Rethinking Forest Health

RethinkingForest Health

27 February 2008

published by

USA — I just read through a portion of the Beaverhead Deerlodge NationalForest (BDNF) revised plan. Among the major components of the plan is supportfor “vegetation management,” a euphemism for logging. The BDNF plan callsfor “treating” its forests by logging to “restore” its ecological health.It has become commonplace for the Forest Service to justify logging for foresthealth reasons instead of timber production. We no longer log just to get theraw material for lumber and profits for timber companies. We log the forest torestore ecological health, or so the agency suggests. 

I personally don’t believe that the BDNF staff is purposefully using“forest health” as an excuse to log. There is a wide-spread assumption amongmany forest ecologists that past forest management, including past logging,along with fire suppression, has radically altered our forests. However, theagency may be unaware of more recent research that calls into question many ofthese previous assumptions about forest condition and health.

Even if the assumptions about forest condition are correct, that doesn’tmean that logging can actually restore the presumed “historic range ofvariability.” One could restore ecological health by permitting more fires toburn, and by the use of more prescribed burning. Since this doesn’t produceprofits for the timber industry, the agency is under a lot of pressure to cuttrees instead of using less intrusive means like prescribed burning and wildfireas a means of restoring the presumed forest conditions. To its credit, in itsAlternative 3 of the forest plan the BDNF does recommend exactly thatprescription—more wildfire and prescribed burning and limited logging.Unfortunately, for the public, Alternative 3 is not selected by the agency asits preferred alternative.

The problem for anyone advocating “restoration” is that we have fewreferences about how the forest looked a hundred years ago. There are somehistoric photographs that provide a valuable perspective, but whether theserepresent just a point in time and at a particular spot, or are characteristicof the forest as a whole is unknown. Furthermore, there is always the potentialfor a selective bias in the choice of photographs by the researcher seeking tofind evidence for a change in forest condition and composition.

The same can be said about written accounts. When someone asserts that theforests were so open they could ride a horse through them could again reflect abias in the observer who either selected the easiest pathway through the woods,avoiding other denser forest stands, or even a failure to note when the forestsencountered were densely forested. Also there is always the chance forresearcher bias that ignores some references to forest condition, in favor ofdescriptions that fit one’s preconceived notions about how the forest appeared.

The further back in time you go, the murkier the record. Most ecologists mustrely upon reconstruction of past “historic conditions” by proxy. One popularmethod involves looking at fire scars on trees, and trying to determine pastfire intervals. The assumption is that low intensity fires do not kill trees,but rather leave a record of their occurrence by a scar. By reading theintervals between such fire scars, researchers can reconstruct past fireoccurrence and severity and make some assumptions about the historic look ofthese forests. However, a recent review of this method by a number ofresearchers has called into question the validity of many of these studies.

For instance, William Baker from the University of Wyoming and colleagues dida review of fire history studies in ponderosa pine forests and found that nearlyhalf of them depended upon only one or two trees. Such a small sample size issuspect. Furthermore, even when a larger sample is used, there is a tendency forfire researchers to sample trees where there is an abundance of fire-scarredtrees. However, such a bias in sampling may not represent the historicconditions of the forested landscape as a whole. Baker’s research suggeststhat the occurrence of stand replacement fires may have been greater thanpreviously assumed, even for low elevation dry forests.

Another study done by Forest Service researcher Paul Hessburg and associateslooked at the temporal patterns of eastside forests in the Cascades. He startedwith the assumption that past conditions would be reflected by the standcomposition of the present forest. Using randomly selected air photos to reviewforest stand composition, he determined that there was little evidence for socalled “light, low intensity” burns or “open park-like” forests in drylow elevation and moist mixed forests as presumed. Rather partial and standreplacement fires appeared to be the norm—even before fire suppression waseffective and presumably created a “fuels build up.”

A third study in Colorado done by Dominick Kulakowski and his associatescritiqued the Forest Service’s assumption that there was wide-spread“decline” in aspen. Kulakowski was fortunate in finding a highly detailedand accurate 1898 map of forest type and occurrence of recent burns for aportion of the Grand Mesa area of Colorado. Digitizing the map, and thencomparing it to the present vegetation type for the forest, he was able todetermine that relative to the late 1800s, a larger portion of the landscape wascovered with aspen today than a century ago. A rash of fires near the turn ofthe century as a result of more favorable climatic conditions for fires (i.e.drought), as well as burning by sheep herders, miners, and other settlerscontributed to an increase in aspen throughout the 20th Century. So measuredagainst people’s recollection of aspen abundance in the recent past century,there had been a decline in aspen. But what Kulakowski’s research showed isthat the current abundance of aspen was not outside of the historic range ofvariability—and conifer cover was actually greater a hundred years ago thantoday.

A fourth study of wildfires in the northern Rockies by Penny Morgan, of theUniversity of Idaho, found one more piece of evidence that can be used toquestion the assumptions about “historic range of variability.” She mappedknown wildfires on national forests in Idaho and western Montana from 1900through 2003. She found the majority of all large fires occurred in just 11 fireyears. These fire years coincided with extensive drought. The first six big fireyears occurred prior the mid-1930s and the last five years have been since1988—the year that much of the Yellowstone ecosystem burned.  Between the1940s through the late 1980s, moister conditions resulted in virtually no largefires in the entire region. This has major implications for our assumptionsabout fire suppression and fuels.

Many people use the recent past as their point of reference. In other words,people talk about the large fires we are experiencing today as compared to the1940s, 50s, 60s and 70s and presumed that the reason has to be a consequence ofgreater fuels. But what is intriguing about her research is that six of thelarge fires occurred long before anyone can claim that fire suppression wasresponsible for a “fuels buildup.” No one can reasonably assert that firesuppression and fuel buildup was responsible for the huge 1910 Burn that ragedacross more than 3 million acres of northern Idaho and western Montana. Droughtand wind drove those fires, as it has all recent big fires.

The more recent spate of large fires in the 1990s and 2000s are attributed to“fuel buildup” as a consequence of this fire suppression. However, therecent period of large fires also coincides with historically severe droughtconditions across the West—the kind of climatic conditions that has alwaysdriven large blazes. Severe drought and overall warmer temperatures are alsoresponsible for widespread beetle outbreaks. Beetle experts, however, do not seethe large die-off of trees due to beetles as out of the ordinary—and manyassume that such large scale beetles outbreaks have occurred in the past, againcalling into question the assumption that our forests are “unhealthy.”

Temporal scale is an important factor in how we view current conditions—thelonger the time frame of reference, the less current conditions seem unnatural.A study by Boise State University professor Jen Perce and colleagues looked atfire frequency and scale among ponderosa pine forests along the Payette River inIdaho. Using the geological fire history recorded by charcoal buried in soilsediment, she concluded, contrary to popular perception that low intensityblazes are the norm for low elevation dry forests, when viewed over longer timescales, climatic conditions like drought has led to significant standreplacement fires on occasion, even in ponderosa pine ecosystems.

What do all these studies and others suggest about the presumed “historicrange of variability”? The message I take from these studies is that climatecontrols big fires and, when viewed on a landscape scale, our forests may not beout of balance as presumed. In fact our forests are very healthy and what we areseeing with both large blazes and large scale beetle outbreaks are within the“norm” for these forests if climatic conditions are taken into account. Thelarge fires we are experiencing are “resetting” the ecological parameters ofthe region. There is no need to “restore” forest health—the forests areperfectly healthy and are restoring themselves—without the help of the timberindustry, thank you.

Furthermore, even if it can be proved that some forests are somewhat out of“balance” that doesn’t necessarily mean that intrusive logging isnecessary or can restore forest health, especially since logging has many othernegative impacts that are often ignored or glossed over. These include thecreation of access roads that decrease habitat security for wildlife, act asvectors to spread weeds, not to mention are a major source of sedimentation intostreams (sedimentation from fires is short lived—while roads “leak”sediment for decades).

Logging operations seldom leave as many snags as naturally occur as a resultof fire or beetles. Logging also removes snags which are critical to thesurvival of many species—for instance; more than a third of all birds in thenorthern Rockies are cavity nesters, not to mention use of snags by a host ofother species from bats to snails. Plus, logs charred by fires take longer todecompose and last longer as a structural component in the ecosystem—with longterm consequences for wildlife and nutrient flows. The presumption that logging“emulates” nature is a bunch of timber industry propaganda.

Finally, new research is calling into question the other major justificationsfor logging which includes the assertion that logging can stop or reduce largefire risk and/or insect outbreaks. Logging does not affect the conditions thatdrives large blazes namely drought, high temperatures, low humidity, and, mostimportantly, wind. In fact, there is even evidence to suggest that thinning theforest can substantially exacerbate these conditions leading to increased solardrying of fuels, and permitting greater penetration of wind. Even a five mile anhour increase in wind results in an exponential increase in fire spread. Andremoval of competing trees, leads to rapid regrowth of shrubs and smaller treesthat are more flammable. The best way to reduce fire risk to communities is tofire-proof homes, not the forest.

Circling back to the BDNF plan, all of this research calls into question theForest Service assumptions about what is “normal” for the BDNF as well asmany other forests in the region. It is possible that the Forest Serviceassumptions about the forest conditions are accurate. On the other hand, thereis more than a reasonable likelihood that our forests are well within the“historic range of variability” and need no intrusive management other thanto get out of the way and allow fires, beetles, droughts, and other normalecological processes to operate. (By George Wuerthner

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