI) by attempting to quantify the value of using a revitalized timber industry to thin millions of acres of tree-choked, fire-prone forests.
They presented their latest estimates of the value of thinning forests at the recent Conference of Research on the Colorado Plateau in Flagstaff.
Researchers included economist Ching-Hsun Huang, Alex Finkral, Christopher Sorensen and Thomas Kolb, all in the school of forestry.
The conference included a number of other studies documenting the value and complexity of forest restoration projects through a combination of thinning and controlled burns. Reducing tree average densities from perhaps 800 per acre to more like 50 per acre will involve decades of effort and repeated treatments, the studies concluded.
The U.S. Forest Service recently settled on a contractor to thin the first 300,000 acres of ponderosa pine forests. Good Earth hopes to convert the mass of small trees into fuel and finger-jointed furniture. But the NAU estimates suggest the value of the timber removed represents only a fraction of the value to society of the thinning effort. “Our goal was to move towards full economic valuation of fuels-reduction treatments applied to ponderosa pine forests,” the researchers wrote in the abstract of the study.
For starters, they calculated the economic value of the thinning projects based on the amount of carbon locked up in the trees and then removed from the forest through thinning projects. They tried to take into account the extra carbon put into the atmosphere by the thinning projects and production of wood products, which they balanced against the amount that would be released if the thick forest eventually burned or simply died and rotted.
They also made a rough estimate of the value of the wood harvested. They assumed the small diameter trees would produce pallets, paper and construction materials. Good Earth, hopes to produce higher value products from the small trees and brush, so the study estimate could prove conservative.
The researchers also included estimates of the damage inflicted by an uncontrolled wildfire.
Densely packed forests burn very differently from thinned forests or controlled burns. The megafires that have plagued Arizona in the past decade start in the hottest time of the year and often become crown fires affecting hundreds of thousands of acres. Such fires not only consume almost all of the trees in their path, they sterilize the soil and leave it much less able to absorb water — leading to floods and often-permanent changes in the forest. By contrast, periodic, low-intensity fires can actually improve forest health.
The study examined several different forest restoration approaches. The approach that yielded a return of $5,000 per acre assumed that a given acre would have a thinning project and a controlled burn every 20 years and an uncontrolled wildfire once every 50 years. More frequent thinning dramatically reduced the economic benefits.
On the other hand, some of the other studies hinted at the complexity of the task that awaits forest managers attempting to return millions of acres to a more natural state while protecting endangered forest communities from the threat of wildfire.
Studies presented at the conference included:
North Rim Wildfire Severity
Just because an area burns once doesn’t mean it can’t suffer a second, high-intensity wildfire again, concluded researchers from the University of Montana, based on an analysis of fire patterns on the North Rim of the Grand Canyon. They expected to find that once an area burned, it would not sustain another severe fire soon. However, they instead discovered that even a severe fire left enough dead trees and downed wood to sustain a second serious fire soon thereafter. The study focused on both burned and unburned areas during the fire-prone years of 2000 and 2001. They analyzed the severity of the fires in areas that burned once and nearby areas that burned twice. They found little difference in fire severity between the two situations. The study demonstrated that a single controlled burn won’t necessarily protect against future, severe wildfires.
Doubts about open forest model
The forest that existed before the 20th century was surprisingly diverse, with open, grassy stretches like the 4FRI project seeks to restore and much denser patches, according to a study of General Land Office Surveys in the late 1800s, researchers from the University of Wyoming concluded. The researchers studied survey records of forested land before the fire suppression and intense grazing of the 20th century and reconstructed vegetation patterns across nearly 4 million acres. About half of the land included was ponderosa pine forests. They concluded the natural succession of low-intensity fires had created a very diverse forest. “Ponderosa pine forests on the southwestern plateau included both low-density, old-growth forests, but also dense forests, and forests recovering from mixed and high-severity fires.”
Benefits of controlled burn
A 2,300-acre controlled burn in Grand Canyon National Park didn’t kill a single large tree but did reduce total fuel on the ground by 38 percent, pine seedling density by 48 percent and pine sapling densities by 27 percent, according to a report by David Robinson, Windy Bunn and Eric Gdula, with the park service. The October 2012 fire burned in a stretch of forest with 335 trees per acre and an average of 50 tons of downed wood and brush per acre. The burn significantly thinned the forest and reduced fuel loads while still protecting thicker patches of forest intended to offer nesting areas for Mexican spotted owls. The researchers concluded that they could conduct such controlled burns safely even in earlier, warmer, drier months. The study helps support the need for the great increase in controlled burns the Forest Service has undertaken in recent years, trying desperately to reduce fuel loads and so prevent a catastrophic megafire.