CONTEXT AND PERSPECTIVE NEEDED IN BARK BEETLE DISCUSSION

George Wuerthner





In the November 17th Science Section of the New York Times there was an article by Jim Robbins about the current pine beetle event occurring in the West. http://www.nytimes.com/2008/11/18/science/18trees.html?_r=1

There was a lot of good factual information in the piece about pine beetles and their basic ecology, and on the whole, Robbins did a good job of describing some of the concerns that people have about the beetle situation. Nevertheless, the tone and implied message conveyed an overly pessimistic and negative picture of beetles as well as wildfires. It was not so much that it had a lot of false statements as much as the way it was written. Taken together the various quotes, and background in the article leaves one with the perception that somehow beetles, as well as wildfires are “out of control” in the West's ecosystems.

What is lacking is perspective and context. As a writer myself I recognize that space limitations often affect the detail that can be contained in an article. Sometimes you can’t list all the exceptions, nuance, and provide the full context for a piece. Robbins got a lot of ecological information in his piece, and in that regard he did a good job.

However, it seems to me that the real “news” here isn’t that we are having large outbreaks of beetles, but that such events are probably quite normal when looked at from an ecological temporal and spatial perspective. Those who are asserting these are the largest outbreaks in history are only going back a relatively short time—perhaps the past 50-100 years for the context and perspective. At least some beetle researchers I’ve talked with believe the current infestation (infestation is pejorative and not a good word to use here, but I can think of nothing more suitable) is not that out of the ordinary when compared to other large events from the more distance past.

We are seeing unprecedented drought and much warmer temperatures as Robbins noted in the article. But what he did not do is connect the dots. Such droughts mean that our forests are overstocked for current conditions, and the beetles as well as wildfires are doing us all a great favor by thinning them at no cost. Instead of portraying this natural thinning process as a problem, a more ecologically informed perspective might suggest that the beetles are creating forests that are more in balance with available moisture, and other nutrients.

Now the global warming that is occurring may be unnatural--due to human caused climate change--but global warming is the problem, not the response of the beetles, fires, and forest to that climate change.

Large beetle outbreaks and wildfires in particular, rather than being “destructive” as insinuated in the article are the major ecological influences upon these types of forest ecosystems. The real “news” is that what people think about forests and wildfires,is not accurate.

For instance, dead trees do not necessarily increase fire risk, and in fact, green trees might burn better under severe drought conditions. And dead trees provide many ecological benefits—which were not even mentioned in the piece to balance the doom and gloom. This kind of information is really the “news” especially for the Science Section of the New York Times.

The piece also mentions fire suppression as one of the factors that has led to even aged stands of lodgepole vulnerable to pine beetle attack. (Pine beetle typically only attack larger trees so trees growing back from recent burns are not susceptible to attack) Rather than fire suppression contributing to these large beetle events, what is more likely occurring is a significant proportion of lodgepole pine stands in the West created by past large fires and/or beetle outbreaks a century or more ago are now the proper size and age to support sustained beetle population growth. As Robbins does note correctly, when they reach this size, and are stressed by drought, they are less able to extrude beetles attempting to lay eggs in the tree’s cambium layer.

One of the reasons that fire suppression is unlikely to have had much effect upon the region’s lodgepole forest vulnerability to beetles has to do with the typical fire regime of this species. Lodgepole pine usually burns infrequently at relatively long intervals between fires, and generally in stand replacement blazes.

Significant fires in lodgepole pine only occur when there is severe drought--conditions as we are experiencing now. So the idea that past fire suppression reduced fires in these kinds of forests is unlikely or at best probably has had little influence on total fires and acreage burned today. Lodgepole forests don’t burn simply because there are dead trees—whether those trees are a consequence of past fires or beetle attack. It takes specific climatic conditions to sustain a fire.

There is a widespread misuse of the Southwest ponderosa pine model fire regime which is too often indiscriminately applied to all forests. While Southwest ponderosa pine forests are characterized by frequent low intensity fires that may have been altered by fire suppression, this generalization should not be applied to other forest types like lodgepole pine which naturally have much longer fire intervals. Fire suppression simply hasn’t been effective long enough to alter the fire intervals in lodgepole forests.

The other factors listed in Robbin’s piece--drought and warm winters--are the main reasons for this particular spectacular beetle outbreak. And these are largely factors controlled by climate--likely human induced global warming-- rather than fire suppression.

Another factor that was not really addressed in the piece was the current condition of our forests is largely a reflection of either past fires and/or past beetle outbreaks. In other words, the extensive geographic extent of lodgepole of the proper age to make them vulnerable to beetles is a consequence of past events that created large stands of even aged pine.

There is data to suggest that previous beetle outbreaks every bit as large as and/or larger than the current one have repeatedly swept pine in the West. Put into that kind of perspective, the current events do not seem so extraordinary.

The problem is that we humans have such a short temporal viewpoint on ecological change. Events like large wildfires and beetle outbreaks that occur periodically, but only every century or two "seem" large because we are not witness to them but once every generation or two. That is why the Yellowstone fires seemed extraordinary to the country even though research has demonstrated that large blazes, often much larger than those in 1988, occurred in Yellowstone’s forests in centuries past.

Furthermore, just as a hundred year flood does a lot of the real hydrological work of a river in terms of channel morphology changes, these large fires and outbreaks of beetles are the major ecological force in their respective ecosystems. In other words, the small fires and outbreaks that occur on a more frequent basis really don't matter because they don't amount to a hill of beans. It's the occasional, but rather uncommon large events that are the real driver of ecosystems. This perspective was regrettably missing from the article.

Third, the idea that dead lodgepole increases fire risk is also more nuanced than presented. In most of lodgepole pine forests it is too wet to burn most of the time--regardless of the fuels that are present. That is why lodgepole forests tend to burn on long intervals—because conditions that make them dry enough to burn readily do not occur frequently. Just because you have a lot of dead trees, doesn't mean you will have a large fire or the fire risk is higher in those particular forest types.

Beyond that point, the overall fire hazard changes through time, and it is not as neat as presented in the article. Immediately following the attack and the red needle stage, flammability goes up. But what is the likelihood that there will be an ignition and that it will be wet enough for these trees to burn during that short period of several years. Well it turns out it is a very small probability.

Probability is an important factor in these discussions. The fact that you have a lot of red needles out there doesn't translate into higher fire risk unless the other factors that contribute to large blazes like wind, drought, low humidity, and ignition are also present. Getting all these factors together on the same piece of land at the same time that the forest is dominated by red needles is extremely rare--which is why lodgepole pine forests do not burn very often.

But after the needles drop, and small branches break off the trees, the flammability goes down for several decades--so even with drought, wind, etc. the probability of fire actually goes down over that which might occur if the trees were green and alive. In reality, a standing dead tree is not likely to burn except under very severe fire conditions.

Under severe drought conditions, green trees are more flammable than dead trees (where the small branches and needles are gone) because they have flammable resins. Thus under extreme drought conditions, your green forests are more likely to burn than a sea of dead trees at this stage.

The bulk of trees killed by fire or beetles do not fall over for several decades. Even then, what increases flammability aren’t so much the dead trees, but the rapid growth of young trees that take advantage of the opening in the forest canopy and reduction in competition. Since it is fine fuels that sustains fire, not large snags, it is the young trees, grass, shrubs, etc. that rapidly fill up the ground and can carry a fire that leads to greater flammability.

Big logs, as most of us probably know from trying to make campfires, are not easily ignited . If you don’t have a lot of “kindling” under the logs, ignition from a match, spark or any other source, won’t get the log to burn. The larger the log, the more preheating require to get it up to the burning point and keep it there. You need a lot of fine fuels and small branches to carry and sustain a fire. It is the rapid growth of smaller trees, etc. that provides this small fuels, which can heat the larger logs to the ignition point and help to sustain the flames.

Fourth, the article unfortunately had a lot of dire stuff about mudslides, floods, etc. which may or may not follow a fire, but even if it does, even these events must be put into perspective. Research shows these kinds of natural events are relatively rare. And at least in some places, research has shown that the bigger and most severe burns actually have contributed to higher biodiversity, more fish, etc. than lightly burned areas. In other words, contrary to popular perception, severe wildfires might not be “bad” from a biodiversity and ecological perspective—even for things we care about like the quality of the trout fishing.

Another problem with the piece was the use of pejorative language. In my book Wildfire: A Century of Failed Forest Policy I discuss at length about how language helps to promote the idea that wildfires are "bad" by using words like "catastrophic", “disaster”, “damaged”, and other adjectives used to describe wildfires. Such terms are really pejorative words since large fires are not deadly to the landscape or ecosystems as implied.

As mentioned at the beginning, most of the factual content of the article was accurate, but still the author weaved together a report that presented an ecologically inaccurate portrait of the situation. Context and perspective are critical to our collective understanding of ecological events, and without such information, we react with poor policy choices.